| disease | Tetralogy of Fallot |
| alias | Tetralogy of Fallot |
Tetralogy of Fallot is a common congenital cardiovascular malformation and ranks first among cyanotic congenital heart diseases. The condition was reported by Stensen in 1672, Sandifort in 1777, Hunter in 1783, Hope in 1839, and Peacock in 1866. In 1888, Fallot documented 55 cases and described in detail the pathological anatomical features of the disease, namely: ① pulmonary artery stenosis, ② ventricular septal defect, ③ dextroposition of the ascending aorta, and ④ concentric hypertrophy of the right ventricle. Since then, the condition has been named Tetralogy of Fallot. In 1944, Blalock and Taussig recognized that the primary pathophysiological change in tetralogy was insufficient pulmonary blood flow, leading to reduced blood oxygen levels, cyanosis, and death. Based on this understanding, they pioneered the subclavian artery-pulmonary artery shunt to increase pulmonary blood flow and improve hypoxia. Subsequently, Potts, Glenn, and Waterston introduced various systemic-pulmonary shunts in clinical practice. In 1948, Brock and Sellors performed closed-heart surgery on tetralogy patients, directly incising the infundibulum or pulmonary valve stenosis. In 1954, Scott, and in 1955, Lillehei, Kirklin, and Kay, among others, performed open-heart corrective surgeries for tetralogy under hypothermic anesthesia and extracorporeal circulation.
bubble_chart Etiology
In 1970, Van Praagh et al. proposed that the embryonic developmental disorder of tetralogy is due to hypoplasia of the distal pulmonary conus or the infundibular region of the right ventricle, which fails to undergo reverse inversion. As a result, the aortic valve remains in its embryonic position, situated to the right of the pulmonary valve. The infundibular septum, or the parietal band, normally develops in a posterior, inferior, and rightward direction. However, in patients with tetralogy, its orientation shifts anteriorly, superiorly, and leftward, terminating at the anterior wall of the conus. This leads to right ventricular outflow tract obstruction once the proximal conus fuses with the heart. Additionally, because the infundibular septum is positioned anteriorly and superiorly, it fails to occupy the space between the left anterior superior limb and the right posterior limb of the septal band above the ventricular septum. Consequently, a large ventricular septal defect forms below the infundibular septum, or the crista supraventricularis. The underdeveloped pulmonary conus also causes the aortic orifice to shift rightward, overriding the ventricular septal defect.
bubble_chart Pathological ChangesThe two main anatomical anomalies of tetralogy, right ventricular outflow tract stenosis and ventricular septal defect, both exhibit considerable variation (Figure 13).
⑴ Fistula disease with infundibular stenosis, normal pulmonary valve and pulmonary artery pulse. ⑵ Valvular stenosis causing secondary hypertrophy of the infundibulum in fistula disease.
⑶ Fistula disease with infundibular stenosis and hypoplastic pulmonary artery pulse.
⑷ Pulmonary valve stenosis, hypoplastic pulmonary artery pulse, and secondary hypertrophy of the infundibulum in fistula disease.
Figure 13: Right Ventricular Outflow Tract Stenosis
Right Ventricular Outflow Tract: The stenosis in the right ventricular outflow tract can be located in the infundibulum of fistula disease, the valvular membrane of the pulmonary artery, the pulmonary valve annulus, the main pulmonary artery, or its branches. In some cases, stenosis may occur at two sites.
Infundibular Stenosis in Fistula Disease: Almost all patients with tetralogy exhibit some degree of infundibular stenosis in fistula disease. In most cases, infundibular stenosis coexists with pulmonary valvular membrane stenosis. The stenosis is caused by hypertrophy of the parietal band, septal band, and crista supraventricularis. A third ventricle of varying size often forms between the infundibular stenosis and the pulmonary valve. If the infundibular stenosis is located distally in the right ventricular outflow tract, near the pulmonary valve, the third ventricle is small; if the stenosis is proximal, the third ventricle is larger and has a fibrous annular entrance. Occasionally, the infundibulum in fistula disease may be hypoplastic, presenting as a diffuse, long, and narrow tubular stenosis without a third ventricle.
Pulmonary Valvular Membrane Stenosis: 75% of tetralogy patients exhibit pulmonary valvular membrane stenosis. The valve is often bicuspid, with thickened leaflets, restricted mobility, and a narrow orifice.
Pulmonary Valve Annulus: In tetralogy cases, the pulmonary valve annulus is always smaller than the aortic valve annulus, but annular stenosis is relatively rare. In cases with diffuse hypoplasia of the infundibulum, presenting as a long, narrow tubular stenosis, the pulmonary valve annulus is also small. Sometimes, stenosis results from thickening of the annulus due to subendocardial fibrosis.
Main Pulmonary Artery: In tetralogy cases, the main pulmonary artery is always smaller than the aorta. In cases with diffuse hypoplasia of the right ventricular infundibulum, the main pulmonary artery is often short, displaced posteriorly, and divides into two pulmonary arteries, with diameters as small as 50% of the aorta. Rarely, localized severe thickening of the vessel wall above the pulmonary valve annulus causes discrete supravalvular stenosis.
Pulmonary Artery and Its Branches: The left pulmonary artery is usually a direct continuation of the main pulmonary artery, while the right pulmonary artery forms a 90° angle with the main pulmonary trunk. Stenosis may occur at the bifurcation of the pulmonary artery. The proximal segments of the left and right pulmonary arteries are often hypoplastic, with narrow diameters or localized stenosis. In severe cases, one pulmonary artery or its branches may be atretic with single or multiple stenoses. Absence of the proximal pulmonary artery is more common on the left side. Pulmonary blood supply may come from a patent ductus arteriosus, ascending aorta, collateral branches between the aorta and pulmonary artery, or branches of the bronchial, intercostal, or subclavian arteries.
Ventricular septal defect: A typical case of tetralogy, the ventricular septal defect is located below the main stirred pulse and involves the membranous portion of the ventricular septum. It is formed due to the failure of the conal septum and the fistula disease infundibular septum to align in the same plane. Generally, the ventricular septal defect is large in area and positioned anteriorly. The posterior-superior edge of the defect consists of the myocardial fold of the fistula disease infundibulum, adjacent to the non-coronary and/or right coronary cusps of the main stirred pulse. The posterior edge is formed by the base of the anterior and septal leaflets of the tricuspid valve and the right fibrous trigone. Occasionally, myocardial tissue may also be present between the right fibrous trigone and the base of the anterior leaflet. The inferior edge of the defect is the right posterior branch of the septal band, while the anterior edge is the left anterior branch of the septal band. In cases where the fistula disease infundibular ventricular septum is absent, the ventricular septal defect is located below the main stirred pulse valve and the pulmonary stirred pulse valve. Between the posterior edge of the defect and the tricuspid valve annulus, there may be a myocardial bundle 2–5 mm wide. The main stirred pulse valve annulus and the pulmonary stirred pulse valve annulus are separated only by a thin and narrow fibrous ridge. In rare cases, there may be an additional muscular ventricular septal defect below the main stirred pulse valve.
Main stirred pulse: In cases of tetralogy, the main stirred pulse is displaced forward and to the right, originating from both ventricles, with the portion overriding the right ventricle generally accounting for 50% of the main stirred pulse's diameter. The root of the main stirred pulse is larger than normal and rotates clockwise, causing the base of the non-coronary cusp to shift rightward and upward toward the posterior superior edge of the ventricular septum. The right ventricular outflow tract exhibits diffuse hypoplasia, and in cases where the fistula disease has a small infundibular septum with the pulmonary stirred pulse orifice displaced leftward, the rightward position and overriding of the main stirred pulse are more pronounced. Approximately 25% of cases exhibit a right-sided aortic arch, and 10% of cases have an aberrant left subclavian stirred pulse originating directly from the descending aorta. Patients with pulmonary stirred pulse atresia often have a patent ductus arteriosus.
Coronary stirred pulse: The coronary stirred pulse is often tortuous and dilated. The enlarged right coronary stirred pulse's conus branch frequently crosses obliquely over the anterior wall of the right ventricle. Care must be taken during surgery to avoid injury when making an incision in the right ventricle. In rare cases, the anterior descending branch originates from the right coronary stirred pulse.
Right ventricle: The inflow tract of the right ventricle is enlarged, the interventricular groove is displaced leftward, and the ventricle rotates clockwise, with the left ventricle turning posteriorly. The right ventricular wall is hypertrophied, with thickness similar to that of the left ventricle. The trabeculae of the right ventricle are thickened, the end-diastolic volume of the right ventricle is reduced, and due to chronic myocardial hypoxia, the ejection function is weakened.
Conduction system: The sinoatrial node and atrioventricular node are normally positioned. The atrioventricular bundle passes through the right fibrous trigone from the base of the non-coronary cusp, closely following the lower edge or slightly leftward of the ventricular septal defect, and proceeds forward to reach the left ventricular surface, where it branches. In cases with significant clockwise rotation and overriding of the main stirred pulse root, the posterior edge of the ventricular septal defect lacks muscular tissue development, and the atrioventricular bundle is positioned more superficially, close to the right ventricular surface, covered only by dense fibrous tissue formed by the convergence of the main stirred pulse annulus and the tricuspid valve base. This makes it susceptible to injury during ventricular septal repair. If the posterior edge of the defect has more muscular tissue, protruding above the right fibrous trigone, the atrioventricular bundle is positioned deeper, closer to the left ventricular side of the interventricular crest, making it less likely to be injured during ventricular septal defect repair.
Other cardiovascular anomalies: Cases of tetralogy may also include patent ductus arteriosus, right-sided aortic arch, atrial septal defect, patent foramen ovale, left superior vena cava, anterior descending branch of the coronary stirred pulse originating from the right coronary stirred pulse, aberrant subclavian stirred pulse, anomalous pulmonary venous return, and aortic valve insufficiency, among others.
The primary hemodynamic change in tetralogy is right ventricular outflow tract obstruction, leading to increased right ventricular pressure and reduced pulmonary blood flow. In severe cases, right ventricular pressure may rise to equal left ventricular pressure. During ventricular contraction, while the left ventricle ejects blood into the main stirred pulse, the right ventricle also ejects blood into the main stirred pulse through the ventricular septal defect, resulting in a right-to-left shunt. Reduced pulmonary blood flow and right-to-left shunting lead to decreased systemic blood oxygen levels, insufficient tissue oxygenation, cyanosis, and chronic hypoxia, with significant increases in hemoglobin and red blood cells. Reduced pulmonary blood flow also promotes the formation of bronchial stirred pulse collateral circulation. In cases of moderate right ventricular outflow tract obstruction with less severe right ventricular pressure elevation, bidirectional shunting may occur. If the obstruction is mild, pulmonary blood flow reduction is not significant, and the shunt direction through the ventricular septal defect is primarily left-to-right, resulting in mild hypoxia and no clinical cyanosis, known as acyanotic tetralogy.
bubble_chart Clinical Manifestations
The most common primary clinical symptoms of tetralogy are cyanosis and hypoxia. The timing and severity of clinical manifestations depend on the degree of right ventricular outflow tract obstruction and the volume of pulmonary blood flow. Shortly after birth, since the {|###|}stirred pulse{|###|} duct has not yet closed, pulmonary blood flow can come from the patent {|###|}stirred pulse{|###|} duct, so cyanosis is often not clinically apparent. In the vast majority of cases, cyanosis begins to appear and gradually worsens only after the {|###|}stirred pulse{|###|} duct closes several weeks or months after birth. However, if the right ventricular outflow tract obstruction is severe—such as in cases of pulmonary {|###|}stirred pulse{|###|} atresia, diffuse hypoplasia of the outflow tract, or grade III stenosis at multiple sites including the {|###|}fistula disease{|###|} infundibulum, pulmonary {|###|}stirred pulse{|###|} valve annulus, and pulmonary {|###|}stirred pulse{|###|} valve membrane—cyanosis may be present immediately after birth. In cases with mild right ventricular outflow tract obstruction and minimal right-to-left shunting, cyanosis is mild; if the ventricular-level shunt is predominantly left-to-right, cyanosis may not occur. Cyanosis worsens during feeding, crying, or activity, accompanied by dyspnea. Pediatric patients often prefer a squatting posture. Squatting reduces venous return from the lower limbs and increases systemic vascular resistance, thereby increasing pulmonary blood flow, raising {|###|}stirred pulse{|###|} oxygen saturation, and alleviating cyanosis and dyspnea. In cases with {|###|}fistula disease{|###|} infundibular stenosis, spasm of the infundibulum can worsen the stenosis, leading to a sudden reduction in pulmonary blood flow and triggering hypoxic episodes, manifesting as dyspnea, {|###|}syncope{|###|}, and {|###|}spasm{|###|}, which can be fatal in severe cases. These episodes are more likely to occur in hot weather or with elevated body temperature. During an episode, the ejection systolic murmur often weakens or disappears. Intramuscular injection of morphine (0.2 mg/kg) or propranolol (2.5 mg/kg daily) can relieve hypoxic episodes. In a few cases, if the ventricular septal defect is large, the left-to-right shunt increases when pulmonary vascular resistance decreases 1–2 months after birth, leading to pulmonary congestion and clinical symptoms of heart failure. However, cyanosis gradually worsens after 6 months of age. In cases with severe cyanosis and marked polycythemia, cerebral thrombosis may occur, leading to hemiplegia or brain abscess. Cerebral thrombosis is more likely to occur in dehydrated states. In older patients with severe cyanosis, abundant bronchial {|###|}stirred pulse{|###|} collateral circulation may rupture, causing massive {|###|}hemoptysis{|###|}.
Signs: Physical growth and development are delayed. Cyanosis is prominent in the face, lips, tongue, {|###|}eyelid{|###|} conjunctiva, and other areas. Clubbing of fingers and toes is common in pediatric patients. The cardiac dullness area is not enlarged, but the left anterior chest may be prominent. An ejection systolic murmur caused by right ventricular outflow tract stenosis can be heard at the left sternal border in the 2nd and 3rd intercostal spaces, possibly accompanied by a {|###|}tremor{|###|}. If the stenosis is severe, the murmur becomes softer and shorter due to increased right ventricular ejection into the main {|###|}stirred pulse{|###|} and reduced pulmonary {|###|}stirred pulse{|###|} blood flow. In cases of pulmonary {|###|}stirred pulse{|###|} atresia, the systolic murmur may disappear and be replaced by a continuous murmur from collateral circulation or a patent {|###|}stirred pulse{|###|} duct. The second heart sound at the pulmonary {|###|}stirred pulse{|###|} valve area is diminished or normal and may sometimes be a single loud sound transmitted from the second heart sound of the main {|###|}stirred pulse{|###|} valve.
bubble_chart Auxiliary Examination
Chest X-ray examination: In typical cases of tetralogy, the heart is not enlarged, the lung fields are abnormally clear, and vascular markings are sparse. In cases with a smaller pulmonary artery trunk, the left border of the heart appears flat or concave. If the third ventricle is larger, the pulmonary artery segment on the left border of the heart protrudes. Due to right ventricular hypertrophy, the cardiac apex is tilted upward. On posteroanterior X-ray films, the cardiac shadow appears boot-shaped. In about one-fourth of cases, the aortic arch is located on the right side.
Electrocardiogram (ECG) examination: Shows right ventricular hypertrophy and strain, with right axis deviation. The R wave is significantly increased in the right precordial leads, and the T wave is inverted. In some patients, leads I and II show tall, peaked P waves indicative of right atrial hypertrophy. The left precordial leads do not display Q waves, and the R wave voltage is low.
Right heart catheterization: Reveals increased right ventricular pressure, which may reach the level of left ventricular pressure. The catheter can pass directly from the right ventricle into the aorta, indicating the presence of a ventricular septal defect and aortic override. Due to right ventricular outflow tract and/or pulmonary artery stenosis, a systolic pressure gradient is observed between the right ventricle and pulmonary artery. Analysis of the pressure curve morphology can determine the location, type, and presence of a third ventricle. Oxygen saturation is reduced, generally below 89%, and further decreases after exercise.
By injecting an indicator separately into the right ventricle and pulmonary artery via right heart catheterization, the peripheral artery records an indicator dilution curve, showing early appearance of the indicator injected into the right ventricle and a biphasic descending limb of the curve, indicating a right-to-left shunt. Injection of the indicator into the pulmonary artery yields a normal curve.
Echocardiography: Cross-sectional echocardiography is highly valuable for diagnosing tetralogy. It can directly show significant thickening of the right ventricular wall; tubular narrowing of the right ventricular outflow tract or the formation of a third ventricle; pulmonary valve stenosis; a pulmonary artery diameter smaller than the aorta; interruption of the ventricular septal echo; and anterior displacement of the aortic wall, overriding the ventricular septum.
Selective right ventriculography: Essential for tetralogy cases before surgical treatment. A catheter is placed in the right ventricular cavity to inject contrast medium, and continuous X-ray imaging shows simultaneous opacification of the pulmonary artery and aorta, as well as the degree of aortic override. Meanwhile, the contrast medium flows from the right ventricle through the ventricular septal defect into the left ventricle. Angiography can also reveal the location and severity of right ventricular outflow tract and/or pulmonary artery stenosis, assess pulmonary artery development, and measure the diameters of the pulmonary trunk and ascending aorta to calculate their ratio.
Retrograde aortography: Can reveal patent ductus arteriosus, bronchial artery collateral circulation, and aortic valve function. McGoon's measurement compares the sum of the diameters of the left and right pulmonary arteries with the descending aorta at the diaphragmatic level. If the ratio exceeds 2.0, it indicates no obstruction to pulmonary blood flow.
Blood tests: Red blood cell count, hemoglobin, and hematocrit are significantly elevated. In grade III cyanosis cases, the red blood cell count may reach 10 million, hemoglobin 258%, and hematocrit generally ranges from 50% to 70%, but can be as high as 90%.
bubble_chart Treatment Measures
The only effective treatment for tetralogy is to perform surgical procedures to increase pulmonary blood flow, improve hypoxia, or correct intracardiac malformations. More than 40 years ago, the surgical treatment for tetralogy of Fallot involved systemic-pulmonary shunt procedures to alleviate hypoxia, improve symptoms, and prolong life. After the introduction of open-heart surgery under cardiopulmonary bypass, radical correction of tetralogy gradually replaced palliative systemic-pulmonary shunts, with increasingly better outcomes. However, opinions remain divided regarding staged surgeries for infants and young children—i.e., performing a shunt first, followed by radical correction or an initial-stage [first-stage] radical correction. Some advocate that patients with clinically significant symptoms, regardless of age, should undergo initial-stage [first-stage] radical correction to avoid the risks of two surgeries. Early surgery may also prevent worsening right ventricular hypertrophy and outflow tract stenosis. Others argue that the mortality rate for radical correction within three months after birth is 25–67%, significantly higher than for systemic-pulmonary shunts, whereas delaying radical correction until 1–2 years of age substantially reduces mortality. Thus, they favor staged surgeries—performing a systemic-pulmonary shunt for patients aged 6 months to 1 year, followed by an intermediate-stage [second-stage] radical correction later. With accumulated clinical experience, the mortality rate for radical correction has decreased, and outcomes continue to improve. Currently, surgical plans are tailored based on the patient’s age and pathological anatomy. Radical surgery in infants carries a higher mortality rate, so the optimal age for surgery is typically over 6 months. For infants under 6 months requiring urgent intervention due to severe symptoms, a palliative systemic-pulmonary shunt should be performed first. However, if angiography reveals that right ventricular outflow tract obstruction is due to infundibular stenosis with well-developed pulmonary valve annulus and pulmonary artery, and recurrent hypoxic spells are caused by infundibular spasm, medical treatment (e.g., propranolol) may be administered until the patient reaches 6 months of age for radical correction. For infants under 6 months with selective right ventricular angiography showing diffuse hypoplasia of the infundibulum, pulmonary valve annular stenosis, or stenosis of the main pulmonary artery or branches—requiring transannular patch repair—radical correction carries a high mortality rate, so a palliative shunt is preferred initially, followed by radical correction later.
Surgical Procedures:
Systemic-Pulmonary Shunt: A vascular anastomosis is created between the systemic and pulmonary circulations to divert some systemic blood flow into the pulmonary circulation, thereby increasing pulmonary blood flow and improving arterial oxygen levels. Clinically, this results in reduced cyanosis, improved exercise tolerance, decreased red blood cell count, hemoglobin, and hematocrit, and increased arterial oxygen content and saturation. Systemic arteries or the superior vena cava can be used for the shunt, but due to low venous pressure and slow blood flow, thrombosis and vessel occlusion are more likely. Thus, systemic artery-to-pulmonary artery anastomosis is preferred for tetralogy of Fallot. Several surgical techniques are available:
1. Blalock-Taussig Operation In 1945, Taussig and Blalock first reported the successful treatment of three cases of clinically severe cyanotic tetralogy of Fallot by performing end-to-side anastomosis between the subclavian artery or innominate artery and the pulmonary artery. Subsequently, systemic-pulmonary circulation shunt procedures involving anastomosis between branches of the aortic arch and the pulmonary artery were referred to as the Blalock operation. In 1971, Taussig reported the long-term outcomes of systemic-pulmonary circulation shunt procedures in nearly 1,000 patients with cyanotic congenital heart disease. The use of the subclavian artery resulted in the lowest surgical mortality and avoided potential cerebral complications that might arise from ligating the common carotid artery or innominate artery. For children under 12 years of age, it is preferable to use the subclavian artery originating from the innominate artery, as the transected and downwardly rotated root of the subclavian artery forms a right angle with the innominate artery post-anastomosis, ensuring smoother blood flow. In contrast, using the subclavian artery directly originating from the aortic arch for anastomosis may lead to twisting at its root when transected and rotated downward, potentially compromising blood flow.
To allow systemic circulation blood to be shunted through the anastomosis into both lung tissues for oxygenation, it is advisable to perform an end-to-side anastomosis between the proximal cut end of the subclavian artery and the incision of the pulmonary artery.
General anesthesia with tracheal intubation. During the procedure, care should be taken to prevent exacerbation of hypoxia. The patient is placed in a supine position with the operative side slightly elevated at the back. A thoracotomy incision is made from the sternal border to the anterior axillary line at the third or second intercostal space. To improve exposure, one rib cartilage may be divided. After entering the pleural cavity, the lung tissue is retracted downward, and the subclavian artery and pulmonary artery are examined. Once deemed suitable in length and size, the mediastinal pleura is incised to mobilize the subclavian artery and pulmonary artery. For anastomosis using the right subclavian artery, the azygos vein needs to be ligated and divided, and the superior vena cava retracted anteromedially to facilitate exposure of the right pulmonary artery and innominate artery. A non-traumatic vascular clamp is placed at the root of the subclavian artery. After occlusion, the distal segment of the subclavian artery is ligated at the apex of the thoracic cavity. To increase the length of the proximal subclavian artery, branches such as the vertebral artery, internal thoracic artery, and thyrocervical trunk may be ligated separately. The subclavian artery is then divided, and the adventitial tissue at the cut end is trimmed. The pulmonary artery is mobilized, and a non-traumatic vascular clamp is placed on its proximal segment. The distal pulmonary artery can be occluded by placing thick silk sutures around its branches. The proximal cut end of the subclavian artery is turned downward to approximate the pulmonary artery, ensuring the vessel is not twisted. A transverse incision is made on the corresponding part of the pulmonary artery wall, slightly larger than the diameter of the subclavian artery cut end. Using a fine curved needle and 5-0 suture, the posterior wall of the anastomosis is continuously sutured, with an additional interrupted suture at each end for fixation. The anterior wall is then sutured continuously or interrupted (Figure 1). After completing the anastomosis, the occluding sutures on the distal pulmonary artery branches are removed sequentially, followed by the proximal pulmonary artery clamp. Once hemostasis at the anastomosis is confirmed, the subclavian artery root clamp is released. A thrill can then be palpated on the pulmonary artery, and the patient's cyanosis shows significant improvement. A chest drainage tube is placed, and the wound is closed in layers. If the subclavian artery is too short for direct subclavian-pulmonary artery anastomosis or if the anastomotic tension is too high, a 5mm diameter Gortex graft can be used, with end-to-side anastomoses performed at both the subclavian and pulmonary arteries (Figure 2).
(1) Exposure of the surgical field
(2) Incision of the right pulmonary artery
(3) Division of the right subclavian artery, with the proximal segment turned downward
(4) Anastomosis of the posterior wall
(5) Anastomosis of the anterior wall (6) Blood flow direction after anastomosis completion
Figure 1 Subclavian artery-pulmonary artery anastomosis
(1) Exposure of the subclavian artery and pulmonary artery (2) End-to-side anastomosis of the graft to the left subclavian artery
(3) The other end of the artificial blood vessel is anastomosed end-to-side with the pulmonary stirred pulse. (4) The anastomosis is completed.
Figure 2 Connecting the subclavian stirred pulse and the pulmonary stirred pulse with an artificial blood vessel.
2. Potts Procedure This refers to the side-to-side anastomosis between the descending aortic stirred pulse and the left pulmonary stirred pulse. In 1946, Potts, Smith, and Gibson first applied this procedure clinically in three patients with tetralogy of Fallot, hence the name. Prior to this, Gross and Hufnagel, as well as Blalock and Park, had performed this surgery on experimental animals. However, since the procedure required complete occlusion of the descending aortic stirred pulse blood flow, it often led to spinal cord ischemia and subsequent hindlimb paralysis. To avoid this severe complication, Potts and Smith developed a ring-shaped stirred pulse clamp. Placing this aortic clamp on the descending aorta allowed partial occlusion of the aortic wall for anastomosis while maintaining uninterrupted blood flow in the descending aorta, ensuring the spinal cord's blood supply remained unaffected.
The surgery is performed under general anesthesia, with care taken to avoid hypoxia throughout the procedure. The patient is placed in the right lateral decubitus position. A left posterolateral thoracotomy is performed through the fourth intercostal space. The left lung is retracted anteroinferiorly, and the pulmonary hilum is dissected to free the left pulmonary stirred pulse and expose its branches. The mediastinal pleura is then incised to mobilize the upper segment of the descending thoracic aorta below the aortic arch. Often, one or two intercostal stirred pulses need to be ligated and divided to facilitate the placement of the ring-shaped aortic clamp, which is applied to the anteromedial portion of the descending aortic wall for anastomosis. A suture is looped around the proximal and distal segments of the left pulmonary stirred pulse to occlude blood flow, and the sutures are tied to the ring-shaped aortic clamp, bringing the pulmonary stirred pulse and descending aorta into close proximity. The clamped portions of the aortic wall and the outer membrane tissue of the left pulmonary stirred pulse are trimmed. A sharp blade is used to make a longitudinal incision approximately 6 mm long in the middle of the clamped descending aortic wall, followed by a corresponding incision of similar length in the occluded left pulmonary stirred pulse. Fine curved needles with 5-0 sutures are used to suture the aortic and pulmonary stirred pulse walls at both ends of the incisions, with the sutures tied outside the vessel walls. The posterior wall of the anastomosis is then continuously sutured, with the needle passing through the full thickness of the vessel walls to ensure proper alignment. Upon reaching the lower corner of the incision, the suture is tied outside the vessel wall to the anchoring suture, and the anterior wall of the anastomosis is either continuously or intermittently sutured. Once the anastomosis is complete, the sutures around the distal and proximal segments of the left pulmonary stirred pulse are sequentially removed (Figure 3). If bleeding is observed at the suture line, gentle pressure with gauze or additional sutures (1–2 stitches) may be applied. After ensuring hemostasis, the ring-shaped aortic clamp is slowly released, and the anastomosis is checked for bleeding before the clamp is fully removed. At this point, a strong tremor from blood flow through the anastomosis can be palpated on the pulmonary stirred pulse. A drainage tube is placed in the pleural cavity, and the thoracic incision is closed in layers. Due to the difficulty of dismantling the Potts anastomosis during corrective surgery, it is now rarely used.
Figure 3 Side-to-side anastomosis between the descending aortic stirred pulse and the left pulmonary stirred pulse
3. Waterston Procedure Ascending Aortic stirred pulse–Right Pulmonary stirred pulse Anastomosis Waterston reported the ascending aortic stirred pulse–right pulmonary stirred pulse anastomosis in 1962. Subsequently, Cooley, Hallman, and Edwards also shared their clinical experiences with this procedure in 1966.
General anesthesia, with attention to avoiding hypoxia. Semi-lateral position, entering the chest through a right anterior thoracotomy incision at the third intercostal space. The right lung is retracted posteriorly, and the pericardial membrane is longitudinally incised anterior to the phrenic nerve. The pulmonary artery is dissected and freed between the ascending aorta and the superior vena cava, as well as medial to the ascending aorta. Thick sutures are looped around the proximal and distal segments of the right pulmonary artery for occlusion. The ascending aorta is lifted, and a partial non-traumatic vascular clamp is applied to the posterior wall of the ascending aorta for occlusion. A 5mm longitudinal incision is made in the middle of the clamped ascending aortic wall using a sharp blade. The sutures looped around the proximal and distal segments of the right pulmonary artery are then tightened for occlusion. A transverse incision is made on the anterior wall of the right pulmonary artery corresponding to the aortic incision. The posterior and anterior walls of the anastomosis are continuously sutured using a fine curved needle with 5-0 or 6-0 sutures (Figure 4). After completing the anastomosis, the sutures around the distal and proximal segments of the right pulmonary artery and the aortic clamp are sequentially removed. The pericardial incision is loosely sutured. A drainage tube is placed in the right thoracic cavity, and the thoracotomy incision is closed in layers.
(1) Exposure of the surgical field (2) Ascending aorta stirred pulse and right pulmonary artery stirred pulse incision
(2) Posterior wall anastomosis (4) Anterior wall anastomosis (5) Completion of anastomosis
(6) Schematic diagram of anastomosis 1. Single anastomosis 2. Sequential anastomosis 3. "Y" anastomosis
Figure 4 Ascending aorta stirred pulse-right pulmonary artery stirred pulse anastomosis
Among the three types of systemic-pulmonary shunt procedures, the subclavian stirred pulse-pulmonary stirred pulse anastomosis is the most widely used clinically. Its advantage lies in the limited diameter of the subclavian stirred pulse, preventing an overly large anastomotic opening that could lead to excessive pulmonary blood flow, resulting in pulmonary hyperemia and edema. Additionally, dismantling and closing the systemic-pulmonary shunt during subsequent corrective surgery is relatively straightforward. In contrast, anastomosis using the descending aorta stirred pulse or ascending aorta stirred pulse with the pulmonary stirred pulse is prone to an overly large anastomotic opening or poor alignment of the vessels, causing twisting, poor blood flow, or blockage. Moreover, dismantling the systemic-pulmonary shunt during corrective surgery is highly challenging. Therefore, the Potts and Waterston procedures are rarely used nowadays.
The surgical mortality rate for systemic-pulmonary shunts is relatively low, ranging from 3% to 6% for infants under 6 months of age. Symptoms may remain in remission for about 1.5 years after a subclavian stirred pulse-pulmonary stirred pulse anastomosis performed within the first month of life. For older children, the remission stage can last many years. For example, in 1953, Zhongshan Hospital in Shanghai performed an end-to-side anastomosis between the left subclavian stirred pulse and left pulmonary stirred pulse on a 13-year-old child, who maintained good outcomes even 38 years postoperatively.
Corrective surgery for tetralogy:
For pediatric cases, surgery is performed under cardiopulmonary bypass combined with 25°C low warm purgation. For infants, deep hypothermic circulatory arrest may be employed. This involves surface cooling until nasopharyngeal temperature reaches approximately 24°C, followed by thoracotomy and establishment of cardiopulmonary bypass. Further cooling via blood flow reduces nasopharyngeal temperature to around 18°C, after which circulation is halted for intracardiac repair. Upon completion of the intracardiac procedure, cardiopulmonary bypass is resumed for rewarming. The procedure concludes when nasopharyngeal temperature reaches 35°C, rectal temperature exceeds 28°C, and cardiac activity resumes, at which point cardiopulmonary bypass is discontinued.
Make a midline incision on the anterior chest, longitudinally saw open the sternum, incise the pericardium, and expose the heart. After exposing the heart, carefully observe the right ventricular outflow tract, the main pulmonary artery, and the stenotic lesions of the left and right pulmonary arteries. Compare the external diameters of the ascending aorta and the main pulmonary artery, as well as check for any abnormally coursing coronary artery branches in the right ventricular outflow tract. Dissect and free the ascending aorta, insert venous drainage catheters into the superior and inferior vena cava through incisions in the right atrium and right atrial appendage, insert an arterial perfusion catheter into the ascending aorta, and place a decompression tube in the left atrium or left ventricle. After establishing hemodilution cardiopulmonary bypass, lower the body temperature to around 25°C through blood diversion, and place cold saline in the pericardial cavity for local profound hypothermia. Clamp the ascending aorta and inject cold cardioplegic solution into the coronary circulation. Select the right ventricular incision based on the stenotic lesions in the right ventricular outflow tract. If there is no significant stenosis in the pulmonary valve annulus, main pulmonary artery, or left and right pulmonary arteries, and only the infundibular stenosis of the right ventricle needs to be relieved, use a transverse or oblique incision in the right ventricular outflow tract. If the pulmonary valve annulus or main pulmonary artery needs to be incised and a patch is required to bridge the annulus for enlargement, use a longitudinal incision in the right ventricular outflow tract, extending it into the main pulmonary artery or even the pulmonary artery branches if necessary. For cases where the anterior descending branch of the coronary artery has an ectopic origin from the right coronary artery, make an oblique incision below the anterior descending branch or, after freeing the anterior descending branch, make a longitudinal incision below it (Figure 5).
(1) (2) (3)
(1) The longitudinal incision in the right ventricular outflow tract can also be made as a transverse or oblique incision
(2) The longitudinal incision in the right ventricular outflow tract extends into the pulmonary artery trunk
(3) The right ventricular outflow tract incision is below the ectopic anterior descending branch
Figure 5: Right Ventricular Incision
Relief of right ventricular outflow tract stenosis: In the more common typical tetralogy, the stenotic lesion involves only the infundibular region and/or the pulmonary valve, while the valve annulus and pulmonary artery are unaffected. In such cases, the right ventricle is incised to expose the right ventricular cavity. The muscular bundles between the free wall of the right ventricle in the infundibular region and the supraventricular crest are severed. A scalpel is used to partially resect the hypertrophied septal myocardium on the left side of the outflow tract, taking care to avoid perforating the ventricular septum. The hypertrophied parietal bundle myocardium is then excised, with caution to avoid damaging the papillary muscles of the tricuspid valve. The hypertrophied myocardium of the supraventricular crest and the anterior wall of the right ventricle is also partially resected. The pulmonary valve is examined through the right ventricular incision. The fused valve commissures can be incised by spreading the valve orifice with forceps. If the valve orifice is funnel-shaped and stenotic, the apex of the funnel can be excised. If the pulmonary valve is difficult to expose through the right ventricular incision, an additional longitudinal incision can be made above the pulmonary valve annulus to expose the valve membrane. After incising the stenotic valve membrane commissures, a cervical dilator is used to measure the internal diameter through the right ventricular outflow tract, pulmonary valve annulus, and pulmonary artery. For infants weighing less than 12 kg, the dilator should pass through a 10 mm diameter; for children, it should pass through 14 mm; and for adults, 17 mm. If not, a transvalvular patch must be sutured to enlarge the valve annulus or pulmonary artery trunk.
Complete relief of right ventricular outflow tract and/or pulmonary artery stenosis is a crucial factor in improving the treatment outcomes for tetralogy of Fallot. In cases of a narrowed pulmonary valve annulus, varying degrees of right ventricular outflow tract hypoplasia, stenosis of the pulmonary trunk or its branches, or even a bicuspid pulmonary valve, performing infundibulectomy and/or pulmonary valvotomy may still fail to alleviate right ventricular outflow obstruction. Postoperatively, right ventricular pressure remains abnormally elevated, with a pressure gradient persisting between the right ventricle and the pulmonary artery, increasing the risk of right heart failure and leading to high postoperative mortality. While transannular patch repair can effectively relieve obstructive lesions, the resulting pulmonary valve insufficiency increases right ventricular end-diastolic volume, reduces systolic ejection fraction, decreases exercise tolerance, and is associated with high early postoperative mortality and unsatisfactory long-term outcomes. Therefore, transannular patch repair should not be routinely performed. The indications for transannular patch repair should be determined based on preoperative selective right ventricular angiography findings, measurements of the pulmonary valve annulus and pulmonary artery diameter, and intraoperative assessment of the right ventricle-to-left ventricle systolic pressure ratio and pulmonary artery pressure. A right ventricle-to-left ventricle systolic pressure ratio exceeding 0.70 and a pulmonary artery pressure below 3.3 kPa (25 mmHg) warrant patch repair. Pericardial patches reinforced with a Dacron mesh are the most suitable material, offering sufficient strength while preventing bleeding. For cases with infundibular hypoplasia and/or a narrowed pulmonary valve annulus, the right ventricular longitudinal incision should be extended across the pulmonary valve annulus to the widest external diameter of the pulmonary trunk. An elliptical patch should be prepared, with its length adjusted to match the incision from the right ventricle to the pulmonary artery. The patch width should ensure that the post-repair pulmonary annulus diameter does not exceed 75% of the ascending aorta's external diameter. After completing the intracardiac procedure, the patch apex is first secured to the distal pulmonary artery incision with 5-0 Prolene sutures in a mattress fashion, followed by continuous suturing of the patch to the pulmonary artery, pulmonary valve annulus, and right ventricular incision edges (Figure 6). For cases with severe pulmonary valve annulus hypoplasia or extreme stenosis, the repair involves incising the right ventricular outflow tract, pulmonary valve annulus, and pulmonary trunk, followed by a cross-shaped patch repair (Figure 7).
(1) Resection of hypertrophic parietal and septal myocardial bundles
(2) Closure of ventricular septal defect
(3) Use of a transannular patch
Figure 6: Radical correction of tetralogy
(1) Pulmonary artery, valve annulus, and outflow tract incision
(2) Patch enlargement of the annulus, pulmonary artery, and outflow tract with a "cross-shaped" patch
(3) Completion of the patch
Figure 7: "Cross-shaped" patch enlargement
Stenosis at the origin of the left pulmonary artery: Usually accompanied by stenosis of the pulmonary valve annulus and main pulmonary artery. After closing the ventricular septal defect, extend the longitudinal incision of the right ventricular infundibulum across the pulmonary valve annulus, main pulmonary artery, stenotic segment of the left pulmonary artery, and proximal left pulmonary artery, then perform patch enlargement with a fabric patch (Figure 8). For cases with stenosis at the origin of the right pulmonary artery, after patch enlargement of the pulmonary valve annulus, main pulmonary artery, and left pulmonary artery, detach the right pulmonary artery from the main pulmonary artery, longitudinally incise the anterior wall of the right pulmonary artery beyond the stenotic segment, and incise the proximal right pulmonary artery. Use another tapered patch to enlarge the incised end of the right pulmonary artery, then perform an end-to-side anastomosis between the enlarged right pulmonary artery and the main pulmonary artery (Figure 9).
(1) Incision of the main pulmonary artery and stenotic segment of the left pulmonary artery (2) Patch enlargement with pericardial and fabric patches
Figure 8: Patch enlargement for stenosis at the origin of the left pulmonary artery
(1) Incision (2) Patch enlargement of the origins of the left and right pulmonary arteries
Figure 9: Repair and enlargement for bilateral stenosis at the origins of the pulmonary arteries
Stenosis at the origin of the right pulmonary artery: Isolated stenosis at the origin of the right pulmonary artery is relatively rare. The patch enlargement technique is also simpler. Detach the right pulmonary artery from the main pulmonary artery, longitudinally incise the stenotic segment and proximal anterior wall of the right pulmonary artery, perform patch enlargement with a fabric patch, then perform an end-to-side anastomosis with the main pulmonary artery (Figure 10).
(1) Detachment of the right pulmonary artery (2) Longitudinal incision of the right pulmonary artery, patch enlargement with pericardial patch
(3) End-to-side anastomosis of the right pulmonary artery with the main pulmonary artery
Figure 10: Patch enlargement for bilateral stenosis at the origins of the pulmonary arteries
Pulmonary stirred pulse occlusion: For cases of pulmonary stirred pulse occlusion, a segment of ascending aorta with a stirred pulse valve is required. The external diameter of the ascending aorta used for infant cases is 14–18 mm, and for children, it is 22–25 mm. The aortic segment is placed into the distal outflow tract and anastomosed end-to-end with the pulmonary trunk. The posterior wall of the proximal end is sutured to the right ventricular outflow tract, and then covered with a pericardial patch to repair the outflow tract incision and the anterior wall of the aortic segment (Figure 11). Another method involves performing an end-to-side anastomosis between the distal end of the valved conduit and the pulmonary trunk, and an end-to-side anastomosis between the proximal end and the right ventricular outflow tract (Figure 12).
(1) Transect the pulmonary stirred pulse trunk (2) End-to-end anastomosis of the homograft aortic stirred pulse and pulmonary stirred pulse trunk
(3) Suture the valved homograft aortic stirred pulse to the incised right ventricular outflow tract (4) Cover the outflow tract incision with a pericardial patch or fabric patch
Figure 11: Pulmonary stirred pulse atresia correction surgery
(1) Incision of the pulmonary stirred pulse trunk and right ventricular outflow tract (2) Artificial vascular patch repair
Figure 12: Enlargement surgery using valved homograft aortic stirred pulse and artificial vascular patch
Repair of Ventricular Septal Defect: Proper relief of right ventricular outflow tract stenosis allows for the repair of the ventricular septal defect. In cases of tetralogy of Fallot, the ventricular septal defect is large, and direct suturing is prone to tearing, necessitating the use of a patch for defect repair. By applying traction sutures or small retractors to pull the infundibular septum upward and the lower edge of the ventricular incision downward, the defect can be fully exposed. Identify the tricuspid valve septal leaflet, the aortic valve annulus, the leaflets, and the location of the conduction tissue. The bundle of His emerges from the edge of the fibrous trigone behind the ventricular septal defect, travels forward along the left ventricular side of the ventricular septum, and reaches the myocardial ridge below the defect to be decocted later. Trim a Dacron or polytetrafluoroethylene patch according to the size and shape of the ventricular septal defect, ensuring the patch is slightly larger than the defect. Using 4-0 or 5-0 Prolene sutures with small curved needles at both ends, first suture the midpoint of the lower edge of the defect. After passing the suture through the patch, insert the needle about 4–5 mm from the edge of the defect in the muscular portion of the ventricular septum. Avoid encircling the edge of the ventricular septal defect or penetrating the myocardium too deeply to prevent injury to the conduction tissue. From this point, continue suturing the patch backward to the base of the tricuspid valve septal leaflet, then upward to the right ventricular myocardium below the non-coronary cusp and the aortic valve annulus. When suturing the patch to the aortic valve annulus, take care to avoid injuring the aortic valve leaflets. Proceed forward to the supraventricular crest. During suturing, gently pulling the supraventricular crest downward beneath the patch can enlarge the outflow tract. Next, use the other needle of the suture to begin continuous suturing from the first insertion point at the midpoint of the lower edge of the defect, staying 4–5 mm from the defect edge, moving forward and upward until reaching above the conus papillary muscle. At this point, there is no longer a risk of injuring the conduction bundle, allowing for continuous suturing around the defect edge. Upon reaching the supraventricular crest, tie the two sutures to complete the ventricular septal defect patch repair. Close the right ventricular incision. For cases where the outflow tract stenosis has been adequately relieved, the transverse or oblique right ventricular incision can be closed with a two-layer continuous suture. Longitudinal right ventricular incisions that do not cross the valve annulus should be repaired with a patch to avoid narrowing the infundibular diameter due to direct suturing. Longitudinal incisions in the pulmonary trunk made to relieve pulmonary valve stenosis should also be patched to enlarge the vascular lumen. Release the ascending aortic clamp, allow the heart to resume beating, and ensure the systolic blood pressure is above 12 kPa (90 mmHg) and the body temperature rises above 35°C before discontinuing cardiopulmonary bypass. Measure pressures in the right ventricle, left ventricle, and pulmonary trunk. Collect blood samples from the superior vena cava, pulmonary artery, and systemic circulation for oxygen content and saturation measurements. If the right ventricle-to-left ventricle systolic pressure ratio exceeds 0.70, the pressure gradient between the right ventricle and pulmonary trunk is over 8 kPa (60 mmHg), the pulmonary artery systolic pressure is below 3.3 kPa (25 mmHg), or there is residual left-to-right shunting across the ventricular septum with a pulmonary-to-systemic flow ratio of 2:1, consider further relieving the outflow tract and/or pulmonary artery stenosis under continued cardiopulmonary bypass. After closing the ventricular septal defect, ensure hemostasis at the surgical site. Close the surgical incision in layers. Postoperatively, closely monitor blood pressure, heart rate, respiration, electrocardiogram, central venous pressure, and left atrial pressure. Observe skin color and peripheral circulation. Record fluid intake and output, urine output, and mediastinal/pericardial drainage. Maintain fluid and electrolyte balance. Promptly replenish blood volume. Administer routine medications such as digitalis, antibiotics, diuretics, and procoagulants. Ensure airway patency.
Early postoperative complications may include bleeding, atrioventricular block, low cardiac output syndrome, heart failure, respiratory failure caused by pulmonary interstitial and alveolar edema, etc.
The prognosis of tetralogy of Fallot cases depends on the severity of the right ventricular outflow tract and/or pulmonary {|###|} stenosis, as well as the development of pulmonary collateral circulation. Although a very small number of untreated cases may survive beyond the age of 40, the vast majority of patients die during childhood. According to data from Bertranou et al., 66% survive to 1 year of age; 49% survive to 3 years; 24% survive to 10 years; and fewer than 10% survive to 20 years. Common causes of death include cerebrovascular accidents due to hypoxia, brain abscesses, congestive heart failure, bacterial {|###|} endocarditis, etc. With increasing age, pulmonary {|###|} stenosis worsens, and thrombosis occurs in the branches of the pulmonary {|###|}, reducing pulmonary blood flow and gradually exacerbating cyanosis and hypoxia. Cases with pulmonary {|###|} atresia have the worst prognosis, as the pulmonary blood supply mainly relies on the {|###|} ductus. Closure of the {|###|} ductus can lead to death due to severe hypoxia. The mortality rate is 50% within the first year of life, 75% by 3 years, and 92% by 10 years. However, if there is abundant collateral circulation between the systemic and pulmonary circulations, survival can be prolonged.
The surgical mortality rate for radical correction of tetralogy of Fallot has gradually decreased over time and is now approximately 5–10%. Factors influencing surgical outcomes include the patient's age, weight, degree of cyanosis, hemoglobin level, hematocrit, type of right ventricular outflow tract stenosis, pulmonary {|###|}, development of the pulmonary {|###|} valve annulus and left ventricle, whether a systemic-to-pulmonary shunt has been performed previously, whether a transannular patch or valved conduit is required during radical correction, the adequacy of intracardiac defect repair, and the presence of other congenital cardiovascular anomalies.
Postoperatively, symptoms improve significantly, cyanosis disappears, exercise tolerance increases, and patients can participate in normal studies or work. The 10- and 20-year survival rates post-surgery are approximately over 90%. However, if complications such as pulmonary {|###|} valve insufficiency, residual ventricular septal defect, or right ventricular hypertension (systolic pressure exceeding 9.3 kPa, 70 mmHg) are present, functional recovery may be impaired, and the efficacy of {|###|} advanced-stage treatment may be unsatisfactory.
