Time to dP/dt(max), a useful index for evaluation of contractility in the catheterization laboratory

Hypothesis: The time from onset of contraction to dP/dt(max), td, is suggested as an index of contractility in the catheterization laboratory. Methods: We studied 22 normal patients and 18 patients with myocardial failure in the catheterization laboratory. The two groups were completely separated on the t(d)-heart rate (HR) plane. In the normal patients. HR = 73 ± 19 beats/min, t(d) = 73 ± 11 ms, and an inverse linear relation t(d) = 109-0.49 X HR (p<0.001) exist. In the patients with myocardial failure, despite significantly higher HR than in normal patients (HR = 93 ± 14 beat/min) (p < 0.001 t(d) to paradoxically increased (t(d) = 89 ±11 ms, p<0.0001). Conclusions: These findings support a mathematical analysis of the left ventricular pressure (LVP) during isovolumic contraction in the time domain which shows that to and (dP/dt)/P reflect the time-dependent aspects of contraction and, hence, decrease with increasing contractility. This study shows that t(d), at any given HR, is a reliable index of contractility. Thus, a ready-to-use t(d)-HR plot containing a well-based separation line can provide a reliable and simple method for determining contractility in the catheterization laboratory by examining whether a patient's to value at any HR is below (normal) or above (impaired contractility) the separation line.