Clinical Utility of N-13 Ammonia Cardiac PET Perfusion Imaging in the Assessment of Epicardial Coronary Lesions of Intermediate Range

Objective: To identify the high risk myocardial perfusion defects which prognosticate the future ischemic cardiac events, on Positron emission tomography (PET) myocardial perfusion imaging (MPI) of intermediate coronary stenosis (ICS) on coronary angiogram (CAG) with negative single photon emission computed tomography (SPECT) MPI in chronic stable angina (CSA) patients. Methods: For this study non-infarcted CSA patients of single vessel disease (SVD) on CAG with ICS and normal LV function were selected. In all patients with negative stress SPECT MPI, stress PET MPI was done. In both scans, extent score (ES), severity score (SS), total severity/extent score ratio (TS-ES R) and Left ventricular dilatation (LVD) were noted. Patients with Positive PET MPI were closely followed for 2yrs and PCI was performed depending on symptoms. Results: Out of 47 study group patients, during 2yr follow up period, 11 out of 15 patients with ischemia positive PET MPI underwent percutaneous coronary intervention (PCI). Indication for PCI was rest or persistence or recurrence of angina. Four of 15 patients remained asymptomatic. In medically managed vs. PCI done patients, mean of ES was 1.2 ± 0.5 vs. 2.3 ± 1, SS was 1.2 ± 0.5 vs. 5.3 ± 1.9, TS-ESR was 1 vs. 2.5 ± 0.5 which was statistically significant (p = 0.01). Conclusion: It was inferred that subgroup of PET MPI positive ICS patients with basal PET MPI showing SS > 5 and TS-ES R > 1.5 with LVD during stress required close follow up as they are likely require PCI subsequently. Condensed Abstract: As negative for inducible ischemia by single photon emission computed tomography myocardial perfusion imaging (SPECT MPI) is associated with low cardiac event rate, even though positive imaging by Positron emission tomography myocardial perfusion imaging (PET MPI), in patients with intermediate Coronary stenosis (ICS) may not require immediate percutaneous coronary intervention (PCI). We fol-lowed these patients for two 2yrs and identified that basal PET MPI showing total severity score > 5 and total severity/ extent score ratio > 1.5 with Left ventricular dilatation during stress required PCI subsequently.