Can you have a heart attack even with no blockage?

Heart attack: Some heart attacks are triggered by spasm of a heart artery, this is a blockage but not the same as the usual plaque/clot pathophysiology.

Yes: But very unusual. Congenital anomaly with atypical origin and ischemia. Dissection of aorta with coronary obstruction by flap. Coronary embolism with atrial fibrillation, or septal defect and paradoxical embolus. Cocaine, other cause of hypoxia ( and also usually damages brain. Trauma with tear of heart or stab etc whew that' s enough bad news!