Extent of CAD in dilated cardiomyopathy
When accounted for moderate CAD, our study reveals that at least 53% of the NICM cohort, with known nonischemic triggers, would be reclassified as mixed CMP. This cohort accounts to 30.6% of the total cohort of cardiomyopathies in this study. Cardiomyopathies with overlapping ischemic and nonischemic aetiologies is not uncommon in clinical practice.10 In a histopathological study on hearts excised at transplantation in patients diagnosed with idiopathic DCM, coronary atherosclerosis was diagnosed in 65.5% of the hearts with 43.6% showing moderate to severe lesions.12
In our study, nearly 77% of the mixed CMP patients had moderate CAD in more than one epicardial vessel and the majority had double vessel involvement. Concomitant CAD in DCM has been studied previously; however, they have been largely on idiopathic DCM. In addition, the results of prognosis reported in these studies are contradictory. In a study on idiopathic DCM patients, CAD burden had significant correlation with major adverse cardiovascular events.7 Yet another large-scale study in over 12,000 heart failure patients had also shown that the prognosis in nonobstructive CAD (<70% stenosis) is worse than in heart failure with no CAD.8 However, a few other studies did not show differences in survival between idiopathic DCM with moderate CAD and no CAD.3,6 Our study is different from the above studies in that it reveals poor prognosis in patients with implanted defibrillators and DCM secondary to definite nonischemic triggers and with concomitant CAD (\(\geq\) 50% to < 70% stenosis). This subset has been largely excluded from the previous studies of DCM with coexisting CAD.