Effect of heart rate on the end-systolic wall stress-mean velocity of circumferential fiber shortening relation.

The correlation of left ventricular end-systolic wall stress (ESS) with the mean velocity of fiber shortening (mVcf) is an index of the myocardial contractile state, independent of the ventricular loading conditions (afterload). However, there have been few reported estimates of the effect of changes in the heart rate on the ESS-mVcf relationship. In the present study, 25 subjects with histories of Kawasaki disease (mucocutaneous lymph node syndrome: MCLS) were evaluated for the effects of changes in heart rate, afterload and preload, on the ESS-mVcf relationship. The latter was independent of afterload. After atrial pacing, ESS decreased and mVcf increased, both significantly, compared to those of subjects at rest. The change of the ESS-mVcf relationship induced by atrial pacing approximately paralleled the mean regression line obtained in the resting state. However, the shift induced by preload was not parallel to the mean regression line for the resting population. These data suggest that the ESS-mVcf relationship is independent of any change in heart rate, and that it may depend on preload.