Angled interventricular septum on echocardiography: anatomic anomaly or technical artifact?

An acutely angled interventricular septum has been reported to constitute a distinct two-dimensional echocardiographic geometric pattern that may permit a false M-mode echocardiographic recording of asymmetric septal hypertrophy. In light of experience suggesting that the angle between the aortic root and interventricular septum varied with the intercostal space of the transducer, 45 subjects were prospectively studied by two-dimensional and M-mode echocardiography. Parasternal long- and short-axis views were obtained from two to four intercostal spaces in each subject. Two-dimensional echographic cursor-generated M-mode echocardiograms were obtained from the long-axis views; interventricular septal and left ventricular posterior wall thickness was measured from both the two-dimensional and M-mode echocardiograms. On two-dimensional echocardiography, the angle between the aortic root and septum became more acute as a progressively lower intercostal space was used (p less than 0.001). Although no change in septal thickness was apparent, the septal thickness significantly increased as a progressively lower intercostal space was used. On M-mode echocardiography, 21 subjects (47%) demonstrated asymmetric septal hypertrophy (septal/posterior wall thickness ratio greater than 1.3) from at least one intercostal space, but this was confirmed by the two-dimensional technique in only 4 subjects (9%). Thus, a two-dimensional echocardiographic recording of an angled interventricular septum can be produced by positioning the transducer in a low intercostal space, and caution must be used in the interpretation of asymmetric septal hypertrophy on M-mode echocardiograms. Two-dimensional echocardiography is a useful means of identifying subjects with apparent asymmetric septal hypertrophy that often may be the result of a technical artifact.