Somatostatin receptor based PET/CT in patients with the suspicion of cardiac sarcoidosis: an initial comparison to cardiac MRI

Abstract

Diagnosis of cardiac sarcoidosis is often challenging. Whereas cardiac magnetic resonance imaging (CMR) and positron emission tomography/computed tomography (PET/CT) with 18F-fluorodeoxyglucose (FDG) are most commonly used to evaluate patients, PET/CT using radiolabeled somatostatin receptor (SSTR) ligands for visualization of inflammation might represent a more specific alternative. This study aimed to investigate the feasibility of SSTR-PET/CT for detecting cardiac sarcoidosis in comparison to CMR.15 patients (6 males, 9 females) with sarcoidosis and suspicion on cardiac involvement underwent SSTR-PET/CT imaging and CMR. Images were visually scored. The AHA 17-segment model of the left myocardium was used for localization and comparison of inflamed myocardium for both imaging modalities. In semi-quantitative analysis, mean (SUVmean) and maximum standardized uptake values (SUVmax) of affected myocardium were calculated and compared with both remote myocardium and left ventricular (LV) cavity.SSTR-PET was positive in 7/15, CMR in 10/15 patients. Of the 3 CMR+/PET- subjects, one patient with minor involvement (<25% of wall thickness in CMR) was missed by PET. The remaining two CMR+/PET- patients displayed no adverse cardiac events during follow-up.In the 17-segment model, PET/CT yielded 27 and CMR 29 positive segments. Overall concordance of the 2 modalities was 96.1% (245/255 segments analyzed). SUVmean and SUVmax in inflamed areas were 2.0±1.2 and 2.6±1.2, respectively. The lesion-to-remote myocardium and lesion-to-LV cavity ratios were 1.8±0.2 and 1.9±0.2 for SUVmean and 2.0±0.3 and 1.7±0.3 for SUVmax, respectively.Detection of cardiac sarcoidosis by SSTR-PET/CT is feasible. Our data warrant further analysis in larger prospective series.

Keywords: DOTATOC; PET; SSTR; sarcoidosis; somatostatin receptor.

Figure 1. Display of a patient with active myocardial sarcoidosis

Consistency of ⁶⁸Ga-DOTATOC-PET and CMR Display of transaxial ⁶⁸Ga-DOTATOC-PET (A., color bar indicating standardized uptake values), fused PET/CT B., short-axis late gadolinium enhanced (LGE) (C., insert: corresponding PET slice), and short-axis T2-weighted CMR D. slices in a 42-year-old woman (patient #8) with multi-organ sarcoidosis. PET presents enhanced tracer uptake in large portions of the left ventricle, highly consistent with cardiac involvement of sarcoidosis. CMR yields corresponding results. Of note, the patient experienced sustained ventricular tachyarrhythmia with subsequent cardiogenic shock five days after somatostatin-directed imaging requiring mechanical circulatory support with a percutaneous microaxial blood pump and veno-arterial extracorporeal membrane oxygenation.

Figure 2. Display of a patient without myocardial sarcoidosis

Consistency of ⁶⁸Ga-DOTATOC-PET and CMR Display of transaxial ⁶⁸Ga-DOTATOC-PET (A., color bar indicating standardized uptake values), fused PET/CT B., short-axis late gadolinium enhanced (LGE) C., and short-axis T2-weighted CMR D. slices in a 51-year-old woman (patient #6) with multi-organ sarcoidosis. PET presents enhanced tracer uptake in a left axillary and mediastinal lymph nodes, highly consistent with active sarcoidosis. In correspondence to CMR, no signs of myocardial involvement can be recorded. Follow-up is unremarkable regarding cardiac events.