Effect of mechanical synchrony on ventricular contractility

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We investigated how myocardial mechanical synchrony influences ventricular contractility. To dissociate the myocardial time varying property E(t) and synchrony s(t) of cardiac contraction, we hypothesized that the time varying ventricular property e(t) can be approximated by a convolution of s(t) and e(t). To examine the hypothesis, we determined e(t) of isolated crosscirculated canine heart using a time domain direct deconvolution technique. The result indicated that a(t) derived from the early phase of contraction has longer duration of the mechanical contraction than that obtained from the late phase of contraction. Since the electrical depolarizaion propagates from the endocardium to epicardium, this is to say that the duration of the mechanical contraction would be longer in the endocardial myocardium than epicardial myocardium. This was evidenced by the fact that the mass pacing of the heart resulted in lower contractility than atrial pacing.If the convolutional model is sound, we should be able to obtain e(t) even from the heart in ventricular fibrillation. We Fourier analyzed left ventricular pressure of fibrillating heart and deconvolved it using a homomorphic deconvolution technique. The e(t) thus determined matched reasonably well with that obtained by the time domain deconvolution. Therefore the convolutional model of the left ventricle appears to integrally characterize the relationship between myocardial property e(t) and synchrony s(t) of cardiac contraction.