Comparing Two Vagal Maneuvers for Paroxysmal Supraventricular Tachycardia

The goal of this clinical trial is to compare two physical techniques for treating paroxysmal supraventricular tachycardia in adults. This condition causes a fast, regular heartbeat that starts and stops suddenly. Participants must be medically stable and have the condition confirmed by an electrocardiogram (ECG). The main question is: Does the reverse vagal maneuver restore normal heart rhythm more often than the modified Valsalva maneuver before rescue treatment is needed? Researchers randomly assign participants to one of the two maneuvers. Participants assigned to the modified Valsalva maneuver sit in a partly upright position. They blow into a 10-mL syringe for 15 seconds with enough force to move the plunger. They then lie flat while their legs are raised for 15 seconds. Participants assigned to the reverse vagal maneuver sit upright and breathe out normally. They then close their nose and mouth and try to breathe in forcefully for 15 seconds. All participants have an ECG before the maneuver and continuous heart rhythm monitoring. If normal rhythm is not restored, the assigned maneuver may be repeated up to three times. An ECG is recorded 45 seconds after each attempt. Participants receive standard rescue treatment if the assigned maneuver does not restore normal rhythm or if continuing becomes unsafe. Researchers also record first-attempt success, rescue medication, electrical cardioversion, return of the fast heartbeat, hospital disposition, unwanted effects, repeat emergency department visits, and catheter ablation during one year of follow-up.