Ventricular performance in patients based upon rate of change of power during isovolumic contraction

Energy is expended by the ventricle during isovolumic contraction as the blood within the ventricle is compressed. This isovolumic energy of compression, as well as the isovolumic rate of energy transfer (power) and acceleration of energy transfer (rate of change of power), was calculated in 17 patients with angina pectoris who underwent diagnostic cardiac catheterization. The peak isovolumic rate of change of power in patients with normal left ventricular performance (based upon the ejection fraction, mean velocity of circumferential fiber shortening and end-diastolic volume index) was 31,000 plus or minus 3,000 dynes cm sec-2 (mean plus or minus standard error), whereas in those with poor ventricular performance it was 18,000 plus or minus 2,000 dynes cm sec-2 (P less than 0.01). None of the patients with poor ventricular performance had a peak isovolumic rate of change of power that exceeded 25,000 dynes cm sec-2. Overlap between patients with normal performance and those with reduced performance was less with the peak rate of change of power than with peak power, peak rate of change of intraventricular pressure (dp/dt), maximal (dp/dt)/p or Vmax. The derivation of these isovolumic energy transfer rates requires no assumptions related to ventricular geometry or characteristics of muscle fibers. Peak isovolumic rate of change of power may be a useful and sensitive indicator of ventricular performance in patients with coronary artery disease.