EFFECT OF AMINOPHYLLINE IN PATIENTS WITH ATROPINE-RESISTANT LATE ADVANCED ATRIOVENTRICULAR-BLOCK DURING ACUTE INFERIOR MYOCARDIAL-INFARCTION

Background: Advanced atrioventricular (AV) block is a frequent complic ation in patients with acute inferior myocardial infarction (AIMI). Th is conduction abnormality is associated with narrow QRS complex in con ducted or junctional escape beats, suggesting that the site of block i s the AV node; however, its pathophysiology has not been properly esta blished. Hypothesis: This study investigated the effect of aminophylli ne in eight patients (5 men, 3 women, age range 51 to 78 years, mean 6 7.5 +/- 8.8 years) with atropine-resistant late advanced AV block duri ng AIMI. Methods: Advanced AV block was late in appearance in all pati ents, starting 2 to 5 days after AIMI, and consisted of second-degree Mobitz II type in two patients and of complete AV block in six patient s; all patients had narrow QRS complexes. Before aminophylline adminis tration, all patients had a temporary pacemaker installed which was sw itched off throughout the study. They were given intravenous atropine (1 mg) that was found to be ineffective. One-half h after atropine, th e first aminophylline injection (240 mg) was given intravenously over 10 min. One h following the first injection, a second aminophylline do se (240 mg) was administered. Electrocardiographic rhythm strips were obtained before and after drug administration, and the type of AV bloc k and atrial and ventricular rate were noted. Results: Aminophylline r estored 1:1 conduction with first-degree AV block in six patients, Mob itz I AV block in one patient, and normal sinus rhythm in one patient. Mean atrial and ventricular rates before aminophylline were 104 +/- 1 6 beats/min and 57 +/- 9 beats/min, respectively, and after drug admin istration 95 +/- 25 beats/min and 89 +/- 17 beats/min, respectively, ( p = 0.012). Conclusion: These results indicate that aminophylline impr oves AV conduction in atropine-resistant late advanced AV block compli cating AIMI.