The inadequate window. Cardiac positional variability in congenital heart disease

This study aims to investigate an explanation for the inadequate echo window in relation to positional variability of the heart in congenital heart disease. In 46 patients with congenital heart malformations anatomical and echocardiographic studies were done during cardiac surgery. All hearts had situs solitus. Looking in craniocaudal direction, the angle between the frontal plane and the line through the anterior margins of the atrial auricles was measured. This angle was called β-anatomy (mean 24°, SD 31°, range - 70-80°). To assess the validity of β-anatomy in relation to the anatomic position of reference, a series of relevant anomalous and normal heart specimens was investigated. In the specimens the angle between the plane through the posterior borders of the atrioventricular valves and the plane through the anterior margins of the auricles was measured and reported as γ-anatomy (mean 0°, SD 12°, range - 30-45°). The AVSD group showed some difference in this regard, with the right auricle more anterior than the (left 33°, SD 9°, range 20-45°, p < 0.05). Intraoperatively and also looking in a craniocaudal direction, the angle between the frontal plane and the assumed midpoints of the semilunar valves was assessed. This angle was called α-anatomy (mean 188°, SD 51°, range 20-315°). The same assessment was done in 31 patients intraoperatively by epicardial echocardiography and called α-echocardiography (mean 158°, SD 30°, range 117-225°). The mean difference between α-anatomy and α-echocardiography was 4° (SD 4°, range 0-25°), with a correlation coefficient 0.92. Interindividual intrathoracic positional variability of the heart was demonstrated. Our study shows that the so-called anatomic golden standard shows positional variability as well. Our findings offer an explanation for the inadequate echo window.

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