Demonstration of the relationship between heart dimensions and QRS voltage amplitude.

This study was undertaken to elucidate the still debated question of the relationship between cardiac volume and QRS voltage amplitude. The authors studied 14 healthy men, aged 24-61 years (mean age, 41.2 +/- 12.1 years). They underwent a reduction in venous return, produced by simultaneously inflating sphygmomanometric cuffs placed around the most proximal portion of each of the four limbs. In basal conditions and 5 minutes after cuff inflation, two-dimensional and M-mode echocardiograms were recorded with vectorcardiographic loops and scalar Frank leads. The reduction of the venous return to the heart induced a significant decrease of the end-diastolic left ventricular diameter (from 52.4 +/- 4.2 to 48.5 +/- 4.6 mm, P < .001), of the R wave amplitude in leads X and Y, of the sum of the R wave amplitudes in the three leads,and of the maximal vector in the frontal and horizontal planes. No significant changes in the heart rate or arterial blood pressure were observed. These results support Brody's theory concerning the relationship between cardiac blood volume and QRS voltage.