Cardiac action potential to fail, then the heart could continue to beat, albeit at a lower rate (AVN= 40-60 beats per minute, purkinje fibres = 20-40 beats per minute). These pacemakers will keep a patient alive until the emergency team arrives. An example of premature ventricular contraction, is the classic athletic heart syndrome. Sustained training of athletes causes a cardiac adaptation where the resting SAN rate is lower (sometimes around 40 beats per minute). This can lead to atrioventricular block, where the signal from the SAN is impaired in its path to the ventricles. This leads to uncoordinated contractions between the atria and
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