Internal Medicine

Sudden cardiac death (SCD)


Death due to a cardiovascular cause that occurs within one hour of the onset of symptoms.

  • Other terms:
    • Sudden unexplained death syndrome (unexplained sudden death in > 1 year age)
    • Sudden unexplained death in infancy (unexplained sudden death in > 1 year age)
    • Sudden arrhythmic death syndrome (SCD with negative pathological and toxicological assessment)


The spectrum of epidemiology underlying sudden cardiac death. Causes of sudden cardiac death (SCD) and rates (a) and age of SCD onset in each disease (b). A, Coronary heart disease is the leading cause of SCD, but the rates of baseline heart disease differ between Western countries and Japan. B, SCDs occur in elderly populations in coronary heart disease and valvular disease, whereas most SCDs in catecholaminergic polymorphic ventricular tachycardia (CPVT) and long-.QT syndrome (LQTS) develop at age <35 years. ARVC indicates arrhythmogenic right ventricular cardiomyopathy; BrS, Brugada syndrome; ERS, early repolarization syndrome; HCM, hypertrophic cardiomyopathy; NIDCM, non-.ischemic dilated cardiomyopathy; and PUFA, polyunsaturated fatty acids. | Hayashi et al.



  • Ischaemia, myocardial infarction, inherited channelopathies


  • Heart failure, cardiomyopathies, valve disease, congenital heart disease
Echocardiogram showing left ventricle |

Coronary angiography :

  • CAD, congenital coronary anomalies, coronary spasm).

Exercise test:

  • Ischaemia, long QT syndrome [LQTS], catecholaminergic polymorphic ventricular tachycardia [CPVT]).

Electrophysiology testing:

  • Induction of arrhythmia, pharmacological provocation for Brugada syndrome, LQTS, CPVT
A cardiac electrophysiology study (EP study) is a minimally invasive procedure that tests the electrical conduction system of the heart to assess the electrical activity and conduction pathways of the heart. During EPS, sinus rhythm as well as supraventricular and ventricular arrhythmias of baseline cardiac intervals is recorded. The study is indicated to investigate the cause, location of origin, and best treatment for various abnormal heart rhythms. This type of study is performed by an electrophysiologist and using a single or multiple catheters situated within the heart through a vein or artery.

Cardiac MRI:

  • ARVC, sarcoidosis, myocarditis, myocardial injury from coronary spasm
A short axis view of the heart showing a cine cardiac magnetic resonance. In this case, the scan demonstrates features of Arrhythmogenic right ventricular dysplasia with fatty infiltration of the left and right ventricles. | Jccmoon – CC BY 3.0,
  • Genetic testing is indicated when an inherited phenotype is detected (ARVC, Brugada syndrome, CPVT, LQTS).


The Chain of Survival rubric | Ackerman, M., Atkins, D. L., & Triedman, J. K. (2016). Sudden Cardiac Death in the Young. Circulation, 133(10), 1006–1026.


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