Maximal negative dP/dt as an indicator of end of systole.

The maximal negative peak of the first derivative of left ventricular pressure was examined as an index of the end of ventricular ejection by comparing it with the end of aortic flow. Under varying heart rate and afterload situations in anesthetized dogs, a correlation coefficient of 0.982 was obtained with a mean error of less than 0.4 ms. This may be a useful end point for determining systolic time where only ventricular pressure is available.