DENVER – Major new guidelines on the diagnosis and management of patients with inherited primary arrhythmia syndromes have been jointly issued by the Heart Rhythm Society and its European and Asian counterparts.
The guidelines were sorely needed, according to Dr. Silvia G. Priori, cochair of the expert consensus panel writing group.
The field of inherited arrhythmias is rapidly evolving, with new pathogenic genetic mutations being found all the time. Much has changed in the 7 years since issuance of the last major guidelines: the American College of Cardiology/American Heart Association/European Society of Cardiology guidelines on prevention of sudden cardiac death (Circulation 2006;114:e385-484), noted Dr. Priori of the University of Pavia (Italy).
Dr. Silvia Priori
Her cochair, Dr. Arthur A. Wilde of the University of Amsterdam pointed out that the new 69-page report is the first major document to address some of the newer inherited arrhythmia syndromes, including catecholaminergic polymorphic ventricular tachycardia (CPVT), short QT syndrome, early repolarization, and progressive cardiac conduction disease (PCCD). In addition, the new report proposes major changes in the diagnostic criteria for the two most common primary arrhythmia syndromes: long QT syndrome (LQTS) and Brugada syndrome.
"Many of our colleagues in the field will be surprised," Dr. Priori predicted.
Here are the highlights:
• LQTS: With an estimated prevalence of roughly 1 per 2,000 live births worldwide, this is the most common of the inherited arrhythmia syndromes. What is likely to come as a surprise to many physicians is the expert consensus panel’s recommendation that the diagnosis of LQTS requires either the finding of an unequivocally causative mutation in one of the LQTS genes or, in the absence of such a defect, either a QTc interval of 480-499 ms in repeated 12-lead ECGs in a patient with unexplained syncope or a QTc of 500 ms in repeated ECGs in the absence of a secondary cause for QT prolongation in a nonsyncopal patient.
"A single ECG reading 10 ms above the upper limit of normal is not enough to establish the diagnosis. That’s quite different from what’s being done in common practice. Many of the patients who are referred to the centers of expertise on inherited arrhythmias are borderline patients in whom maybe one ECG was abnormal, and yet because of that they’ve been labeled as being affected by a genetic disease even if the genetic studies were negative. A single abnormal QTc measurement in a patient with negative genetic testing is not enough," Dr. Priori declared.
Dr. Wilde said the new guidelines loosen up the guidance on participation in competitive sports. The blanket prohibition of the past has been replaced by a case-by-case approach, with a Class I recommendation for routine referral to a clinical expert for evaluation of the risk posed by athletic activity. For example, although swimming is a very-high-risk activity for patients with the LQTS1 genotype, that’s not true for those who have LQTS2 or -3.
"It’s clear that if a patient with long QT syndrome has exercise-related syncopal events, that patient should not participate in competitive sports. But if the patient is asymptomatic and has minor QT prolongation, there’s probably not much reason for concern," he said.
Dr. Arthur Wilde
"This is a sharp departure," Dr. Priori observed. "In several European countries, if you have the diagnosis of long QT syndrome, sports participation is not permitted, even if your physician clears you. So we hope with this document to slowly, carefully, begin to allow patients with this condition to do sports safely. We wanted to lift the ban so that a physician who feels a specific patient would have a low risk in the proper environment could make that recommendation."
• Brugada syndrome: Far more common in Asia than the western world, Brugada syndrome is 8- to 10-fold more frequent in males than females. The big change in the new guidelines is that the diagnosis no longer requires specific ECG changes plus clinical manifestations. Now, Brugada syndrome, like LQTS, is a pure ECG diagnosis. It is made definitively when a type 1 ST-segment elevation is noted either spontaneously or after administration of an intravenous sodium channel-blocking agent; the ST finding has to be observed in at least one right precordial lead placed in a standard or superior position up to the second intercostal space.
An implantable cardioverter-defibrillator is clearly indicated in a Brugada syndrome patient with a prior cardiac arrest or documented ventricular arrhythmias. The controversy lies in how to manage the asymptomatic patient. The guidelines give ICD implantation a weak Class IIb recommendation – meaning it "may be considered" – when such patients exhibit inducible ventricular arrhythmias during programmed electrical stimulation in the electrophysiology lab.