Influence of cardiac stress protocol on myocardial perfusion imaging accuracy: The role of exercise level on the evaluation of ischemic burden

Some specifics of cardiac stress protocols, i.e., stressor used or exercise level achieved, may impact myocardial perfusion imaging (MPI) accuracy. Four-hundred and seventy-five patients were submitted to MPI and coronary angiography. MPI was performed after exercise (303 patients) or dipyridamole stress (172 patients). A coronary stenosis aeyen70% was considered significant. In case of exercise test, a peak heart rate (HR) < 85% of the maximal age predicted was considered submaximal and categorized as follows: > 75% and < 85% ("Group 1"); < 75% ("Group 2"). At coronary angiography, 312/475 (66%) patients showed significant stenosis. In the overall population, MPI showed a high accuracy in unmasking significant coronary stenosis, independently of the stress protocol adopted (AUC .76 for exercise vs .78 for vasodilator; P = NS). However, in case of an exercise stress test, a significant interaction between peak %HR and MPI diagnostic power was evident. While an elevated accuracy was still maintained in "Group 1" patients (AUC .79; P vs maximal exercise = NS), a significant drop was demonstrated in "Group 2" patients (AUC .66; P vs maximal exercise = .012, and P vs "Group 1" = .042). The accuracy of MPI is not influenced by the stress protocol adopted. Exercise MPI maintains an elevated accuracy as long as the %HR remains > 75%.