TETRALOGY OF FALLOT
- Ventricular septal defect
- Pulmonic stenosis and
- Dextroposition of the aorta which overrides the VSD
- Right ventricular hypertrophy
The patient will present with a right to left type of shunt.
85% of these patients will have central cyanosis which is increased by exertion and emotional stress.
The degree of right to left shunt will result from the degree of Pulmonic Stenosis.
The total heart size will be normal or moderately enlarged.
The aortic flow will be increased and the aortic arch may be prominent with small pulmonic arch.
Reduction of pulmonary blood flow is the case in most of these patients.
Abnormal origin of the left anterior descending artery arising from the right coronary system can be seen at times.
- Cyanosis is the outstanding feature. (It can appear from birth until the patients is two years old.) However, 10 % of these patients never present cyanosis.
- Dyspnea with exertion is the second most frequent symptom.
- Squatting mainly in early childhood is noted in more than 60 % of cases.
- Clubbing in fingers and toes is seen in at least 75 % of patients.
- Polycythemia (Hematocrit of 55 to 80%) is characteristic.
- Hypoxic crisis with typical worsening of cyanosis and critical shortness of breath, which may produce convulsions and even death, is common.
- Congestive heart failure is unusual.
- The more frequent ones are:
- Hypoxic crisis (HC) induced by polycythemia with hematocrit higher than 75 %
- Hypoxic crisis induced by anemia
- CHF (rare) induced by anemia
- CHF (rare) due to hypertension
- Acute glomerulonephritis
- Arterial hypertension
- Bacterial endocarditis
- Brain abcess
- Hypoxic crisis may often result from respiratory tract infection, dehydration, fever, warm environment
- Iron deficiency anemia which in turn may generate HC or CHF (rare)
- Brain transient ischemic attacks (TIA)
- CNS arterial thrombosis
- CNS vein thrombosis (insidious clinical picture)
- Hemoptysis from large, hypertrophic bronchial arteries or bronchial collaterals
- Thrombocytopenia and other coagulopathies
Lack of normal ... Lack of normal physical development
Cyanosis - clubbing
Systolic thrill in the second and third left intercostal space
Pulmonic ejection systolic murmur, which will vary in relation to the degree of Pulmonic Stenosis.
Loud, single second sound the aortic valve is forward to the pulmonic valve in these patients.)
If a PDA is present, a continuous murmur in the second left intercostal space may be present.
The electrocardiogram is not characteristic but will be helpful as an adjunct element in the clinical diagnosis.
- The P wave will be higher than normal in more than 50 % of these cases, correlating with right atrium hypertrophy. In a signficiant number of patients, a normal P wave may be seen. The P wave will be taller than normal in leads I and II, and will be of normal height in lead III.
- The PR interval is usually within normal range, and the duration of the QRS complex is usually less than 0.10 seconds.
- Right axis deviation will be observed in more than 90 % of the cases (main axis over the frontal plane between + 100° and + 140°). The magnitude of the right axis deviation is important in the differential diagnosis with isolated pulmonary artery or pulmonary valve stenosis where the right axis deviation will be more accentuated (more than + 150° over the frontal plane).
- Marked clockwise rotation over the horizontal plane will be observed with tall R waves in leads V1, V2 and V3, and at times T wave inversion in the same leads. The magnitude of right ventricular systolic overload will be less significant than the one observed in pulmonary stenosis, and so the voltage of the R wave and the inversion of the T wave in the right precordial leads will be, in general, not so significant as in isolated pulmonary stenosis.
- The electrocardiogram will show signs of systolic overload of the right ventricle and no diastrolic overload as seen in atrial septal defect (incomplete right bundle branch block not so frequent). In 70 % of the cases, the area of transition (R/S = 1) will be in leads V5 and V6. A tall R wave in leads V6, V7, and V8 may be seen, suggesting left ventricular hypertrophy.
- As previously mentioned, the T wave can be negative in the right precordial leads. Upright T waves are seen anyway in these leads in 70 % of the cases, and a negative T wave in V1 and V2 is less frequent than in pulmonary stenosis (less than 20% of the patients with Tetralogy of Fallot).
- When the systolic pressure in the right ventricle surpasses 100 mm Hg, typical ST-T changes will be observed in leads V1, V2 and V3 and occasionally all throughout the precordial leads and bipolar leads. ST segment and T wave will become negative in important systolic overload. The changes are going to be observed more typically in leads V1 and V2 but may be noted in lead III, aVF, V3 and in the most extreme cases in leads II, V3, V4, V5, and V6. Although the hemodynamic correlation of the electrocardiogram is not extremely accurate, we can state in a general manner that with a systolic pressure in the right ventricle below 40 mm Hg, the electrocardiogram, as far as the right ventricle is concerned, will more probably be normal. If the systolic pressure in the right ventricle is between 40 and 60 mm Hg, signs of moderate right ventricular hypertrophy will be present in about 35-45 % of patients. A tall R wave in leads V1 and V2 (less than 10 mm) will be observed with probably normal ST-T wave configuration if the systolic pressure in the right ventricle is between 60-80 mm Hg. If the pressure inside the right ventricle surpasses the 100 mm Hg barrier, taller R wave in lead V1 (more than 10 mm Hg) with secondary ST-T changes in the right precordial leads, I, III, aVF and aVR will be present. In any event, the absence of significant secondary ST-T changes does not rule out extreme systolic right ventricular overload.
ECHOCARDIOGRAM IN TETRALOGY OF FALLOT
Probably the most important finding is the lack of continuity between the echoes of the intraventricular septum and the aorta, due to the VSD overriding of this vessel. Anterior displacement of the aortic root wall echoes is also described.
The hypertrophy of the right ventricle and thickening of the ventricular walls is easily recorded.
Overriding of the ventricular septum by aorta is allegedly more often seen by cross sectional echocardiography than with the traditional M mode scanning. Cross sectional scanning can be used too in assessing the size of pulmonary artery.
In any event, echocardiography is still far from reliable in Tetralogy of Fallot to be taken seriously into account in evaluating these patients.
In cases of Truncus and Pseudo Truncus Arteriosus many echocardiographic changes are similar to those of Tetralogy of Fallot.
Real time echocardiography may eventually be useful for the evaluation and diagnosis of this pathology.
The cardiac silhouette in the AP projection shows "coer in cabot" features due to the lack of pulmonary arch and elevation of the heart apex.
In the lateral view, there is approximation of the cardiac shadow to the thorax anterior wall (RVH).
Lung fields indicate normal or diminished blood flow depending on the degree of Pulmonic Stenosis. Sometimes increased collateral vasculature can be seen.
The most typical features are:
Normal right atrium pressure with equal right ventricle, left ventricle and aortic systolic pressures.
Catheter will pass easily to left ventricular and aorta from the right ventricle.
The pulmonary artery is difficult to enter and at times impossible. Normal pulmonary artery pressure beyond the valve is typical.
Significant gradient of pulmonary stenosis and at times, typical chamber of pressures indicative of infundibular pulmonary stenosis will be seen (outflow tract of the right ventricle).
Injecting in the right ventricle will demonstrate premature opacification of ascending aorta and left ventricle with the aorta located anteriorly to pulmonary artery. Pulmonary infundibular or valvular stenosis is often seen.
The catheterization and angiography should include the search of associated pathologies, such as:
- Atrial septal defect (Pentology of Fallot)
- Stricutres in the pulmonary artery main branches.
- Different anomalies of the aortic arch.
- Aortic stenosis
- Abnormal origin of carotid, vertebral or bronchial arteries.
The most important aspects to consider are:
Prevention of CNS vascular thrombosis.
Keeping the hematocrit between 50 to 70% with phlebotomy if necessary.
Oxygen therapy in case of hypoxia.
Prevention of hypoxic crisis (correction of anemia, infections, fever, dehydration).
Prevention of SBE
Correction of Metabolic acidosis during HC (injecting Sodium Bicarbonate if necessary).
Propranolol is a debatable drug in the treatment of HC and its real value is not yet proven.
The ideal procedure is:
Anatomical reconstruction at age 5 or 6 with cardiopulmonary hypothermic bypass.
If the patient is deeply cyanotic:
Anatomical reconstruction at 2 to 4 years of age should be attempted.
Below 2 years of age profound hypothermia with total cardiac arrest may be necessary.
If the situation is critical in newborns, aorto-pulmonary side to side anostomosis may be indicated.
If the situation needs correction before one year of age, try Blalock operation with right or left pulmonary-subdavian anostomosis.
Tetralogy of Fallot. There is a powerful muscular mass obstructing the right ventricular outflow tract. Hypoplasia of the pulmonary artery is noted too. In case of extreme reduction of the pulmonary circulation, a predominant right to left ventricular shunt will necessarily develop.
Portrayal of pressure and oxygen saturation findings in a patient with Tetralogy of Fallot. The similar pressures recorded from both ventricles, the right ventricle step-up in oxygen saturation, with 80 % saturation in the left ventricle, clearly indicate a bidirectional shunt at ventricular level. There is a 105 mm Hg gradient across the pulmonary valve with normal pulmonary artery pressure.
The Indocyanine green dye curves indicate sign ficant right to left shunting when the dye is inlected in the right atrium or right ventricle, which indicates that the defect is in the ventricular septum.
Roentgenogram of an infant with Tetralogy of Fallot.
Electrocardiogram of an adolescent with moderately cyanotic Tetralogy of Fallot.