TREATMENT OF OUT-OF-HOSPITAL SUPRAVENTRICULAR TACHYCARDIA - ADENOSINEVS VERAPAMIL

Objective: To compare the use of adenosine and the use of verapamil as out-of-hospital therapy for supraventricular tachycardia (SVT). Metho ds: A period of prospective adenosine use (March 1993 to February 1994 ) was compared with a historical control period of verapamil use (Marc h 1990 to February 1991) for SVT. Data were obtained for SVT patients treated in a metropolitan, fire-department-based paramedic system serv ing a population of approximately 1 million persons. Standard drug pro tocols were used and patient outcomes (i.e., conversion rates, complic ations, and recurrences) were monitored. Results: During the adenosine treatment period, 105 patients had SVT; 87 (83%) received adenosine, of whom 60 (69%) converted to a sinus rhythm (SR). Vagal maneuvers (VM ) resulted in restoration of SR in 8 patients (7.6%). Some patients re ceived adenosine for non-SVT rhythms. 7 sinus tachycardia, 18 atrial f ibrillation, 7 wide-complex tachycardia (WCT), and 2 ventricular tachy cardia; no non-SVT rhythm converted to SR and none of these patients e xperienced an adverse effect. Twenty-five patients were hemodynamicall y unstable (systolic blood pressure < 90 mm Hg), with 20 receiving dru g and 13 converting to SR; 8 patients required electrical cardioversio n. Four patients experienced adverse effects related to adenosine (che st pain, dyspnea, prolonged bradycardia, and ventricular tachycardia). In the verapamil period, 106 patients had SVT; 52 (49%) received vera pamil (p < 0.001. compared with the adenosine period), of whom 43 (88% ) converted to SR (p = 0.11). Two patients received verapamil for WCT; neither converted to SR and both experienced cardiovascular collapse. VM resulted in restoration of SR in 12 patients (11.0%) (p = 0.52). S ixteen patients were hemodynamically unstable, with 5 receiving drug ( p = 0.005) and 5 converting to SR; 9 patients required electrical card ioversion (p = 0.48). Four patients experienced adverse effects relate d to verapamil (hypotension, ventricular tachycardia, ventricular fibr illation). Recurrence of SVT was noted in 2 adenosine patients and 2 v erapamil patients in the out-of-hospital setting and in 23 adenosine p atients and 15 verapamil patients after ED arrival, necessitating addi tional therapy (p = 0.48 and 0.88, for recurrence rates and types of a dditional therapies, respectively). Hospital diagnoses, outcomes, and ED dispositions were similar for the 2 groups. Conclusion: Adenosine a nd verapamil were equally successful in converting out-of-hospital SVT in patients with similar etiologies responsible for the SVT. Recurren ce of SVT occurred at similar rates for the 2 medications. Rhythm misi dentification remains a common issue in out-of-hospital cardiac care i n this emergency medical services system.