The effect of atropine on cardiac arrhythmias and conduction. Part II

The effects of atropine on various components of the specialized conduction system of the heart and the myocardium itself are reviewed. These actions are sometimes unpredictable or paradoxical, depending on the component showing the dominant effect and the health of the entire system. Atropine is best known for its chronotropic effect. Improved sinoatrial conduction has been demonstrated but the effect on the refractoriness of atrial muscle is unsettled. Atropine stimulates the atrioventricular (A-V) junctional pacemaker and facilitates conduction through the A-V node. The response of the subjunctional portion of the specialized conduction system to the drug is unpredictable and controversial in some respects. Atropine is useful in the diagnosis of sinus node dysfunction, in the evaluation of coronary artery disease during atrial pacing, and in attempting to produce normal conduction in patients with the Wolff-Parkinson-White Syndrome. Its principal therapeutic application is in correcting the hypotension-bradycardia syndrome occurring during acute myocardial infarction. Atropine may also cause arrhythmias, including atrial fibrillation, A-V dissociation, ventricular tachycardia, and ventricular fibrillation. The clinical settings in which atropine may be arrhythmogenic are discussed.