Extent of late gadolinium enhancement on cardiovascular magnetic resonance imaging and its relation to left ventricular longitudinal functional reserve during exercise in patients with hypertrophic cardiomyopathy

Background: The aim of this study was to investigate whether the extent of late gadolinium enhancement (LGE) on cardiovascular magnetic resonance imaging reflecting myocardial fibrosis correlates with left ventricular (LV) longitudinal function during exercise in hypertrophic cardiomyopathy (HCM). Methods and Results: Mitral annular velocities (E' and S') were measured on echocardiography at rest and during graded bicycle exercise (25W, 3-min increments) in 46 HCM patients (mean age, 53 years; 32 men). LV longitudinal diastolic and systolic functional reserve indices were calculated as ΔE'×E'_base and ΔS'×S'_base, where ΔE' and ΔS' are the changes in E' and S' from baseline to 50W of exercise, respectively. The patients were divided into 2 groups according to the extent of LGE (as "percentage of LV mass containing LGE": %LV with LGE; range, 0-37%; median, 6%): group 1 (n=23), %LV with LGE <6%, and group 2, %LV with LGE ≥6%. Baseline echocardiographic parameters were similar between the 2 groups, but changes in E' and S' during exercise were smaller in group 2 (ΔE': 2.8±1.8cm/s vs.1.5±1.0cm/s, P=0.007; ΔS': 2.2±1.2cm/s vs. 0.9±0.8cm/s, P<0.0001). LV functional reserve indices were also significantly lower in group 2 (ΔE'×E'_base: 12.8±7.7 vs. 5.5±3.4, P=0.001; ΔS'×S'_base: 12.6±7.4 vs. 4.7±4.5, P<0.0001). Conclusions: LV longitudinal function during exercise is influenced by the extent of LGE in HCM. Myocardial fibrosis may represent a pathologic substrate that determines LV functional reserve in patients with HCM.