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Asystole
Classification and external resources
A rhythm strip showing a couple beats of normal sinus followed by an atrial beat and asystole.
ICD-10	I46.0
ICD-9	427.5

In medicine, asystole (colloquially known as flatline) 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 that may be used for a medical practitioner to certify clinical or legal death.

Asystole is treated by cardiopulmonary resuscitation (CPR) combined with an intravenous vasopressor such as epinephrine (adrenaline). Sometimes an underlying reversible cause can be detected and treated (the so-called 'H's and T's', an example of which is hypokalaemia). Several interventions previously recommended - such as intravenous atropine and defibrillation - are no longer part of the routine protocols recommended by most major international bodies. ^[1]

Survival rates in a cardiac arrest patient with asystole are much lower than a patient with a rhythm amenable to defibrillation. Out of hospital survival rates (even with emergency intervention) are less than 2 percent.^[2]

Cause[link]

Possible underlying causes include the Hs and Ts.^[3][4][5]

• Hypovolemia
• Hypoxia
• Hydrogen ions (acidosis)
• Hypothermia
• Hyperkalemia or hypokalemia
• Hypoglycemia
• Tablets or toxins (drug overdose)
• Cardiac Tamponade
• Tension pneumothorax
• Thrombosis (myocardial infarction)
• Thrombosis (pulmonary embolism)
• Trauma (hypovolemia from blood loss)

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 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 reappears, if asystole has persisted for fifteen minutes or more the brain will have been deprived of oxygen long enough to cause brain death.

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  ECG lead showing Asystole (Flatline)

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See also[link]

• Cardiac arrest
• Myocardial infarction
• Ventricular fibrillation

References[link]