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Key Points

  • Cardiac disease is the most common cause of nontraumatic death in the United States.

  • There are more than 300,000 sudden cardiac deaths (SCD) each year in the United States. The survival rate of SCD is dependent on the length of time without a pulse, the underlying cardiac rhythm, and comorbidities.

  • Early and uninterrupted chest compressions and early defibrillation are the keys to successful resuscitation.


Cardiopulmonary arrest is defined by unconsciousness, apnea, and pulselessness. Sudden cardiac death (SCD) is associated with an underlying history of coronary artery disease (CAD), but an acute thrombotic event is causal in only 20-40% of cardiac arrests. Twenty-five percent of cardiac arrests may have a noncardiac origin (eg, pulmonary embolus, respiratory arrest, drowning, overdose). The most common initial rhythm is ventricular fibrillation (VF), found in approximately 30% of patients. Asystole and pulseless electrical activity (PEA) are the next most common presenting rhythms.

The risk of SCD is 4 times higher in patients with coronary artery disease risk factors and 6–10 times higher in patients with known heart disease. Structural heart disease (eg, cardiomyopathy, heart failure, left ventricular hypertrophy, myocarditis) accounts for 10% of cases of SCD. Another 10% of SCD cases occur in patients with no structural heart disease or CAD. These cases are thought to originate from Brugada syndrome, commotio cordis, prolonged QT syndrome, and familial ventricular tachycardia (VT), which all cause dysrhythmias leading to SCD.

Other risk factors associated with an increased risk of SCD include smoking, diabetes mellitus, hypertension, dyslipidemia, and a family history of cardiac disease. Moderate alcohol consumption (1–2 drinks per day) is considered protective, whereas heavy alcohol consumption (>6 drinks per day) is a risk factor for SCD.

Despite advances in the field of cardiac resuscitation, the survival rate of out-of-hospital SCD is estimated to be 3–8%. Survival to discharge in out-of-hospital SCD is largely determined by the presenting rhythm. Patients with VF are 15 times more likely to survive to discharge than patients in asystole (34% vs 0–2%).

Clinical Presentation


Obtain history from paramedics, bystanders, or any available family members. Inquire about medications, past medical history, allergies, trauma, and events leading up to SCD.

Physical Examination

Do not halt treatment (including chest compressions and bag-valve-mask ventilation) to perform a complete physical exam. If the patient has an endotracheal tube in place, verify position by using end-tidal CO2 capnography or capnometry.

Diagnostic Studies


If the patient has a return of spontaneous circulation (ROSC), order a complete blood count, electrolytes, renal function, and myocardial markers (ie, troponin). Coagulation studies, an arterial blood gas, and a lactate may also be useful.



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