Oral Abstract Session
SCMR 22nd Annual Scientific Sessions
Carlos Rochitte, MD, PhD, FSCMR
Academic Coordinator of Cardiovascular MRI and CT at Heart Institute (InCor), University of São Paulo Medical School
Director of Cardiovascular MRI and CT at Heart Hospital, Hospital do Coração, HCOR
Heart Institute (InCor), University of São Paulo Medical School and Heart Hospital, Hospital do Coração, HCOR
Identifying the patients with Hypertrophic Cardiomyopathy (HCM) in whom the risk of sudden cardiac death (SCD) justifies the implantation of a cardioverter-defibrillator (ICD) remains challenging. European and American guidelines use different methods for risk stratification and different criteria for ICD implantation in this setting. We sought to evaluate the role of late-gadolinium enhancement (LGE) in improving the risk stratification of arrhythmic events provided by these clinical criteria.
Methods: We conducted a multicentric retrospective analysis in HCM patients who underwent CMR for diagnostic confirmation and/or risk stratification. Eligibility for ICD was assessed according to the HCM Risk-SCD score  and the American College of Cardiology Foundation/American Heart Association (ACCF/AHA) algorithm . LGE was defined as an area with signal intensity ≥6 SD exceeding the mean of normal myocardium and was expressed as the % of total left ventricular mass (LGE%), and subsequently categorized into: <10%, 10-19.9% and ≥20% . The primary endpoint was a composite of SCD, aborted SCD, sustained ventricular tachycardia (VT), or appropriate ICD discharge.
A total of 413 patients were available for analysis (58% male, mean age 47±17 years). According to the ACCF/AHA criteria, ICD would not be recommended in 59%, could be useful in 14%, and would be reasonable in 27%. The median HCM Risk-SCD score was 2.3% (IQR 1.6-4.1%). According to this score, ICD would not be indicated in 75%, could be considered in 12%, and should be considered in 13%. LGE was present in 82% of patients, with a median LGE% of 3.2% (IQR 0.6-10%). The concordance between risk assessment by these methods was relatively modest (Figure 1).
During a median follow-up of 28 months (IQR 14-77 months), 22 patients experienced an event (11 SCDs, 1 aborted SCDs, 7 sustained VTs, and 3 appropriate ICD discharges). LGE% predicted arrhythmic outcomes even after adjustment for the HCM Risk-SCD score (adjusted HR 1.09 per 1% increase in LGE%, 95%CI 1.05-1.12; p<0.001) and ACCF/AHA criteria (adjusted HR 1.08, 95%CI 1.04-1.11; p<0.001). LGE revealed better discriminative ability than the HCM Risk-SCD (AUC 0.83 [95%CI 0.75-0.91] vs. 0.68 [95%CI 0.58-0.78], respectively; p-value for comparison=0.01) and the ACCF/AHA algorithm (0.63 [95%CI 0.51-0.75], p-value for comparison <0.001). Survival analysis was consistent with the better discriminative ability of LGE (Figure 2). LGE was able to significantly enhance the risk stratification of the ACCF/AHA and HCM Risk-SCD criteria, with net reclassification improvements of 0.39 and 0.45, respectively (Figure 3).
Conclusion: There is considerable discordance between the clinical criteria for ICD implantation for primary prevention of SCD in HCM patients, and between these and LGE amount. The amount of LGE seems to outperform the HCM Risk-SCD score and the ACCF/AHA algorithm in the identification of HCM patients at increased risk of SCD.