What is the first line treatment for a stable patient experiencing paroxysmal supraventricular tachycardia (PSVT)?

In a stable patient experiencing paroxysmal supraventricular tachycardia (PSVT), the first line of treatment involves the application of vagal maneuvers. This is because these maneuvers help to stimulate the vagus nerve, which can increase parasympathetic tone, subsequently slowing down the heart rate and potentially converting the PSVT to normal sinus rhythm. Techniques such as the Valsalva maneuver or carotid sinus massage are commonly used and have proven effective in a significant number of cases.

The emphasis on vagal maneuvers as the first line reflects their non-invasive nature and the fact that they can be performed rapidly in an acute setting, offering a safe first approach before considering pharmacological interventions. If vagal maneuvers are unsuccessful, other options like adenosine or beta-blockers may be employed, but they are usually considered after these initial non-invasive measures.