DIPYRIDAMOLE-THALLIUM IMAGING - USE IN PREOPERATIVE CARDIAC RISK ASSESSMENT IN VASCULAR SURGICAL PATIENTS

Background: The objective of this study was to determine whether routi ne performance of dipyridamole thallium imaging adds to the power of a careful clinical evaluation in the risk stratification of patients un dergoing major vascular surgery. Methods: In this retrospective study, 115 cases evaluated by dipyridamole thallium imaging before major vas cular surgery were reviewed. Patients were assigned to a high-risk coh ort if they had a history of congestive heart failure or evidence of p revious myocardial infarction. Results: Six (8%) patients from the hig h-risk cohort developed major cardiovascular complications. Reversible perfusion defects, present in 67% of the high-risk patients, did not predict complications. None of the patients in the low-risk cohort dev eloped complications despite the presence of reversible perfusion defe cts in 33%. Patients in the high-risk cohort who underwent cardiac cat heterization and selective coronary bypass grafting were uniformly fre e of perioperative complications. The extent and severity of fixed or reversible thallium perfusion did not predict the occurrence of cardio vascular complications. However, three patients were denied surgery fo llowing an unacceptable cardiovascular risk assessment based on clinic al findings and multiple reversible thallium perfusion defects. Conclu sion: In low-risk patients, screening with dipyridamole thallium can i dentify patients with redistribution defects whose risk of perioperati ve ischemic events can be reduced by intensifying perioperative anti-i schemic management. If the patient is in the high-clinical-risk subgro up, screening with dipyridamole thallium does not identify a cohort wi th negligible perioperative risk; thus, further evaluation of these pa tients by cardiac catheterization should be considered.