Acknowledgement of Catecholaminergic Polymorphic Ventricular Tachycardia has not been added yet.

The prevalence of CPVT is estimated to be about one in every 10,000 people. The true prevalence is unknown.

Name	Abbreviation
Catecholaminergic Polymorphic Ventricular Tachycardia	CPVT
bidirectional tachycardia induced by catecholamines	CPVT
Catecholamine-induced polymorphic ventricular tachycardia	CPVT
familial polymorphic ventricular tachycardia	FPVT

CPVT is caused by mutations in the RYR2 gene or the CASQ2 gene. Mutations in the RYR2 gene account for about half of all cases while mutations in the CASQ2 gene account for about 1 percent to 2 percent of all cases. In the remaining cases, the genetic cause of the disorder is unknown. These two genes provide instructions for making proteins that maintain a regular heartbeat. The proteins are involved in transporting calcium within myocytes (heart muscle cells), which is critical for the regular contraction of these cells.

When CPVT results from mutations in the RYR2 gene, it has an autosomal dominant pattern of inheritance. Autosomal dominant inheritance means that one copy of the altered gene in each cell is sufficient to cause the disorder. In about half of these cases, an affected person inherits an RYR2 gene mutation from one affected parent. The remaining cases result from new mutations in the RYR2 gene and occur in people with no history of the disorder in their family.

When CPVT is caused by mutations in the CASQ2 gene, the condition has an autosomal recessive pattern of inheritance. Autosomal recessive inheritance means that both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

The symptoms typically start between 7 and 9 years of age. The first symptom observed are frequently syncopal (fainting) spells brought on by exercise or acute emotion. Sudden death can also be the first manifestation of the disease in 10 to 20 percent of patients. Major symptoms include arrhythmia and episodes of ventricular tachycardia which lead to lightheadedness, dizziness, and fainting. However, this disorder does not cause any structural damage or structural problem with the heart.

In terms of diagnosis, subjects with a family history of CPVT or sudden death during stress or fainting induced by exercise/emotion should undergo an exercise stress test and Holter monitoring (a period of electrocardiogram monitoring lasting 24 hours or longer with the use of a portable device). Graded exercise is of utmost diagnostic relevance because arrhythmias are usually reproducible. Holter monitoring is also indicated for rarer cases where acute emotion is a more powerful trigger. Resting electrocardiogram (ECG) is usually unremarkable and cardiac imaging is typically normal for affected individuals. The principal differential diagnoses are Long QT Syndrome (LQTS), arrhythmogenic right ventricular cardiomyopathy (ARVC), and Andersen-Tawil Syndrome.

Diagnostic tests include genetic testing. Screening for the RYR2 mutation (which follows an autosomal dominant pattern of inheritance) is indicated in all patients. In the case of negative RYR2 screening and in the case of parental consanguinity, screening of CASQ2 is indicated with evidence of recessive inheritance.

Beta blockers (nadolol and propranolol) are the first treatment option for patients and the maximum tolerated dose should be administered to control arrhythmias. Recently, flecainide (a sodium channel blocker), has shown good results in suppressing arrhythmias in CPVT patients. Implantable cardioverter defibrillators (ICDs) are recommended in patients with recurrent fainting (despite full dose beta blockers and flecainide therapy) to prevent cardiac arrest and sudden death. Left cardiac sympathetic denervation has been successful in eliminating arrhythmias in a few cases where the patient did not respond to other treatments. Other possible drugs include Sotalol HCl, which is used for the treatment of life-threatening ventricular tachyarrhythmias, and Amiodarone HCl, which is used for initiation of treatment and prophylaxis of frequently recurring ventricular fibrillation and hemodynamically unstable ventricular tachycardia in patients refractory to other therapy.

Although CPVT is a severe and often deadly disease, early diagnosis and proper treatment can greatly increase life expectancy. Exercise restriction along with beta-blocker therapy and ICD implants in patients has resulted in a favourable prognosis. However, if it is not recognized and treated, an episode of ventricular tachycardia may lead to sudden death. This may be a significant cause of sudden death in children and young adults without recognized heart abnormalities.

High-intensity physical activity is to be strongly limited.

Bidirectional Tachycardia. National Institutes of Health website. Available at: https://rarediseases.info.nih.gov/gard/878/bidirectional-tachycardia/resources/1.

Catecholaminergic polymorphic ventricular tachycardia. Orphanet website. Available at: http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=3286. 

Catecholaminergic polymorphic ventricular tachycardia. Genetics Home Reference website. Available at: https://ghr.nlm.nih.gov/condition/catecholaminergic-polymorphic-ventricular-tachycardia.

Catecholaminergic Polymorphic Ventricular Tachycardia. NCBI Website. Available at: http://www.ncbi.nlm.nih.gov/books/NBK1289/.

Inherited arrhythmias: The cardiac channelopathies. NCBI Website. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4608198/.