The Management of the Cardiac Patient Requiring Noncardiac Surgery: Preoperative Evaluation and Management of the Surgical Patient with Heart Disease

Symposium on Surgery in the Cardiac Patient

The Management of the Cardiac Patient Requiring Noncardiac Surgery Preoperative Evaluation and Management of the Surgical Patient with Heart Disease

john Hermanovich, Jr., M.D.*

CORONARY ARTERY DISEASE Patients with coronary artery disease undergoing noncardiac surgery are at significant risk of developing perioperative myocardial infarction or cardiac death. Steen and co-workers 18 reviewed the cases of 587 patients with a previous myocardial infarction who underwent anesthesia and noncardiac surgery during 1974 and 1975. They found 36 patients (6.1 per cent) had a reinfarction, and 25 of these (69 per cent) died. The reinfarction rate was 27, 11, and 5 per cent, respectively, if the myocardial infarction had occurred within three months, three to six months, or more than six months before the noncardiac surgical procedure. Though the analysis of Goldman et al. 6 did not identify angina pectoris as an independent descriptor of postoperative myocardial infarction Qr cardiac death, other studies 16· 17 have suggested a 5 to 11 per cent perioperative mortality for patients with chronic stable angina, unstable angina, or angina pectoris after remote myocardial infarction. The clinical indications for coronary artery bypass graft (CABG) surgery include the prolongation of life expectancy and the relief of disabling angina not well controlled with maximum medical therapy. It is generally accepted that in symptomatic patients with stenosis of the left main coronary artery or three-vessel coronary artery disease, longevity is enhanced with a CABG 4 · 5 · 7 · 1.;, 19 if the surgical mortality is minimal (currently less than 2 per cent at most major centers). With significant two-vessel coronary artery disease, CABG surgery is usually recommended for relief of medically uncontrolled angina. In patients with obstruction of a single coronary artery *Assistant Professor of Medicine; Assistant Director, Cardiac Catheterization Laboratory, Cardiology Division, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey, Pennsylvania

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whose angina is inadequately controlled with maximum medical therapy, coronary artery bypass surgery or percutaneous transluminal coronary angioplasty is generally recommended. To date, no prospective studies have compared cardiac risk during subsequent noncardiac surgery in patients having angiographically documented coronary artery disease treated by medical therapy vs. patients treated by coronary artery bypass surgery. However, several groups have reported a marked reduction in perioperative myocardial infarction and cardiac death in patients having had previous CABG surgery. McCollum and colleagues 13 reported on 60 patients with prior CABG surgery who had 77 subsequent noncardiac operations with no postoperative myocardial infarctions and no occurrence of postoperative death. Mahar and co-workers 11 examined the influence of prior CABG surgery upon cardiac morbidity in patients with angiographically documented coronary artery disease who were undergoing subsequent noncardiac surgery. Ninety-nine patients with previous CABG surgery (54 with prior myocardial infarction) had 168 noncardiac operations with no myocardial infarction during the seven days after the noncardiac procedure and no perioperative deaths. A control group of 49 patients with previous coronary angiography but no CABG surgery with similar extent of coronary artery disease, preoperative myocardial infarctation, and symptomatic status had three postoperative myocardial infarctions and one postoperative cardiac death. The authors of this study suggested that in patients with coronary artery disease undergoing noncardiac surgery (1) three-vessel coronary artery disease without previous CABG surgery is associated with a high (approximately 20 per cent) risk of myocardial infarction; (2) the risk of postoperative myocardial infarction with one- or two-vessel coronary artery disease appears to be relatively low; and (3) the risk of postoperative myocardial infarction in patients having CABG surgery is significantly less than in patients with similar coronary artery disease who have not first undergone CABG surgery. More recently, Akl and associates 1 reported similar results suggesting that myocardial revascularization provides significant protection against the risk of cardiac complications and death with ischemic heart disease in whom general anesthesia and noncardiac procedures are needed. Though the studies are few and the number of patients so analyzed is small, the data to date suggest that CABG surgery may be protective in selected subsets of patients undergoing subsequent noncardiac surgery. In general, the decision for CABG surgery versus medical treatment in patients with angina pectoris or previous myocardial infarction is usually determined by the extent and the severity of the coronary artery obstructive disease coupled with an analysis of left ventricular function determined by cardiac catheterization plus coronary and ventricular angiography. The primary decision of performing cardiac catheterization with angiography is usually based on multiple factors, such as the physiologic and chronologie age of the patient, severity of underlying angina pectoris and its response to medical therapy, history of prior myocardial infarction, presence of other noncardiovascular systemic disease, and noninvasive

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Table 1. Indications for Complete Cardiac Catheterization and Coronary Angiography in Patients Undergoing Elective Major Noncardiac Surgery Preoperative Assessment of Coronary Artery Disease Stable angina pectoris Unstable angina pectoris Status post myocardial infarction with: Recurrent angina Adequate left ventricular function and inducible ischemia Preoperative Assessment of Valvular Heart Disease Symptomatic aortic stenosis Symptomatic aortic regurgitation, less than Class II Mitral stenosis, less than Class II Mitral regurgitation, less than Class II

diagnostic and prognostic test results (exercise treadmill testing, exercisethallium scintigraphy, echocardiography, and nuclear angiography). The epidemiologic as well as the more recent angiographic data about the cardiac patient undergoing elective noncardiac surgery suggest that patients with angina pectoris or a previous myocardial infarction be seriously considered for preoperative cardiac catheterization and coronary angiography (Table 1). Patients with left main coronary artery disease or threevessel coronary artery disease in particular may be recommended for elective preoperative coronary artery bypass grafting before major noncardiac surgery. CONGESTIVE HEART FAILURE The preoperative management of patients with congestive heart failure (CHF) requires assessment of the degree of functional impairment as well as the cause of the cardiovascular dysfunction. The final common pathway leading to the syndrome of congestive heart failure is a reduction in myocardial contractility, which in turn produces pulmonary vascular congestion (dyspnea) and diminished cardiac output (fatigue). In the following section, CHF due to a disturbance in myocardial function (cardiomyopathy) will first be considered. Thereafter, CHF secondary to valvular heart disease will be discussed. Cardiomyopathy The most common causes of CHF are hypertensive heart disease and dilated cardiomyopathy. 8 The most common cause of dilated cardiomyopathy in North America and Europe is the cardiomyopathic syndrome resulting from multiple infarctions caused by coronary artery disease (socalled "ischemic cardiomyopathy"). Other less common causes of dilated cardiomyopathy include idiopathic congestive cardiomyopathy, alcoholic cardiomyopathy, infectious myopericarditis, and peripartum cardiomyopathy. With each disease, myocardial pump dysfunction is the primary abnormality, with any associated valvular abnormality, especially mitral regurgitation, existing on a secondary functional basis.

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Patients with hypertensive or dilated cardiomyopathy and mild CHF (New York Heart Association Classification I or II) can usually be maintained in a compensated state with digitalis and diuretic therapy. Preoperative management usually requires no more than maximizing such therapy based upon clinical history, physical examination, and chest x-ray examination. In addition, fluid balance must be carefully maintained during the intraoperative and postoperative periods with additional digitalis, diuretic therapy, or both as clinically indicated. In contradistinction, patients with severe CHF (New York Heart Association Classification III and IV) despite digitalis and diuretic therapy form a subset with an annual mortality approaching 50 per cent and constitute a high risk group when undergoing major noncardiac surgical procedures. Many of these patients demonstrate major improvement in their daily functional capacity with oral vasodilator therapy designed to alter the loading conditions under which the impaired left ventricle must operate. 3 · 12 Long-acting nitrate preparations by their predominant venodilation can substantially reduce left ventricular preload and thereby decrease left ventricular end-diastolic volume and pressure producing a reduction in pulmonary venous congestion. Oral arteriolar dilators such as hydralazine and minoxidil produce a significant reduction in left ventricular afterload by reducing the systemic vascular resistance and allowing the diseased left ventricular to pump against a reduced impedance to ejection. Other oral agents such as prazosin and captopril have balanced vasodilator properties producing both a reduction in the left ventricular end-diastolic volume and pressure (preload) in addition to a decrease in the impedance to left ventricular ejection (afterload) thereby reducing pulmonary vascular congestion and promoting an increase in cardiac output. The preoperative management of patients with severe chronic CHF therefore requires optimum treatment with digitalis and diuretics plus vasodilator therapy with the appropriate agent or combination of agents based upon the individual's baseline hemodynamic profile. Before the proposed surgical procedure, catheterization of the right side of the heart should be performed with a Swan-Ganz balloon-tipped thermodilution catheter to assess the left ventricular filling pressure (LVFP) measured as the pulmonary capillary wedge pressure and the resting supine cardiac output. An intraarterial line should be percutaneously inserted to allow continuous monitoring of the systemic arterial pressure. Thereafter, the patients with a markedly abnormal LVFP, cardiac output, or both may be titrated preoperatively to more optimum hemodynamics by using intravenous vasodilators and inotropic agents as described below. If the patient's baseline LVFP is markedly elevated and the cardiac output and mean arterial pressure are normal, then preload reduction with intravenous nitroglycerin can easily be accomplished by beginning a constant infusion at 15 j.Lg/min and gradually increasing the infusion rate until the LVFP is reduced to 15 to 18 mmHg. If the LVFP is normal, but the cardiac output is reduced and the mean arterial pressure is reduced or normal, then dobutamine, i. v., 5 to 15 j.Lg/kg/min, can be used to augment the cardiac output without any untoward effect on the LVFP or mean arterial pressure. If the LVFP is markedly elevated, and cardiac output is

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reduced (as is the case in most patients with severe CHF) and the blood pressure is normal, intravenously administered sodium nitroprusside can be used for balanced preload and afterload reduction beginning at 15 fLg/ · min and titrating upward to a LVFP of 15 to 18 mmHg by using the mean arterial pressure as the limiting factor in the dose titration. During this titration, the cardiac output should be sequentially determined until the interplay between LVFP, cardiac output, and mean arterial pressure is optimal. If further augmentation of the cardiac output is necessary, dobutamine intravenously administered may then be added for positive inotropic support. In the highly select subgroup of patients requiring emergency noncardiac surgery who have profound heart failure and are relatively hypotensive (mean arterial pressure < 70 mmHg), inotropic support with intravenously administered dobutamine or dopamine (5 to 20 fLg/kg/min) should be used initially with intravenous sodium nitroprusside or nitroglycerin added judiciously thereafter for afterload reduction. After stabilization of the hemodynamic factors preoperatively, infusion of the vasodilator, inotropic agents, or both may be continued during the operative and postoperative period. Continuous monitoring of the L VFP and cardiac output will allow for appropriate fluid management as well as for maintenance of optimum pump function. Later in the postoperative course, the appropriate oral congestive heart failure regimen may be reinstituted, if necessary, by using sequential data from catheterization of the right side of the heart as an indicator of acute hemodynamic efficacy. Valvular Heart Disease

In patients with symptomatic aortic stenois (angina, congestive heart failure, or syncope), ideal preoperative management would allow for a complete cardiac catheterization with angiography (see Table 1) in addition to an aortic valve replacement if critical aortic valvular stenosis is identified (aortic valve index :s 0.5 cm 2/m 2). With mitral stenosis and less than stable class II New York Heart Association functional capacity, ideal preoperative management would again imply complete cardiac catheterization with angiography and mitral valve replacement or repair if severe mitral stenosis is documented (mitral valve area :s 1.0 cm 2). However, in the urgent or emergent noncardiac surgical situation when preoperative valve replacement cannot be done electively, insertion of a Swan-Ganz catheter and monitoring of intraarterial blood pressure is recommended. In both the above mentioned diseases, adequate left ventricular filling must be maintained to prevent episodes of profound hypotension in the perioperative period. With conditions of chronic overload of left ventricular volume such as in aortic regurgitation and mitral regurgitation, the climate is changing with respect to earlier elective replacement of valves in minimally symptomatic or asymptomatic patients to prevent irreversible myocardial dysfunction. Presently, this is a controversial issue whose final answer is yet to be established. The classic indications for aortic or mitral valve replacement due to valvular regurgitation are less than stable Class II functional status in addition to severe valvular regurgitation and adequate left ventricular function defined by cardiac cineangiography (see Table 1). However, unlike

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the left-sided lesions of aortic stenosis or mitral stenosis, cardiovascular function in patients with chronic aortic regurgitation or mitral regurgitation greatly depends on afterload. When Class III or IV congestive heart failure is present due to aortic regurgitation or mitral regurgitation, catheterization of the right side of the heart and subsequent vasodilator therapy with intravenous sodium nitroprusside can significantly reduce the impedance to left ventricular ejection and thereby cause a substantial increase in the forward cardiac output, a reduction in the regurgitant fraction, and a reduction of the left ventricular filling pressure. 2 • 14

PROSTHETIC HEART VALVES The preoperative management of the patient with a mechanical cardiac valve prosthesis involves the discontinuance of warfarin sodium (Coumadin) anticoagulation. Studies to date 10• 20 suggest that discontinuing administration of oral anticoagulants one to three days prior to surgery and allowing the prothrombin time to return to within 20 per cent of the normal range and then resuming the long-term anticoagulation regimen one to seven days after surgery is not associated with a substantial increase in the risk of thromboembolic events. However, with mitral or combined valve prostheses (and possibly with atrial fibrillation), the risk of thromboembolism may be higher than in patients with isolated aortic valve prostheses. In these cases, serious consideration should be given to the use of a preoperative minidose of subcutaneous heparin and then an early postoperative full dose of intravenous heparin anticoagulation before resuming chronic oral anticoagulant therapy.

PREVENTION OF BACTERIAL ENDOCARDITIS The indications and antibiotic regimens for the prevention of bacterial endocarditis in patients with structural abnormalities of the heart or great vessels and in patients with prosthetic heart valves are well outlined in the official recommendations of the American Heart Association. 9 See "Evaluation of the Pediatric Surgical Patient with Congenital Heart Disease" in this issue for further discussion.

REFERENCES l. Akl, B. F., Talbot, W., Neal, J. F., et a!.: Noncardiac operations after coronary revascularization. West. J. Med., 136:91-94, 1982. 2. Chatterjee, K., Parmley, W. W., Swan, H. J. C., eta!.: Beneficial effects of vasodilator agents in severe mitral regurgitation due to dysfunction of subvalvar apparatus. Circulation, 48:684-690, 1973. 3. Cohn, J. N.: Physiologic basis of vasodilator therapy for heart failure. Am. J. Med., 71:135-138, 1981.

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4. Epstein, S. E., Palmeri, S. T., and Patterson, R. E.: Evaluation of patients after acute myocardial infarction. Indications for cardiac catheterization and surgical intervention. N. Engl. J. Med., 307:1487-1492, 1982. 5. European Coronary Surgery Study Group: Coronary artery bypass surgery in stable angina pectoris: Survival at two years. Lancet, 1:889-893, 1979. 6. Goldman, L., Caldera, D. L., Nussbaum, S. R., et al.: Multifactorial index of cardiac risk in noncardiac surgical procedures. N. Engl. J. Med., 297:845-850, 1977. 7. Harrison, D. C.: Coronary bypass: The first ten years. Hosp. Pract., 16:49-56, 1981. 8. Johnson, R. A., and Palacios, I.: Dilated cardiomyopathies of the adult. N. Engl. J. Med., 307:1051-1058, 1119-1126, 1982. 9. Kaplan, E. L., Anthony, B. F., Bisno, A., et al.: Prevention of bacterial endocarditis. AHA Committee on Rheumatic Fever and Bacterial Endocarditis. Circulation, 56:139A143A, 1977. 10. Katholi, R. E., Nolan, S. P., and McGuire, L. B.: Living with prosthetic heart valves. Subsequent noncardiac operations and the risk of thromboembolism or hemorrhage. Am. Heart. J., 92:162-167, 1976. 11. Mahar, L. J., Steen, P. A., Tinker, J. H., et al.: Perioperative myocardial infarction in patients with coronary artery disease with and without aorta-coronary bypass grafts. J. Thorac. Cardiovasc. Surg., 76:533-537, 1978. 12. Mason, D. T.: Afterload reduction and cardiac performance. Physiologic basis of systemic vasodilators as a new approach in treatment of congestive heart failure. Am. J. Med., 65:106-125, 1978. 13. McCollum, C. H., Garcia-Rinaldi, R., Graham, J. M., et al.: Myocardial revascularization prior to subsequent major surgery in patients with coronary artery disease. Surgery, 81:302-304, 1977. 14. Miller, R. R., Vismara, L. A., DeMaria, A. N., et al.: Afterload reduction therapy in severe aortic regurgitation: Improved cardiac performance and reduced regurgitant volume. Am. J. Cardiol., 38:564-567, 1976. 15. Rahimtoola, S. H.: Coronary bypass surgery for chronic angina-1981. Circulation, 65:225241, 1982. 16. Sapala, J. A., Ponka, J. L., and Duvernay, W. F. C.: Operative and nonoperative risks in the cardiac patient. J. Am. Geriatr. Soc., 23:529-534, 1975. 17. Skinner, J. F., and Pearce, M. L.: Surgical risk in the cardiac patient. J. Chron. Dis., 17:57-72, 1964. 18. Steen, P. A., Tinker, J. H., and Tarhan, S.: Myocardial reinfarction after anesthesia and surgery. J.A.M.A., 239:2566-2570, 1978. 19. Takara, T., Hultgren, H. N., Lipton, M. H., et al.: The VA cooperative randomized study of surgery for coronary arterial disea~e-11. Subgroup with significant left main lesions. Circulation (Suppl 3), 54:107-117, 1976. 20. Tinker, J. H., and Tarhan, S.: Discontinuing anticoagulant therapy in surgical patients with cardiac valve prostheses. J.A.M.A., 239:738-739, 1978. Cardiology Division Milton S. Hershey Medical Center Hershey, PA 17033