Alternating Wenckebach periods in acute inferior myocardial infarction: clinical, electrocardiographic, and therapeutic characterization.

We report on twelve patients with alternating Wenckebach periods (AWP) occurring during an acute inferior myocardial infarction (AIMI). There were nine males and three females, with a mean age of 61 years (range, 43 to 75). AWP appeared during the first 48 hours of the AIMI in 10 patients and on the fourth day of hospitalization in two patients. AWP occurred spontaneously in nine patients and following the administration of atropine in the remaining three patients. Mean systolic blood pressure significantly decreased during AWP as compared to the period preceding or following the bradyarrhythmia (93 +/- 42 mmHg vs 123 +/- 37 mmHg, p less than 0.02). Killip functional class was significantly higher during AWP as compared to the period preceding or following the bradyarrhythmia (2.1 +/- 1.2 vs 1.5 +/- 0.8, p less than 0.02). Pacemaker therapy was initiated prophylactically in two patients, because of syncope in six, because of hemodynamic deterioration in two, and for syncope and hemodynamic deterioration in two. Three patients died in cardiogenic shock despite pacemaker therapy. No evidence of right ventricular infarction was seen in the patients. Atropine administration during AWP significantly increased the sinus rate and significantly decreased the ventricular rates and the systolic blood pressure. In addition, three patients developed long bouts of paroxysmal AV block. Isoproterenol administration improved AV conduction in one patient, caused no change in two patients and induced non-sustained ventricular tachycardia in three patients. In conclusion, AWP occurring during AIMI is a symptomatic bradyarrhythmia associated with hemodynamic deterioration.(ABSTRACT TRUNCATED AT 250 WORDS)