Initial coronary air embolus in the differential diagnosis of coronary artery spasm

Angiographic and electrocardiographic manifestations of initial coronary air embolism were seen in 4 patients and in a dog. All 4 patients had angina pectoris, 2 had ST elevation, 1 patient had ST depression and 1 had no electrocardiographic change after the air embolus. Although the initial diagnosis in these 4 patients was coronary artery spasm, a subsequent ergonovine test response for coronary artery spasm was negative in the 3 patients in whom it was performed. In a dog, initial injection of air in a coronary artery produced ST-segment elevation and delayed clearance of contrast material. The angiographic appearance of initial air embolus was similar in the 4 patients and in the dog. The leading edge of contrast material that followed an air embolus stopped abruptly, appeared hazy and blunt, and pulsated back and forth. The air embolus produced temporary cessation of flow in the main artery and its branches. Initial injection of air during coronary arteriography mimics coronary artery spasm by producing a syndrome characterized by angina, ischemic changes on the electrocardiogram, and delayed flow of contrast material. An initial air embolus may be differentiated from true coronary spasm by several distinctive angiographic features.