Relationship Between The Risk Stratification Of Myocardial Perfusion Imaging And The Clinical Risk Stratification In Patients With Unstable Angina

Objective: To investigate the correlations of the risk stratification of ^99mTc-MIBI gated stress and rest myocardial perfusion imaging(MPI) and the myocardial perfusion with the clinical risk stratification in patients with unstable angina(UA) .Methods: 25 patients with determinated or suspected UA were enrolled in the study. Patients with cardiac insufficiency, sick sinus syndrome(SSS),â…¡-â…¢atrioventricular block, cardiac arrhythmia, bronchial asthma, congenital heart disease(CHD), cardiac valve disease, cardiomyopathy or pulmonary heart disease were excluded .At first, the Global Registry of Acute Coronary Events(GRACE) risk score was calcluded and the clinical risk stratification of ACC/AHA guideline update for the management of patients with unstable angina and non-ST segment elevation myocardial infarction(2005) was assessed in each patient. And then all the patients received the ^99mTc-MIBI exercise or adenosine stress and rest gated myocardial perfusion imaging in two days. Based on the summed difference score(SDS) and post-stress left ventricular ejection fraction(LVEF) of myocardial perfusion imaging, the patients were classified into 2 groups: the low risk group and the intermediate risk group. The correlations of the risk stratification assessed by myocardial perfusion imaging and myocardial perfusion with the GRACE risk score and the clinical risk stratifications of ACC/AHA were analysed.Results: All the 25 patients completed the ^99mTc-MIBI gated stress and rest myocardial perfusion imaging successfully. Based on the risk stratification of myocardial perfusion imaging, 16 patients were in low riskgroup and 9 patients in intermediate risk group. The GRACE risk scores in intermediate risk groups were obviously higher than those in low risk group(P<0.05). The relevant analysis showed that the GRACE risk score was positively correlated with the summed stress score(r=0.601 P<0.01) and the summed difference score(r=0.642 P<0.01), and had no relation with the summed rest score(r=0.311 P>0.05). The accuracy of the risk stratifications of ACC/AHA on the patients with unstable angina was 68.0%. In the low risk patients, the sensitivity was 75.0% and the specificity was 66.7%. In the intermediate risk patients, the sensitivity was 55.6% and the specificity was 75.0%.Conclusions:1. In UA patients, the GRACE risk score is closely related to the risk stratification of myocardial perfusion imaging.2. The GRACE risk score has important value in predicting the extent of stress inducing myocardial ischemia and reversible ischemia, but can't predict the extent of myocardial ischemia at rest.3. The risk stratification of ACC/AHA guideline for the patients with UA has certain predicting value in the risk stratification of myocardial perfusion imaging.4. ^99mTc-MIBI gated stress and rest myocardial perfusion imaging(MPI) is a credible method for more accurate clinical risk evaluation in patients with unstable angina.