What is paroxysmal supraventricular tachycardia (PSVT)?
The heart is a two-stage electrical pump. A coordinated electrical signal is required for the heart muscle cells to contract in a coordinated way and generate a heartbeat. Normally, an electrical signal is generated in special pacemaker cells found in the sinoatrial (SA) node located in the right atrium or upper chamber of the heart. This impulse spreads to the whole atrial muscle causing it to contract and push blood into the ventricle or the lower chamber of the heart. The electrical signal continues to a junction box between the atrium and ventricle (the AV node), where there is a slight delay that allows the ventricle to fill before it contracts and pumps blood to the body. The signal continues throughout the ventricles and causes them to beat and push blood to the body.
In paroxysmal supraventricular tachycardia (PSVT), abnormal conduction of that electricity causes the atrium, and secondarily the ventricles, to beat very rapidly. It is referred to as paroxysmal, because the rapid rate can occur sporadically and without warning and may also stop on its own. The rapid heartbeat may last a few seconds or many hours. Often the PSVT resolves before the patient reaches a health care professional.
In many patients with PSVT, there is a “wiring” problem in the AV node and instead of having just one pathway for electricity to travel to the ventricle, there are two. This allows electricity to circle back and cause the atrium to beat more quickly than it should normally. PSVT is one of many electrical abnormalities that cause the atrium to beat too quickly. These abnormalities were once lumped together and called paroxysmal atrial tachycardia or PAT but, as more has been learned about the electrical wiring of the heart, terminology has been updated to better reflect the specific abnormal rhythm. Some examples include atrial tachycardia, multifocal atrial tachycardia, atrial fibrillation, atrial flutter, and Wolfe-Parkinson-White (WPW) syndrome. As well, there are numerous abnormalities in the AV node that cause rapid heartbeats and palpitations. PSVT and other electrical abnormalities located in the atrium or AV node should not be confused with ventricular tachycardia, which arises from the ventricle and is potentially life-threatening.Picture of the interior of the heart and chambers of the heart.