ICD discharge rate in patients with hypertrophic cardiomyopathy who do not have massive left ventricular hypertrophy but extensive myocardial fibrosis.

The current ACC/AHA guidelines recommend implantation of an ICD in patients who have hypertrophic cardiomyopathy (HCM) and wall thickness of ≥30 mm (massive LVH, class IIa) due to increased risk of sudden cardiac death (SCD). We hypothesize that patients who do not meet this cut off but have extensive myocardial fibrosis are at equally increased risk as measured by the rate of ICD discharge. We conducted a cohort study of people with HCM who received a CMR and an ICD between 2002-2022. We divided the patients into those with massive LVH (≥30 mm) vs. not and then further into those with extensive late gadolinium enhancement (LGE) (defined as LGE ≥15%) based on cardiac MRI (CMR). We assessed the incidence of device discharge and the Kaplan Meyer Curves of shock-free survival between groups. 222 patients were identified. Overall, the presence of massive LVH was associated with a significantly higher hazard ratio for receiving an appropriate device discharge as compared to those with LV wall thickness <30 mm (HR 2.37, 95%CI 1.10 to 5.10, p = 0.023). However, when CMR data were considered, the presence of LGE >15% identified a subgroup of patient without massive LVH who had a higher incidence of device discharge that was not statistically significant when compared to those with massive LVH (28% vs. 35%, HR 1.01, 95%CI 0.45-2.71, p=0.834). Furthermore, when only patient with massive LVH and LGE <15% were considered, the incidence of device discharge was almost identical to those with LVH <30 mm but with LGE >15% (30% vs. 28%, HR 1.14, 95%CI 0.41-3.17, p=0.797) (Figure 1). In this high-risk population with ICD implanted for primary prevention of SCD in the setting of HCM, the presence of massive LVH predicts a high incidence of ICD discharge. The presence of extensive myocardial fibrosis, however, identifies a subgroup of patient without massive LVH who have equally high incidence of receiving appropriate device discharge. These findings suggest that the presence of extensive LGE on CMR might need to be considered in the same category of massive LVH when assessing HCM patients for ICD implantation. [ABSTRACT FROM AUTHOR]