• Catecholaminergic polymorphic ventricular tachycardia: The prevalence of CPVT is unclear, but it has been estimated at 1 per 5,000 live births, according to Dr. Wilde. This highly malignant condition is diagnosed in patients with a known pathogenic mutation, or in the presence of a structurally normal heart, a normal resting ECG, and unexplained exercise- or catecholamine-induced bidirectional VT of polymorphic ventricular premature beats or VT before age 40 years. First-line therapy is a long-acting beta-blocker such as nadolol, coupled with exercise restriction. ICD therapy is problematic because the inevitable inappropriate shocks increase sympathetic tone, triggering true shockable arrhythmias in a vicious cycle.
• Short QT syndrome: This is a rare channelopathy. It is diagnosed on the basis of a QTc of 330 ms or less, or a QTc of less than 360 ms in the presence of a pathogenic mutation, family history of sudden death before age 40 years, cardiac arrest in the absence of structural heart disease, or a family history of short QT syndrome.
• Progressive cardiac conduction disease: Still incompletely understood, PCCD is diagnosed in individuals under age 50 years who have unexplained progressive conduction abnormalities and a structurally normal heart with no skeletal myopathies. Pacemaker implantation is the most useful therapy.
• Early repolarization: The first report linking this extremely common ECG finding to sudden death came less than 5 years ago. Early repolarization, as characterized by J-point and ST-segment elevation in two or more contiguous leads, is present in up to 10% of normal individuals. In preparticipation athletic screening programs, it can be found in up to 15%-20% of subjects.
"There’s no reason for concern if that’s the only thing you find. It’s something you shouldn’t even communicate if there is no other issue. If a patient with early repolarization has no symptoms and no family history of premature sudden death, just leave it," Dr. Wilde advised.
On the other hand, if a patient with the early repolarization ECG pattern in two or more contiguous inferior and/or lateral leads experiences exercise-induced syncopal symptoms, further evaluation is warranted. Given how common and generally benign the early repolarization ECG pattern is, the expert panel recommended a conservative approach to diagnosis, urging that the formal diagnosis of early repolarization syndrome be restricted largely to those with the characteristic ECG findings who in addition have been resuscitated from unexplained ventricular fibrillation or polymorphic VT.
Dr. Priori emphasized that the guidelines have as a Class I recommendation that patients with a diagnosed or suspected inherited arrhythmia syndrome that can result in sudden cardiac death – and their first-degree relatives, as well – should be evaluated in a specialized multidisciplinary inherited arrhythmia clinic. Such clinics are more common in Europe than the United States; however, thought leaders in American electrophysiology now recognize that the increasing complexity of the field requires that more of these dedicated clinics be created in the United States, she said.
The expert consensus statement was a joint project of the Heart Rhythm Society, the European Heart Rhythm Association, and the Asia Pacific Heart Rhythm Society. The document is available at the HRS website and will be published this fall in Heart Rhythm, EP Europace, and the Journal of Arrhythmias.
Dr. Priori reported serving as a consultant to Medtronic, Boston Scientific, Biotronic, and Transgenomic. Dr. Wilde disclosed serving as a consultant to Sorin.