PREOPERATIVE CARDIAC ASSESSMENT OF THE CANDIDATE FOR MAJOR RESECTIVE PANCREATIC SURGERY

Abstract

Once a surgeon has determined that a patient with malignant pancreatic or periampullary disease is a candidate for operative intervention, cardiac assessment is an important next step before surgery. Often, these patients are elderly, malnourished, or have significant comorbid medical problems, including chronic obstructive pulmonary disease and diabetes mellitus, which increase the risk for noncardiac surgery. Preoperative preparation can maximize these organ systems, but the fear of a major perioperative cardiac event exists for every surgeon. That 40% of patients undergoing noncardiac surgery in the United States each year have, or are at risk for, coronary artery disease supports this concern.⁸ Cardiac complications are a leading cause of death in the intraoperative and postanesthesia period. Cardiology consultation should be obtained to help identify patients at high risk for perioperative morbidity and mortality, especially among candidates for extensive surgical resection.

Congestive heart failure, hypertension, and atrial fibrillation can increase perioperative risk. Clinical detection and adequate management of these problems can decrease risks in the postoperative period. Identification of asymptomatic left ventricular dysfunction by preoperative echocardiography can alert the physician to potential problems of fluid management to avoid postoperative pulmonary edema. Symptomatic critical aortic stenosis should be corrected before any elective surgery; however, in most patients, evaluation is performed primarily to predict the probability of a perioperative myocardial ischemic event.

Although an electrocardiogram is a routine first screen, determining which patients need further noninvasive testing is less clear. Certainly, it is not cost-effective to subject every patient to a battery of tests. Risk classification based on clinical assessment has been developed and validated to help answer this question. Two major indices are available. The first classification, the Eagle Index,² gives 1 point to each of the following categories:

• 1
  A history of myocardial infarction or angina
• 2
  A Q wave on preoperative ECG
• 3
  Diabetes mellitus requiring drug therapy
• 4
  Age of more than 70 years
• 5
  A history of ventricular arrhythmia requiring therapy

The second index, the Revised Cardiac Risk Index,⁶ as described by Lee and associates, assigns 1 point to each of the following variables:

• 1
  High-risk surgery
• 2
  A history of ischemic heart disease as manifested by a history of myocardial infarction, a positive exercise test, current complaints of ischemic chest pain, the use of nitrate therapy, or an ECG with Q waves
• 3
  A history of congestive heart failure
• 4
  A history of cerebral vascular disease
• 5
  Insulin therapy for diabetes mellitus
• 6
  Preoperative creatinine level of more than 2.0 mg/dL

If no Eagle Index points are present, the patient is considered to be at low risk; 1 or 2 points classifies the patient as an intermediate risk; more than 2 points, high risk. In the Revised Cardiac Risk Index, high risks include class III and class IV patients having two risk factors or more than two risk factors, respectively. Both classifications advocate the use of noninvasive testing in the intermediate-risk group. Lower-risk patients had a 3.1% risk for a perioperative myocardial event; the intermediate group, a 15% risk; and the high-risk group, a 50% risk. Intermediate-risk patients who were negative for ischemia on their workup had a risk factor of just 3.2%, similar to that of the low-risk group. Those who were positive had a risk of 29.6% of having a perioperative myocardial event. L'Italien et al⁷ validated these results in their studies. Persantine-thallium screening provided no stratification for low and high-risk patients based on their clinical model. For patients in the intermediate risk category, 80% were classified as low risk after the study, and only 20%, as high risk.

Basic noninvasive testing for risk stratification includes the ECG stress test, which is conducted in patients who can exercise and have normal ST segments at rest.¹⁰ Poor exercise capacity and the development of ECG changes consistent with myocardial ischemia, particularly if it occurs at a rate less than 75% of predicted maximal heart rate is associated with a high risk for perioperative ischemic events. Patients who achieve greater than 75% of their predicted maximal heart rate without ST segment changes are at low risk. Those who achieve a greater than 75% maximal heart rate and show ischemic changes are at intermediate risk.

Many patients are unable to exercise or have an abnormal ECG at rest, rendering an ECG response to exercise nondiagnostic. In these patients, pharmacologic nuclear perfusion imaging using thallium or dobutamine echocardiography can be used to detect myocardial ischemia.3, 4, 11, 13

Today, practice guidelines are available that support the concept of risk stratification based on a clinical risk index.1, 5 Patients at low risk need no additional testing. Those at high risk and intermediate risk with large zones of myocardial ischemia by noninvasive testing should undergo angiography and revascularization as indicated by angiographic findings before undergoing major intra-abdominal surgery. Findings requiring revascularization include left main trunk disease or triple vessel disease with left ventricular dysfunction.

Coronary intervention in high-risk patients identified by myocardial perfusion scintigraphy may improve outcomes in major, noncardiovascular surgery.¹⁴ Although revascularization in high-risk coronary patients seems to improve the long-term outcome of these patients, no prospective, randomized trials show that coronary artery surgical intervention in these patients reduces short-term perioperative ischemic complications. This has led to the use of β-blockade in patients undergoing major noncardiac surgery.¹² In one randomized trial, high-risk patients, defined as having an abnormal dobutamine stress echocardiogram, were randomized to receive β-blockade versus placebo. The group on β-blockade had a 3.4% prevalence of a perioperative myocardial ischemic event compared with a 33.9% prevalence in the placebo group. This remarkable reduction in risk was noted and the trial was halted early by an independent safety committee.

Today, β-blockade has been used not only with increasing frequency in high-risk surgical patients but also in conjunction with coronary stenting when used as a method for coronary revascularization.

To diminish the risk for stent thrombosis, intensive antiplatelet therapy is needed for at least 4 weeks. If possible, elective surgery should be delayed during this period.

Based on the available literature and the authors' personal experience, the following recommendations are suggested for the evaluation and care of potential cardiac patients facing major pancreatic surgery.

• 1
  Patients with an unstable coronary syndrome should undergo angiography and appropriate revascularization, as indicated, before any elective surgery.
• 2
  Patients with clinical indications for revascularization (independent of their noncardiac condition) should undergo revascularization before noncardiac surgery.
• 3
  Patients with strongly positive noninvasive tests, such as dobutamine stress echocardiography, stress ECG, or nuclear perfusion imaging, should undergo angiography and revascularization as appropriate.
• 4
  Patients with symptomatic critical aortic stenosis should undergo aortic valve replacement before elective surgery.
• 5
  Noninvasive testing should be limited to intermediate-risk patients stratified by clinical criteria. High-risk patients should undergo angiography and appropriate revascularization before elective surgery, although the current literature offers no prospective study validating that such an intervention would reduce perioperative events. Low-risk patients require no further testing.
• 6
  Patients who have had revascularization in the previous 5 years, and those who have had noninvasive testing within the past 2 years without evidence of clinical ischemia, require no further preoperative testing.
• 7
  All clinically determined intermediate- and high-risk patients should receive β-blockade perioperatively unless contraindicated, such as in the setting of asthma, sinus bradycardia, and second- and third-degree arteriovenous blockade.⁹

Following these guidelines, a concise recommendation can be given to the surgeon concerning the risks of surgical intervention for individual patients. These evaluations are vital to clinicians when deciding whether to perform surgery on a high-risk patient. The risks of operative intervention must be balanced with the outlook that each patient has in terms of his or her existing pancreatic disease.