Tetralogy of Fallot and pulmonary stenosis with intact interventricular septum: Anatomic and electrocardiographic study

Abstract

1. 1. An electrocardiographic-anatomic correlation of cases of tetralogy of Fallot and pulmonary stenosis with intact interventricular septum (trilogy of Fallot) was made, in an attempt to explain the electrocardiographic similarities and differences between these two malformations on the basis of the anatomic findings. 2. 2. Fifty autopsy specimens were studied: 39 were cases of tetralogy, 9 were cases of pulmonary stenosis with intact interventricular septum and 2, stenosis of the pulmonary valvular ring with interventricular septal defect and agenesis of the pulmonary sigmoid valve cusps. An electrocardiogram was available for 39 cases. 3. 3. The anatomic findings showed that hypertrophy of the right ventricle was homogeneous and generalized in pulmonary stenosis with intact interventricular septum; in tetralogy it was limited to a hemispheric area located at the union of the upper and the middle third of the right border of the heart. The left ventricle in tetralogy was generally hypotrophic; it was normal in pulmonary stenosis with intact interventricular septum. 4. 4. In tetralogy of Fallot, ÂQRS in the frontal plane pointed downward and to the right; in trilogy it tended to be more horizontal. SÂQRS in the majority of instances of tetralogy pointed to the right, forward and downward; in pulmonary stenosis with intact interventricular septum it generally pointed predominantly forward. In the precordial leads the greater number of cases of tetralogy showed a predominant R wave only in V 1; in the majority of cases of trilogy, the predominant R wave was recorded beyond V 1. The T wave tended to be positive in the precordial leads in tetralogy of Fallot and negative in the right precordial leads or in all of the precordial leads in trilogy. 5. 5. The sequence of the activation process of the ventricular walls in both malformations is discussed in relation to the different hypertrophic patterns and to the position of the interventricular septum with respect to the frontal plane.