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
Cardiac contractility modulation the electrical non-excitatory state of the cardiac muscle cells (the absolute refractory period) cause an increase in myocyte calcium in the cytosol during systole. This increases the muscle contraction strength. Additionally, within minutes, cell metabolism and gene expression, which are typically abnormal in heart failure, improve towards their normal state. This beneficial effect occurs initially only in the area adjacent to the electrodes, but with time also spreads to remote areas of the cardiac muscle. Cardiac contractility modulation therefore restores the structure and function of damaged cells back towards their normal state. In some cases, disease-related changes in the ventricular