| PartⅠImpact of myocardial perfusion imaging on in-hospital coronary angiography and revascularization of patients with suspected coronary artery diseaseBackground:Noninvasive cardiac imaging is now central to the diagnosis and management of patients with moderate risk of coronary artery disease (CAD). The aim of this study was to assess the impact of stress myocardial perfusion imaging on in-hospital coronary angiography and revascularization for such patients.Methods:Between January 2005 and June 2007,1053consecutive in-hospital patients (423 female, the average age of 57.2±11.2 years-old) with suspected CAD but without any prior interventional treatment were retrospectively analyzed. All patients underwent a 2-day stress/rest 99Tcm-MIBI SPECT myocardial perfusion imaging, including 984 system-limited exercise test and 69 adenosine test. A dose of 99Tcm-methoxyisobutylisonitrile (MIBI) (925 MBq) was injected intravenously at peak exercise or 3 min after adenosine injection. Patients underwent stress imaging at 45 to 60 min after radiotracer injection. Resting 99Tcm-MIBI perfusion imaging was performed with the same dose of 99Tcm-MIBI on a separate day 24 to 72 h after the stress imaging. A semi-quantitative visual interpretation was made using short axis-, horizontal-, and vertical long axis-myocardial tomograms and a 5-grade (0-4) scoring system in a 17-segment model. A study was judged as normal, mild ischemia or severe ischemia according to the summed difference score. Patients were classified into normal, small and large ischemia extension groups by numbers of ischemic segments. The impact of SPECT result on coronary angiography and revascularization was analyzed by use of the X2 test.Results:Overall, stress/rest SPECT was normal in 973 patients (92.4%) and abnormal in 80 patients (7.6%).190 patients underwent coronary angiography,46 underwent percutaneous coronary intervention (PCI) and 10 coronary artery bypass grafting (CABG) during hospitalization. From the whole perspective, only 14.7%of patients with normal SPECT underwent coronary angiography while 58.8%of patients with abnormal SPECT did (x2=97.0, P<0.001); the rates of revascularization in patients with normal and abnormal SPECT were 2.8%and 36.3%, respectively (27 out of 973 versus 29 out of 80, x2=157.9, P<0.001). The referral rate for angiography was the lowest in normal myocardial perfusion SPECT group (14.8%), but there was no statistical difference between mild (55.6%) and severe myocardial ischemia groups (66.7%); while the severe group had highest rate of revascularization (48.9%) compared to mild group (22.2%). Patients without ischemic segments (14.8%) were less likely referred to angiography than patients with ischemic segments. Patients in large extension group (75.9%) showed no difference with patients in small extension group (53.5%) in referral rate for angiography but had a much higher revascularization rate (55.2%) than that in small extension group (27.9%). Multivariate analysis showed that reversible perfusion defect on SPECT was the most predictive variable for referral to coronary angiography (odds ratio=7.5, P<0.001).Conclusion:Abnormal SPECT is a powerful referral for in-hospital coronary angiography and revascularization during the same hospitalization. Thus, stress/rest SPECT myocardial perfusion imaging is an effective gatekeeper for early coronary angiography and invasive treatment for patients with suspected CAD. The extent and severity of ischemia could not add more predictive value for subsequent coronary angiography, but did have an impact on revascularization. Part IIComparison of coronary CT angiography and stress/rest SPECT myocardial perfusion imagingBackground:The relationship between luminal stenosis measured by coronary CT angiography and stress-induced ischemia by SPECT myocardial perfusion imaging is not clearly defined. The aim of this study was to evaluate the relationship between stenosis severity by coronary CT artery and abnormal SPECT, to explore impact of clinical factors on this relationship, and to find predictive factors for prognosis.Methods:Consecutive patients with symptoms suspected of coronary artery disease (CAD) between January 2008 and October 2010 were prospectively studied. Stress/rest gated SPECT and coronary CT angiography were performed. The result of coronary CT angiography was classified into four degrees of stenosis of 0-49%,50%-74%,75-89% and 90%-100%. The result of SPECT was classified as normal or abnormal (with reversible and/or fixed defects). During the 1-12 months follow-up period, patients or their relatives were contacted using telephone or mail. The study endpoints were difined as cardiac death, myocardial infarction, or clinical need for coronary revascularization. Survival analyses were performed using the Cox proportional-hazards model.Results:Overall 706 patients (450 men and 256 women) with an average age of 56.1±9.9 were enrolled. SPECT revealed 348 reversible and 58 fixed defects in 91 patients. Coronary CT angiography revealed 367 patients had a maximal luminal stenosis of 0-50%,236 had a maximal stenosis of 50%-75%,66 had a maximal stenosis of 75%-89%, and 37 had a maximal stenosis of 90%-100%. Coronary artery calcification was described in 677 patients, of which calcification was present in 356 patients (50.4%). Total coronary artery calcium (CAC) score was calculated in 428 patients, including 193 without calcification (CAC score=0),128 with mild calcification (1-100),59 with moderate calcification (101-400), and 48 with severe-to-extensive calcification (≥400). Sensitivity, specificity, and positive predictive values (PPV) and negative predictive values (NPV), respectively, of coronary CT angiography in the detection of abnormal myocardial perfusion imaging defects were 48.4%,90.4%,42.7%, and 92.2%on a patients’level and 40.2%,95.6%,33.6%, and 96.6%on vascular level when cutoff value of stenosis was set at 75%. ROC analysis showed the best cutoff value of stenosis for detecting abnormal SPECT was 55%on patients’level and 43%on vascular level. Patients with coronary calcification had a lower specificity and NPV (87.2%and 89.5%) than patients without calcification (96.3%and 95%, P<0.01 and P=0.013, respectively). Patients with severe-to-extensive calcification (CAC score>400) had lowest specificity (56.3%) and NPV (69.2%). The sensitivity and PPV of coronary CT angiography were not affected by clinical factors (P=ns). The specificity and NPV were affected by several clinical factors (P<0.05). During follow-up, there were 53 cardiac events. Cox regression demonstrated that SPECT myocardial perfusion imaging and coronary CT angiography were independent predictors of cardiac events.Conclusion:Coronary CT angiography has good agreement with stress/res SPECT by SPECT, and is good at excluding hypodynamic CAD due to high NPV. Coronary calcification and some clinical factors may affect the specificity and NPV for luminal stenosis by coronary CT angiography detecting abnormal SPECT. SPECT myocardial perfusion imaging and coronary CT angiography had important value for prognosis of patients with suspected CAD. |
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