Cardiomyopathy
Spectrum and Clinical Significance of Systolic Function and Myocardial Fibrosis Assessed by Cardiovascular Magnetic Resonance in Hypertrophic Cardiomyopathy

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In hypertrophic cardiomyopathy (HCM), the clinical significance attributable to the broad range of left ventricular (LV) systolic function, assessed as the ejection fraction (EF), is incompletely resolved. We evaluated the EF using cardiovascular magnetic resonance (CMR) imaging in a large cohort of patients with HCM with respect to the clinical status and evidence of left ventricular remodeling with late gadolinium enhancement (LGE). CMR imaging was performed in 310 consecutive patients, aged 42 ± 17 years. The EF in patients with HCM was 71 ± 10% (range 28% to 89%), exceeding that of 606 healthy controls without cardiovascular disease (66 ± 5%, p <0.001). LGE reflecting LV remodeling showed an independent, inverse relation to the EF (B-0.69, 95% confidence interval −0.86 to −0.52; p <0.001) and was greatest in patients with an EF <50%, in whom it constituted a median value of 29% of the LV volume (interquartile range 16% to 40%). However, the substantial subgroup with low-normal EF values of 50% to 65% (n = 45; 15% of the whole cohort), who were mostly asymptomatic or mildly symptomatic (37 or 82% with New York Heart Association functional class I to II), showed substantial LGE (median 5% of LV volume, interquartile range 2% to 10%). This overlapped with the subgroup with systolic dysfunction and significantly exceeded that of patients with an EF of 66% to 75% and >75% (median 2% of the LV volume, interquartile range 1.5% to 4%; p <0.01). In conclusion, in a large cohort of patients with HCM, a subset of patients with low-normal EF values (50% to 65%) was identified by contrast-enhanced CMR imaging as having substantial degrees of LGE, suggesting a transition phase, potentially heralding advanced LV remodeling and systolic dysfunction, with implications for clinical surveillance and management.

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Methods

The study population included 310 patients with HCM consecutively referred for CMR imaging from 2001 to 2008 at centers in Minneapolis and Boston (Table 1). CMR imaging was routinely offered to all patients with HCM evaluated at our institutions during the study period for the purpose of defining the extent and distribution of LV hypertrophy, LV volumes, LV mass, and LGE. Those with specific contraindications, such as implanted cardioverter-defibrillators or pacemakers, metallic fragments,

Results

The EF in the 310 patients with HCM was significantly greater than in the reference healthy control population (71 ± 10% vs 66 ± 5%; p <0.001). The EF was <50% (overt systolic dysfunction) in 15 (5%), 50% to 65% in 45 (15%), 66% to 75% in 144 (46%), and >75% in 106 (34%). Patients with an EF <50% and an EF of 50% to 65% had similar transverse LV end-diastolic and left atrial dimensions, exceeding those of patients with an EF of 66% to 75% or >75% (Table 1).

In the overall study group, no

Discussion

Remodeling of the LV chamber in HCM has been shown to occur in several clinical circumstances, including progression of LV hypertrophy during adolescence22 and evolution to the end-stage with overt systolic dysfunction.3, 4, 5, 6, 7 In the present cross-sectional analysis, we used CMR in a large consecutive HCM cohort to examine the relation of EF to a variety of clinical variables potentially relevant to LV remodeling and systolic performance.

In our HCM cohort, the EF values encompassed a

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