Aetiology

The underlying causes of death in individuals with morphologically normal hearts include the cardiac channelopathies:

• long QT syndrome - a disorder of cardiac repolarisation causing QT prolongation on the ECG with a risk of ventricular arrhythmias (Torsades de Pointes)
• Brugada syndrome - a disorder of cardiac activation causing right bundle branch block and ST elevation in leads V1-3 on the ECG with a risk of polymorphic ventricular tachycardia
• Progressive Cardiac Conduction Disease - a disorder of cardiac conduction causing variable degrees of heart block predisposing to cardiac arrest
• Catecholaminergic Polymorphic Ventricular tachycardia - a disorder of calcium handling causing exertional ventricular arrhythmias (typically bi-directional)

These are potentially inheritable conditions and, as such, the relatives of the victim may also be at risk of dying suddenly from a treatable condition. Sometimes an underlying diagnosis may only be identified by detecting abnormalities in relatives. This necessitates cardiological evaluation of family members.

Other rare genetic conditions that cause structural cardiac disease, which have been identified in relatives of sudden arrhythmic death syndrome victims even though post-mortems have proved negative or equivocal include:

• arrhythmogenic Right Ventricular Cardiomyopathy
• hypertrophic cardiomyopathy
• dilated cardiomyopathy
• dystrophia myotonica
• Wolff-Parkinson-White syndrome
• mitral valve prolapse

This highlights the diagnostic limitations of standard autopsies when potentially diagnostic features are not obvious. Consequently, coroners' pathologists often refer hearts and/or slides for an expert cardiac assessment.

Reference:

1. British Heart Foundation (Factfile 04/2002). Sudden cardiac death in young people.