Dipyridamole thallium imaging: use in preoperative cardiac risk assessment in vascular surgical patients

The objective of this study was to determine whether routine performance of dipyridamole thallium imaging adds to the power of a careful clinical evaluation in the risk stratification of patients undergoing major vascular surgery.

In this retrospective study, 115 cases evaluated by dipyridamole thallium imaging before major vascular surgery were reviewed. Patients were assigned to a high-risk cohort if they had a history of congestive heart failure or evidence of previous myocardial infarction.

Six (8%) patients from the high-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 developed complications despite the presence of reversible perfusion defects in 33%. Patients in the high-risk cohort who underwent cardiac catheterization and selective coronary bypass grafting were uniformly free of perioperative complications. The extent and severity of fixed or reversible thallium perfusion did not predict the occurrence of cardiovascular complications. However, three patients were denied surgery following an unacceptable cardiovascular risk assessment based on clinical findings and multiple reversible thallium perfusion defects.

In low-risk patients, screening with dipyridamole thallium can identify patients with redistribution defects whose risk of perioperative ischemic events can be reduced by intensifying perioperative anti-ischemic management. If the patient is in the high-clinical-risk subgroup, screening with dipyridamole thallium does not identify a cohort with negligible perioperative risk; thus, further evaluation of these patients by cardiac catheterization should be considered.