The utility of 82Rb PET for myocardial viability assessment: Comparison with perfusion-metabolism 82Rb-18F-FDG PET.

BACKGROUND: 82Rb kinetics may distinguish scar from viable but dysfunctional (hibernating) myocardium. We sought to define the relationship between 82Rb kinetics and myocardial viability compared with conventional 82Rb and 18F-fluorodeoxyglucose (FDG) perfusion-metabolism PET imaging. METHODS: Consecutive patients (N = 120) referred for evaluation of myocardial viability prior to revascularization and normal volunteers (N = 37) were reviewed. Dynamic 82Rb 3D PET data were acquired at rest. 18F-FDG 3D PET data were acquired after metabolic preparation using a standardized hyperinsulinemic-euglycemic clamp. 82Rb kinetic parameters K1, k2, and partition coefficient (KP) were estimated by compartmental modeling RESULTS: Segmental 82Rb k2 and KP differed significantly between scarred and hibernating segments identified by Rb-FDG perfusion-metabolism (k2, 0.42 ± 0.25 vs. 0.22 ± 0.09 min-1; P < .0001; KP, 1.33 ± 0.62 vs. 2.25 ± 0.98 ml/g; P < .0001). As compared to Rb-FDG analysis, segmental Rb KP had a c-index, sensitivity and specificity of 0.809, 76% and 84%, respectively, for distinguishing hibernating and scarred segments. Segmental k2 performed similarly, but with lower specificity (75%, P < .001) CONCLUSIONS: In this pilot study, 82Rb kinetic parameters k2 and KP, which are readily estimated using a compartmental model commonly used for myocardial blood flow, reliably differentiated hibernating myocardium and scar. Further study is necessary to evaluate their clinical utility for predicting benefit after revascularization.

Relationship of non-invasive quantification of myocardial blood flow to arrhythmic events in patients with implantable cardiac defibrillators.

BACKGROUND: Ischemia contributes to arrhythmogenesis though its role is incompletely understood. Abnormal myocardial perfusion measured by PET imaging may predict ventricular arrhythmias (VAs) in a high-risk population. METHODS: Patients with implantable cardiac defibrillators who had undergone rubidium-82 cardiac PET imaging were identified. Patients were stratified by median MBF and MFR values for analysis. The Cox proportional hazards model was used to assess the impact of myocardial perfusion on survival free of VT independent of critical covariates. RESULTS: A total of 159 patients (124 (78%) males, median age 65.9 years, IQR [56.76-72.63]) were followed for 1.43 years IQR [0.83-2.21]. VA occurred in 29 patients (23.7%). After adjustment for ejection fraction, age, and sex, impaired stress MBF was associated with an increased risk of VA (adjusted HR per ml/min/g 1.52, 95% CI (1.01-2.31), P = 0.04). Summed rest and stress scores were not predictive of VA. Among patients with severe LV dysfunction, stress MBF remained an independent predictor of VA (adjusted HR per 1 ml/min/g HR 1.69, 95% CI (1.03-11.36), P = 0.03), while residual EF, summed rest, and summed stress scores were not (P > 0.05). CONCLUSIONS: Impaired stress myocardial blood flow was associated with less survival free of ventricular arrhythmias.