Cardiac action potential action potential (see phase 2, below) and is a fundamental step in cardiac excitation-contraction coupling. There are important physiological differences between the cells that spontaneously generate the action potential (pacemaker cells; e.g. SAN) and those that simply conduct it (non-pacemaker cells; e.g. ventricular myocytes). The specific differences in the types of ion channels expressed and mechanisms by which they are activated results in differences in the configuration of the action potential waveform, as shown in figure 2. The standard model used to understand the cardiac action potential is that of the ventricular myocyte. Outlined below are the five phases of
Heart rate turbulence Heart rate turbulence Heart rate turbulence (HRT) is the return to equilibrium of heart rate after a premature ventricular contraction (PVC). It consists of a brief speed-up in heart rate, followed by a slow decrease back to the baseline rate. An important feature of HRT is that PVCs occur naturally in most adults, so measuring the characteristics of a given person's HRT offers a noninvasive way to evaluate his or her cardiac function without applying artificial external stimuli. The measured values of HRT parameters have been shown to be a statistically significant predictor of the probability of dying from cardiac