Austin, Brett C

Background: Differentiating between causes of non-ischemic cardiomyopathy is important for disease-directed treatment. Cardiac MRI (CMR) and the use of late gadolinium enhancement (LGE) have proven useful for enhancing diagnostic accuracy. Definitive assessment of cardiomyopathy etiology by explant pathology facilitates direct evaluation of CMR utility. Hypothesis: We hypothesized direct comparison between pre-transplant (Tx) CMR and explant pathology will improve the characterization of undifferentiated cardiomyopathy through examination of cases where pre- and post-Tx diagnoses were discordant. Aims: To evaluate discrepant cases to describe imaging patterns in relation to post-Tx diagnosis. Methods: Institutional Tx recipients between 2000 and June 2023 were queried for pre-Tx MRI (n=122). Discrepant cases were identified (n=8). Pre-Tx diagnostic modalities, including CMR, were reviewed, and CMR patterns were evaluated in association with ultimate explant diagnosis. Results: Of the eight patients with discrepant diagnoses, five carried clinical diagnosis of dilated cardiomyopathy, one hypertrophic cardiomyopathy, one peripartum cardiomyopathy, and one congenital heart disease having undergone tricuspid valve and ASD repair. Pathologic evaluation most frequently identified biventricular or left ventricular arrhythmogenic cardiomyopathy (ARVC) (n=6), where CMR disclosed a diffuse pattern of subepicardial LGE and pre-Tx diagnosis of DCM was most common. Two of these pathologic descriptions represented a different disease on genetic evaluation: one patient had Danon disease, another had a LMNA pathogenic variant. The presumed peripartum cardiomyopathy was identified as Fabry’s disease on pathology (however, genetic testing consistent with Danon disease). Both Danon disease patients had primarily subendocardial LGE on CMR. One patient with a DCM phenotype had HCM pathologically. Results summarized in Table 1. Conclusions: Cardiac MRI can be a useful modality for the evaluation of underlying cardiomyopathy and should prompt appropriate genetic testing. Diffuse subepicardial LGE frequently accompanied the diagnosis of ARVC whereas a non-subepicardial pattern reflected alternative etiologies identified only through genetic testing.

Introduction: Unexplained high-grade AV block (AVB) in patients age <65 years is among the salient features of cardiac sarcoidosis (CS). Guidelines recommend that CS patients with high-grade AVB should receive an implantable cardioverter-defibrillator (ICD) or cardiac resynchronization therapy-defibrillator (CRT-D) rather than a permanent pacemaker (PPM). However, in clinical practice, CS may be recognized after PPM implantation for high-grade AVB. Aims: To evaluate the characteristics and outcomes of patients diagnosed with CS after PPM implantation for high-grade AVB and assess the decision-making and rationale for upgrade to ICD/CRT-D. Methods: Retrospective review of the Mayo Clinic Sarcoid Registry (n=848) was performed to identify all patients for which a PPM was implanted for high-grade AVB prior to the diagnosis of CS. Baseline clinical and imaging characteristics were collected during index evaluation at our institution. Decision-making for ICD upgrade, lead management strategy, immunosuppression initiation, and outcomes were assessed. Results: Overall, 29 of 848 (3.4%) of CS patients (62% probable/definite CS; 77% male; median (IQR) age 56 (48-61) years; and median (IQR) LVEF 58% (50-62) received a PPM for high-grade AVB prior to a CS diagnosis. Median (IQR) interval between PPM implant and index evaluation was 10 (3-23) months. Eight of 29 patients underwent upgrade to ICD (n=4) or CRT-D (n=4). Among them, the pacing lead was extracted in 4. All patients were upgraded for primary prevention of sudden cardiac death (SCD), with 3 of them also having LVEF<50% requiring upgrade to CRT-D. Twenty-two (79%) patients in the total cohort were treated with immunosuppression. During median (IQR) follow-up 37 months (11-74), 1 patient in the upgrade group had sustained VT appropriately treated with anti-tachycardia pacing. No events were documented among patients in the non-upgrade group. At last follow-up, 6 (75%) patients in the upgrade group and 12 (57%) in the non-upgrade group were pacemaker dependent. Median LVEF change was 0% in patients who underwent upgrade to CRT-D and –0.2% in those who underwent upgrade to ICD or no upgrade. Conclusions: In this cohort of patients diagnosed with CS several months after a PPM had been implanted for high-grade AVB, incident VT/VF was infrequent with contemporary CS management. In the absence of other SCD risk factors, CS patients who received a PPM for high-grade AVB prior to their CS diagnosis may not require ICD upgrade.