Myocardial rubidium-82 tissue kinetics assessed by dynamic positron emission tomography as a marker of myocardial cell membrane integrity and viability

Background: Recent reports have demonstrated the clinical use of rubidium- 82 chloride (Rb-82) in combination with positron emission tomography (PET) not only as a tracer of myocardial blood flow but also as a marker of cell membrane integrity using static imaging early and late after tracer injection. The purpose of this study was to compare myocardial Rb-82 kinetics assessed by dynamic PET imaging as a marker for tissue viability with regional fluorine-18 fluorodeoxyglucose (FDG) uptake in patients with coronary artery disease. Methods and Results: Twenty-seven patients with angiographically proven coronary artery disease and 5 subjects with a low likelihood for coronary artery disease underwent dynamic PET imaging under testing conditions using Rb-82 and FDG. Both image sequences served as input data for a semiautomated regional analysis program. This program generated polar maps representing Rb-82 tissue half-life and FDG utilization assessed by Patlak's approach. Myocardial tissue viability was visually determined from static Rb-82 and FDG images. Regions were categorized as normal, ischemically compromised, and scar tissue. Their coordinates were subsequently copied to the functional polar maps for further analyses. In normal subjects, Rb-82 tissue half-life was homogeneous throughout the left ventricle (90±11 seconds). In coronary patients, differences between Rb-82 tissue half-lives in normal and scar tissue were highly significant (95±10 and 57±15 seconds, respectively; P<.0001). FDG uptake in these two tissue groups was 78±12% and 40±13%, respectively (P<.0001). Ischemically compromised tissue with reduced perfusion but maintained FDG uptake displayed an Rb-82 half-life of 75±9 seconds, indicating active cellular tracer retention, which was significantly different from scar tissue. Overall agreement of tissue categorization as either viable or scar was 86% between Rb-82 kinetics and FDG utilization. In a subgroup of 11 patients with all three tissue types within one image set, Rb-82 tissue half-life discriminated between normal, ischemic, and scar tissue (97±9, 75±9, and 60±15 seconds, respectively; P<.01). Conclusions: This study demonstrated a significant relationship between cell membrane integrity as assessed by dynamic Rb-82 PET imaging and myocardial glucose utilization as a marker for tissue viability. In regions with reduced perfusion, Rb-82 kinetics was different in compromised but metabolically active and irreversibly injured myocardium. The predictive value of this approach must he evaluated in follow-up studies.