Combined coronary artery bypass grafting and carotid endarterectomy

PII: S0967-2109(97)00017-3

Cardiovascular Surgery, Vol. 5, No. 3, pp. 266–270, 1997  1997 The International Society for Cardiovascular Surgery Published by Elsevier Science Ltd. Printed in Great Britain 0967–2109/97 $17.00 + 0.00

OF INTEREST TO BOTH SPECIALITIES Combined coronary artery bypass grafting and carotid endarterectomy M. Vicaretti, J. P. Fletcher, P. Klineberg, A. J. Richardson, S. Hazelton, R. Allen, P. Tomlinson, G. Nunn, R. Chard and W. Meldrum-Hanna Division of Surgery, Westmead Hospital, Westmead, NSW 2145, Australia Combined carotid endarterectomy and coronary artery bypass grafting was performed in 52 patients between January 1982 and September 1994. Forty-nine patients had stable or unstable angina and three had symptom-free coronary artery disease detected by stress testing. Thirty-one patients had triple-vessel disease and 17 had left main trunk or left main equivalent coronary artery disease. Five patients had symptom-free carotid artery disease, 12 had non-specific neurological symptoms, and 35 had transient ischaemic attacks. Carotid endarterectomy was performed first, followed by coronary artery bypass grafting. There were three postoperative deaths, two cardiac and one neurological, for a mortality rate of 5.8%. One patient suffered a permanent neurological deficit (1.9%). It is concluded that combined carotid endarterectomy/coronary artery bypass grafting can be performed in selected patients with acceptable neurological morbidity, although cardiac mortality was not eliminated by the combined approach.  1997 The International Society for Cardiovascular Surgery Keywords: coronary artery bypass, carotid endarterectomy

Coronary artery disease and carotid artery disease commonly coexist. Management of the patient with simultaneous significant carotid and coronary pathology varies widely between different institutions. Since Bernhard et al.[1] reported their experience with combined carotid endarterectomy and coronary artery bypass grafting, many other centres have reported their experience with such a problem[2–8]. It has been the authors’ policy that patients with significant carotid and coronary artery disease undergo combined revascularization. This report is a review of their experience with patients who underwent synchronous coronary artery bypass grafting and carotid endarterectomy. During the period of the study all patients submitted for carotid endarterectomy were given a cardiac exercise stress test or dipyridamole thallium scan to identify cardiac risk.

Correspondence to: Dr J. P. Fletcher, Department of Surgery, Westmead Hospital, Hawkesbury Road, Westmead NSW 2145, Australia

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Patients and methods Records were kept prospectively and a retrospective analysis was then performed of 52 patients undergoing coronary artery bypass grafting and carotid endarterectomy during the period January 1982 to September 1994. This represents 1.5% of the total coronary artery bypass grafting experience and 15% of the total carotid endarterectomy experience during this period. There were 33 men and 19 women in the study; mean age was 63 (range 50–77) years. Clinical features recorded were: atherosclerotic risk factors, coexisting vascular disease, nature of the carotid artery disease (symptomatic or symptomfree), functional severity of angina (based on the New York Heart Association, NYHA, classification), number of diseased coronary arteries, presence of left main coronary artery disease, internal carotid artery stump pressure, internal carotid artery clamp and/or shunt time, number of coronary artery grafts, aortic clamp time, result of intraoperative electroencephalography and postoperative morbidity and mortality. The group of patients presented with their carotid disease and were identified as at increased CARDIOVASCULAR SURGERY

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cardiac risk because of positive cardiac exercise stress test or dipyridamole thallium scan. Significant coronary artery disease was noted if the vessel’s luminal diameter was reduced by at least 50% on coronary angiography. All patients’ carotid artery disease was assessed angiographically and a significant stenosis was assessed as > 70%. Following radial artery and central venous cannulation all patients were anaesthetized with fentanyl (25–30 µg/kg) with pancuronium for muscle relaxation. Maintenance anaesthesia was with 100% oxygen and isoflurane (0–2.5%). A further 12–15 µg/kg of fentanyl was given during the procedure. The patient was placed in the supine position, prepared and draped to expose the neck, chest, abdomen and saphenous vein territory. Carotid endarterectomy and saphenous vein harvesting were performed simultaneously by the vascular and cardiac surgeons respectively preceding coronary artery bypass grafting. Internal carotid artery stump pressure was measured and if the mean internal carotid pressure was < 50 mmHg, a shunt was used. Early in the series, electroencephalography monitoring was used during clamping of the internal carotid artery. Patch grafts were used if the carotid artery was judged too small to close primarily. Carotid endarterectomy was performed following systemic heparinization (100 units/kg). On completion of the carotid endarterectomy, the neck wound was left open. Cardiopulmonary bypass was then performed in the standard way for the authors’ unit and coronary artery bypass grafting commenced. On completion of coronary artery bypass grafting the chest, neck and legs were closed and the patient transferred to the cardiothoracic intensive care unit.

Results Atherosclerotic risk factors and severity of angina are listed in Tables 1 and 2, respectively. Three patients with transient ischaemic attacks had significant symptom-free coronary artery disease which was Table 1 Atherosclerotic risk factors Risk factor

No. of patients

Smokers Never Ex-smoker Still smoking Hypertension Hypercholesterolaemia (>6 mmol/l) Diabetes mellitus Diet-controlled Non-insulin-dependent Insulin-dependent Positive family history

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18 16 18 29 19 11 0 5 6 19

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Table 2 New York Heart Association classification of angina Class Symptom-free I II II IV

No. of patients 3 10 24 10 5

Table 3 Presenting neurological symptoms Symptom Symptom-free Amaurosis fugax Transient ischaemic attack alone Previous cerebrovascular accident + transient ischaemic attack Non-specific neurological symptoms

No. of patients 5 11 20 4 12

detected on exercise stress testing. Other significant cardiovascular disease included re-do coronary artery bypass grafting (four), previous acute myocardial infarction (22), coexisting abdominal aortic aneurysm (two), peripheral vascular disease (20) and renal artery stenosis (two). The presenting neurological symptoms are listed in Table 3. Some 9.6% of patients were symptomfree, 23% had non-specific neurological symptoms, while 67% had appropriate lateralizing amaurosis fugax, transient ischaemic attacks or previous stroke with good recovery. Four patients with transient ischaemic attacks had previous documented cerebrovascular accidents. Significant carotid artery disease (>70% stenosis) involved predominantly the left internal carotid in 26 patients and the right in 26. Bilateral significant disease was present in nine patients. One patient had an occluded contralateral internal carotid artery. The nature of the coronary artery disease is outlined in Table 4. The median number of coronary vessels involved was three. Electroencephalography monitoring was used in the first five patients in the series and no abnormality was detected on carotid clamping. Twenty-eight patients did not require carotid artery shunting (recorded in 48). Median clamp time in Table 4 Extent of coronary artery disease Extent Single-vessel Double-vessel Triple-vessel Left main trunk/left main equivalent

No. of patients 1 20 31 14

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non-shunted patients (recorded in 24) was 37 (range 19–64 min) and median internal carotid artery stump pressure was 58 (range 37–105) mmHg. Five patients had stump pressures , 50 mmHg (44, 37, 46, 47 and 40 mmHg respectively) but a shunt was not used. In the first of these patients (stump pressure 44 mmHg) a normal electroencephalogram was noted on clamping the internal carotid artery. The remaining four patients had carotid endarterectomy without shunts because it was judged by the surgeon technically difficult to proceed with the endarterectomy with a shunt in situ. Twenty patients required a shunt. In these patients the median internal carotid artery pressure (recorded in 19) was 33 (range 0– 43 mmHg). Median clamp time (recorded in 18 patients) was 4 min and median shunt time (recorded in 16) was 34 min. A patch graft was used in four patients. Coronary artery bypass grafting followed carotid endarterectomy with a median number of grafts of four (range three to six), one patient in addition requiring aortic valve replacement. The median aortic cross-clamp time (recorded in 47) was 49 (range 29–116) min and median bypass time (recorded in 47) was 70 (range 44–161) min. Thirtyday mortality included three postoperative deaths (6%). The first was a 54-year-old woman, with significant symptomatic bilateral carotid artery disease, NYHA class III angina, and significant upper- and lower-extremity peripheral vascular disease which made palpation of peripheral pulses difficult. Cardiac tamponade was clinically diagnosed at 3 h after surgery (in the intensive care unit) and the chest was reopened. No tamponade was present but in the process the coronary graft was avulsed. The patient was returned to the operating suite but could not be resuscitated. The second death was in a 72-year-old man with unilateral non-specific neurological symptoms, pinhole stenosis of his left internal carotid artery and class III angina who underwent left carotid endarterectomy, coronary artery bypass grafting six times, and aortic valve replacement. The aortic cross-clamp time was 116 min and bypass time 161 min. He became hypotensive following heparin reversal with protamine and required the insertion of an intra-aortic balloon pump. On return to the intensive care unit he was coagulapathic and, despite appropriate resuscitation and maximal inotropic support, died the following day. The third death occurred in a 72-year-old woman, with recurrent left hemispheric transient ischaemic attacks and significant three-vessel coronary artery disease. She underwent left carotid endarterectomy using a shunt and a patch graft followed by two coronary artery bypass grafts. At 1 week after surgery she developed a dense right hemiparesis with a supervening right lower-lobe pneumonia. Despite vigorous physiotherapy she succumbed to the pneumonia 4 weeks 268

after surgery. During this period she had not recovered from her hemiparesis. Morbidity as outlined in Table 5 occurred in seven patients. One patient had a permanent neurological deficit in addition to the patient with a permanent neurological deficit who died (total neurological morbidity, 3.8%). There were no temporary neurological deficits. Two patients had transient recurrent laryngeal nerve weakness and one patient had a transient hypoglossal nerve weakness. The median postoperative length of hospitalization was 8 (range 7– 33) days.

Discussion Coronary artery disease is recognized as the leading cause of death in patients with carotid artery disease[1, 19–22]. Rihal et al.[22] established that complications of coronary artery disease rather than stroke were the leading cause of late mortality and morbidity after carotid endarterectomy (49% versus 7% of all deaths, respectively). The incidence of significant carotid stenosis in patients requiring surgery of the coronary arteries, cardiac valves or ventricular aneurysms appears to be small[10, 11, 14, 16]. Jones et al.[9] in a retrospective analysis of risk factors for perioperative stroke after coronary artery bypass grafting reported an overall incidence of 0.9% which increased to 8.6% in those with a previous history of transient ischaemic attack or focal deficit. Brenner et al.[23] similarly showed an increased incidence of cerebrovascular accident during cardiopulmonary bypass in those with carotid disease. The European[24] and North American[25] trials have shown that carotid endarterectomy in patients with significant symptomatic carotid disease provide a better long-term prognosis. The dilemma is how to approach the patient with significant pathology in Table 5 Complications Complication type Cardiorespiratory Asystolic cardiac arrest, day 2 Ventricular tachycardiac arrest, day 2 Post-operative bleeding from avulsed left internal mammary artery Respiratory failure requiring reintubation Tension haemothorax, returned to theatre

No. of patients

1 1 1 1 1

Neurological Left recurrent laryngeal nerve neuropraxia Hypoglossal nerve neuropraxia Right hemiparesis

2 1

Other Renal failure requiring dialysis Mediastinal abscess

2 1

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1

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both carotid and coronary circulations. It has been the authors’ practice that at-risk patients undergo simultaneous surgical repair of both the coronary and carotid circulations. Since Bernhard and colleagues[1] first demonstrated reduced cardiac mortality in patients undergoing simultaneous carotid endarterectomy and coronary artery bypass grafting, several other groups[2–18] have reported favourable outcomes from combined operations and have advocated combined carotid endarterectomy/coronary artery bypass grafting. Brenner et al.[23] advocated against the combined procedure as they could not show that it improved the outlook for neurologic complications during cardiopulmonary bypass. Lord et al.[26] found no statistical difference between combined and staged procedures but preferred the staged approach. Schwartz et al.[15] similarly showed no statistical difference between the two approaches and concluded that patients with both left main trunk and carotid artery disease should have staged procedures as they constituted a higher operative risk. The institution of cardiopulmonary bypass is often associated with an initial period of hypotension with subsequent risk of cerebral hypoperfusion, especially in patients with an uncorrected significant carotid stenosis[27]. Large swings in mean arterial blood pressure have also been noted at the onset of and frequently during cardiopulmonary bypass which in part contribute to the risk of neurological complication[28, 29]. Proponents of carotid endarterectomy before cardiopulmonary bypass argue that cerebral hypoperfusion is caused by the non-pulsatile cerebral flow associated with cardiopulmonary bypass placing the patient with an uncorrected significant carotid artery lesion at risk[8, 10, 30]. Minami et al.[5] preferred using the advantages of cardiopulmonary bypass for cerebral protection during carotid endarterectomy, though they conceded that there was no clear definition of what constituted optimal mean arterial pressure for cerebral protection. Much variation exists in the approach to the simultaneous repair. Some groups[8, 10, 30] perform carotid endarterectomy prior to sternotomy, while others[11, 13, 14] recommend performing sternotomy simultaneously with carotid endarterectomy, and others recommend sternotomy with[31] or without[11, 15] cannulation before making the neck incision. Reis et al.[31], Minami et al.[5] and Schwartz et al.[15] perform the carotid endarterectomy while cardiopulmonary bypass is in effect. The present authors’ approach is routinely to perform carotid endarterectomy before median sternotomy as it their belief that instability occurs at the time of initiation of cardiopulmonary bypass. It is also their practice to measure internal carotid artery backpressure as an indicator for intraoperative shunting. CARDIOVASCULAR SURGERY

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Moore et al.[32] proposed internal carotid artery back-pressure to be an indication of collateral cerebral circulation. The misgivings of internal carotid artery back-pressure measurement alone in an assessment of cerebral circulation is that subsequent changes in cerebral perfusion during carotid artery clamping are not identified. The first five patients in the present series had electroencephalography monitoring with no electroencephalographic changes noted. One patient had no electroencephalographic changes despite internal carotid artery back-pressure ,50 mmHg and was not shunted on the grounds that the electroencephalogram was normal. The authors showed that it was safe to proceed with carotid endarterectomy with a low internal carotid artery back-pressure provided that there were no electroencephalographic changes[33]. Conversely, shunting was recommended if there were electroencephalographic changes after carotid artery clamping, irrespective of internal carotid artery backpressure. Electroencephalography monitoring can be affected by general anaesthesia[34] and previous cerebrovascular events[35, 36]. The present authors could not confirm more frequent changes in electroencephalography in those operated on for complicated stroke than in those operated on for other indications. Patients undergoing carotid endarterectomy do not routinely have electroencephalography monitoring now at the authors’ institution because of the expense involved. The need for intraoperative shunting is assessed by angiographic findings and internal carotid artery back-pressure measurement. Naylor et al.[37], in a review of monitoring and cerebral protection during carotid endarterectomy, noted that the key to the reduction in operative morbidity and mortality for carotid endarterectomy was meticulous technique, as most of the factors associated with operation-related morbidity were secondary to technical error. The present authors were a little disappointed in their study that cardiac mortality was not reduced when compared with their experience of carotid endarterectomy alone (1.7%)[38] but it is acknowledged that patients having combined carotid endarterectomy/coronary artery bypass grafting have more extensive cardiac disease and are not directly comparable with those having carotid endarterectomy alone. The challenge with carotid endarterectomy/coronary artery bypass grafting is to select out appropriate higher-risk cardiac patients and to ensure that cardiac mortality associated with the combined procedure is kept to a minimum. It is concluded that combined carotid endarterectomy/coronary artery bypass grafting can be performed with acceptable neurological morbidity, although cardiac mortality is not eliminated by the combined approach. 269

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