COMPARISON OF THE EFFECT OF THREE DIFFERENT DIETARY MODIFICATIONS ON MYOCARDIAL SUPPRESSION IN 18F-FDG PET/CT EVALUATION OF PATIENTS FOR SUSPECTED CARDIAC SARCOIDOSIS

Abstract

Rationale: A definitive dietary preparation recommendation is not possible based on literature in achievement of myocardial suppression for diagnosis of cardiac sarcoidosis (CS) with ¹⁸F-FDG PET/CT. Our goal is to compare three different dietary preparations in achievement of the best myocardial suppression and CS diagnosis. Methods: We retrospectively reviewed and compared three dietary preparations used at our institution. Three different diets were applied from 03/2014 to 12/2019. 24-h ketogenic diet with overnight fasting (n = 94); 18h-fasting (n = 44); 72-h daytime ketogenic diet with 3-day overnight fasting (n = 98). The interpretation of initial reports was recorded, and an independent radiologist (observer) retrospectively re-evaluated each case regarding CS diagnosis (Negative, Positive, Indeterminant) and myocardial suppression (Complete, Failed, Partial). Interobserver agreement was analyzed. We measured MaxSUV from bloodpool, liver, and the most suppressed normal myocardium. Results: We identified superior myocardial suppression with the 72-h preparation indicated by a higher bloodpool/myocardium and liver/myocardium ratios (P<0.001). Myocardial suppression rates for 72-h ketogenic diet, 24-h ketogenic diet and 18-h fasting preparations are as follows; Complete myocardial suppression: 96.9%/68.1%/52.3%, Failed myocardial suppression: 0%/23.4%/25%, Partial myocardial suppression: 3.1%/8.5%/22.7%) (P<0.001). The 72-hour preparation had significantly fewer "indeterminant" and "positive" exams. CS diagnosis rates for 72-h ketogenic diet, 24-h ketogenic diet and 18-h fasting preparations are as follows; Negative: 82.7%/52.1%/27.3%, Indeterminant: 2.0%/24.5%/40.9%, Positive: 15.3%/23.4%/31.8% (P<0.001). High agreement was present with the observer and the report (κ=0.88) Conclusion: A 72-h daytime ketogenic diet with 3-day overnight fasting, achieved substantially superior myocardial suppression versus 24-h ketogenic diet with overnight fasting and 18h-fasting using ¹⁸F-FDG PET/CT. This 72-h preparation results in significantly fewer "indeterminant" and potentially "false positive" CS results.

Keywords: Cardiac sarcoidosis; Cardiology (basic/technical); Cardiology (clinical); Fasting; Ketogenic diet; Myocardial suppression; PET/CT.

Graphical abstract

FIGURE 1.

A 62-y-old woman with inferior wall motion abnormality, arrythmia, and an old outside PET/CT report raising suspicion of CS. Prior endomyocardial biopsy was negative; there was no pathologic or imaging proof of sarcoidosis elsewhere in the body. On the basis of clinical findings, patient was considered as presumably having CS and referred for PET/CT. First PET/CT was obtained with Diet-B (top: ¹³N-ammonia; middle: ¹⁸F-FDG/PET), which was reported as active CS with complete myocardial suppression. However, the observer evaluated as indeterminant secondary to partial suppression. Patient subsequently received steroids, and a follow-up study was performed with Diet-C (bottom). This time, both report and observer agreed that there was complete suppression with no active CS. While it is possible that this presumable CS case might have responded to treatment, it is also possible that the initial interpretation was incorrect, and patient might have received unnecessary treatment.

FIGURE 2.

A 73-y-old man with chronic pericarditis and suspicion of CS. First examination was obtained with Diet-B: ¹³N-ammonia (A) and ¹⁸F-FDG (B). Initially, this examination was interpreted as incomplete myocardial suppression and indeterminant CS, in agreement with the observer. Repeated ¹⁸F-FDG study with Diet-C (C) showed complete myocardial suppression with negative CS (the observer and the report were in agreement).

FIGURE 3.

A 35-y-old man with systemic sarcoidosis. The first examination was obtained with Diet-A. Because of incomplete myocardial suppression, examination was repeated 2 d later with Diet-B. Results of this second examination showed partial myocardial suppression in lateral wall with indeterminant result. Patient underwent follow-up MRI (not shown here), which was negative for CS at that time. A third follow-up with Diet-C showed complete myocardial suppression. Note the persistence of hypermetabolic mediastinal lymph nodes in all 3 examinations.

FIGURE 4.

A 65-y-old man with new arrythmia and cardiac MRI (not shown), suggestive of sarcoidosis. Patient was referred for PET/CT obtained with Diet-C. Top row is ¹⁸F-FDG and lower row is ¹³N-ammonia. Both report and observer called this examination as active CS with complete myocardial suppression. Note mismatch pattern at regions with active CS (pink arrows) and how myocardium is well suppressed at normally perfused areas (blue arrows).