Left ventricular dimensions and systolic function during spontaneous heart rate changes: an echocardiographic study.

We examined the relationships between spontaneous heart rate (or conversely cycle length) changes and left ventricular diastolic dimensions and indices of systolic function in twenty-three subjects. In most there was clearly an inverse relationship between rate and these indices and nearly always a positive correlation between performance and end-diastolic dimension. Previously described relationship between heart rate and mean velocity of circumferential fiber shortening are applicable only when the heart rate is constant.