Catecholaminergic Polymorphic Ventricular Tachycardia
What is Catecholaminergic polymorphic ventricular tachycardia (CPVT)?
Catecholaminergic polymorphic ventricular tachycardia, or CPVT, is a potentially fatal cardiac arrhythmia (irregular heartbeat) in individuals with a structurally normal heart. The first symptom of this disorder is syncope – fainting because of a sudden loss of blood pressure – triggered by physical activity or intense emotion, and typically happening in the first decade of life. In patients with CPVT, catecholamines (hormones) induce irregular heartbeats, which then lead to syncope or sudden cardiac death. Sudden death may be the first manifestation of the condition.
CPVT occurs in about 1 in 10,000 people in the population, and affects men and women equally. If untreated, about 30 percent of patients will have at least one cardiac arrest, and 80 percent will have at least one syncopal spell.
What causes Catecholaminergic polymorphic ventricular tachycardia?
It has been found that mutations in two genes, RYR2 and CASQ2, can result in CPVT. About half of all CPVT cases have been linked to RYR2 mutations, while CASQ2 mutations are found in one to two percent of cases.
In cases of CPVT caused by RYR2 gene mutations, it is inherited in an autosomal dominant pattern, where one copy of the altered gene can cause the condition. It has been found that this gene mutation is inherited from an affected parent in half of all CPVT cases caused by RYR2 gene mutations.
In CPVT cases caused by CASQ2 gene mutations, an autosomal recessive pattern of inheritance has been found, where both parents who may not have symptoms of the condition, pass on a copy of the mutated gene to their children.
Who should test for Catecholaminergic polymorphic ventricular tachycardia?
Diagnostic genetic testing for CPVT can be considered for patients with symptoms of CPVT, and patients who may not have symptoms but have family members with a known mutation. Testing should be first performed on the family member who is symptomatic of CPVT, as identification of a mutation can lead to genetic identification of family members who may have normal ECGs but may be at risk. Following genetic testing, family members who test positive for the familial mutation should have regular cardiac evaluations. In the same way, repeated follow-up examinations would not be needed if there is a negative result in genetic testing.
How does the test work?
The CPVT genetic test is a blood test ordered by your physician. Your DNA is extracted from the blood and analyzed by searching for mutations that are associated with CPVT. The test takes approximately eight weeks to complete, and the results will be sent to your physician, who will explain the test results to you.
We will need two tubes of blood (about 7 to 10ml) and a signed consent form from you to send to the laboratory. We recommend genetic counselling before genetic tests are ordered to discuss the implications of the testing and potential results.