Correlation of vulnerable coronary plaques to sudden cardiac events. Lessons from a myocardial infarction-prone animal model (the WHHLMI rabbit).

It is generally considered that coronary rupture-prone plaques play an important role in the onset of sudden cardiac events (acute coronary syndromes/sudden cardiac death). However, it is not clear which factors or stimuli are required to trigger plaque rupture and whether coronary plaques without occlusive thrombi can cause sudden cardiac events. To address these issues, recently, we developed a rabbit model of spontaneous myocardial infarction [the Watanabe heritable hyperlipidemic (WHHL) MI rabbit] and found that this model possessed several types of coronary plaques that are possibly correlated to sudden cardiac events. Although many of the coronary plaques of the WHHLMI rabbits appeared histologically to be rupture-prone in nature, true rupture was detected only in the few animals that died of MI. In addition, no occlusive thrombus was detected in any WHHLMI rabbit. These findings suggest that some additional stimuli play a definitive role in causing disruption of rupture-prone plaques and thrombosis. Nearly-occluded plaques caused by a luminal macrophage accumulation are the most common feature of WHHLMI rabbits, suggesting that they are responsible for sudden cardiac events. The WHHLMI rabbit could be a useful model for studying the mechanism(s) of plaque rupture and thrombogenesis if plaque rupture/thrombus formation is induced in the rupture-prone plaques of WHHLMI rabbits by administration of additional triggering factors, and could provide a novel means for developing new therapies.