Pre-Treatment Myocardial ¹⁸FDG Uptake Predicts Response to Immunosuppression in Patients With Cardiac Sarcoidosis

Objectives: This study identified predictors of clinical (CR) and echocardiographic response (ER) following immunosuppressive therapy (IST) in patients with cardiac sarcoidosis (CS).

Background: IST has been the cornerstone of treatment for patients with CS and active myocardial inflammation. However, there are little data to explain the variable response to IST in CS.

Methods: Data of 96 consecutive patients with CS from the Granulomatous Myocarditis Registry were analyzed. All patients underwent a ¹⁸fluorodeoxy glucose positron emission tomography-computed tomography (¹⁸FDG-PET-CT) before initiation of IST. Response was assessed after 4 to 6 months of therapy. CR was defined as an improvement in functional class (New York Heart Association functional class ≥I) and freedom from ventricular arrhythmias and heart failure hospitalizations. ER was defined as an improvement in left ventricular ejection fraction (LVEF) ≥10%. ER was assessed only in patients with a LVEF <50%. Complete responders had no residual myocardial FDG uptake and fulfilled both response criteria. Partial responders fulfilled only 1 response criteria or had residual FDG uptake. Nonresponders did not fulfill either CR or ER criteria. The uptake index (UI) was defined as the product of maximum standardized uptake value and the number of LV segments with abnormal uptake on ¹⁸FDG-PET-CT.

Results: Among 91 patients included in the final analysis, 54.9%, 20.9%, and 24.2% of patients were classified as complete and partial responders and nonresponders, respectively. Cox regression analysis (all responders vs. nonresponders) identified the following as independent predictors of response following immunosuppression: LVEF >40% (hazard ratio: 1.61; 95% confidence interval: 1.06 to 7.69; p = 0.031) and myocardial UI >30 (hazard ratio: 1.28; 95% confidence interval: 1.05 to 6.12; p = 0.010). The final model had a good discriminative power (area under the curve [AUC]: 0.85) and predictive accuracy (sensitivity: 85.5%; specificity: 86.4%). Pre-treatment myocardial UI had a strong positive correlation with change in LVEF following immunosuppression.

Conclusions: Pre-treatment ¹⁸FDG myocardial uptake was a predictor of CR and ER response to immunosuppression in patients with CS.