Role of exercise tolerance test (ETT) and gated single photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) in predicting severity of ischemia in patients with chest pain.

ABSTRACT

This was an observational study carried out in the department of cardiology. Bangabandhu Shikh Mujib Medical University (BSMMU), Dhaka in collaboration with Institute of Nuclear Medicine (INM), Shabag, Dhaka during the period October 2002-March 2003. A total of 54 patients presenting with Canadian Cardiovascular Society (CCS) class I-II severity of chest pain with mean +/-SD age 49.88 +/- 8.44 yrs and having male to female ratio 5.751 were included in the study. The main objective of the study was to predict severity of myocardial ischemia by Exercise Tolerance Test (ETT) determined by Duke Treadmill Score (DTS) and by perfusion pattern observed following Single-Photon Emission Computed Tomography myocardial perfusion imaging (SPECT-MPI). All patients underwent ETT and then SPECT-MPI scan using Tc-99m-tetrofosmin in one-day stress and rest protocol. Coronary angiogram (CAG) was done with in six months of the perfusion study. After performing ETT, patients were categorized by DTS and myocardial perfusion studies were also stratified according to severity of perfusion defect. The formula used to calculate the score was Exercise time- (5 x ST segment deviation)-(4 X Treadmill angina index). The angiographic findings (significant >50% stenosis) and perfusion defects in MPI were compared with the severity of DTS. There were 31 patients who had CAG proven (>50% luminal diameter narrowing) CAD and 23 patients free of CAD. After ETT patients were categorized by Duke Treadmill Score into high DTS 12 (22.22%) patients, intermediate DTS 20 (37.03%) patients low DTS 22 (40.74%) patients. In high DTS group 91.66% patients had perfusion defect, whereas in intermediate and low risk group it was 60% and 40.9% respectively. In high DTS group 91.66% of patients had angiographicaly proven CAD, 58.33% of them had triple vessel disease (TVD) while in intermediate and low risk groups angiographically proven CAD were 65% and 22.72% of whom TVD only in 15% & 0% respectively. The results of ETT using DTS score were satisfactorily correlated with SPECT-MPI scanning in high DTS subsets of patients only. It is therefore, suggested that patient of high risk DTS do not need for myocardial perfusion imaging study and should undergo CAG for further evaluation. But the intermediate and low risk groups were needed myocardial perfusion imaging study to guide for further evaluation.