What is the primary medical treatment for paroxysmal supraventricular tachycardia (SVT)?

The primary medical treatment for paroxysmal supraventricular tachycardia (SVT) is adenosine. Adenosine works through a rapid mechanism to interrupt the reentrant pathways that are often responsible for SVT, particularly in cases of reentrant tachycardias involving the atrioventricular node.

When administered intravenously, adenosine produces a transient block of conduction through the AV node, effectively interrupting the circuit that causes the fast heart rhythm. This can lead to the restoration of normal sinus rhythm in patients experiencing an SVT episode. The use of adenosine is typically safe and well-tolerated, with rapid onset and short duration of action, making it an ideal choice in acute scenarios.

The other options listed are not indicated for the treatment of SVT. Sildenafil is a phosphodiesterase type 5 inhibitor used primarily for erectile dysfunction and pulmonary hypertension, heparin is an anticoagulant, and prostacyclin is used primarily for pulmonary hypertension and certain other vascular conditions. None of these medications have a role in treating paroxysmal SVT, which underscores the importance of adenosine as the primary therapeutic agent in this context.