American College of Cardiology

EAGLE ET AL., PERIOPERATIVE CARDIOVASCULAR EVALUATION FOR NONCARDIAC SURGERY UPDATE
http://www.acc.org/clinical/guidelines/perio/update/periupdate_index.htm

ACC/AHA Guideline Update for Perioperative Cardiovascular Evaluation for Noncardiac Surgery

A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery)

X. Postoperative and Long-Term Management

It has been recognized since the early 1980s that cardiac events are a frequent outcome in postoperative vascular surgery patients ⁽³⁵⁸⁾. Over the course of the last decade, advances in preoperative, intraoperative, and postoperative management have resulted in better patient outcomes in noncardiac (especially vascular) surgery ^(359,360). This is due to a number of factors that involve better detection of underlying CAD in preoperative patients, as well as greater skill and experience in the perioperative care of such patients. The combination of improved medical therapy, which typically includes beta blockers, aspirin, and lipid-lowering agents, and coronary revascularization in appropriate cases should result in improved event-free survival.

Despite optimal perioperative management, some patients will experience perioperative MI, which is associated with a 40% to 70% mortality ⁽³⁶¹⁾. The reason for the high mortality is undoubtedly multifactorial and related in part to significant comorbidity in such patients. However, the inability to administer reperfusion therapy undoubtedly contributes to the high mortality associated with MI early after noncardiac surgery.

Many perioperative MIs are a result of a sudden thrombotic coronary occlusion, as is the case with MI that occurs in the nonoperative setting ^(362,363). Among eligible patients, rapid reperfusion therapy is the cornerstone of therapy ⁽³⁶⁴⁾. Thrombolytic therapy markedly reduces mortality when administered to patients who have MI unrelated to a surgical procedure. However, because of the substantial risk of bleeding at the surgical site, patients who have recently undergone surgery have been excluded from all trials of thrombolytic therapy, and recent surgery is generally considered a strong contraindication to thrombolytic therapy. Although thrombolytic therapy has been administered to patients for life-threatening pulmonary embolus shortly after noncardiac surgery, the thrombolytic dosage has generally been less and has been administered over a longer time interval than is standard for the treatment of acute MI ^(365,366). Immediate coronary angioplasty has been favorably compared with thrombolytic therapy in the treatment of acute MI ⁽³⁶⁷⁾, but of greater importance is that the risk of bleeding at the surgical site is believed to be less with direct angioplasty than with thrombolytic therapy. Only a single small study ⁽³⁶⁸⁾ has evaluated the role of immediate angiography and angioplasty among 48 patients who were believed able to take aspirin and intravenous heparin, and to undergo immediate angiography and PCI. This study suggested that such a strategy is feasible and may be beneficial. However, time to reperfusion is a critical determinant of outcome in acute MI, and any hope of benefiting patients who have a perioperative acute MI due to an acute coronary occlusion requires that angiography and revascularization be rapidly performed (i.e., within 12 hours of symptom onset) ^(368,369). In addition, these reperfusion procedures should not be performed routinely on an emergency basis in postoperative patients in whom MI is not related to an acute coronary occlusion. For instance, in cases of increased myocardial demand in a patient with postoperative tachycardia or hypertension, lowering the heart rate or blood pressure is likely to be of greater benefit, and certainly less risk. There is also no evidence to support immediate angiography in patients found to have an elevated cardiac marker, such as CK-MB band or cardiac troponin, who are otherwise clinically stable.

Although reperfusion therapy is an important therapy in acute ST-segment-elevation MI, the emphasis on reperfusion therapy should not detract from pharmacological therapy, which is also very important and has been shown to reduce adverse events in such patients, as well as in patients with non-ST-elevation acute coronary syndromes. Therapy with aspirin, a beta blocker, and an ACE inhibitor, particularly for patients with low ejection fractions or anterior infarctions, may be beneficial, whether or not the patients are rapidly taken to the catheterization laboratory ⁽³⁷⁰⁾. An extensive evidence-based review of therapy for acute MI can be found in the ACC/AHA guidelines for the management of patients with acute MI ⁽³⁷⁰⁾. Although not intended specifically for patients who have a postoperative MI, they are nonetheless appropriate for these high-risk patients. Similarly, the ACC/AHA guidelines for unstable angina represent an important template for management of this condition in the postoperative setting ⁽³⁷¹⁾.

In the approach to the long-term postoperative management of noncardiac surgery patients, one should first appreciate that the occurrence of an intraoperative nonfatal MI carries a high risk for future cardiac events that are often dominated by cardiovascular death ^(214,372). Therefore, patients who sustain acute myocardial injury in the perioperative or postoperative period should receive careful medical evaluation for residual ischemia and overall left ventricular function. The ACC/AHA guidelines for post-MI evaluation in these types of patients should be followed as soon as possible after surgical recovery. The use of pharmacological stress ⁽²⁶⁾ or dynamic exercise (if feasible) for risk stratification should also be a priority in patients to help determine who would benefit from coronary revascularization. In all cases, the appropriate evaluation and management of complications and risk factors such as angina, HF, hypertension, hyperlipidemia, cigarette smoking, diabetes (hyperglycemia), and other cardiac abnormalities should commence before hospital discharge. It is also important to communicate these new observations and determinations of cardiac status and risk to the physician who will be responsible for arranging subsequent medical care and follow-up.

It is also appropriate to recommend secondary risk reduction in the relatively large number of elective-surgery patients in whom cardiovascular abnormalities are detected during preoperative evaluations. Although the occasion of surgery is often taken as a specifically high-risk time, most of the patients who have known or newly detected CAD during their preoperative evaluations will not have any events during elective noncardiac surgery. A recent review ⁽²⁶¹⁾ of a national Medicare population sample identified a cohort of patients (n=6895) who underwent elective vascular surgery during a 17-month period in 1991 and 1992. The authors noted a relatively high mortality rate (15%) at 1 year of follow-up among patients who did not undergo preoperative stress testing. However, in those patients (19%) undergoing preoperative stress testing with or without coronary bypass surgery, the mortality rate was lower (less than 6%). In other follow-up studies ^(372,373) of vascular surgery patients who were followed up for a mean of 40 to 48 months, cardiac events were significantly more frequent in those who had a reduced LVEF of less than 35% or 40% and who demonstrated ischemia of at least moderate size on dipyridamole-thallium imaging. Therefore, it is important to consider which preoperative clinical risk factors and noninvasive testing parameters can be used to help predict long-term cardiac risk.

Most of the long-term follow-up studies in postoperative patients involve vascular surgery. Figure 3 summarizes some large follow-up studies in patients undergoing major vascular surgery who were followed up over the next 2 to 5 years for subsequent cardiac death or MI. It is clear that preoperative clinical risk assessment as determined by the Goldman criteria, LVEF, coronary angiography, dipyridamole-thallium imaging, and dobutamine echocardiography can also be used to evaluate long-term cardiac risk. Cardiac mortality in the postoperative period increases with higher clinical risk, lower LVEF (less than 35%), multivessel CAD, abnormal thallium scans, or multiple ischemic segments on dobutamine echocardiography studies. Other studies ^(374-376) also confirm the value of semiquantitative analysis of myocardial perfusion imaging when using these types of perioperative tests to predict future cardiac events. All these studies have the ability to combine an assessment of myocardial ischemia and left ventricular function into a more useful clinical index.

It is clear from these and other imaging studies ^(377-379) that the extent of ischemia or reduced ventricular function achieves the best level of prognostic utility for future cardiac events. Overall, a normal or near-normal stress imaging study suggests a relatively small risk, but the positive predictive accuracy of abnormal studies is greatly enhanced by the establishment of a progressive gradient for that abnormality.

Although the perioperative cardiac event rate for renal and liver transplantation is fairly low, the long-term risk for MI or cardiovascular death associated with such transplants often results in referrals for preoperative cardiac consultation and testing. Compared with the data for long-term follow-up in vascular surgery patients, the results in renal and liver transplants are somewhat less compelling. Not all publications support the routine use of cardiac screening to help stratify renal patients according to risk ⁽³⁸⁰⁾, but more recent publications ^(262,381) have shown significant prognostic value for preoperative stress testing in these patients. This is especially true if there are cardiac risk factors and for patients with diabetes ⁽³⁸²⁾. There are only a few reports ^(264,383) dealing with the evaluation of cardiac risk in liver transplant patients, and the data are not compelling for routine testing. This is most likely because of the very low incidence of cardiac events in these studies. However, until more data are available, it may be prudent to consider preoperative testing in those liver transplant patients who have clinical cardiac risk factors.

These types of observations should encourage us to pay closer attention to the medical outcome of patients seen for perioperative evaluations, especially in the context of vascular surgery. After the preoperative cardiac risk has been determined by clinical or noninvasive testing, most patients will benefit from pharmacological agents to lower low-density lipoprotein cholesterol levels, increase high-density lipoprotein levels, or both. On the basis of expert opinion, the goal should be to lower the low-density lipoprotein level to less than 100 mg per deciliter (2.6 mmol per deciliter) ^{(229,384,385)}.

In general, the indications for additional screening or testing in postoperative patients depend on individual patient characteristics. A recent decision-tree model ⁽²⁴⁴⁾ was constructed to compare cost-effectiveness of various preoperative screening protocols in postoperative vascular surgery patients for up to 5 years after discharge. The best event-free survival and cost-effectiveness ratio were noted for selective preoperative stress testing (using dipyridamole-thallium imaging) in patients with intermediate clinical risk, whereas high-risk patients were referred to coronary angiography and low-risk patients were sent to elective surgery without further workup. This is the general approach suggested in these guidelines. In addition, another recent report ⁽³⁸⁶⁾ showed that the clinical risk factors used in these guidelines were more sensitive than surgical factors for predicting perioperative cardiac events. These recent studies confirm the importance of clinical evaluations for both the perioperative and long-term follow-up periods. The performance of prospective clinical trials would be an important addition to this overall clinical analysis. Finally, as noted for patients having a perioperative MI, it is important that the physician(s) responsible for the long-term care of the patient be provided with complete information about any cardiovascular abnormalities or risk factors for CAD identified during the perioperative period.