In Tetralogy of Fallot are present four heart defects: ventricular septal defect (large), pulmonary stenosis (narrowed pulmonary valve), right ventricular hypertrophy and the aorta that sits astride the septum. Symptoms are: cyanosis (bluish coloration), dyspnea (shortness of breath) during feeding, growth deficit, seizures, hypoxia / anoxia (episodes that can be fatal). Disease diagnosis is done using echocardiography or cardiac catheterization. Treatment consists of surgery.
Tetralogy of Fallot is quite common, accounting for 7 to 10 percent of congenital heart diseases. Also, besides the four defects mentioned above may be present: right aortic arch, coronary artery with abnormal anatomy, stenosed branch of pulmonary artery, communicating vessels between the aorta and pulmonary artery, patent ductus arteriosus (PCA), a complete septal defect, aortic insufficiency.
Large ventricular septal defect will determine the pressures between the left and right ventricle to equalize. If pulmonary valve stenosis is mild then through ventricular septal defect will appear left-right shunt, otherwise (severe pulmonary stenosis) the shunt is going to be from right to left which will cause cyanosis (not responsive to O2).
In case of some patients may appear anoxic episodes, with a lethal potential. These episodes may be caused by: any event that diminishes slightly oxygen saturation, any event that suddenly drops into a peripheral vessel resistance (kicking leg during play), a sudden onset of a tachycardia (increased heart rate), sudden onset of a hypovolemia.
Symptoms and signs in tetralogy of Fallot
If pulmonary valve stenosis is severe, infants will present severe cyanosis (bluish discoloration of the skin and mucous membranes), dyspnea (shortness of breath) during feeding, growth deficiency.
Anoxic crises are usually determined by activity and are described by rapid and deep breathing, irritability, crying with prolonged duration, accentuation of cyanosis, cardiac murmurs diminish in intensity (can not be heard). These crises occur predominantly in infants aged 2-4 months. If the crisis is severe there may occur alteration of consciousness, seizures, even death. Young children, during play, take a knee to chest position (this will eventually lead to increased oxygen saturation because in that position the venous return decreases and increases systemic vascular resistance).
Diagnosis of Fallot Tetralogy
Diagnosis is based on history of the disease, signs and symptoms, data obtained through the chest radiography, electrocardiogram, two-dimensional and Doppler echocardiography. Heart on chest x-ray looks like a “boot” and right aortic arch may be present. ECG shows a right ventricular hypertrophy and possible a hypertrophy of the right atrium. Before surgery it will be performed cardiac catheterization that will detect other concomitant abnormalities.
Treatment of tetralogy of Fallot
In young children the communication between the aorta and pulmonary artery will be reopened by administration of prostaglandin E1. Anoxic crises will be treated by putting in position “knees to chest”, administration of morphine and intravenous fluid. If these measures are not effective blood pressure will be augmented by the administration of phenylephrine or ketamine (plus a sedative effect). Relapses can be prevented by administration of propranolol to 6 hours after the onset of the crisis. Oxygen has very limited benefits.
Surgical treatment consists of ventricular septal defect closure and pulmonary valve dilation usually within the first 12 months of life.
An important aspect is bacterial endocarditis prophylaxis which should be performed in all patients.
Blalock-Taussig procedure (subclavian artery is connected to the pulmonary artery on the same side) is made for those who are not candidates for complete surgical treatment or for patients with anoxic seizures.