Acute myocardial infarction complicated by hemodynamically unstable bradyarrhythmia: Prehospital and ED treatment with atropine

The purpose of this study was to investigate the therapeutic response to at ropine of patients experiencing hemodynamically compromising bradyarrhythmi a related to acute myocardial infarction (AMI) in the prehospital(PH) setti ng and the therapeutic impact of the PH response to atropine on further Eme rgency Department (ED) care. In addition, the prevalence of AMI in patients presenting with atrioventricular block (AVB) is noted. Retrospective revie w of PH, emergency department (ED), and hospital records. PH patients, with hemodynamically compromising bradycardia or AVE with evidence of spontaneo us circulation, who received atropine as delivered by emergency medical ser vices (EMS) personnel, were used. Urban/suburban fire department-based emer gency medical services (EMS) system with on-line medical control serving a population of approximately 1.6 million persons. Hemodynamic instability wa s defined as the presence of any of the following: ischemic chest pain, dys pnea, syncope, altered mental status, and systolic blood pressure less than 90 mm Hg. Bradycardia was defined as sinus bradycardia, junctional bradyca rdia, or idioventricular bradycardia (grouped as bradycardia), whereas AVE included first-, second (types I and Il), or third-degree (grouped as AVE). The response that occurred within 1 minute of atropine dosing was recorded as none, partial, complete, or adverse. Comparisons were made between pati ents with AMI and non-AMI hospital discharge diagnoses. The diagnosis of AM I was confirmed by abnormal elevations in creatinine phosphokinase MB fract ion. One hundred seventy-two patients meeting entry criteria were identifie d. Of these, 131 (76.1%) had complete PH, ED, and hospital records and were used for data analysis. Forty-five patients (34.3%) had a primary hospital discharge diagnosis of AMI; the remaining patients had a non-AMI discharge diagnosis. AMI patients were significantly younger (67 +/- 12 V 73 +/- 13 years, P =.025), were less likely to have a history of heart disease (35.5% v54.7%, P =.038), and were more likely to present with chest pain (68.9% v 24.4%, P <.001) or hypotension (60% v37.2%, P =.013) compared with non-AMI patients. Forty-five of 131 patients presented with AVE, of which 25 had a hospital discharge diagnosis of AMI (55.6%). The mean time from first dose of atropine to ED arrival and the total dose of atropine received in the PH setting did not differ between AMI and non-AMI groups (15.2 +/- 7.7 v 16.2 +/- 8.7 minutes, P =.5; and 0.9 +/- 0.49 v 1.0 +/- 0.58 mg, P=.25). The li kelihood of achieving normal sinus rhythm in the PH setting did not differ between AMI and non AMI groups (40% v 18.6%, P =.07). Ho differences were f ound between AMI and non AMI groups in the amount of additional atropine gi ven (1.2 +/- 0.58 v 1.3 +/- 1.1 mg, P=.58) or the use of other resuscitativ e therapies after ED arrival (isoproterenol, 13.3% v12.8%, P =.93; dopamine , 28.9% v26.7% P =.79; transcutaneous pacing, 26.7% v 26.7%, P=.99; transve nous pacing, 8.9% v5.8%, P =.51), with the exception of thrombolytic therap y (24.4% v 0%, P<.001) and cardiac catheterization (22.2% v 3.4%, P=.001). Despite a tack of significant difference in achieving a normal sinus rhythm in the prehospital or ED setting, AMI patients were more likely to achieve a normal sinus rhythm over the total course of PH and ED care than non-AMI patients (44.4% v 24.4%, P=.019). Hemodynamically unstable (by ACLS criter ion) AVE presenting in the PH setting is associated with a hospital diagnos is of AMI in most (55.6%) patients in this study. AMI patients with hemodynamically unstable AVB or bradycardia are no more l ikely to respond to atropine therapy in the PH setting than patients with n on-AMI hospital diagnoses. Finally, although there is no difference in the treatment of compromising AVE or bradycardia received by AMI versus non-AMI patients in the PH or ED setting, AMI patients are more likely to achieve a normal sinus rhythm over the total course of care than non AMI patients.( Am J Emerg Med 1999;17:647 652. Copyright (C) 1999 by W.B. Saunders Company ).