Breakthroughs in Understanding PSVT Lead to New Treatments

March 28, 2011
Edward Pullen, MD

Dr. Pullen discusses the clinical characteristics of PSVT, the tests used to diagnose this condition, and new treatment methods.

This article originally appeared online at DrPullen.com, part of the HCPLive network.

Paroxysmal Supraventricular Ventricular Tachycardia, or PSVT, is a common medical condition in which sudden paroxysms or attacks of very rapid heart rate seem to arise out of nowhere. They can be brief, just a few seconds or a minute or two, or can last hours and lead to circulatory compromise. PSVT is also one of the cardiac conditions where over the last few decades researchers have made tremendous progress in diagnosis, treatment, and even cure of the condition.

When everything is working normally in our heart, each heartbeat is triggered by the sinoatrial node in the right atrium. This node starts causing heart muscle fibers in the heart to depolarize, an amazing electrical/chemical reaction that rapidly spreads to all adjacent heart muscle cells. Special heart muscle cells called Purkinje cells, that connect to form Purkinje fibers, are able to incredible quickly transmit this depolarization from cell to cell and through the atria until they reach the atrioventricular node (AV node) where after a momentary pause, the depolarization races through bundles of Purkinje fibers in the ventricles called bundle branches out to the ventricular heart muscle. In the perfectly formed heart there is a fibrous tissue that separates the atria and the ventricles so that the depolarization of heart muscles can only pass from the atria to the ventricles through the AV node.

In most patients with PSVT there is an aberrant group of muscle cells that goes through this connective tissue separator allowing the depolarization to get from the atria to the ventricles, or backwards, other than through the AV node. When this is present sometimes a circular movement of the depolarization can occur, leading to a very rapid heart rate. This very rapid heart rate, often at rates as high as 190-200 beats/ minute, is called PSVT.

Some patients with PSVT have a resting EKG that shows a specific abnormality where the PR interval is very short and there is a “slur” on the QRS wave. This specific type of PSVT is called Wolfe-Parkinson-White syndrome.

Treatment of PSVT can be with medications to slow the ability of the heart to beat, and make PSVT less rapid and so better tolerated. The biggest breakthroughs though in PSVT management have been the ability to use cardiac catheters along with tiny instruments to map the conducting ability of the heart and find the aberrant tissue that connects the atria to the ventricles. If this can be located the cardiologist can then destroy the aberrant fibers usually using thermal probes and so effectively cure PSVT. In patients with frequent, prolonged, or very rapid PSVT this has revolutionized therapy, and been life-changing and at times lifesaving therapy.

Experienced cardiology electophysiologists have rates of success with PSVT ablation of 95% or higher. It has become a standard of therapy for many patients where PSVT is not easily controlled medically. Newer cryoablation procedures are being developed to allow treatment of the few PSVT patients who cannot have radiofrequency ablation. The cryotherapy procedures allow treatment of aberrant pathways in areas too close to key structures like the AV node to treat with radiofrequency.

Ed Pullen, MD, is a board-certified family physician practicing in Puyallup, WA. He blogs at DrPullen.com — A Medical Bog for the Informed Patient.