Abstract
The degree of A‐V block increased after intravenous administration of atropine in 10 nondigi‐talized patients with acute inferior myocnrdial infarction who had narrow QRS complexes during periods of 1:1 A‐V conduction. Short episodes of 3:1. 4:1 and 5:1 A‐V block were seen to emerge: (a) in 6 patients, directly from Wenckebach periods; (b) in 3 patients, from alternating Wenckebach periods; and (c) in 1 patient, from a 3:2 Wenckebach period which led to a short‐lived alternating Wenckebach period. Apparently, the predominance of the chronotropic effects on the sinus node over the dromotropic effects on the A‐V node led to a tachycardia‐dependent (more ischemic than vagail process, exposing or producing multi‐ (two, three or four) level block involving the A‐V node (and perhaps the His bundle). Subsequently, therapeutic pacing was instituted in 9/10 patients because they developed spontaneous symptomatic advanced A‐V block. Therefore, it is possible that the early effects of atropine identified a narrowly‐defined subset of patients in whom prophylactic pacing may be indicated. However, more studies are necessary to corroborate these assumptions, (PACE, Vol. 4, September‐October, 1981)
