In this post I link to and excerpt from The Athlete With Catecholaminergic Polymorphic Ventricular Tachycardia from Latest In Cardiology from The American College of Cardiology Jul 28, 2017 | Michele A Murphy, MD; John D. Ferguson, ChB, MBExpert Analysis [PubMed Abstract] [Full-Text HTML] [Full-Text PDF].
All that follows is from the above resource.
Background
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is uncommon but recognized as a cause of sudden cardiac death (SCD) in those with structurally normal hearts. It typically presents with palpitations or syncope during intense physical or emotional stress and may be fatal. Genetic advances in the last decade have allowed for improved diagnosis, risk stratification, and treatment of this disorder. Given the association to intense physical activity, CPVT deserves special consideration in athletes participating in competitive sports.
The incidence of SCD in young competitive athletes is relatively low (1:42,000-200,000 athletes) and is more commonly related to cardiac structural abnormalities such as hypertrophic cardiomyopathy (HCM) and coronary anomalies.1,2 Contrary to previous belief, a recent study found that the most cause of SCD at autopsy was autopsy-negative sudden unexplained death (ANSUD) (25%) followed by HCM (8%). It is thought that the cause of ANSUD is likely due to unrecognized channelopathies.3,4 CPVT is an uncommon condition, accounting for about 12% of autopsy-negative sudden deaths and 1.5% of sudden infant deaths.5 The true prevalence is unknown, though a possible prevalence of 1 in 10,000 has been quoted in the literature.6 There is ongoing controversy regarding the optimal screening and prevention of SCD in athletes.
Genetics
CPVT is a highly malignant inheritable cardiac channelopathy. CPVT was originally described by Coumel et al. in 1978 and later further characterized by Leenhardt et al. in 1995 as a distinct genetic arrhythmogenesis disorder of unknown origin in individuals without structural heart disease and QT prolongation.10,11 Affected individuals often present in childhood or adolescence with symptoms such as syncope or catecholamine-mediated ventricular arrhythmias that may result in cardiac arrest and sudden death. The untreated mortality rate as high as 50%.12-14
Clinical Presentation
CPVT is widely accepted to be a disease of childhood, with most patients presenting with symptoms (syncope or SCD) before the age of 21, with a median age of 15±10 years (range 2 to 51 years).12,13 The incidence of cardiac events (syncope under physical or emotional stress, aborted cardiac arrest, appropriate ICD discharges, or SCD) during 4- and 8- year follow-up was 12% and 32% respectively. In other studies, the occurrence of cardiac events varied from 2% to 62% of the patients.13,19
More recently, a bimodal distribution of symptom onset has been highlighted, with a juvenile type presenting in the first two decades of life and the adult type of CPVT presenting at 32-48 years.15,20 The adult form tends to present around the age of 40 years, have a female predominance, usually RYR2-genotype negative, and associated with less risk of SCD. Further, Priori et al. showed that variable expressivity of RYR2 mutations was seen in 17% of gene carriers.15 These patients were phenotype negative for CPVT as well as other inherited arrhythmogenic diseases suggesting that RYR2 CPVT has incomplete penetrance.
Diagnosis
CPVT patients usually have a normal resting ECG. The delay between initial presentation and diagnosis is often between 2 to 9 years.12,21 A high index of suspicion for CPVT should be held in patients with palpitations or syncope during physical or emotional stress, especially in those who have a family history of premature death.
The diagnosis of CPVT relies on the demonstration of ventricular arrhythmias (VA) during standard noninvasive exercise treadmill testing and epinephrine drug challenge. A positive test is defined when complex ventricular ectopy, bidirectional ventricular tachycardia (VT), and/or polymorphic VT occurs (Figure 1). A negative stress test, however, does not exclude CPVT. Several studies have shown that VA provoked with exercise range from 30%-76% and epinephrine in 82% of patients with CPVT.22,23 The epinephrine drug challenge may be considered as an alternative to exercise treadmill testing, with sensitivity and specificity of 28% and 98% respectively.24 Holter monitoring, loop recorder monitoring and implanted loop recorders may be useful in this case when exercise testing or drug challenge is either negative or cannot be performed. Genetic testing and family screening should then be performed in affected individuals and asymptomatic genotype positive family members should be treated with β-blockers.
For decisions on therapy, involvement of an electrophysiologist can be very helpful
