Although clinical practice may differ, vagal maneuvers are still the first step in attempting to convert supraventricular tachycardia (SVT) to sinus rhythm prior to adenosine. The reason why they are rarely attempted is because of relatively low (5-20%) success rates.
A recent study published in The Lancet describes a method of Valsalva maneuver which has improved success rates significantly. In this study (the REVERT trial), 433 patients presenting with SVT (AVNRT or undetermined narrow complex tachycardia) were randomized to either performing their modified Valsalva or the standard Valsalva maneuver. Atrial fibrillation/flutter were excluded from the study.
The standard maneuver involved having the patient sit at 45 degree angle in the stretcher and to blow into a standard manual manometer tube at a pressure of 40mmHg for 15 seconds while on a cardiac monitor. The modified maneuver proceeded exactly the same as the standard maneuver, except after the patient’s Valsalva maneuver was completed patients were placed flat and their legs were raised at 45 degrees for an additional 15 seconds. This was designed to increased venous return during the relaxation phase of the vagal maneuver. Cardiac rhythms were checked 60 seconds later.
The results of the trial were positive. In the control group, only 17% converted to sinus rhythm. In the intervention group, 43% converted to sinus rhythm. As a result, significantly less adenosine was given in the intervention group. No serious adverse events were reported in either group, although the modified maneuver group did experience more non-serious adverse events than the control group (9 vs 21 including sinus tachycardia, PVCs, musculoskeletal pain, headache, shortness of breath). 86% patients were found to have AVNRT and 6-7% patients were noted to have undetermined narrow complex tachycardia. Of note, 6% of patients were found to have atrial flutter during their management, presumably because AF with 2:1 conduction is difficult to distinguish from AVNRT in the emergency department.
The researchers go as far as to suggest that their modified Valsalva should be used a standard approach to SVT vagal maneuvers given the significant increase in conversion success rates and lack of apparent risk or cost involved.
For more information and a video showing the manometry setup and modified Valsalva maneuver check out http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(15)61485-4/abstract (open access)
Appelboam A et al. Postural modification to the standard Valsalva manoeuvre for emergency treatment of supraventricular tachycardias (REVERT): a randomised controlled trial. Lancet 2015. PMID 26314489