Rate of change of ventricular power: an indicator of ventricular performance during ejection.

An expression representative of the rate of change of ventricular power during ejection was derived. The primary advantages of the expression are its theoretical value and its ability to characterize ventricular performance. The rate of change of ventricular power, measured during ejection, is virtually free of assumptions. It has a fluid dynamic as well as a physiological meaning. It serves in an integrative fashion by combining terms previously shown to be of functional significance. Studies in dogs show that it reflects alterations of the inotropic state yet is relatively independent of alterations of preload or afterload. In nine dogs isoproterenol caused the peak rate of change of power to increase from (10 +/- 2) X 10(8) to (15 +/- 3) X 10(8) dynes-cm. sec.-2 (mean +/- S.E.) (P less than 0.01). Propranolol produced a reduction from (10 +/- 2) X 108 to (6 +/- 1) X 10(8) dynes-cm. sec.-2 (P less than 0.001). An increased afterload induced by angiotensin caused no change of the peak rate of change of power. Augmentation of the preload with dextran, which caused a 40 per cent increase of the end-diastolic volume, produced a statistically insignificant increase of the peak rate of change of power from (12 +/- 3) X 10(8) TO (16 +/- 4) X 10(8) dynes-cm. sec.-2 The rate of change of ventricular power, measured during ejection, therefore appears to be a useful and meaningful indicator of ventricular performance that has many desirable characteristics.