sudden cardiac death
Sudden cardiac death is exactly what the name says: an abrupt, unexpected death from a cardiac cause, usually within an hour of the first symptoms, in someone who may have seemed well. In most cases the immediate mechanism is a sudden, fatal arrhythmia — typically ventricular fibrillation — that stops the heart pumping so the brain and body lose their blood supply within seconds.
It is the end-point of sudden cardiac arrest, the moment the heart stops; if blood flow is restored quickly the person can survive, so “arrest” and “death” are not the same event. The most common underlying cause in adults is coronary artery disease, where ischemia or scar from a heart attack sparks the lethal rhythm; in the young, inherited cardiomyopathies and channel disorders such as long QT syndrome predominate.
Because it strikes so fast, prevention and rapid response matter far more than treatment after the fact. Identifying high-risk people for an implantable defibrillator, treating the underlying disease, and building a chain of survival — bystander CPR, public defibrillators and fast emergency care — are what turn a potential sudden death back into a survived arrest.
A man with a weakened heart after a previous infarction is fitted with an implantable defibrillator for primary prevention; months later it detects ventricular fibrillation and shocks him back to a normal rhythm, averting sudden death.
An implantable defibrillator can convert a would-be sudden death into a survived arrest.
Sudden cardiac arrest and sudden cardiac death are not synonyms: arrest is potentially reversible with prompt CPR and defibrillation, and only becomes death if circulation is not restored.