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LGE CMR and Sudden Death in Hypertrophic Cardiomyopathy
Quick Takes
- In a meta-analysis of 11 studies, LGE on CMR in HCM patients highly correlated with SCD risk with a pooled odds ratio of 4.9.
- The association between LGE on CMR and SCD risk in HCM did not vary by differences in techniques for LGE assessment.
- An LGE extent of 10% of LV mass had the best cutoff for SCD risk stratification with a sensitivity of 0.73 and specificity of 0.67, suggesting that LGE on CMR should be considered in combination with other clinical risk factors for SCD risk stratification.
Study Questions:
What is the prognostic value of extent of late gadolinium enhancement (LGE) in predicting sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM)?
Methods:
This study is a meta-analysis of all studies of HCM patients with cardiac magnetic resonance imaging (CMR) who had quantitative LGE reported as a fraction of the left ventricular (LV) mass. The primary outcome of interest was SCD. Additional subgroup comparisons were made by method of LGE assessment, risk for SCD, and existence of LV outflow tract obstruction.
Results:
Overall, 11 studies were included with 1,550 patients with a mean age of 51 years and 64% were male. The median follow-up period was 5.2 years. Heterogeneity across studies was low. SCD highly correlated with LGE with a pooled odds ratio of 4.93 (95% confidence interval, 3.75-6.47). There was no statistical difference in association between LGE and SCD by method of ascertaining LGE on CMR. Most studies (n = 6) described significant LGE as 6 standard deviations (SD) above normal. With this technique, an LGE extent of 10% of LV mass had the best threshold for predicting SCD risk with a sensitivity of 0.73 and specificity of 0.67. Overall incidence of SCD was 10% in patients with LGE >10% and 2.4% in those with LGE <10%.
Conclusions:
In a meta-analysis of CMR studies in HCM patients, LGE was a robust predictor of SCD irrespective of technique used to assess LGE. However, it is unlikely to be the stand-alone predictor for SCD risk and is best considered as an additional risk stratifier in patients at intermediate risk based on clinical characteristics.
Perspective:
Prediction of SCD remains among one of the most challenging aspects of managing HCM patients. There are currently two different risk scores endorsed by the European Society of Cardiology and American College of Cardiology/American Heart Association (ACC/AHA) with both using different clinical characteristics to assess SCD risk and both demonstrate modest efficacy in SCD risk prediction. CMR is now increasingly used in HCM and is endorsed as a Class 1 recommendation in the 2024 ACC/AHA HCM guideline (epub May 8, 2024) in patients who are not clearly high risk for SCD to help with SCD risk stratification.
In this meta-analysis, LGE on CMR was an excellent risk predictor for SCD. This association held up despite differences in methods used to assess LGE; however, the number of studies using various different techniques was small, limiting the power. Most studies used the 6 SD approach for LGE assessment and an LGE extent of 10% was the best cutoff for risk stratification. Yet, it is noteworthy that despite significant LGE based on this definition, only 10% of patients experienced an SCD event and SCD was noted in 2% of patients without LGE too. As the authors suggest, CMR may lend itself as a tie breaker in determining SCD risk in combination with clinical characteristics, but it is inadequate as a sole predictor.
Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, SCD/Ventricular Arrhythmias, Magnetic Resonance Imaging
Keywords: Cardiomyopathy, Hypertrophic, Death, Sudden, Cardiac, Magnetic Resonance Imaging
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