svts

Supraventricular tachycardia (SVT) refers to a rapid heart rhythm that originates above the ventricles, most commonly from the atrioventricular node or atria. In adults, SVT typically presents with a sudden onset of palpitations and a fast heart rate, often between 150 and 250 beats per minute. Symptoms may include lightheadedness, shortness of breath, chest discomfort, or faintness, and episodes can start and stop abruptly. On the electrocardiogram, the rhythm is usually narrow-complex unless there is rate-related aberrancy or preexisting bundle-branch block; P waves may be hidden within the QRS complexes or appear abnormally shaped.

Most SVTs are caused by reentrant circuits or ectopic atrial activity. The two most common forms are AV nodal reentrant tachycardia (AVNRT) and AV reentrant tachycardia (AVRT) associated with an accessory pathway, such as Wolff-Parkinson-White syndrome. Other contributors include focal atrial tachycardias and, less commonly, atrial flutter presenting as a rapid SVT. The underlying mechanism often involves a reentry circuit within or near the AV node or conduction system, though ectopic atrial foci can also initiate rapid rates.

Diagnosis relies on clinical presentation and rhythm analysis during tachycardia. Acute management for stable SVT begins with vagal maneuvers (such as the Valsalva maneuver) and, if needed, pharmacologic therapy with adenosine. Intravenous beta-blockers or nondihydropyridine calcium channel blockers may be used if adenosine is ineffective or contraindicated. Unstable patients require synchronized cardioversion. Long-term management may include lifestyle modification and catheter ablation, which is highly effective for AVNRT and AVRT. Antiarrhythmic medications can be considered when ablation is not appropriate or available.

Prognosis after effective treatment is generally favorable. Many SVTs can be cured by catheter ablation, reducing recurrence risk and improving quality of life; however, recurrent episodes may occur in some individuals.