Supraventricular Tachycardia (SVT)
What is a supraventricular tachycardia?
Simply stated, an SVT is an arrhythmia that originates from above (“supra”) the ventricle. This term encompasses a large number of arrhythmias and therefore the term “SVT” is only a general description, not a specific diagnosis. Most commonly, however, it refers to one of 3 commons types of arrhythmias, AV Nodal Reentrant Tachycardia, Atrial Tachycardia, and Wolff-Parkinson-White syndrome.
An “extra nerve” exists in the heart of nearly all patients with SVT, which over time becomes active and causes fast heartbeat. Most cases of SVT are genetic. In other words, patients are born with this “extra nerve” in the heart but it may remain dormant for many years, often surfacing when patients reach their 20s and 30s. Rarely, some patients may be diagnosed for the first time in their 60s and 70s.
Importantly, one must distinguish between the cause and the trigger for SVT. This is often a source of confusion for patients. While the “extra nerve” causes SVT, an attack of SVT may require certain triggers, which include caffeine, alcohol, some herbal medications, and some over-the-counter cold medications containing stimulants. Just because a large ice tea triggered an SVT attack, it does not mean that it caused the SVT. For, without the ice tea, the “extra nerve” is still present, just waiting for another trigger to cause another attack later.
Symptoms of SVT
Palpitation, or racing heartbeat, is the predominant symptom in SVT. Occasionally, some patients have no awareness of rapid heartbeat, whose only symptoms may be fatigue and fainting. Other patients describe chest paint, shortness of breath, and a sense of fullness in the neck. Children with SVT often report to their parents that their “heart hurts” since they do not have the full vocabulary that adults do.
Consequences of SVT.
Most patients with SVTs usually have a benign clinical course. In other words, SVTs as a rule do not usually cause fatality. However, in some patients when heart rate reach very high level (above 250 bpm) serious consequences can occur, including fainting spells and Sudden Death. In some cases, heart failure can result from chronic uncontrolled rapid SVT.
Most SVTs can be treated with medications but medications represent a temporizing measure, not a cure for the condition. For children or young adults, life-long therapy with medication(s) may not be reasonable. Ablation is the only curative treatment options for SVT. It works by selectively destroying the “extra nerve” via a minimally invasive procedure.