The histologic basis of late gadolinium enhancement cardiovascular magnetic resonance in hypertrophic cardiomyopathy.

OBJECTIVES We sought to identify the histologic basis of myocardial late gadolinium enhancement cardiovascular magnetic resonance (CMR) in hypertrophic cardiomyopathy (HCM). BACKGROUND The histologic basis of late gadolinium CMR in patients with HCM is unknown. METHODS A 28-year-old male patient with HCM and heart failure underwent late gadolinium enhancement CMR and, 49 days later, heart transplantation. The explanted heart was examined histologically for the extent of collagen and disarray, and the results were compared with a previous in vivo CMR scan. RESULTS Overall, 19% of the myocardium was collagen, but the amount per segment varied widely (SD +/- 19, range 0% to 71%). Both disarray and collagen were more likely to be found in the mesocardium than in the endo- or epicardium. There was a significant relationship between the extent of late gadolinium enhancement and collagen (r = 0.7, p < 0.0001) but not myocardial disarray (p = 0.58). Segments containing >15% collagen were more likely to have late gadolinium enhancement. Regional wall motion was inversely related to the extent of myocardial collagen and late gadolinium enhancement but not disarray (p = 0.0003, 0.04, and NS, respectively). CONCLUSIONS In this patient with HCM and heart failure, regions of myocardial late gadolinium enhancement by CMR represented regions of increased myocardial collagen but not disarray.