[Counterclockwise rotation of the heart: a correlative study with tomographic echocardiography].

On the long-axis view of tomographic echocardiography, the aorto-septal angle (AS angle) of cases with straight back syndrome was wide and was thought to be due to clockwise rotation of the heart rather than right ventricular enlargement. In the present study, the AS angle of 21 cases with counterclockwise rotation of the heart (CCW) was measured on the long-axis view. The counterclockwise rotation of the heart defined here as having a shift of the transitional zone to the right with a small septal q wave at V2 and/or V3 to V6 in the precordial leads. Every case of CCW was found to have an absence of main pulmonary artery shadow on posteroanterior projection of the chest X-ray film. The control groups consisted of 40 normal individuals and 14 cases of straight back syndrome. The AS angle of normals ranged from 120 degrees to 158 degrees with a mean of 142 degrees. The AS angle of the latter varied from 140 degrees to 165 degrees with a mean of 150 degrees. On the other hand, the 21 cases with CCW showed the AS angle from 80 degrees to 129 degrees with a mean of 102 degrees. Since every CCW showed dilatation and/or elongation of the thoracic aorta on their radiographs, the narrowed AS angle was probably due to rightward twist of left ventricular outflow tract with some posterior retraction of the aorta. This causes the rightward twist of upper portion of the septum and results in a shift of the transitional zone to the right with a small q wave at V2 and/or V3 to V6 in the precordial leads. When normally visible main pulmonary artery shadow disappears on the postero-anterior chest X-ray film, the CCW is indicated radiographically. The narrowing of the AS angles on the long-axis views of tomographic echocardiography also indicates the CCW and correlate with both electrocardiographic and radiographic findings of CCW. The cause of CCW has not been well delineated. In the previous paper, we have suggested that the left ventricular overloading has little influence in producing CCW. In the present study, the 21 cases with CCW did not show either the left ventricular hypertrophy or the dilatation on their echocardiograms further supporting our hypothesis.