SVT is a narrow complex tachycardia commonly seen in the emergency department. In hemodynamically stable patients the first-line treatment is vagal stimulation, usually the Valsalva maneuver. However, success rates for this approach are low, with data citing success rates of around 5-25%. The modified Valsalva maneuver was recently developed and trialed with successful conversions in 43% of patients, compared to 17% with the standard Valsalva maneuver. No serious adverse outcomes were described. This is a safe, simple, and low-resource technique that can be taught to emergency physicians, prehospital care providers, and even to patients themselves. Use of this technique can minimize the use of costlier, resource-heavy, and uncomfortable treatments, such as adenosine or electrical cardioversion.
So, what exactly is the modified Valsalva maneuver?
The standard Valsalva maneuver is usually performed by having patients “bear down” to stimulate the Vagus nerve. This can be done either by instructing them to push like they’re having a bowel movement or having them blow into a syringe with the plunger in place. The modified Valsalva maneuver more precisely describes this procedure and adds a passive leg raise. This is designed to stimulate vagal tone through a different mechanism (baroreflex activation). To remember the steps of the modified Valsalva maneuver just think of “SVT”:
S = Strain (just enough to make the plunger of a 10cc syringe move, equal to 40mmHg)
V = Venous return (supine with passive leg raise)
T = Time (15s at each stage)
Paroxysmal supraventricular tachycardia (PSVT) is treated with vagal maneuvers, including the Valsalva maneuver, followed by medication or electrical cardioversion if vagal maneuvers are unsuccessful. Turkish investigators performed a randomized, controlled trial comparing the standard Valsalva maneuver with a previously described modified Valsalva maneuver in 56 patients with PSVT (NEJM JW Emerg Med Oct 2015and Lancet 2015; 386:1747.)
In the standard group (control), the seated patient was asked to blow into the tip of a 10-mL syringe for 15 seconds, hard enough to move the plunger. In the modified group (experimental), the same procedure was used but was followed by quickly bringing the patient to a supine position and then lifting the patient’s legs to a 45-degree angle. The procedure was repeated three times, and if unsuccessful, was followed by other interventions as needed. Sinus rhythm was restored in 11% of the standard group and 43% of the modified group after the vagal maneuver, a significant difference of 32%. Adverse events were mild and rare, limited to dizziness and dyspnea, each occurring once in each group.