Preoperative cardiac risk assessment in vascular surgery patients: seeing beyond the perioperative period.

Patients scheduled for non-cardiac vascular surgery are at significant risk of cardiovascular morbidity and mortality due to underlying symptomatic or asymptomatic coronary artery disease (CAD). As was shown by Hertzer et al. in their landmark study in 1984 using coronary angiography in 1000 patients undergoing non-cardiac vascular surgery, 61% of all patients did have at least one significant lesion. In fact, only 8% of all patients had no abnormalities. More recent studies using functional tests for CAD such as dobutamine stress echocardiography confirmed these findings. In a study population of 1097 vascular surgical patients, the incidence of rest wall motion abnormalities was nearly 50%, while one-fifth of patients had stress-induced myocardial ischaemia. The high prevalence of CAD in vascular surgical patients explains the adverse outcome in this patient population. The incidence of perioperative myocardial infarction, defined as the presence of two out of three of the following markers: (i) the presence of typical chest pain complaints; (ii) ECG abnormalities; and (iii) increased troponin levels, is 5%. Importantly, 75% of the perioperative myocardial infarctions remain asymptomatic and may therefore be difficult to assess. This might be attributable to the disguising effects of sedation and the simultaneous occurrence of symptoms directly related to surgery such as nausea. The incidence of troponin release is even up to 25% in the vascular surgery population. However, the impact of perioperative asymptomatic myocardial ischaemia on long-term outcome is not fully appreciated. The preoperative evaluation offers a unique opportunity to identify patients at increased perioperative risk and initiate appropriate lifestyle changes and risk reduction therapy, as these will also improve long-term outcome. Importantly, patients should live long enough to enjoy the benefits of surgery. The preoperative evaluation of high risk patients is hampered by the complex pathophysiology of a perioperative myocardial infarction (MI). Both coronary plaque rupture, leading to thrombus formation and subsequent vessel occlusion, and a sustained oxygen supply–demand mismatch contribute equally to the incidence of a perioperative MI. The former is related to the inflammatory status of the coronary artery tree. This has important implications on perioperative and long-term risk reduction strategies. A single intervention, for instance aiming at restoration of the supply– demand mismatch, may offer insufficient protection for coronary plaque instability. Therefore, treatment of the coronary culprit lesion only offers limited protection as the disseminated inflammatory disease of the coronary artery tree progresses. Recently Kertai et al. used a total of 2310 patients to develop a Bayesian model for the prediction of all-cause mortality in patients undergoing all types of open vascular surgery. The type of surgery was a strong risk factor; patients with a ruptured abdominal aortic aneurysm had the worst outcome, followed by elective thoracoabdominal and abdominal aortic surgery, lower extremity arterial bypass surgery, and carotid surgery. Risk factors based on medical history, in order of descending risk, were: renal dysfunction, congestive heart failure, ischaemic heart disease, cerebrovascular event, hypertension, and pulmonary disease. The data of the Coronary Artery Revascularization Prophylaxis (CARP) study of McFalls et al. confirm these preoperative risk factors and offer the clinician hints for long-term outcome. Recently biomarkers such as high sensitive C-reactive protein (hsCRP) have also emerged as potential predictors of adverse cardiovascular events after vascular surgery. As shown by Owens et al. in a group of 91 vascular surgery patients, a preoperative hsCRP level .5 mg/ L was associated with a 2.3-fold increased risk for adverse cardiovascular events during a mean follow-up of 12 months.