Cardiac pacemaker ventricles, within the atrial septum. If the AV node also fails, Purkinje fibers are occasionally capable of acting as the default or "escape" pacemaker. The reason Purkinje cells do not normally control the heart rate is that they generate action potentials at a lower frequency than the AV or SA nodes. Cardiac pacemaker The contraction of cardiac muscle (heart muscle) in all animals is initiated by electrical impulses known as action potentials. The rate at which these impulses fire controls the rate of cardiac contraction, that is, the heart rate. The cells that create these rhythmic impulses, setting the pace
Cardiac contractility modulation heart structure can be partially reversed by Cardiac contractility modulation through a process known as reverse remodeling of the heart. Development of cardiac contractility modulation began in the late 1990s. Studies on individual cardiac muscle cells using a patch-clamp technique had already shown, in 1969, that a voltage applied during the absolute refractory period through leads between the interior of the cell and its outside environment increased the calcium influx through the cell membrane and improved the contraction of cardiac muscle cells. In 2001, scientists observed that a similar effect occurs even if the voltage is applied exclusively outside the