Three trials show this simple procedure increases converts SVT to NSR in up to 46% of patients.
Background: In patients with hemodynamically stable supraventricular tachycardia (SVT), vagal maneuvers are the traditional first step in management. The success rate of the Valsalva maneuver alone is documented at 5 to 20%. According to guidelines, the next option for patients, who still remain in SVT, is intravenous adenosine.
This option basically stops the heart (i.e asystole), even if for a few seconds, which causes patients to feel a sense of doom or like they are about to die. The modified Valsalva maneuver (mVm) helps increase venous return and vagal stimulation by laying patients supine and elevating their legs, which may increase the rate of conversion when added to the standard vagal maneuver (sVm).
We now have three trials that have evaluated the effectiveness of the mVm compared to sVm.[1 – 3] Two of these were multicenter in the UK and China, while the final one was a single center study performed in Turkey.3 All three trials measured the conversion to sinus rhythm after the sVm compared to the mVm in adult patients at varying time intervals.
A mVm is performed by placing a patient in a semi-recumbent position, having the patients produce 40mmHg of pressure for 15 to 20 seconds and then repositioning them in a supine position with a passive leg raise immediately after the Valsalva strain. From there, 40mmHg is measured by having the patient attempt to push a plunger of a 10cc empty syringe (≈40mmHg) or by blowing into a syringe connected to a sphygmomanometer.
Taking it to trial
The REVERT trial, which was the first trial published on the mVm, had 428 patients with hemodynamically stable SVT. Their primary outcome was return to normal sinus rhythm at one minute. This was achieved in 17% of patients with standard Valsalva and 43% of patients with the mVm (NNT = 3).
With the second trial, Chen et al. recruited 238 patients with hemodynamically stable SVT and had a primary outcome of conversion to sinus rhythm at 60 seconds. This was achieved in 16% of patients with sVm and 46% in patients with mVm (NNT = 3).
The final trial published by Ceylan et al. recruited 98 patients with hemodynamically stable SVT. Immediate cardioversion was achieved in 24.2% of patients with sVm and 43.7% of patients with mVm (NNT = 5). However, the primary outcome was sustained normal sinus rhythm at five minutes. This was achieved in 6.1% of patients in the sVm and 28.1% of patients in the mVm (NNT = 4.5).
There some major strengths in each of these three trials that should be pointed out. First, the most impressive thing is that there were zero serious adverse events. Next, the mVm is an easily reproducible intervention, with meaningful patient-oriented outcomes. Finally, the mVm costs nothing.
To be fair, the biggest limitation of these three trials is that treating clinicians could not be blinded and therefore could bias the results of these studies. Also, none of the trials are very large, which means in larger trials we may have had a regression to the mean showing that modified Valsalva is not as successful as shown in these studies.
Treatment of hemodynamically stable SVT has many different options. Vagal maneuvers are still considered first line therapy. With the use of the mVm, fewer patients will be required to have the sense of doom that adenosine produces. Finally, how many things in medicine are simple, cost zero dollars, are well tolerated by patients and have zero serious adverse events?
We now have three randomized clinical trials, although small, that show the superiority of the mVm compared to sVm in patients with hemodynamically stable SVT. This should be the first maneuver attempted to convert hemodynamically stable SVT.
- Appelboam A et al. Postural Modification to the Standard Valsalva Manoeuvre for Emergency Treatment of Supraventricular Tachycardias (REVERT): A Randomised Controlled Trial. Lancet 2015. [epub ahead of print] PMID: 26314489
- Chen C et al. A Multicenter Randomized Controlled Trial of a Modified Valsalva Maneuver for Cardioversion of Supraventricular Tachycardias. Am J Emerg Med 2019. PMID: 31422858
- Ceylan E et al. Initial and Sustained Response Effects of 3 Vagal Maneuvers in Supraventricular Tachycardia: A Randomized, Clinical Trial. JEM 2019. PMID: 31443919