Sudden cardiac death

Not to be confused with Sudden unexpected death syndrome or Cardiac arrest.

"Cardiac death" redirects here. For the legal definition, see organ donation § Brain death versus cardiac death.

Sudden cardiac death
Classification and external resources
Specialty
ICD-10	I46.1
eMedicine	article/151907
Patient UK	Sudden cardiac death
MeSH	D016757

Sudden cardiac death (SCD) is usually from cardiac causes, heralded by abrupt loss of consciousness within one hour of the onset of acute symptoms.

Signs and symptoms

Signs of sudden cardiac death include the following:

• loss of consciousness
• racing heartbeat
• dizziness
• chest pain/shortness of breath (an hour before SCD)

Causes

File:Cardiac myofiberbreak-up -- intermed mag.jpg

Cardiac myofiber break-up(MFB) is a marker of ventricular fibrillation in SCD.

Coronary artery disease

The most common cause of sudden cardiac death in adults is ventricular fibrillation (v-fib), brought on by acute coronary ischemia. Cases have shown that the most common finding at postmortem examination of SCD is chronic high-grade stenosis of at least one segment of a major coronary artery, the arteries that supply the heart muscle with its blood supply. Left ventricular hypertrophy is thought to be the leading cause of sudden cardiac death in the adult population. This is most commonly the result of longstanding high blood pressure which has caused secondary damage to the wall of the main pumping chamber of the heart, the left ventricle.

Although the most frequent cause of sudden cardiac death is ventricular fibrillation, other causes include the following:

• Coronary heart disease
• Physical stress
  • low levels of magnesium
  • low levels of potassium
  • major blood loss
  • lack of oxygen
  • severe physical activity which triggers adrenaline
• Inherited disorders
  • Hypertrophic cardiomyopathy
• Enlarged heart due to increased blood pressure
• Commotio cordis

Mechanism

Ventricular fibrillation

The mechanism of death in the majority of patients dying of sudden cardiac death is ventricular fibrillation. Structural changes in the diseased heart as a result of inherited factors (mutations in ion-channel coding genes for example) cannot explain the suddenness of SCD. Also, sudden cardiac death could be the consequence of electric-mechanical disjunction and bradyarrhythmias.

Diagnosis

Sudden cardiac death by definition cannot be diagnosed as it has already happened. However, the risk factors for sudden cardiac arrest and subsequent death can be diagnosed in a variety of ways via an EKG, echocardiogram, MUGA test, cardiac catheterization, and blood tests.

Treatment

Coronary artery bypass graft

Should coronary heart disease be diagnosed, percutaneous coronary intervention or coronary artery bypass grafting (procedures performed to help restore blood flow via narrowed arteries) may be the procedures of choice. Treatment with marine-derived omega-3 polyunsaturated fatty acids (PUFAs) has been promoted for the prevention of sudden cardiac death due to its postulated ability to lower triglyceride levels, prevent serious arrhythmias, decrease platelet aggregation, and lower blood pressure. However, according to a recent systematic review and meta-analysis, omega-3 PUFA supplementation has not been associated with a lower risk of sudden cardiac death based on absolute measures of association (RD, −0.01; 95% CI, −0.02 to 0.00; P = .09; I2 = 78%).

Epidemiology

Sudden cardiac death accounts for more than half of all cardiac deaths. In the United States, it claims the lives of 250,000 to 310,000 people annually. It is also the first manifestation of heart disease for the majority of individuals. Consequently, better management of heart disease through lifestyle factors is recommended.

See also

• Cardiac arrest
• Clinical death
• Coronary thrombosis
• Myocardial infarction
• Ventricular fibrillation

External links

• Heart Rhythm Society