[Interventricular septal motion in hypertrophic cardiomyopathy. Additonal knowledge from real-time b-scan...

M-scan echocardiography had suggested that interventricular septal motion in patients with Hypertrophic Cardiomyopathy is immobile. In this study special attention was paid to this septal motion during Real-time B-scan (RTBS) investigations of 15 patients with proven Hypertrophic Cardiomyopathy. RTBS recordings have shown that the basal part of the interventricular septum (IVS), which bulges into the left ventricular outflow tract (LVOT), exhibits a forceful contraction towards the cardiac apex, while the more apical portion moves normally towards the left ventricular posterior wall. The direction of the basal septal motion is more or less at right angles to the single ultrasonic beam in M-scanning. The amplitude of this motion, therefore, can only be appreciated with M-mode according to that component of motion which moves parallel to the ultrasonic beam. According to the angle of incidence of the ultrasound waves, septal motion may be recorded as mobile or apparently immobile, and the transition zone from apical to posterior septal motion can be appreciated in a semiquantitative manner by using a Continuous Sweep Technique. From these observations and considerations it has emerged that the left ventricular internal diameter and the rate of change of this dimension in the region of the "immobile" basal septum does not allow conclusions to be drawn about the overall haemodynamic situation of the left ventricle in patients with Hypertrophic Cardiomyopathy. Furthermore, this study is another demonstration of the importance of the combined application of M-and RTBS echocardiography for optimal non-invasive clinical cardiac diagnosis.