Cardiac positron emission tomography enhances prognostic assessments of patients with suspected cardiac sarcoidosis

Abstract

Objectives: This study sought to relate imaging findings on positron emission tomography (PET) to adverse cardiac events in patients referred for evaluation of known or suspected cardiac sarcoidosis.

Background: Although cardiac PET is commonly used to evaluate patients with suspected cardiac sarcoidosis, the relationship between PET findings and clinical outcomes has not been reported.

Methods: We studied 118 consecutive patients with no history of coronary artery disease, who were referred for PET, using [(18)F]fluorodeoxyglucose (FDG) to assess for inflammation and rubidium-82 to evaluate for perfusion defects (PD), following a high-fat/low-carbohydrate diet to suppress normal myocardial glucose uptake. Blind readings of PET data categorized cardiac findings as normal, positive PD or FDG, positive PD and FDG. Images were also used to identify whether findings of extra-cardiac sarcoidosis were present. Adverse events (AE)-death or sustained ventricular tachycardia (VT)-were ascertained by electronic medical records, defibrillator interrogation, patient questionnaires, and telephone interviews.

Results: Among the 118 patients (age 52 ± 11 years; 57% males; mean ejection fraction: 47 ± 16%), 47 (40%) had normal and 71 (60%) had abnormal cardiac PET findings. Over a median follow-up of 1.5 years, there were 31 (26%) adverse events (27 VT and 8 deaths). Cardiac PET findings were predictive of AE, and the presence of both a PD and abnormal FDG (29% of patients) was associated with hazard ratio of 3.9 (p < 0.01) and remained significant after adjusting for left ventricular ejection fraction (LVEF) and clinical criteria. Extra-cardiac FDG uptake (26% of patients) was not associated with AE.

Conclusions: The presence of focal PD and FDG uptake on cardiac PET identifies patients at higher risk of death or VT. These findings offer prognostic value beyond Japanese Ministry of Health and Welfare clinical criteria, the presence of extra-cardiac sarcoidosis and LVEF.

Keywords: CMR; CT; EMBx; FDG; ICD; JMHW; Japanese Ministry of Health and Welfare; LVEF; PET; RV; VT; cardiac magnetic resonance imaging; computed tomography; endomyocardial biopsy; fluorodeoxyglucose; implantable cardiac defibrillator; left ventricular ejection fraction; positron emission tomography; prognosis; right ventricular; sarcoidosis; ventricular tachycardia.

Figure 1. Classification of cardiac PET/CT perfusion and metabolism imaging

Normal perfusion and metabolism (Category 1), abnormal perfusion or metabolism, (Category 2), abnormal perfusion and metabolism (Category 3).

Figure 2. Examples of focal right ventricular FDG uptake

Example 1: 50 year old female who had pacemaker implantation for heart block after presenting with episodes of lightheadedness. PET/CT obtained for suspected cardiac sarcoidosis identified a medium sized perfusion defect throughout the basal septum with increased FDG uptake (“mismatch pattern”). There was also FDG uptake involving the apex and the RV free wall (arrow). The whole body images show FDG uptake in the liver and spleen and in paratracheal lymph nodes. EMBx identified the presence of granulomas consistent with the diagnosis of sarcoidosis. Interrogation of her ICD 3 month later identified the presence of rapid VT at a rate of 200 beats per minute which required anti-tachycardia pacing therapy. Example 2: 48 year old male with pulmonary sarcoidosis who was referred to PET/CT for suspected cardiac involvement. He was found to have a perfusion defect associated with focal FDG uptake along the basal anterior- and inferior-septum as well as multiple focal areas of FDG uptake throughout the right ventricle (arrows). Lymph node biopsy confirmed the presence of sarcoidosis. Less than 1 month following ICD implantation, he had an episode of VT (see rhythm strip).

Figure 3. Guidelines for Diagnosis of Cardiac Sarcoidosis from the Japanese Ministry of Health and Welfare

Guidelines for Diagnosis of Cardiac Sarcoidosis from the Japanese Ministry of Health and Welfare.

Figure 4. Survival free of death or VT stratified by cardiac PET exam results

Survival free of death or VT stratified by cardiac PET exam results.

Figure 5. Survival free of death or VT stratified by focal RV inflammation

Survival free of death or VT stratified by the presence or absence of focal right ventricular FDG uptake among individuals with abnormal cardiac PET exam.