Supraventricular tachycardia: back to basics

In The Lancet, Andrew Appelboam and colleagues present the fi ndings of a simple but clinically relevant investigation of a safe and non-invasive treatment for patients with stable supraventricular tachycardia who present to emergency departments. This topic is important because patients with supraventricular tachycardia are common, often recurrent, emergency department attenders, and can require critical care interventions. A Cochrane review did not fi nd suffi cient evidence to support or refute the eff ectiveness of the Valsalva manoeuvre to end supraventricular tachycardia. The study by Appelboam and colleagues adds signifi cantly to the evidence base for the Valsalva manoeuvre. 214 patients were randomly assigned to each of two groups, treated with a standard semi-recumbent Valsalva manoeuvre or a modifi ed manoeuvre (done semi-recumbent with supine repositioning and passive leg raise after the Valsalva strain). In terms of the primary endpoint, return to sinus rhythm 1 min after the intervention, 93 (43%) of 214 participants assigned to the modifi ed Valsalva manoeuvre group achieved sinus rhythm, compared with 37 (17%) of 214 participants in the standard Valsalva manoeuvre group (adjusted odds ratio 3·7 [95% CI 2·3–5·8]). Whenever a new potential standard of care is proposed, its risks and benefi ts must be considered. The principle of never causing harm to patients is enshrined in the Hippocratic oath and is a concept increasingly challenged by both modern medicine and societal expectations. Although more observations are necessary, the ease and safety of the modifi ed Valsalva manoeuvre described by Appelboam and co-workers suggest that this procedure could rapidly be incorporated into standard practice. The Valsalva manoeuvre is well known, but the technique used is variable. By using a standardised implementation of 40 mm Hg pressure, followed by supine positioning and leg elevation, Appelboam and colleagues have created a minimally invasive, straightforward procedure with which almost 50% of patients can achieve cardioversion. Blowing into a 10 mL syringe with suffi cient force to move the plunger, as described by Smith and Boyle, will probably generate a similar pressure to that used by Appelboam and colleagues. There is no suggestion that the modifi ed Valsalva manoeuvre will not be as eff ective outside hospital, although Appelboam and co-workers did not test this specifi cally. Thus, the technique might enable patients to avoid admission to hospital. Even when unsuccessful, it is unlikely to cause harm or signifi cantly delay transfer to a medical facility. In fact, when the Valsalva manoeuvre fails, continued symptoms would justify presentation to an emergency department for more aggressive interventions, as occurs now in most cases. Although the accompanying study is too small to be absolutely certain of safety, there is no sign of increased risk of adverse events from attempting the modifi ed Valsalva manoeuvre (there were no serious adverse events), and, because the attempt at self-cardioversion would take less than 30 s, it is unlikely to signifi cantly delay seeking a higher level of care. Compared with the other options available to treat supraventricular tachycardia, the advantage of the Valsalva manoeuvre, regardless of being at home or in hospital, is that it helps to identify a population in whom aggressive treatment is justifi ed. Adenosine is often used, but it is expensive and unpleasant for the patient, and most clinicians would prefer to avoid it if possible. Other treatments such as calcium channel blockers, β blockers, or even electrical cardioversion, have a small but important rate of adverse events. The modifi ed Valsalva manoeuvre seems to be easy, inexpensive, non-invasive, and reproducible (162 diff erent clinicians did the manoeuvre in Appelboam and colleagues’ study); thus, an attempt by all patients before invasive treatment seems a reasonable part of standard of care.