Asystole

Asystole is a state of no cardiac electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow. Asystole is one of the conditions required for a medical practitioner to certify death.

In asystole, the heart will not respond to defibrillation because it is already depolarized, however some emergency physicians advocate a trial of defibrillation in case the rhythm is actually fine ventricular fibrillation, although little evidence exists to support the practice. Asystole is usually a confirmation of death as opposed to a heart rhythm to be treated, although a small minority of patients are successfully resuscitated, if the underlying cause is identified and treated immediately.

Possible underlying causes include the Hs and Ts.^[1][2][3]

• Hypovolemia
• Hypoxia
• Acidosis
• Hypothermia
• Hyperkalemia or Hypokalemia
• Hypoglycemia
• Cardiac Tamponade
• Tension pneumothorax
• Thrombosis
• Myocardial infarction
• Thrombosis
• Pulmonary embolism
• Cardiogenic shock
• Degeneration of the sinoatrial or atrioventricular nodes
• Ischemic stroke

Shown below are EKGs depicting asystole.

It is important to exclude fine ventricular fibrillation in the patient presumed to have asystole. If VF is present, then cardioversion should be performed.

While the heart is asystolic, there is no blood flow to the brain unless CPR or internal cardiac massage (when the chest is opened and the heart is manually compressed) is performed, and even then, it is still a small amount. After many emergency treatments have been applied but the heart is still unresponsive, it is time to consider pronouncing the patient dead. Even in the rare case that a rhythm should reappear, if asystole has persisted for fifteen minutes or more the brain will have been deprived of oxygen long enough to cause brain death.

• Cardiac arrest
• Myocardial infarction
• Ventricular fibrillation

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