Sudden Cardiac Death

How to Cite This Chapter: Acosta Velez JG, Amit G, Hernández Ruiz EA, Trusz-Gluza M, Leśniak W. Sudden Cardiac Death. McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. Accessed May 30, 2024.
Last Updated: February 8, 2022
Last Reviewed: February 8, 2022
Chapter Information

Definition and EtiologyTop

Sudden cardiac death (SCD) is defined as death due to cardiac causes preceded by a sudden loss of consciousness in a patient in whom a change in clinical status heralding cardiac arrest was observed ≤1 hour prior to SCD.

Causes: SCD is usually triggered by malignant ventricular arrhythmias that may be caused by ischemic heart disease (IHD), any type of cardiomyopathy, congenital heart disease, or genetic channelopathy (eg, long QT, Brugada pattern). IHD is the most common cause (in 80% of patients). Severe left ventricular dysfunction significantly increases the risk of SCD.


1. Prevention of ischemia in IHD patients.

2. Prevention of specific triggers according to the disorders listed above (eg, QT-prolonging drugs in patients with long QT syndrome).

3. Placement of an implantable cardioverter-defibrillator (ICD) for prevention of SCD is recommended in high-risk patients with life expectancy >1 year and good functional status, in jurisdictions where the device is available. High-risk patients include:

1) Patients ≥40 days after myocardial infarction (MI) with a left ventricular ejection fraction (LVEF) ≤35%.

2) Patients with dilated nonischemic cardiomyopathy with an LVEF ≤35% and New York Heart Association (NYHA) class II or III heart failure (see Table 1 in Chronic Heart Failure).


ICD implantation in survivors of SCD unless a reversible cause (eg, acute phase of MI, drug-related QT prolongation, bradycardia-induced polymorphic ventricular tachycardia) or noncardiac cause is documented.

For the investigation of SCD of unclear cause, a detailed personal and family history is essential, with attention to sentinel symptoms during life such as syncope or seizures, witness accounts, premorbid investigations, and inspection of any cardiac rhythm monitoring around the time of death.

For victims of SCD or survivors of cardiac arrest with a known or suspected form of cardiomyopathy (other than IHD), genetic testing of the proband focused on likely candidate genes, along with clinical evaluation of family members, aids in identifying family members with or at risk of the same condition.

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