The efficacy of single-photon emission computed tomography in risk stratification of major cardiac events in patients over 60 years old undergoing non-cardiac surgery
AbstractAim. To evaluate the prognostic value of myocardial perfusion imaging with gated-SPECT (MPI/SPECT) in patients over 60 years old with known coronary artery disease (CAD) before non-cardiac surgery.
Materials and methods. Overall 225 patients with known CAD were studied (average age of 66,11±1,1). Patients were classified into 3 groups according to age: 1) <65 years, 2) 65-74 and 3) over 75 years old. The Cardiac Risk Index was used to assess patient cardiac risk and included 6 clinical variables. All of them were referred to “stress/rest” MPI/SPECT using two-detector rotating gamma-camera (“Discovery NM/CT 670”, GE) before non-cardiac surgery. A 20-segment model of the LV was applied. “Summed stress score” (SSS) was used for estimation of intensity of perfusion disorder in stress. Normal myocardial perfusion was considered if SSS<4; slightly abnormal: SSS=4-7; moderate and significantly abnormal: SSS≥8. The degree of ischemia was also assessed on a semiquantitative basis by “summed difference score” (SDS): SDS<2 - no ischemia, SDS=2-7 moderate ischemia and SDS>7 - significant ischemia.
Results. 160 (71,1%) were proceeded to non-cardiac surgery after MPI/SPECT without any additional cardiac testing. The rest 65 (28,9%) patients weren’t allowed to surgerys due to high risk for major cardiac events (MCE) in peri- and/or postoperative periods. Coronary angiography (CAG) was performed to 47 (72,3%) from them, and 44 (93,6%) had hemodynamically significant stenosis at least in one coronary artery. Coronary revascularization was made to 22 (46,8%) patients. On the whole, SSS and SDS were statistically higher in patients, whom surgery was cancelled (p<0,05). Moreover, SSS and SDS were significantly higher in patients over 75 years old (p<0,05). There was significantly reduction of SSS and SDS (p<0,05) when comparing results of MPI/SPECT before and after coronary revascularization. All patients were operated on without any MCE after myocardial revascularization. However from 160 patients, whom non-cardiac surgery was performed directly after MPI/SPECT MCE occurred in 13 (8,1%). Myocardial perfusion analysis showed significantly high rates of SSS (7,77±3,79), SDS (3,39±1,69) in these patients compared with those without MCE (p<0,05). For the rest 143 patients without MCE SSS and SDS were below 4 and 2, respectively.
Conclusions. MPI/SPECT is an important tool in prediction of MCE in peri- and/or postoperative periods after non-cardiac surgery in patients with known CAD. It is also a reliable method for screening patients with stable CAD for CAG. CAG with subsequent revascularization should be considered in SSS>4 and SDS>2 in patients with high cardiac risk.