The quality of evidence is downgraded by study limitations (lack of/unclear allocation concealment and blinding) and by imprecise results (few patients).
A Cochrane review [Abstract] 1 included 3 studies with a total of 316 subjects. The studies compared the effectiveness of Valsalva manoeuvre (VM) in reverting SVT with that of other vagal manoeuvres in a cross-over design. Only those study results identifying the effectiveness of the VM for SVT reversion were included in this review, whilst reported comparisons of effectiveness of VM with other vagal manoeuvres (such as Carotid Sinus Massage or Dive Reflex) within included studies were excluded. In two laboratory studies participants had ceased all medications prior to study participation. One study was on patients at a hospital emergency department due to an episode of SVT and these patients were not controlled for medications or other factors prior to intervention. Each study included application of the VM between one and three times to achieve effect.
In the two laboratory studies 46% and 54% of the patients reversed to sinus rhythm after VM, whilst the hospital study demonstrated reversion success of 19%. This discrepancy may be due to different type of SVT (induced SVT versus spontaneous episodic SVT), and participant factors such as medications and comorbidities. Adverse effects were either not described in enough detail or not reported at all in the studies.
An RCT (n=433) 2 conducted at emergency departments in England randomly allocated adults presenting with SVT to undergo a modified Valsalva manoeuvre (done semi-recumbent with supine repositioning and passive leg raise immediately after the Valsalva strain), or a standard semi-recumbent Valsalva manoeuvre. 17% (37/214) of participants assigned to standard Valsalva manoeuvre achieved sinus rhythm compared with 43% (93/214) in the modified Valsalva manoeuvre group (adjusted OR 3.7, 95% CI 2.3 to 5.8). No serious adverse events were recorded.
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