Abstract Body (Do not enter title and authors here): Introduction

In patients with cardiac sarcoidosis, high-grade atrioventricular (AV) block is an indication for implantable cardioverter-defibrillator (ICD) placement. However, critical gaps remain in our understanding of arrhythmic risk in patients with AV block and suspected cardiac sarcoidosis, particularly in the absence of late gadolinium enhancement (LGE) on cardiovascular magnetic resonance imaging (CMR).

Research Question

We investigated the arrhythmic risk in patients with extracardiac sarcoidosis, high-grade AV block, and no LGE on CMR.

Methods

We studied consecutive patients with histology-supported sarcoidosis who underwent CMR for the evaluation of suspected cardiac involvement at three centers between 2004 and 2023. High-grade AV block was defined as a second-degree type 2 or third-degree block. The cardiac sarcoidosis CMR phenotype was defined as featuring at least one of four LGE features: subepicardial, multifocal, septal, and right ventricular free wall involvement. The study outcome was a composite of fatal or life-threatening ventricular arrhythmia. The incidence of the study outcome was compared using cumulative incidence function analyses accounting for competing risks.

Results

Among 1,632 patients with histology-supported sarcoidosis who underwent CMR, 116 (7.1%) had presented with high-grade AV block. Of these, 72.0% had LGE, and the cardiac sarcoidosis CMR phenotype was seen in 68.1%. Overall, 95 (81.9%) had a cardiac fluorodeoxyglucose-positron emission tomography (FDG-PET) scan within one year of the CMR, and 69 (72.6%) had cardiac FDG uptake. At a median follow-up of 3.5 years, 25 patients experienced the study outcome. Of these, only one patient (4.0%) had no LGE. Patients with LGE had a significantly greater incidence of the study outcome than those without LGE (Gray’s P=0.004); those with the cardiac sarcoidosis CMR phenotype had an even greater incidence than those without the phenotype (Gray’s P=0.001). Among patients with no LGE, cardiac FDG uptake was not associated with the study outcome (Gray’s P=0.34). Among patients with no LGE and no cardiac FDG uptake, all of whom had extracardiac FDG uptake, none experienced the study outcome.

Conclusions

In patients with suspected cardiac sarcoidosis and high-grade AV block, LGE effectively risk-stratifies those who would benefit from primary prevention ICDs, regardless of cardiac or extracardiac FDG-PET findings, with improvements achieved through CMR phenotyping.