Examples of common conditions that can result in secondary asystole include suffocation, near drowning, stroke, massive pulmonary embolus, hyperkalemia, hypothermia, and sedative-hypnotic or narcotic overdoses leading to respiratory failure. If available, institute cardiopulmonary bypass immediately, because it can accomplish both of these goals. Primary asystole develops when cellular metabolic functions are no longer intact and an electrical impulse cannot be generated. With severe ischemia, pacemaker cells cannot transport the ions necessary to control the transmembrane action potential. Proximal occlusion of the right coronary artery can cause ischemia or infarction of both the SA and the AV nodes.
Extensive infarction can cause bilateral bundle-branch block.
Idiopathic degeneration of the SA or AV node can result in sinus arrest or heart block, respectively. This process is slow and progressive, but the symptoms may be acute and lead to asystole. Occasionally, asystolic sudden death occurs from congenital heart block, tumor, or cardiac trauma. A rhythm may return spontaneously or shortly after CPR is initiated. These patients may survive intact if given immediate attention.