Evaluation of Coronary Circulation by 13N-Ammonia Myocardial Perfusion Positron Emission Tomography in Patients with Right Coronary Artery Occlusion Due to Kawasaki Disease.

BACKGROUND: Although occlusion of the right coronary artery (RCA) is common in the remote stages of Kawasaki disease, revascularization of the RCA is challenging in children and is usually managed by observation without intervention. METHODS: Using adenosine-stress 13N-ammonia myocardial perfusion positron emission tomography, we evaluated coronary circulation in 14 patients (12 males) with RCA occlusion to identify ischemia (myocardial flow ratio < 2.0) in the RCA region and examined hemodynamics, cardiac function, and coronary aneurysm diameter. These variables were also compared in patients with/without RCA segmental stenosis (SS). RESULTS: There were five cases of ischemia in the RCA region. RCA myocardial blood flow (MBF) at rest was higher in patients with ischemia than in those without ischemia, but the difference was not significant (1.27 ± 0.21 vs. 0.82 ± 0.16 mL/min/g, p = 0.2053). Nine patients presented with RCA SS, and age at onset of Kawasaki disease tended to be lower in those with SS. The maximum aneurysm diameter of RCA was significantly smaller in patients with SS (10.0 ± 2.8 vs. 14.7 ± 1.6, p = 0.0239). No significant differences in other variables were observed between patients with/without ischemia and SS. CONCLUSIONS: At rest, MBF in the RCA region was relatively well preserved, even in patients with RCA occlusion, and there was no progressive deterioration in cardiac function. Adenosine stress showed microcirculatory disturbances in only half of the patients, indicating that it is reversible in children with Kawasaki disease.

Risk Stratification Using Right Ventricular Longitudinal Strain Ratio Derived from 13N-Ammonia PET in Patients with Ischemic Heart Disease.

Purpose To investigate whether right ventricular (RV) myocardial strain ratio (RVMSR) assessed using nitrogen 13 ammonia (13N-NH3) PET can predict cardiovascular events in patients with ischemic heart disease (IHD). Materials and Methods This retrospective study included 480 consecutive patients (mean age, 66 years ± 12 [SD]; 334 males and 146 females) with IHD who underwent 13N-NH3 PET. RVMSR was defined as the ratio of RV strain during stress to that at rest. The primary end point was major adverse cardiac events (MACEs), defined as cardiac death or heart failure hospitalization. The ability of RVMSR to predict MACE was assessed using receiver operating characteristic (ROC) curve and Kaplan-Meier analyses. Cox proportional hazards regression analysis was used to calculate hazard ratios (HRs) with 95% CIs. Results ROC curve analysis identified a sensitivity and specificity of 84% and 82%, respectively, for predicting MACE from RVMSR. Patients with reduced RVMSR (<110.2) displayed a significantly higher rate of MACE than those with a preserved RVMSR (34 of 240 vs four of 240; P < .001). Cox proportional hazards regression analysis of imaging parameters, including myocardial flow reserve, indicated that RVMSR was an independent predictor of MACE (HR, 0.94 [95% CI: 0.92, 0.97]; P < .001). Conclusion RVMSR was an independent predictor of MACE and has potential to aid in the risk stratification of patients with IHD. Keywords: Right Ventricular Myocardial Strain Ratio, Myocardial Flow Reserve, Ischemic Heart Disease, 13N-Ammonia Positron Emission Tomography Supplemental material is available for this article. © RSNA, 2024.

Effect of Luseogliflozin on Myocardial Flow Reserve in Patients with Type 2 Diabetes Mellitus (LUCENT-J Study).

INTRODUCTION: In patients with type 2 diabetes (T2D), treatment with sodium-glucose cotransporter-2 (SGLT2) inhibitors has been shown to reduce hospital admission rates for heart failure (HF). However, the multiple mechanisms hypothesized and investigated to explain the cardioprotection of SGLT2 inhibitors are not fully understood. OBJECTIVES: The effect of luseogliflozin on myocardial flow reserve (MFR) in patients with T2D (LUCENT-J) study aims to examine the effects of SGLT2 inhibitors on myocardial perfusion. METHODS: The LUCENT-J study is a prospective, single-center, randomized, two-arm, parallel-group, open-label (i.e., the radiology readers are blinded), active-controlled study. A cohort of 40 patients with T2D with no or stable (with no history of myocardial infarction and with or without previous percutaneous coronary intervention) coronary artery disease will be included. Patients will be randomized in a 1:1 ratio to luseogliflozin or control and treated for 24 weeks. The primary outcome is the change in MFR, as measured by 13N-ammonia positron emission tomography/computed tomography, from baseline to 24 weeks after treatment initiation. PLANNED OUTCOMES: The LUCENT-J study will elucidate the mechanisms of cardioprotection by SGLT2 inhibitors in patients with T2D. TRIAL REGISTRATION: Japan Registry of Clinical Trials (JRCTs051220016).

Prediction of cardiovascular events using myocardial strain ratio derived from 13N-ammonia positron emission tomography.

OBJECTIVES: Myocardial flow reserve (MFR), derived from ammonia N-13 positron emission tomography (NH3-PET), can predict the prognosis of patients with various heart diseases. We aimed to investigate whether myocardial strain ratio (MSR) was useful in predicting MACE and allowed for further risk stratification of cardiovascular events in patients with ischemic heart disease (IHD) in addition to MFR. METHODS: Ninety-five patients underwent NH3-PET because of IHD. MFR was determined as the ratio of hyperemic to resting myocardial blood flow (MBF). MSR was defined as the ratio of strains at stress and rest. The endpoint was major adverse cardiac events (MACE), including all-cause death, acute coronary syndrome, heart failure hospitalization, and revascularization. The ability to predict MACE was assessed using receiver operating characteristic (ROC) analysis, and the predictability of ME was analyzed using Kaplan-Meier analysis. The Cox proportional hazards regression model was used to calculate the hazard ratio (HR) with 95% confidence interval (CI). RESULTS: The ROC curve analysis demonstrated a cutoff of 0.93 for MACE with MSR (sensitivity and specificity of 77% and 71%, respectively). Patients with MSR < 0.93 displayed a significantly higher MACE rate than those with MSR ≥ 0.93 (p = 0.0036). The Cox proportional hazards regression analysis indicated that MSR was an independent marker that could predict MACE in imaging and clinical parameters (HR, 7.32; 95% CI: 1.59-33.7, p = 0.011). CONCLUSIONS: MSR was an independent predictor of MACE and was useful for further risk stratification in IHD. MSR has the potential for a new indicator of revascularization in patients with IHD. KEY POINTS: • We hypothesized that combining myocardial flow reserve (MFR) with the myocardial strain ratio (MSR) obtained by applying the feature-tracking technique to ammonia N-13 PET would make it predictive of major adverse cardiac events (MACE) compared to MFR alone. • MSR was an independent predictor of MACE, allowing for further risk stratification in addition to MFR in patients with ischemic heart disease. • MSR is a potential new indicator of revascularization.

Diagnostic accuracy of 13N-ammonia myocardial perfusion imaging with PET-CT in the detection of coronary artery disease.

BACKGROUND: 13N-ammonia positron emission tomography-computed tomography (PET-CT) is being increasingly used as a non-invasive imaging modality for evaluating patients with known or suspected coronary artery disease (CAD), but information about the diagnostic accuracy of PET-MPI is sparse. Objectives: Our objective was to determine the accuracy of 13N-ammonia PET-CT myocardial perfusion imaging (MPI) for detecting CAD. METHODS: We retrospectively evaluated 383 patients with suspected CAD who underwent rest-stress 13N- ammonia PET-CT MPI. Invasive coronary angiography (ICA) was performed within 60 days for all patients with abnormal PET-MPI findings and for selected patients with normal PET-MPI findings. RESULTS: The mean age of the patients was 64±11 years, and the mean body mass index was 32±7 kg/m2. Stress perfusion defects were identified in 147 (34%) out of a total of 383 patients. ICA was performed in 213 patients (145 patients with abnormal PET and 68 patients with normal PET). The sensitivity of PET-MPI for detection of obstructive CAD based on ≥50% stenosis was 90%; specificity, 90%; positive predictive value, 96%; negative predictive value, 76%; and diagnostic accuracy, 80%. CONCLUSIONS: PET-MPI with 13N-ammonia affords high sensitivity and overall accuracy for detecting CAD. The addition of coronary artery calcium score (CACS) can improve CAD risk stratification.

Diagnostic Performance of Resting and Hyperemic Invasive Physiological Indices to Define Myocardial Ischemia: Validation With 13N-Ammonia Positron Emission Tomography.

OBJECTIVES: The authors sought to compare the diagnostic performance of fractional flow reserve (FFR), instantaneous wave-free ratio (iFR), and resting distal coronary artery pressure/aortic pressure (Pd/Pa) using 13N-ammonia positron emission tomography (PET). BACKGROUND: The diagnostic performance of invasive physiological indices was reported to be different according to the reference to define the presence of myocardial ischemia. METHODS: A total of 115 consecutive patients with left anterior descending artery stenosis who underwent both 13N-ammonia PET and invasive physiological measurement were included. Optimal cutoff values and diagnostic performance of FFR, iFR, and resting Pd/Pa were assessed using PET-derived coronary flow reserve (CFR) and relative flow reserve (RFR) as references. To compare discrimination and reclassification ability, each index was compared with integrated discrimination improvement (IDI) and category-free net reclassification index (NRI). RESULTS: All invasive physiological indices correlated with CFR and RFR (all p values <0.001). The overall diagnostic accuracies of FFR, iFR, and resting Pd/Pa were not different for CFR <2.0 (FFR 69.6%, iFR 73.9%, and resting Pd/Pa 70.4%) and RFR <0.75 (FFR 73.9%, iFR 71.3%, and resting Pd/Pa 74.8%). Discrimination and reclassification abilities of invasive physiological indices were comparable for CFR. For RFR, FFR showed better discrimination and reclassification ability than resting indices (IDI = 0.170 and category-free NRI = 0.971 for iFR; IDI = 0.183 and category-free NRI = 1.058 for resting Pd/Pa; all p values <0.001). CONCLUSIONS: The diagnostic performance of invasive physiological indices showed no differences in the prediction of myocardial ischemia defined by CFR. Using RFR as a reference, FFR showed a better discrimination and reclassification ability than resting indices.