Treadmill ECG test combined with myocardial perfusion imaging for evaluation of coronary artery disease: analysis of 340 cases.

AIM

Using Coronary arteriogram as the gold standard, stress ECG (Treadmill Test - TMT) has a sensitivity of 68% and specificity (77%) for the detection of coronary artery disease (CAD). Stress myocardial perfusion imaging (MPI) with Tc-99m Sestamibi gated SPECT has a sensitivity of 85% and specificity of 90%. The aim of the study was to ascertain if the combined use of the two physiologic tests will raise the predictive value for the presence or absence of physiologically significant CAD to 100%.

METHODS AND MATERIAL

Three hundred and fourty patients (200 with suspected and 140 proved CAD) were studied with the same day rest and stress protocol. A rest MPI image was acquired with 8 mCi Tc-99m Sestamibi, followed by TMT; at the peak exercise 20 mCi tracer was injected and post-stress MPI image was acquired after 1 hour. 12-lead ECG at rest and during stress and recovery period was analyzed.

RESULTS

Out of 200 patients with a prior probability of CAD 40-50% (151 with pain in chest, 81 with shortness of breath on exertion and 68 asymptomatic high risk for CAD--more than 5/9 risk factors), a normal stress MPI result in 150 patients excluded the probability of physiologically significant CAD. Fifty patients with abnormal stress MPI were refered for coronary arteriography. Stress ECG had 17% "false negative" and 23% "false positive" compared to stress MPI. In this group out of 140 known CAD, (56 post-infarct, 52 post-CABG and 32 post-PTCA), all sent for evaluation of ischemic symptoms, MPI documented 101 infarcts (fixed defects with no wall motion and thickening), 20 of them were "silent" (with no history of previous infarct) ECG did not help in picking them up. 58/101 infarcts had only fixed defects while 43/101 were accompanied by reversible ischaemia in same or other vascular territories. Thirty nine patients showed only reversible ischaemia without any infarct. Risk stratification was possible based on the extent and severity of the perfusion defects and number of territories in which defects were seen, rest LVEF, size of LV and transient dilation

CONCLUSIONS

Combined stress ECG and stress MPI perform "gate keeper" function for referral for angiography, as well as for risk stratification of those who already have coronary angiograms. Decisions for revascularization should be based on combined evaluation--a shift from stenosis- based to ischaemic--based evaluation. Success or failure of revascularization was also documented by this evaluation.