This paper describes a retrospective study of supraventricular tachycardia (SVT) management in the pre-hospital setting of an Australian embulance service. Using patient data from the Victoria Ambulance Clinical Information System (VACIS), accuracy of rhythm recognition and the efficacy of differing treatment modalities in reverting SVT was examined; additional analysis examined patient characteristics, response data and adverse events (AE) related to treatment.
Despite a confusing inaccuracy in the abstract, where in the results section it states that ‘933 patients were enrolled, including 882 (94.5%) adults and 564 (60.5%) women’; a quick glance at the comprehensive results data in Table 1 reveals a total sample of 933; 882 adults (of which 564 were women) and 51 paediatric (defined as <18 years old).Furthermore, the reader should be aware that this study is conducted in a two-tier paramedic system, that of Victoria, Australia, which employs ALS paramedics and a more extensively trained mobile intensive care ambulance (MICA) cohort; it is notable that within their Clinical Practice Guidelines only MICA paramedics were authorised to provide specific treatment for patients presenting with SVT.
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The treatment modalities examined are mechanical —comprising the Valsalva manoeuvre (VM); pharmacological—consisting of the calcium channel blocker Verapamil and the sympathomimetic Aramine (Metaraminol), a potent α1 agonist that increases systemic blood pressure (Katzung et al, 2012); and electrical in the form of 70 joule DC synchronised cardioversion.
The flow diagram indicating inclusion criteria (Figure 2) in the paper is comprehensive; as are the results in Tables 1, 2 and 3, which provide the reader with additional contextual data.
The rhythm recognition rates for SVT of 96.7% (119/123) are impressive; indeed this has proved a particular challenge in the management of SVT in the past (O’Rourke et al, 2004). The results, however, should be examined against the backdrop that only 123 (13%) of rhythm strips were actually analysed for this study, of which four errors of interpretation were noted.
Smith G, Taylor D, Morgans A, Cameron P (2014) Prehospital management of supraventricular tachycardia in Victoria, Australia: Epidemiology and effectiveness of therapies. Emerg Med Australas26(4): 350–55
The results indicate 273/882 adult patients spontaneously reverted during paramedic care, while an additional 171 were successfully treated by paramedics; of the total 882 adults, 438 (49.7%) remained in SVT on ED arrival.
Similar efficacy was demonstrated for both Verapamil and Aramine at 86.8% (33/38) and 81.4% (35/43) respectively; while synchronised cardioversion was 100% successful, albeit on only four patients. Of perhaps equal interest is the success of the Valsalva manoeuvre (VM); discussed in the termination of SVT over a century ago (Cohn and Fraser, 1913) and in this study demonstrating a 27.7% (99/358) reversion rate; good efficacy when one considers the simplicity and safety of this intervention when performed correctly.
Overall the paper offers an interesting insight regarding the management of SVT in the pre-hospital setting, as the study indicates paramedics are thought likely to attend 80% of SVT patients as first contact clinicians. The study suggests good rhythm recognition and efficacy of the Valsalva manoeuvre when used by MICA paramedics; these skills are currently available to UK paramedics and may prompt readers to consider if they are using these therapies optimally.
Finally, readers may also be more familiar with Adenosine as the treatment modality of choice for SVT; something the paper alludes to, indicating that Adenosine has subsequently replaced Verapamil towards the end of 2013 for the treatment of SVT, hopefully more research will follow.