Date of JC: 18/5/16
Paper: Postural Modification to the standard valsalva for the emergency treatment supraventricular tachycardia (REVERT): A randomised controlled trial.
Published: The Lancet 2015.
Your next patient in resus is a 20-year-old guy who’s self presented with feeling breathless and the symptom of his heart racing, he’s alert but looks worried. Vitals are RR of 18, SpO2 98 in air, HR 180 and BP 145/88. Clinical examination is unremarkable.
An ECG is taken which shows a regular narrow complex tachycardia. Have a look at this round-up of SVT subtypes from the guys over at Life in the Fast lane to hone those ECG skills….
Clinical question: Does a modified valsalva could improve conversion to normal sinus rhythm in these patients.
Population: Adult patients with SVT, excluding those who had hypotension or other indication for immediate cardioversion, atrial fibrillation or flutter.
Intervention: Modified valsalva: At the end of the ‘strain’ patient moved from recumbant to laid flat with legs elevated for 15 seconds.
Control: Standardised strain: 15 seconds of ‘blowing’ 40mmHG on a manometer.
Outcome: Primary outcome: Sinus rhythm at 1 minute post intervention. Secondary outcomes: Use of adenosine, admission to hospital, length of stay in ED, adverse outcome.
Generalisabity: For us, these patients are probably the same as ours. They’re all ED patients. The patients were recruited across the south West of England, which is similar to Yorkshire – hills, fresh air, occasional arrhythmia – although us Yorkshire folk (adopted and native) prefer brown beer and Henderson’s Relish to cider and samphire; we’re pretty much the same…..I think.
Design: Good attempts to maintain allocation concealment with numbered envelopes, randomisation in permuted blocks and whilst the clinicians and patients couldn’t be blinded, the ECG activity of each patient was reviewed by a blinded independent cardiologist.
The study had 80% power to detect a 12% difference which was deemed clinically significant. Have a read of this from St Emlyns on power calculations in clinical trials.
They recruited the patients required for the power calculation with 214 patients included in the intention to treat analysis in each group.
Primary outcome: 17% (37/214) control arm Vs 43% (93/214)Intervention arm
This gives a an absolute difference of 26% and therefore an NNT of 1/0.26 = 4.
Sadly no 95% confidence intervals are reported for these figures.
The adverse events recorded were short-lived and no patient harm resulted.
There was no significant increase in ED length of stay by utilising the modified valsalva.
The discharge from ED rate seemed low to us: 68% vs 63% – I contacted Andy Applebaum (lead Author) about this and he told me that patients were admitted for reasons of comoribidty and concurrent disease.
No mention is made as to the spread of SVT sub type amongst the groups and this could be a potential confounder, but this is probably not significant.
Whilst the standardised valsalva looks great and certainly reduces bias from the treating clinician we were worried about how we could ensure there was no cross contamination of saliva etc – again a small theoretical risk but something we think about with anaesthetic circuits by using a filter in every patient we intubate. Andy again had addressed this in our emails – he tells me that the volume required to get to the pressure of 40 was low, and that they used 90cm of fresh oxygen tubing for every patient hence no saliva/exhaled badness was thought to reach the manometer.
All in this is a really well conducted RCT in patients similar to ours, with a significant treatment effect, an NNT of 4 and no significant patient harm events. We have some minor concerns with the above mentioned points but group consensus is that we’ll be REVERTing the next SVT we see……..
A link to the One minute Wonder for this paper can be found here.
Keep your eyes (well ears) open for the audio summary coming soon.
Keep fighting the good fight
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