Fibrillating atria or ventricles cannot efficiently pump blood and in the case of ventricular fibrillation that lasts more than a few minutes it is fatal if the patient is not treated. Electronic defibrillators can stop ventricular fibrillation by initiating an electric shock that resets and restores normal rhythm to the heart. Myocardial infarction Ischemic necrosis of the myocardium results from inadequate blood flow and therefore oxygen delivery to the myocardium that causes irreversible cell damage and cellular death. Symptoms are pain similar to angina pectoralis , shock , arrhythmias , cardiac failure, and possibly sudden death. Laboratory tests are often inconclusive but several parameters give abnormal results in most patients and can therefore be used as indicative of an infarct.
Cellular death releases myocardial enzymes that can be used to diagnose the severity of the infarct.
Enzymes such as lactate dehydrogenase, creatine phosphokinase, and serum aspartate aminotransferase levels are elevated at certain times after an infarct has occurred and may also give some indication of the severity of the damage. The time between the onset of ischemia and muscle cell death is about 15 to 20 minutes in most cases. Almost always the infarction occurs in the left ventricle and left ventricular function may be significantly diminished. The larger the affected area of the myocardium the greater the loss of contractility. All myocardial infarctions have a central area of necrosis that is surrounded by an area of injury.