PET MPI Results Can Improve Prediction of Cardiac-Related Death

A recent study has found evidence that supports the use of positron emission tomography (PET) myocardial perfusion imaging to help identify diabetic patients that are at an increased risk of a heart attack.

After examining a group of more than 7000 patients, investigators found that abnormal PET myocardial perfusion imaging results were associated with a significantly increased risk of cardiac-related deaths.

"The data from the stress test among diabetic patients actually allowed us to better risk-stratify people in greater than 39 percent of the cases," said study lead author Hicham Skali, MD, MSc, of Brigham and Women's Hospital and Harvard Medical School. "Patients with diabetes remain at a significantly higher risk of cardiac death compared to patients without diabetes, and the data from a stress test helps us further stratify those at greatest risk."

Investigators used data from a group of 7061 patients who were enrolled at 4 participating centers. Of the 7061, the mean age was 63.3, 3348 (47.4) were women, 2296 had known coronary artery disease, and 1895 had previously undergone revascularization. A cohort of 1966 (27.8%) had diabetes were identified for inclusion in the retrospective analysis.

All participants underwent a clinically indicated rest-stress rubidium 82 myocardial perfusion PET. The primary outcome measure of the study was cardiac death, which was assessed at a mean of 2.5 years. Cox proportional hazards models and risk classification measures stratified according to diabetes status were used by the investigators.

A total of 3109 of the original 7061 patients had a normal myocardial perfusion study and 659 had a severely abnormal scan, which was defined as 20% or more myocardium abnormal. Compared to patients without diabetes, diabetics patients were less likely to have normal scans (47.0% and 36.4%, respectively) and more likely to have severely abnormal scans (7.7% and 13.5%).

After performing multivariable analyses for established clinical predictors, investigators found that increasing magnitude of stress myocardial perfusion abnormality was associated with a greater risk of cardiac death in patients with diabetes (HR: 7.2, 95% CI: 3.1, 16.8). Investigators also noted that the addition of stress myocardial perfusion imaging results significantly improved the fit of a clinical model for the prediction of cardiac death in patients with or without diabetes.

Additionally, myocardial perfusion PET improved risk reclassification for cardiac death in diabetic patients (0.39; 95% CI: 0.15, 0.60, P=0.001) and an abnormal myocardial perfusion PET scan was associated with increased risk of cardiac death (HR: 4.4; 95% CI: 2.0, 9.7) among diabetic patients in all clinical subgroups based on age, obesity, sex, or prior revascularization.

"In patients without diabetes, being a woman confers a certain advantage in that their risk of death is much lower, regardless of their stress findings," Skali said. "However, when you look at patients with diabetes, men and women have relatively the same risk of cardiovascular death, and that risk increases with worsening findings on the PET stress test."

This study, titled “Stress Myocardial Perfusion PET Provides Incremental Risk Prediction in Patients with and Patients without Diabetes,” is published in Radiology: Cardiothoracic Imaging.