Computer model study of electrocardiologic manifestations in asymmetric left ventricular hypertrophy

Electrocardiologic criteria of left ventricular enlargement do not take into consideration the eventuality of asymmetric hypertrophy. Since experimental techniques for production of this condition are not available, computer modeling was utilized to study its electrocardiologic manifestations. A computer model of human ventricles with analytically defined geometry, consisting of 142,000 elements (1.2 mm spatial resolution), was used to produce models of circumscribed hypertrophies by increasing the wall thickness to 150% in various regions of the free left ventricular wall, the septum and the apex. Gradients of simulated transmembrane action potentials were utilized to compute resultant heart vectors at any instant of ventricular activation and recovery, as well as time courses of their characteristics and planar projections of vectorgraphic loops. Involvement of the septum and/or the anterior wall decreased the maximum QRS vector magnitude, an opposite effect resulted from involvement of the lateral and posterior wall segments. Directional vector changes predicted the diagnostic value of S waves in precordial leads. Asymmetric hypertrophy did not produce abnormal Q waves. The maximum T vector increased in hypertrophy of any part of the free wall along with an increase of the spatial angle between maximum QRS and T vectors. The results of this study may be useful for refinement of electrocardiographic and vectorcardiographic diagnostic criteria of asymmetric left ventricular hypertrophy.