Abstract 11984: SPECT and Cardiac Catheterization Concordance Rates in Obese Patients Referred for PTCI; a Game of Chance?

Abstract

Background: With obesity on the rise in our country obtaining diagnostic quality images becomes increasingly difficult. SPECT myocardial perfusion images (MPI) have higher percentage of artifacts in obese patients necessarily increasing false positivity rates leading to inappropriate cardiac catheterization. This increases radiation exposure to the patient while jeopardizing cost effectiveness of diagnostic testing for CAD and puts increasing financial burden on our already taxed health system. Thus, intrinsic accuracy between SPECT-MPI and cardiac catheterization is of clinical importance. Taken together, with the results of the CE-MARC Trial, obesity per se may be partially explanatory for the inacuracy of nuclear imaging

Methods: We hypothesize that due to the lower resolution image quality, MPI will be less accurate relative to obesity when compared to the 'gold standard' cardiac catheterization. We retrospectively and consecutively performed a chart review of patients who within the period of 3/1/2009 - 6/30/2011 underwent cardiac catheterization and percutaneous coronary intervention (PTCI) in our hospital after positive results of the MPI. All patients were grouped in accordance to their WHO BMI classification. Each subgroup was analyzed to determine a degree of concordance between MPI and cardiac catheterization.

Results: There were 161 pts who underwent cardiac intervention in our institution after the performance of stress/nuclear perfusion test: 29 pts in normal weight group, 48 in the overweight (mean BMI 27.9±1.5), 41 in obese class I (32.0±1.5), 30 in obese class II (37.3±1.5) and 13 in obese class III (46.2±4.8). ROC analysis demonstrated that as BMI increases, concordance between MPI and catheterization exists in only approximately 50% of cases. A pattern of prognostic discordance existed for increasing tertiles of obesity.

Conclusions: In those patients referred for PTCI following SPECT, the discordance rates as related to MPI were poor; analagous to the CE-MARC Trial and currently tested in the NHLBI-ISCHEMIA Trial. However, no specific pattern relating the inaccuracy to obesity was evident. However, the overall concordance/discordance rates for the entire population were no better than those of ‘chance’.: