Sudden death has been described in a condition called bridging.6,7 In this entity, the left anterior descending coronary artery (very rarely the right coronary), instead of lying in the epicardial fat of the heart, dips down into the myocardium (Figure 3.2). Coronary angiography has demonstrated bridging in from 0.5 to 1.6% of individuals.7 In adults with hypertrophic cardiomyopathy, bridging occurs in 30-50% of individuals.7 In bridging, there is compression of the vessel during systole with either partial or complete occlusion of the lumen. Generally, this is a benign phenomenon, because nearly all coronary blood flow to the left ventricle occurs during diastole. With tachycardia, however, there is a shortening of diastolic perfusion. This may allow the systoli compression to become significant. This would explain the observation that sudden death in bridging is seen more often in association with exercise. Septal fibrosis from repeated systolic compression may occur. Death from bridging is rare.
A dissecting aneurysm of the coronary artery may be either secondary to extension of an aortic root dissection or primary and limited to the coronary artery. Primary dissecting aneurysms may be either spontaneous or due to trauma (e.g., chest trauma, coronary angiography). Spontaneous coronary artery dissection is a rare condition, usually presenting as sudden death.8-10 It consists of an intramural hematoma of the media of the vessel wall, which flattens and occludes the lumen, reducing blood flow (Figure 3.3). Communication with the lumen may occur. There may be a diffuse adventitial inflammatory reaction consisting mainly of eosinophils present. This is felt to be reactive and not related to causation. Most (80%) spontaneous dissecting aneurysms occur in females, particularly in the peripartum period. Three quarters of the cases involve the left anterior descending coronary artery. In men, dissection of the right coronary artery appears to be more frequent.10 Changes of cystic medial necrosis may be present.
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