The effect of reduced intercellular coupling on electrocardiographic signs of left ventricular hypertrophy.

BACKGROUND The electrocardiographic (ECG) diagnosis of left ventricular hypertrophy (LVH) is based on the assumption that QRS voltage increases with left ventricular mass. However, most of patients with echocardiographically detected LVH do not have increased QRS voltage. Reduced intercellular coupling has been observed in LVH patients and animal models. The purpose of this study was to show that this uncoupling can explain relatively low QRS voltage in LVH patients. METHODS Electrocardiograms and vectorcardiograms (VCG) were simulated with a realistic large-scale computer model of the human heart and torso that reliably represented the effects of reduced coupling on both propagation and ECG voltage. RESULTS Uncoupling reduced QRS voltage in all leads except aVL, reflecting a decrease in vector amplitude as well as a leftward axis deviation that suggested left anterior fascicular block. CONCLUSIONS Low QRS voltage does not necessarily contradict a diagnosis of LVH but may be an indication for electrical uncoupling. The diagnostic value of this "relative voltage deficit" needs to be demonstrated in clinical studies.