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Hypertrophic Cardiomyopathy, Risk Stratification
Study Questions:
What is the incremental prognostic utility of late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) in patients with hypertrophic cardiomyopathy (HCM)?
Methods:
The investigators studied 1,423 consecutive low-/intermediate-risk patients with HCM (age ≥18 years) with preserved left ventricular (LV) ejection fraction (mean age 66 ± 14 years, 60% men) who underwent transthoracic echocardiography (TTE) (including dimensions and LV outflow tract gradients) and CMR (including LGE as a % of LV mass) at a single center between January 2008 and December 2015. The primary composite endpoint was sudden cardiac death (SCD) and appropriate implantable cardioverter-defibrillator discharge. The percent 5-year SCD risk score was calculated. To assess for the association of various predictors with all-cause mortality and appropriate ICD discharge, multivariable Cox proportional hazards analysis was utilized.
Results:
The mean 5-year SCD risk score was 2.3 ± 2.0. Mean maximal LV outflow tract gradient (TTE) was 70 ± 55 mm Hg (median 74 mm Hg [interquartile range (IQR): 10-67 mm Hg]); indexed LV mass and LGE (both on CMR) were 91 ± 10 g/m2 and 8.4 ± 12% (IQR, 0-19%); 50% had LGE on CMR. Of these, 458 were nonobstructive and 965 were obstructive (of which 686 were underwent myectomy). At 4.7 ± 2.0 years of follow-up, 60 (4%) met the composite endpoint. On quadratic spline analysis, LGE ≥15% was associated with increased risk of composite events. In the obstructive subgroup, on competing risk regression analysis, ≥15% LGE (subhazard ratio, 3.04; 95% confidence interval, 1.48-6.10) was associated with a higher rate, and myectomy (subhazard ratio, 0.44; 95% confidence interval, 0.20-0.76) was associated with a lower rate of composite endpoints (both p < 0.01). Similarly, sequential addition of LGE ≥15% and myectomy to % 5-year SCD risk score improved the log likelihood ratios from –227.85 to –219.14 (chi-square 17) and to –215.14 (chi-square 8; both p < 0.01). Association of % LGE with composite events was similar even in myectomy and nonobstructive subgroups.
Conclusions:
The authors concluded that in low-/intermediate-risk adult patients with HCM (obstructive, myectomy, and nonobstructive subgroups) with preserved systolic function, % LGE was significantly associated with a higher rate of composite endpoint.
Perspective:
This study reports that LGE (quantified as a % of LV mass) provided incremental prognostic utility over standard SCD risk stratification such as the European Society of Cardiology SCD risk score. In addition, % LGE also significantly reclassified risk of SCD and/or appropriate ICD discharge. It appears that in patients with HCM, SCD risk could be refined based on specific patient population characteristics, presence/absence of obstruction, and potential additional risk factors like LGE assessed by CMR. Additional prospective, multicenter studies are indicated to validate risk stratification algorithms for HCM that use LGE.
Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Echocardiography/Ultrasound, Magnetic Resonance Imaging
Keywords: Arrhythmias, Cardiac, Cardiomyopathy, Hypertrophic, Death, Sudden, Cardiac, Defibrillators, Implantable, Echocardiography, Gadolinium, Heart Failure, Magnetic Resonance Imaging, Risk Factors, Secondary Prevention, Stroke Volume
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