Effects of myocardial fibrosis assessed by MRI on dynamic left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy: A retrospective database analysis

Seventy-six HCM patients with normal ejection fraction at rest underwent cardiac MR and performed bicycle exercise echocardiogram within a month. Results: LGE was present in 54 patients (71%), ranging from 0.2% to 32.4% of LV mass. There was a weak correlation between the amount of fibrosis and LVOT gradient variation during exercise in the overall population (r=−0.243, p=0.034) and a stronger correlation in patients with obstructive HCM at rest (r=−0.524, p=0.021). Patients with an LVOT gradient increase ≥50 mm Hg during exercise had a significantly lesser extent of fibrosis than those with an increase <50 mm Hg (0.7% (IQR 0–2.4) vs 3.2% (IQR 0.2–7.4), p=0.006). The extent of fibrosis was significantly lower among the highest quartiles of LVOT gradient increase (p=0.009). Conclusions: In patients with HCM and normal ejection fraction at rest, myocardial fibrosis was associated with a lower increase in LVOT gradient during exercise, probably due to a lesser degree of myocardial contractility recruitment. This negative association was more evident in patients with an obstructive form at rest.