Late gadolinium enhancement in hypertrophic cardiomyopathy: When should we use it in risk stratification of our patients?
Hypertrophic cardiomyopathy (HCM) is associated with complications including heart failure and sudden cardiac death (SCD). The implantable cardioverter defibrillator (ICD) reduces risk of SCD and provides primary prophylaxis for selected patients. Current risk stratification strategies include traditional and novel risk markers. In the United States, presence of ³1 traditional risk marker is sufficient to consider ICD implantation: family history of HCM-related SCD ³1 close relative; unexplained syncope; massive left ventricular (LV) hypertrophy (wall thickness ³30mm); repetitive or prolonged non-sustained ventricular tachycardia; and/or attenuated or hypotensive blood pressure response to exercise.(1) In Europe, an HCM risk calculator including additional parameters (left atrial size and LV outflow tract gradient) has been developed to estimate the SCD risk at 5 years and provide ICD implantation advice.(2) Late gadolinium enhancement (LGE) demonstrated on cardiac magnetic resonance (CMR) imaging has been shown to represent myocardial fibrosis. There has been considerable interest in the role of LGE in HCM risk assessment, but the prognostic importance has been controversial.
In the most recent meta-analysis published in JACC imaging, Weng et al. have pooled data from almost 3000 HCM patients representing the largest combined experience to date.(3) LGE was present in 55% of HCM patients. Although presence of LGE was associated with increased risk for SCD (OR 3.41; 95% CI 1.97-5.95; p<0.001) and a trend towards increased heart failure death (OR 2.21; 95% CI 0.84-5.80), the high frequency of this finding limits its role as an independent risk marker or as a practical strategy for clinical decision making. More relevant appears to be the extent of LGE. Extensive LGE conferred greater SCD risk and there was a linear relationship between LGE extent and risk (adjusted HR 1.36; 95% CI 1.10-1.69; p=0.005 for each 10% increase in LGE as a proportion of LV mass). Present guidelines do not include LGE as a risk marker in HCM but there is increasing evidence for its role. It has been suggested that in borderline risk assessment cases, extensive and diffuse LGE may help arbitrate in favour of ICD implantation.
- Gersh BJ et al. 2011 ACCF/AHA guidelines for the diagnosis and treatment of hypertrophic cardiomyopathy. J Am Coll Cardiol 2011;58:e212-60.
- Elliott PM et al. 2014 ESC guidelines on diagnosis and management of hypertrophic cardiomyopathy. Eur Heart J 2014;35:2733-79.
- Weng Z et al. Prognostic importance of LGE-CMR in HCM: A meta-analysis. JACC Cardiovasc Imaging 2016 Jul 19 (Epub ahead of print).