37 patients with chaotic atrial mechanism (CAM) were identified, treated sequentially with corrective anti-arrhythmic agents according to protocol, and analyzed. 30 patients with CAM had chronic obstructive lung disease, and 14 patients developed CAM in association with acute CHF. In five patients, CAM resulted from acute pulmonary embolism. Excessive use of isoproterenol was responsible for CAM in nine patients, while in four digitalis toxicity was the underlying agent. Five patients suffered from space-occupying lesions of the posterior atrial walls.Management was directed toward relief of the underlying responsible illness: 6 of 9 patients with isoproterenol overdose, and 3 of 4 patients with digitalis excess responded to removal of the offending agents. Quinidine and propranolol in combination appeared most efficacious in those patients not responding to control of the immediate underlying event: 10 of 20 of such patients benefited.Distention of either the right or left atrial walls, drug-induced automaticity, invasion of the atria, and acute ischemia or chronic diffuse fibrotic atrial disease accounted for the cases. These are not dissimilar to the currently accepted responsible events for pathologic ventricular automaticity.

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