January 1, 2012Open Access
Effects of myocardial fibrosis assessed by MRI on dynamic left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy: a retrospective database analysis
Key Result
Myocardial fibrosis assessed by MRI in patients with hypertrophic cardiomyopathy was inversely correlated with LVOT gradient variation during exercise (r=-0.243, p=0.034).
Study Design
Type
Observational (n=76)
Multicenter
No
Structured PICO
Does the extent of myocardial fibrosis assessed by MRI correlate with dynamic LVOT gradient during exercise in patients with HCM?
P
Population
76 patients with hypertrophic cardiomyopathy (HCM) and normal ejection fraction at rest, from a single Italian referral centre.
I
Intervention
Assessment of myocardial fibrosis by MRI late-gadolinium enhancement (LGE)
O
Outcome
Influence of myocardial fibrosis on left ventricular outflow tract (LVOT) gradient variation during exercisesurrogate
In patients with HCM and normal resting ejection fraction, greater myocardial fibrosis is associated with a blunted increase in dynamic LVOT gradient during exercise, likely reflecting reduced myocardial contractility recruitment.
Main Result
Effect estimate: r=-0.243
p-value: p=0.034
Abstract
Background While implications of myocardial fibrosis on left ventricular (LV) function at rest have been studied in hypertrophic cardiomyopathy (HCM), the pathophysiological consequences on dynamic LV outflow tract (LVOT) gradient have so far not been investigated in detail. Objective To evaluate the influence of myocardial fibrosis, detected by MRI as late-gadolinium enhancement (LGE), on LVOT gradient in HCM. Design Retrospective database analysis. Setting A single Italian cardiomyopathies referral centre. Patients Seventy-six HCM patients with normal ejection fraction at rest. Interventions Patients 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.