CPVT (catecholaminergic polymorphic ventricular tachycardia)

CPVT (catecholaminergic polymorphic ventricular tachycardia)

CPVT in short for catecholaminergic polymorphic ventricular tachycardia is probably the most lethal of the cardiac channelopathies. It is characterized by life threatening ventricular arrhythmias induced by exercise or emotional stress. Majority of cases of CPVT are caused by an autosomal dominant mutation in the cardiac ryanodine receptor gene RYR2. Less than two percent are caused by a recessive mutation of the calsequestrin gene (CASQ2). Mutations of Ankyrin B genes have also been implicated in the genesis of CPVT. Thirty to fifty per cent mortality can be expected in untreated cases of CPVT. Symptoms of CPVT commonly start in childhood or adolescence. About thirty percent become symptomatic by the age of ten and eighty percent by the age of forty years, according to one report [1] .

The classical exercise induced arrhythmia of CPVT is a bidirectional ventricular tachycardia. It may be noted that CPVT cannot be diagnosed by a resting ECG. Even though exercise testing is the most important investigation in a suspected CPVT, up to one fifth of them may not develop ventricular ectopy during an exercise stress test. Sometimes CPVT may be misdiagnosed as LQT1 with a normal QT, which can occur in LQT1 during certain periods of time. But genetic testing is certainly useful in differentiating the two. Even though beta blockers are the sheet anchor of therapy in CPVT, some studies have shown that as many as half of them may not respond and require an ICD implantation [2].

References

1. Mohamed U, Napolitano C, Priori SG. Molecular and electrophysiological bases of catecholaminergic polymorphic ventricular tachycardia. J Cardiovasc Electrophysiol. 2007;18:791-797.
2. Priori SG, Napolitano C, Memmi M, et al. Clinical and molecular characterization of patients with catecholaminergic polymorphic ventricular tachycardia. Circulation. 2002;106:69-74.