Comparative surface potential patterns in obstructive and nonobstructive cardiomyopathy

Abstract

Extensive noninvasive electrophysiologic studies have been performed on patients with cardiomyopathy. Body surface potential maps in the nonobstructive patients mimicked the normal in the general progression of the surface manifestations of activation, but demonstrated relatively more prominent patterns of electrical breakthrough in terms of absolute magnitude and in terms of the perimeter of negativity at a given instant in time. The pattern of the obstructive group was distinctly different, being marked by increased magnitude and duration of positivity with an obvious delay in septal, right ventricular, and left ventricular breakthrough contiguous to the septum, with attenuated negativity at the time of those break-throughs. Maximum negativity also usually occurred 15 to 20 msec. later in the patients with IHSS. The patients with nonobstructive disease characteristically had posteriorly and equatorially oriented VCG loops and often lacked evidence of normal early left-to-right activation of the interventricular septum. Loops of the patients with obstructive disease were usually oriented below the horizontal and were less posteriorly oriented. Additional abnormalities noted in some patients with obstructive disease included slowing of the loop through at least 24 msec. The most extreme form of abnormal sequence of ventricular activation was seen in one third of the patients with IHSS in the form of false infarction patterns. An electrophysiologic rationale of this latter abnormality has been suggested by van Dam and Durrer and is thought by us to represent the best current explanation.