Catecholaminergic polymorphic ventricular tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited genetic disorder that predisposes those affected to potentially life-threatening abnormal heart rhythms or arrhythmias. The arrhythmias seen in CPVT typically occur during exercise or at times of emotional stress, and classically take the form of bidirectional ventricular tachycardia or ventricular fibrillation. Those affected may be asymptomatic, but they may also experience blackouts or even sudden cardiac death. CPVT is caused by genetic mutations affecting proteins that regulate the concentrations of calcium within cardiac muscle cells. The most commonly identified gene is RYR2, which encodes a protein included in an ion channel known as the ryanodine receptor; this channel releases calcium from a cell's internal calcium store, the sarcoplasmic reticulum, during every heartbeat. CPVT is often diagnosed from an ECG recorded during an exercise tolerance test, but it may also be diagnosed with a genetic test. The condition is treated with medication including beta-adrenoceptor blockers or flecainide, or with surgical procedures including sympathetic denervation and implantation of a defibrillator. It is thought to affect as many as one in ten thousand people and is estimated to cause 15% of all unexplained sudden cardiac deaths in young people. The condition was first defined in 1978, and the underlying genetics were described in 2001. Although individuals with CPVT may not experience any symptoms, the most commonly reported symptoms are blackouts or sudden loss of consciousness, referred to as syncope. These blackouts often occur during exercise or as a response to emotional stress—situations in which chemical messengers known as catecholamines, such as adrenaline, are released within the body. Blackouts may be misinterpreted as being caused by simple faints or epilepsy, often leading to delays in reaching the correct diagnosis. In a third of those affected, the first manifestation of the disease may be cardiac arrest, potentially leading to sudden death.