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. This can occur in very young children, presenting as sudden infant death syndrome or cot death. Approximately 30% of those with CPVT will have a family member who has experienced blackouts, seizures, or sudden death in response to exercise or stress.In those with CPVT, catecholamine release can lead to an abnormal heart rhythm or arrhythmia known as ventricular tachycardia. The ventricular tachycardia may take a characteristic form known as bidirectional ventricular tachycardia. This form of ventricular tachycardia occurs relatively infrequently, but if seen is suggestive of an underlying diagnosis of CPVT or the related condition Andersen-Tawil syndrome. These ventricular arrhythmias in some cases terminate by themselves, causing a blackout from which the person then recovers. However, if the abnormal heart rhythm continues, it can degenerate into a more dangerous arrhythmia known as ventricular fibrillation causing a cardiac arrest and, if untreated, sudden death.There are typically very few abnormal signs on clinical examination in persons with CPVT. However, those with CPVT may develop a less serious heart rhythm disturbance called atrial fibrillation, which can be detected on examination as an irregular pulse.
Prognosis
A significant proportion of those with CPVT will experience a life-threatening abnormal heart rhythm, with estimates of this risk ranging from 13 to 20% over the course of 7–8 years. Life-threatening arrhythmias are more likely to occur if CPVT has been diagnosed in childhood, if a person with CPVT does not take beta blockers, and if arrhythmias occur on exercise testing despite taking beta blockers.During treatment with nadolol, the preferred beta blocker for the treatment of CPVT, event rates have been estimated to be 0.8% per year. In patients treated with beta blockers, life-threatening arrhythmias are more likely if a person had already survived a cardiac arrest, had a syncope, or are carriers of disease-causing mutations affecting the highly conserved terminal portion of RYR2 gene, called the C-terminal domain (amino acids 4889–4969). Epidemiology
CPVT is estimated to affect 1 in 10,000 people. Symptoms from CPVT are typically first seen in the first or second decade of life, and more than 60% of affected individuals experience their first episode of syncope or cardiac arrest by age 20. Syncope during exercise or strong emotion should be considered a red flag, as it is a characteristic of the disease. Lastly, a small number of patients may present later in life, and genetic testing in these patients frequently fails to identify a causative gene. History
In 1960, Norwegian cardiologist Knut Berg published a report on three sisters who had blackouts during exercise or emotional stress in what is now recognised as the first description of CPVT.