Management of Concomitant Carotid and Coronary Arterial Disease

Cardiac Risk Stratification Prior to Carotid Endarterectomy

An assessment of CAD before vascular reconstruction has several purposes. These include preventing perioperative cardiac ischemic complication and assessing long-term prognosis because natural history implicates CAD as the principal cause of late mortality in patients following carotid endarterectomy (CEA). Several studies have highlighted the prevalence of CAD and its short- and long-term implications for patients treated with CEA. Hertzer and colleagues performed routine preoperative coronary angiography in 506 carotid endarterectomy patients and found that the severity of coronary artery disease was normal in 7%, mild to moderate in 28%, advanced and compensated in 30%, severe and correctable in 28%, and inoperable in 7%.

Mackey and colleagues found that 53% of patients undergoing CEA had evidence of CAD by clinical history or electrocardiographic studies. CEA patients with clinical CAD had an operative mortality of 1.5% and a rate of myocardial infarction (MI) of 4.3% compared with 0% mortality and 0.5% MI rates in patients without CAD. They reported the 5- and 10-year survival rates of patients with CAD to be 68.6% and 44.9%, respectively, versus 86.4% and 72.3% for patients without CAD.

Urbinati and colleagues found that 25% of 106 patients undergoing CEA had significant defects on thallium exercise testing. They noted 7-year freedom from cardiac events after CEA was 51% for patients with silent myocardial ischemia versus 98% for patients with normal stress tests. In our own’ cohort of more than 2000 CEA patients (1990–1999), the rate of perioperative MI was 1.2%, and 10-year actuarial survival was 45%. Among variables associated with increased late mortality, concomitant CAD (odds ratio [OR] 1.4; p = .0002) figured prominently.

Improved perioperative care and adjunctive medical therapy have substantially lowered the risk of coronary ischemic events complicating CEA. Recent American College of Cardiology and American Heart Association (ACC/AHA) guidelines on perioperative cardiovascular evaluation for noncardiac surgery designated CEA as a low- to intermediate-risk procedure. The guidelines suggest that in the absence of active coronary ischemia, clinical profiling based on cardiovascular risk factors and functional capacity is the mainstay of cardiac risk stratification for such procedures. Patients undergoing noncardiac surgery in the absence of active coronary ischemia are best treated with continuance of β-blockers, statins, and aspirin and might benefit from perioperative use of these medications if they are not already taking them. Indeed, Perler and coworkers have reported the favorable role of statin therapy with respect to postoperative stroke (three fold reduction) and cardiovascular mortality (five fold reduction) following CEA.

Causes of Stroke Following Coronary Revascularization

Next to operative mortality, permanent stroke is the most dreaded complication following coronary revascularization because of the devastating consequences to the patient as well as the increased cost of hospitalization and post-hospital care. Major reported risk factors associated with stroke following coronary revascularization include age, ascending aortic atherosclerosis, long cardiopulmonary bypass time, perioperative hypotension, and preexisting cerebrovascular disease. Intracranial hemorrhage can lead to neurologic injury following cardiopulmonary bypass, but this a rare event, despite the degree of anticoagulation necessary for cardiopulmonary bypass.

Neurologic injury can also result from inadequate perfusion pressure on cardiopulmonary bypass, and adequate perfusion is especially important in the presence of carotid stenosis or occlusion. Some investigators have shown a linear relationship between the degree of carotid stenosis and the risk of perioperative stroke; in such analyses, patients with total internal carotid artery (ICA) occlusion are typically the subgroup at highest risk for stroke. Yet carotid revascularization is not possible in the circumstance of total ICA occlusion. When there is occlusion of carotid or intracerebral arteries, brain blood flow depends on collateral circulation, which, in turn, depends on perfusion pressure.

Atheroemboli or thromboemboli remain the most common causes of stroke following CABG. Intracardiac emboli emanate from mural thrombus associated with MI, valvular disease, arrhythmias, surgical suture lines, or, in rare instances, trapped air. Cannulation of the ascending aorta for bypass, aortic cross-clamp application, and intra aortic cardioplegia delivery devices can dislodge existing atherosclerotic material from the aorta. Thus, numerous investigators have identified aortic atherosclerosis as a risk factor for perioperative stroke. Use of preoperative computed tomography angiography (CTA) or intraoperative echocardiography to identify and avoid aortic atherosclerosis during clamping and cannulation has resulted in a reduced stroke risk.