OBJECTIVE: To evaluate the effect of changes to the pre-hospital management of patients with supraventricular tachycardia (SVT) following intervention with a revised Clinical Practice Guideline (CPG). The major CPG revisions were removal of verapamil, addition of adenosine and an emphasis on Valsalva manoeuvre. METHOD: We undertook a retrospective case study using data collected by paramedics. All adult patients attended by paramedics from the periods 14 February 2012 to 14 September 2012 (old CPG) and 14 February 2013 to 14 September 2013 (revised CPG) were included. Patients were excluded if SVT was not recorded during initial assessment on a hardcopy ECG. Management guided by the old and revised CPGs was compared: reversion effectiveness, elements of therapy associated with reversion effectiveness and adverse events. Logistic regression determined patient factors significantly associated with reversion. RESULTS: Patients were predominantly women, aged approximately 57 years old and most lived in the Victorian metropolitan region. Vagal manoeuvre use and effectiveness decreased in the post-intervention group. Fewer patients in the post-intervention group (141/420, 33.6 ) remained in SVT on arrival at hospital compared with the pre-intervention group (205/403, 50.8 ). Initial heart rate >170/min and longer scene time were 2.6 and 1.05 times more likely to result in reversion, respectively. CONCLUSION: The revised CPG improved pre-hospital SVT reversion success. This expansion of practice has not demonstrated improvements to utilisation or effectiveness of the Valsalva manoeuvre. Adenosine is effective and safe for pre-hospital use.