THEOPHYLLINE FOR THE TREATMENT OF ATRIOVENTRICULAR BLOCK AFTER MYOCARDIAL INFARCTION.

Bertolet BD, et al. Ann Intern Med 1995 Oct 1;123(7):509-11.

OBJECTIVE: To show that second- or third-degree atrioventricular block occurring as an early complication of acute inferior myocardial infarction is mediated by adenosine.

SETTING: Cardiac care unit.

DESIGN: Uncontrolled, observational, hypothesis-driven study.

PATIENTS: Patients who developed clinically significant atrioventricular nodal blockade within 4 hours of admission for acute inferior myocardial infarction.

INTERVENTION: Theophylline, 100 mg/min intravenously to a maximum of 250 mg.

MEASUREMENTS: Continuous multilead electrocardiographic monitoring before and after administration of theophylline.

RESULTS: During a 6-month period, eight men who had had acute inferior myocardial infarction developed clinically significant atrioventricular block. Three had third-degree block, and five had high-grade second-degree block. In all patients, 1:1 atrioventricular nodal conduction was restored and normal sinus rhythm reappeared within 3 minutes of the administration of theophylline. All patients remained free of arrhythmia for at least 24 hours.

CONCLUSIONS: Adenosine produced by the ischemic myocardium may induce atrioventricular nodal block. In our patients, atrioventricular nodal block was resistant to conventional therapy such as atropine, but it responded to the adenosine antagonist theophylline.

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

Altun A, Kirdar C, Ozbay G. Clin Cardiol 1998 Oct;21(10):759-62

BACKGROUND: Advanced atrioventricular (AV) block is a frequent complication in patients with acute inferior myocardial infarction (AIMI). This conduction abnormality is associated with narrow QRS complex in conducted or junctional escape beats, suggesting that the site of block is the AV node; however, its pathophysiology has not been properly established.

HYPOTHESIS: This study investigated the effect of aminophylline in eight patients (5 men, 3 women, age range 51 to 78 years, mean 67.5 8.8 years) with atropine-resistant late advanced AV block during AIMI.

METHODS: Advanced AV block was late in appearance in all patients, 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 patients; all patients had narrow QRS complexes. Before aminophylline administration, all patients had a temporary pacemaker installed which was switched off throughout the study. They were given intravenous atropine (1 mg) that was found to be ineffective. One-half h after atropine, the first aminophylline injection (240 mg) was given intravenously over 10 min. One h following the first injection, a second aminophylline dose (240 mg) was administered. Electrocardiographic rhythm strips were obtained before and after drug administration, and the type of AV block and atrial and ventricular rate were noted.

RESULTS: Aminophylline restored 1:1 conduction with first-degree AV block in six patients, Mobitz I AV block in one patient, and normal sinus rhythm in one patient. Mean atrial and ventricular rates before aminophylline were 104 16 beats/min and 57 9 beats/min, respectively, and after drug administration 95 25 beats/min and 89 17 beats/min, respectively, (p = 0.012).

CONCLUSION: These results indicate that aminophylline improves AV conduction in atropine-resistant late advanced AV block complicating AIMI.