“Ask the Experts”
Beta blockers and CPVT
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a genetic heart rhythm disease which can cause a potentially life-threatening abnormal heart rhythm, typically during exercise, stress, or anxiety. During these times the body releases catecholamines, or adrenaline-like substances, and in CPVT, heart muscle cells have a molecular defect making them more prone to arrhythmias in response to catecholamines. Beta-blockers blunt the body’s response to catecholamines, so it makes sense that they would be effective in CPVT, and they are recommended universally for anyone with a CPVT diagnosis.
As for how effective are beta-blockers in CPVT, we know that they are very effective for many patients, but about 30% of patients on beta-blockers continue to have serious clinical events (syncope, cardiac arrest, or sudden death). That means the majority (70%) of CPVT patients do well with beta-blockers as their only medicine. As for specific beta-blockers, some data suggest, but do not prove, that nadolol is superior to other beta-blockers in CPVT. Most of us who treat CPVT patients use nadolol as our first choice. Nadolol is a good beta-blocker in general, as it can be taken once a day and has very few side effects.
For the 30% of CPVT patients who are still at risk despite beta-blockers, there are several additional therapies that may be considered. Surgical procedures such as left cardiac sympathetic denervation and implantation of a defibrillator (ICD) both have potential risks and benefits in CPVT. One of the more exciting developments in the field has been the discovery that the medication flecainide directly blocks the underlying molecular defect in CPVT. Flecainide is an antiarrhythmic drug that has been around for a long time, but this specific action was not known until recently. Flecainide is very effective in animal and cellular models of CPVT, and initial studies in CPVT patients are very promising.
We are currently assisting Vanderbilt to enroll CPVT patients with an ICD in a multicenter clinical trial investigating flecainide. More information about this study can be found on the SADS foundation website in the research section (http://www.sads.org/research/Research/CPVT-Clinical-Trial ), or at ClinicalTrials.gov (NCT01117454).
Prince Joseph Kannankeril, MD, MSCI
Assistant Professor of Pediatrics
Vanderbilt University Medical Center