Modified Valsava for SVT. REVERT trial.

Question:

Is the modified Valsava maneuver (supine positioning with leg elevation immediately after the maneuver) more effective than a standard Valsava maneuver?

Study design and participants:

  • Pragmatic randomized multicentre parallel group trial in 10 emergency departments.
  • Inclusion: patients >18 yo presenting with SVT
  • Exclusion: unstable patients with systolic blood pressure less than 90 mm Hg or an indication for immediate cardioversion and those in atrial fibrillation or fl utter. Other exclusion criteria were suspected atrial fl utter requiring a trial of adenosine, the presence of any contraindication to Valsalva manoeuvre (aortic stenosis, recent myocardial
    infarction, glaucoma, retinopathy), inability to performing a Valsalva manoeuvre, to lie flat, or have legs lifted (or any reason identifed by the patient as to why this manoeuvre would cause discomfort or pain), third trimester.

Intervention:

  • Valsava manuever strain to 40 mmHg sustained for 15s by forced expiration measurd by aneorid manometer.
  • Controlled valsava: patient remained in semi-recumbent position (45 degrees) for 60s
  • Modified valsava maneuver was done by lying patient supine and raising the leg for 45 degrees for 15s immediately at the end of the strain.
  • If initial attempt failed, participants were invited to undertake one more attempt at the allocated valsava maneuver.

Outcomes

  • Primary: sinus rhythm 1 min after Valsava
  • 2ndary: use of adenosine, use of any emergency treatment for SVT, need andreason for admission, length of time participants spend in ED and adverse events.

Results

  • 216 were randomized to standard maneuver and 217 to modified maneuver
  • No crossover and similar number of patients achieved the defined study strain (84% in standard vs 86% in modified)
  • 43% in modified group achieved primary outcome compared to 17% in standard group (NNT=3)
  • No serious adverse events happened. Non serious adverse events were more common in modified group, but not significantly so.

Discussion:

  • The only limitation is that physicians cannot be blinded to the treatment allocation, but since no drugs were given and the way to do the modified valsava was standardised, it didn’t really affect the results.
  • Modified Valsava maneuver is clearly better than standard approach in converting Valsava, with no more adverse events than the standard group.
  • For those who couldn’t measure the strain pressure of 40 mmHg in ED, blowing a 10 mL syringe to just move the plunger also generates the same pressure.

See this link:

Physiological basis of the modified Valsava maneuver

  • First phase of Valsava: CO slightly increases as the blood in pulmonary vessels and LV is squeezed out. Increase in intra-aortic pressure (IAP) causes bradycardia.
  • Second phase: CO decreases, IAP also decreases –> this causes compensatory tachycardia.
  • Third phase (when strain is released): Blood fills up the RV, IAP is still low as CO still remains low
  • Fourth phase: CO increases as blood from RV is now in LV. IAP becomes higher, inducing a compensatory bradycardia. This is the phase in which Valsava will terminate the SVT.

Rationale of modified Valsava

  • By increasing venous return during the third phase, more CO can be pumped out from LV in the fourth phase. A higher intra-aortic pressure will induce a lower HR.

Reference:

Andrew Appelboam, Adam Reuben, Clifford Mann, James Gagg, Paul Ewings, Andrew Barton, Trudie Lobban, Mark Dayer, Jane Vickery, Jonathan Benger. Postural modification to the standard Valsalva manoeuvre for emergency treatment of supraventricular tachycardias (REVERT): a randomised controlled trial. Lancet 2015.

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