Cardiac arrest

Cardiac arrest
Other names	Cardiopulmonary arrest, circulatory arrest, sudden cardiac arrest (SCA)[1]
CPR being administered during a simulation of cardiac arrest
Specialty	Cardiology, emergency medicine
Symptoms	Decreased level or total loss of consciousness, abnormal or no breathing, no pulse[1][2]
Complications	If reversed, coma, persistent vegetative state, post-cardiac arrest syndrome; if not reversed, death
Usual onset	The risk of onset increases with age[3]
Causes	Coronary artery disease, congenital heart defect, major blood loss, lack of oxygen, electrical injury, very low potassium, heart failure, myocardial infarction
Diagnostic method	Finding no pulse,[1] ECG (EKG)[4]
Prevention	Not smoking, physical activity, maintaining a healthy weight, healthy eating[5]
Treatment	Cardiopulmonary resuscitation (CPR), defibrillation[6]
Prognosis	Overall survival rate ≈10% (outside of hospital) 25% (in hospital);[7][8] depends strongly on type and cause
Frequency	13 per 10,000 people per year (outside hospital in the US)[9]
Deaths	> 425,000 per year (U.S.)[10]

Cardiac arrest, also known as sudden cardiac arrest, is when the heart suddenly and unexpectedly stops beating.^[11][1] As a result, blood cannot properly circulate around the body and there is diminished blood flow to the brain and other organs. When the brain does not receive enough blood, this can cause a person to lose consciousness. Coma and persistent vegetative state may result from cardiac arrest. Cardiac arrest is also identified by a lack of central pulses and abnormal or absent breathing.^[1]

Cardiac arrest and resultant hemodynamic collapse often occur due to arrhythmias (irregular heart rhythms). Ventricular fibrillation and ventricular tachycardia are most commonly recorded.^[12] However, as many incidents of cardiac arrest occur out-of-hospital or when a person is not having their cardiac activity monitored, it is difficult to identify the specific mechanism in each case.

Structural heart disease, such as coronary artery disease, is a common underlying condition in people who experience cardiac arrest. The most common risk factors include age and cardiovascular disease.^[13] Additional underlying cardiac conditions include heart failure and inherited arrhythmias. Additional factors that may contribute to cardiac arrest include major blood loss, lack of oxygen, electrolyte disturbance (such as very low potassium), electrical injury, and intense physical exercise.^[14]

Cardiac arrest is diagnosed by the inability to find a pulse in an unresponsive patient.^[4][1] The goal of treatment for cardiac arrest is to rapidly achieve return of spontaneous circulation using a variety of interventions including CPR, defibrillation, and/or cardiac pacing. Two protocols have been established for CPR: basic life support (BLS) and advanced cardiac life support (ACLS).^[15]

If return of spontaneous circulation is achieved with these interventions, then sudden cardiac arrest has occurred. By contrast, if the person does not survive the event, this is referred to as sudden cardiac death. Among those whose pulses are re-established, the care team may initiate measures to protect the person from brain injury and preserve neurological function.^[16] Some methods may include airway management and mechanical ventilation, maintenance of blood pressure and end-organ perfusion via fluid resuscitation and vasopressor support, correction of electrolyte imbalance, EKG monitoring and management of reversible causes, and temperature management. Targeted temperature management may improve outcomes.^[17][18] In post-resuscitation care, an implantable cardiac defibrillator may be considered to reduce the chance of death from recurrence.^[5]

Per the 2015 American Heart Association Guidelines, there are approximately 535,000 incidents of cardiac arrest annually (about 13 per 10,000 people).^[9] Of these, 326,000 (61%) experience cardiac arrest outside of a hospital setting, while 209,000 (39%) occur within a hospital.^[9]

Cardiac arrest becomes more common with age and affects males more often than females.^[11] Twice as many black men die from a cardiac arrest as white men. Asian and Hispanic people are not as frequently affected as white people.^[11]