Coronary Artery Disease in Patients with Aortoiliac Occlusive Disease and Abdominal Aortic Aneurysm

Palaniappan Muthappan and Kim A. Eagle

Diseases of the abdominal aorta and aortoiliac system share many important pathophysiologic factors with coronary artery disease (CAD). Many of the risk factors that contribute to abdominal aortic aneurysms (AAA) and aortoiliac occlusive disease (AIOD), including diabetes, tobacco use, hyperlipidemia, and advanced age, are also risk factors for CAD. Accordingly, a prudent surgeon must always keep CAD in mind when treating a patient who has diseases of the abdominal aorta and aortoiliac system. Despite decreasing morbidity and mortality rates for surgical treatment of abdominal aortic aneurysm and aortoiliac disease, CAD remains an important cause of perioperative morbidity and mortality. Patients with peripheral vascular disease who have significant CAD have been shown to have decreased long-term survival.

Importance of Coronary Artery Disease

A number of studies have reported on the incidence and outcomes of patients with comorbid CAD and AAA or AIOD. In 1989, Johnston and colleagues reported a cardiac event rate of approximately 15% among 666 patients who underwent operation for nonruptured AAAs, with the highest probability of postoperative myocardial infarction (MI) occurring in older patients with a history of angina. In 1994, Chen and colleagues reported that patients with nonruptured AAAs had a fivefold increase in mortality if they experienced a perioperative MI (odds ratio [OR], 5.0; p < .01), and patients with ruptured AAAs who survived the initial operative had a fourfold increase in mortality if they experienced a perioperative MI.

Similarly, in the Coronary Artery Revascularization Prophylaxis (CARP) trial, 5859 veterans undergoing elective surgery for AAA or AIOD at Veterans Administration Hospitals were assessed by for cardiac risk. The study’s 1190 patients judged to have increased cardiac risk underwent coronary arteriography. Nonobstructive coronary artery disease was evident in 363, and 510 had more significant CAD. The latter were randomized to coronary revascularization or medical management with no revascularization. Ninety-nine patients underwent CABG, and 141 underwent a percutaneous coronary intervention. With an average of 2.7 years of follow-up, there was no difference in outcome: 22% of the patients who underwent revascularization and 23% of the patients who underwent medical management with no revascularization died, p = .92.

Endovascular aneurysm repair (EVAR) has become more common. An EVAR trial conducted between 1999 and 2004 randomized 1252 patients to endovascular or open repair of AAA and followed patients for MI, stroke, or death until 2009. The investigators identified a total of 187 cardiovascular events (98 MIs and 89 strokes). The rates of cardiovascular events appeared to be lower in the EVAR group (2.6 vs. 3.2 events per 100 person-years), but this was not found to be statistically significant, p = .199.

Preoperative Cardiac Risk Assessment

It is prudent to take a systematic approach to cardiac risk assessment in any patient with AAA or AIOD and a suspicion of coronary artery disease. The American College of Cardiology and the American Heart Association produced updated guidelines in 2007 for perioperative cardiac evaluation and care before noncardiac operative procedures. A general strategy for preoperative cardiac risk assessment is shown in Figure 1. Optimally, the strategy should be applied in the outpatient setting and should be used for elective operations.

According to these guidelines, the first step in cardiac risk assessment is to determine the urgency of the noncardiac operation. Patients who must undergo operation under emergency conditions should be monitored closely and may have their cardiovascular status more thoroughly evaluated postoperatively. They might benefit from urgent consultation with a cardiologist and from intensified perioperative medical management. Patients who are scheduled to undergo less urgent or elective surgery should be evaluated to see if they have any major cardiac risk factors, including unstable coronary syndrome (unstable or severe angina or recent MI), decompensated heart failure, significant arrhythmias, or severe valvular disease. If so, cancellation or delay of the planned AAA or AIOD intervention until the problem has been evaluated and treated should be strongly considered. Next, the patient’s functional capacity should be evaluated. Patients who can perform more than four metabolic equivalents of task (METs) generally do well through surgery. This level of activity includes washing dishes, climbing a flight of stairs, running a short distance, or playing golf.

Patients with poor functional capacity, evident by the inability to achieve four METs of activity, should then be evaluated for intermediate clinical risk factors. These include history of ischemic heart disease, history of compensated or prior heart failure, history of cerebrovascular disease, presence of diabetes mellitus, and presence of renal insufficiency. In patients who do not have any of these intermediate risk factors, it is generally acceptable to proceed to surgery. For patients who have one or two intermediate risk factors, the decision to perform noninvasive cardiac testing or to proceed directly to surgery should be considered carefully and must be individualized to each patient and situation. In patients with three or more intermediate risk factors, noninvasive cardiac testing is generally advisable if it will change management.

Patients with intermediate clinical predictors commonly are further evaluated with noninvasive cardiac stress testing using electrocardiography (ECG), echocardiography, nuclear imaging, or cardiac magnetic resonance imaging (MRI). The goal of noninvasive cardiac imaging is to establish the extent and severity of CAD. Testing should only be considered if it would change management; if the patient would not be eligible for coronary angiography and possible revascularization as a result of a positive noninvasive imaging test, then testing should not be performed in the first place, and maximal medical treatment should be provided instead.

The negative predictive value for a patient with a normal noninvasive test is generally high. The clinician can be confident in sending such a patient to surgery because cardiovascular morbidity and mortality are extremely low. Stress echocardiography, nuclear imaging, and cardiac MRI can also provide assessments of left ventricular systolic function. Although not necessarily predictive of postoperative MI, left ventricular systolic function may be an important determinant of postoperative congestive heart failure, the presence of which adversely effects hospital length of stay and health care costs.

For patients undergoing interventions for AAA or AIOD, coronary angiography with the intention to perform coronary angioplasty should be considered only if the results of noninvasive testing document abnormalities suggesting severe CAD with extensive myocardium at risk, such as more than 25% ischemic. It is also important to keep in mind that if a flow-limiting coronary stenosis or acute coronary syndrome is found and an intervention is performed, the AAA or AIOD intervention will need to be delayed. The least delay follows balloon angioplasty, after which surgery should be delayed for 2 to 4 weeks to allow the angioplasty site to heal and the coronary inflammatory response to decrease before exposing the patient to the proinflammatory and prothrombotic milieu of vascular surgery. Balloon angioplasty is followed by restenosis in 20% to 35% of patients and typically occurs 8 weeks to 6 months after angioplasty.

Stenting offers a more lasting solution for coronary lesions, but the intervention for AAA or AIOD must be delayed for a longer period than with angioplasty. With bare-metal stenting, it is recommended that the patient receive aspirin and a thienopyridine for a minimum of 30 to 45 days. With a drug-eluting stent, it is recommended that aspirin and a thienopyridine be continued for 1 full year.

With these considerations, it might not be feasible for a high-risk patient to undergo surgery. In these patients, it must be decided whether to cancel the surgery or to proceed with surgery with measures to optimize medical management. For aortic and aortoiliac reconstruction, endovascular approaches may be a reasonable alternative to open approaches; though endovascular procedures are generally considered less intensive and safer, studies have not shown improved long-term outcomes.

Certain patients benefit from perioperative use of β-blockers and statins. The American College of Cardiology (ACC) and American Heart Association (AHA) guidelines on perioperative care recommend β-blockers for patients who have coronary artery disease or cardiac ischemia or who have more than one major or intermediate clinical risk factor (described earlier) undergoing vascular surgery. β-Blockers should be titrated to maintain a heart rate of 60 to 80 beats per minute and to avoid hypotension. Whenever possible, β-blockers should be started days to weeks before surgery. Most importantly, β-blockers should not be stopped before surgery in patients who were already on them.

The guidelines also recommend that all patients who undergo vascular surgery be started on a statin or have their current statin therapy continued. This recommendation is based upon evidence that in addition to lowering lipids, statins have beneficial effects on endothelial function, reduce vascular inflammation, and stabilize atherosclerotic plaques.

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