Ventricular fibrillation and sudden cardiac death

Definition

Sudden cardiac death

• Young athletes (35 years or younger): The most common finding is sudden death with a structurally normal heart at autopsy, often due to an inherited arrhythmia syndrome such as long QT or Brugada syndrome. Other causes are hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, coronary artery anomalies, myocarditis, Wolff-Parkinson-White syndrome, catecholaminergic polymorphic ventricular tachycardia and commotio cordis.
• Older athletes (over 35 years): mainly coronary artery disease, occasionally hypertrophic cardiomyopathy or valvular disease
• Male athletes are affected up to ten times more often than female athletes.

Ventricular fibrillation is uncoordinated quivering of the ventricles without useful contraction. It causes immediate loss of consciousness and, if it persists, death within minutes. Electrophysiologically it is based on reentry of multiple small wavelets. Sudden cardiac arrest is the unexpected cessation of circulation shortly after the onset of symptoms, often without warning.

Occurrence & epidemiology

In the past, ventricular fibrillation was the first documented rhythm in about 75 % of cardiac arrests; more recent data show about 40 %. Because ventricular fibrillation turns into asystole over time, this proportion underestimates its true importance. In infants and children ventricular fibrillation is much less common; asystole predominates there.

Aetiopathogenesis

Most affected people have underlying heart disease, typically ischemic cardiomyopathy, but also hypertrophic or dilated cardiomyopathy and other arrhythmogenic disorders. In adults, sudden cardiac arrest is mainly due to acute coronary syndromes and other cardiovascular diseases; it is often the first manifestation of heart disease. In children and adolescents, channelopathies and structural heart abnormalities are the most common causes.

Electrolyte disorders, acidosis, hypoxemia and ischemia increase the risk in any underlying condition. If no cause is found despite comprehensive investigation, the term idiopathic ventricular fibrillation is used; some of these patients probably have an as yet unknown genetic disorder.

Clinical features

Ventricular fibrillation causes immediate loss of consciousness with pulselessness and absent normal breathing. It may be preceded by chest pain, palpitations, dyspnea or syncope; often there is no warning at all.

Diagnosis

• ECG: ultrarapid baseline undulations, irregular in timing and morphology, without discernible QRS complexes
• Search for the cause after the event: evaluation for coronary artery disease, cardiomyopathies and channelopathies using ECG, imaging (echocardiography, cardiac MRI, coronary angiography) and provocative testing
• Genetic testing if a channelopathy or nonischemic cardiomyopathy is suspected, possibly with cascade testing of relatives; family members with symptoms are evaluated with ECG, exercise testing and echocardiography.

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Further reading (open access)

1. MSD Manual Professional: Ventricular Fibrillation (VF)
2. MSD Manual Professional: Cardiac Arrest
3. StatPearls: Ventricular Fibrillation
4. StatPearls: Sudden Cardiac Death
5. MSD Manual Professional: Sudden Cardiac Death in Athletes

Cross-references