Shruti Sonni, MD

This large study by Sirimarco et al. aimed to examine the association between carotid atherosclerosis, history of atherothrombotic events (including cerebral, cardiac and peripheral vascular disease) and coronary events. 23 364 patients from the Reduction of Atherothrombosis for Continued Health (REACH) Registry with multiple cerebrovascular risk factors or established atherothrombotic events with information regarding carotid atherosclerosis were analyzed. Primary outcome was cardiovascular death, myocardial infarction (MI), or coronary hospitalization. Patients considered to have carotid atherosclerosis were those who had any evidence of carotid plaque, >70% carotid stenosis or history of carotid revascularization. The authors found that the risk of coronary events were 23.2% and 19% in subjects with and without carotid atherosclerosis respectively (an increase of 22%), and risk was increased by 52% for non-fatal MI specifically, leading to a conclusion that carotid atherosclerosis was an independent predictor of coronary events. 

The importance of this study is that, unlike prior studies, it used data from a large international registry of stable outpatients (though not community-based) to evaluate the risk of coronary events, and followed the subjects for a period of 4 years. The authors demonstrated that carotid atherosclerosis predicted risk of coronary events in patients with a history of vascular disease regardless of arterial bed affected- cerebral, cardiac or peripheral. Presence of carotid disease can improve the risk stratification for occurrence of cardiovascular disease, and is likely indicative of coronary artery disease severity. This supports the suggestion that the underlying atherogenic mechanism in carotid and coronary plaque formation are similar, maybe sharing a common inflammatory process. 

One of the limitations of this study however, as acknowledged by the authors, lies in the lack of standard evaluation of the carotid plaques. This study does not answer what the degree of stenosis or plaque amount and morphology were that predisposed to coronary events. The question arises, if carotid atherosclerosis is such a strong predictor of coronary events, can the converse also be assumed to be true? That is, is the incidence of coronary events a strong predictor of carotid atherosclerosis and a stroke risk factor that should be routinely screened for? Although the results are very insightful, the clinical application of this study is unclear. The subjects included in this analysis were those that were likely being treated with maximum medical risk therapy as a result of their prior atherothrombotic disease. Hence, it is unclear what the next diagnostic or therapeutic step in preventing future coronary events should be.