Asian Cardiovasc Thorac Ann 2000;8:103-108
© 2000 Asia Publishing EXchange Pte Ltd
Coronary Artery Bypass Surgery Without Cardioplegia: Early Results
Wong Poo Sing, FRCS(CTh),
Simon Vendargon, MS,
Lim Choon Gek, RN
Department of Cardiothoracic Surgery
Sultanah Aminah Hospital
Johor Bahru, Johor, Malaysia
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For reprint information contact: Wong Poo Sing, FRCS(CTh) Tel: 60 7 223 1666 Ext. 2130/2132 Fax: 60 7 221 3376 email: poosing{at}pc.jaring.my Department of Cardiothoracic Surgery, Sultanah Aminah Hospital, Jalan Skudai, Johor Bahru, Johor 80100, Malaysia.
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Abstract
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From November 1996 to April 1999, 348 patients underwent isolated non-cardioplegic coronary artery bypass grafting at a new center. There were 123 (35%) patients aged over 60 years, 48 (14%) were female, 70 (20%) had a left ventricular ejection fraction below 0.3. Coronary artery bypass graft surgery was performed using hypothermic intermittent ischemic fibrillatory arrest of the heart. The left internal mammary artery was used in 97% of cases. Mean grafts per patient was 3.5. Sixty-three patients (18%) underwent 65 coronary endarterectomies. The overall operative mortality rate was 2.3% (8/348). Follow-up was 97% complete. Mean follow-up was 14.9 ± 8 months (range, 1 to 30 months). Freedom from angina was 98.3% at 6 months, 97% at 12 months, and 97% at 24 months. The overall survival was 96.7% at 6 months, 95.8% at 12 months, and 94.4% at 24 months. It was concluded that this method of myocardial protection for isolated coronary artery bypass graft surgery provided excellent operating conditions in this group of patients.
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Introduction
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Coronary artery bypass grafting (CABG) was first performed in Malaysia in 1982. There are no published reports of patient demographic or data on the outcome of this operation using noncardioplegic methods in our population. Many cardiac surgery centers throughout the world continue to conduct noncardioplegic CABG, particularly with hypothermic intermittent fibrillatory arrest, with excellent results.1–5 Such techniques have been used at our new center in Johor Bahru, Malaysia.
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Patients and Methods
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The study included all 348 patients who underwent isolated CABG without cardioplegia, by one surgeon (WPS), since the inception of the cardiothoracic surgery program in November 1996 up to April 1999. Over 1100 cardiac and thoracic operations were performed during this period. The total number of open heart operations was 910, of which 430 (47%) were isolated CABG. Cold crystalloid cardioplegia was used for CABG by other surgeons in 82 patients. Data were collected retrospectively up to August 1997 and prospectively since then, and entered into a com-puterized database. Definitions of terms were according to those of The Society of Thoracic Surgeons National Cardiac Surgery Database.6
Clinical characteristics are listed in Table 1
. Amongst the racial groups, Chinese formed 43%, Malays 31%, Indians 25%, and others 1%. Thirty-five percent of patients were older than 60 years. Eighty percent were from the state of Johor, 13% from East Malaysia, 3% from Malacca, and the rest from other states in West Malaysia. Thirteen percent of patients had endoscopic evidence of peptic ulcer, 60% had hypertension, 39% had diabetes, 44% had hypercholesterolemia, 15% had family history of ischemic heart disease, 40% had a previous history of smoking, 1.3% had evidence of lower limb peripheral vascular disease, and 3.2% had carotid arterial disease. Almost 6% of patients had renal impairment (serum creatinine above 130 µmol•L–1), 48% required urgent or emergency operations, 46% had electrocardiographic evidence of old myocardial infarction (MI), 3% had MI within the previous 2 weeks, and 1% had an evolving acute MI. Left ventricular ejection fraction (LVEF) was assessed by angiography in some and by echocardiography in all patients. Evidence of left ventricular hypertrophy on electrocardiography and echocardiography was found in 35%. Two patients had angiographically documented left ventricular aneurysm. Mean length of preoperative hospital stay was 3.7 ± 3.15 days (range, 1 to 22 days).
Anesthesia was induced with midazolam and sufentanil, followed by pancuronium, and maintained with a com-bination of air-oxygen mixture and inhalational sevo-flurane, propofol, and sufentanil. All operations were performed under cardiopulmonary bypass stabilized at a nasopharyngeal temperature of 33°C. Extracorporeal circulation was established with a heart-lung machine using a membrane oxygenator, venous drainage with a Ross basket in the right atrium, and aortic return to the ascending aorta. Ventricular fibrillation was induced and the heart was rendered ischemic before the distal anas-tomosis was constructed. Each distal anastomosis was completed with a single running suture, usually during a brief period of aortic crossclamping. After the distal anastomosis, the heart was defibrillated with low energy levels (10 W•sec–1), the proximal anastomosis was con-structed with the heart beating and with a partial occlusion clamp on the ascending aorta. The patient was rewarmed during construction of the last anastomosis, usually the left internal mammary artery-to-left anterior descending artery graft.
Statistical analysis was performed using Statistics/Data Analysis (Stata Corp., College Station, TX, USA). Actuarial survival was used to estimate probability of survival and the log-rank test was used to compare survival with left ventricular ejection fraction and operative basis. All data were expressed as mean ± standard deviation. A p value less than 0.05 was considered significant.
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Results
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The operative characteristics are listed in Table 2. There were 345 first-time CABG operations and 3 redo cases. Three patients had off-pump beating heart CABG, 2 had severe atheromatous disease of the aorta and underwent hypothermic intermittent fibrillation of the heart without application of an aortic crossclamp. The other 343 patients had CABG under hypothermic intermittent ischemic fibrillatory arrest. Inotropic support was required for weaning from cardiopulmonary bypass in 9/125 (7%) patients with good LVEF, 23/153 (15%) with moderate LVEF, and 22/70 (31%) with poor LVEF. Intraaortic balloon pump requirements for those with good, moderate, and poor LVEF were 3 (2.4%), 4 (2.6%), and 11 (15.7%), respectively. Two patients had concomitant left ventricular aneurysmectomy. Most patients (67%) did not require any blood or blood products. Of those who had blood transfusion, the mean units of blood transfused per patient was 2.3 (range, 1 to 7).
Postoperative complications are listed in Table 3. Seven patients developed perioperative MI defined by electro-cardiographic criteria (new Q waves, loss of R waves, or new intraventricular conduction defect). Serial post-operative creatine kinase measurement was not routinely carried out. None of the patients with neurological deficits had preoperative evidence of carotid arterial disease nor documented atheromatous disease of the aorta. Of 11 patients with significant unilateral carotid artery stenosis (> 50% stenosis on carotid duplex Doppler ultrasono-graphy or magnetic resonance imaging), none developed post-operative neurological deficits. All of these who developed wound infection or sternal dehiscence had received left internal mammary artery grafts and only one was diabetic.
Persistent air leak was the most common pulmonary complication (18 patients; 5.2%), atelectasis occurred in 8 (2.3%), and none of these patients required chest tube drainage for more than 6 days postoperatively. Total lung collapse occurred in 1 patient, requiring emergency rigid bronchoscopy and ventilatory support. Pleural effusion needing drainage occurred in 7 patients (2%). One patient who had a left internal mammary artery graft, developed left chylothorax requiring chest tube drainage for 20 days before the chylous leak sealed spontaneously. Seventeen patients (4.9%) developed new atrial fibrillation and 2 (0.6%) required cardioversion for atrial flutter.
Gastrointestinal complications included 1 case of massive hematemesis requiring emergency laparotomy im-mediately after CABG, 1 case of acute peptic ulcer, 3 cases of paralytic ileus, and 1 of acute pancreatitis. One patient developed acute lower limb ischemia secondary to intraaortic balloon pump placement, which resolved successfully with embolectomy. Five patients (1.4%) developed acute renal failure requiring peritoneal dialysis; only one of these had an elevated serum creatinine level preoperatively (240 µmol•L–1). Another 20 patients with elevated serum creatinine (130 to 200 µmol•L–1) did not develop worsening of renal function during the post-operative period. Postoperative renal failure requiring peritoneal dialysis was seen only in patients with low cardiac output syndrome needing large doses of inotropic and mechanical support. All of these patients died.
There were 8 (2.3%) operative deaths defined as before discharge or within 30 days of surgery. Five patients died of low cardiac output, of whom 3 were in a low output state or actual cardiogenic shock prior to surgery. Two died of generalized sepsis, secondary to methicillinresistant Staphylococcus aureus mediastinal infection in 1 case and in another who had preoperative pneumonia with ischemic left ventricular failure. Another patient had poor LVEF preoperatively and died from intractable ventricular fibrillation 2 days postoperatively. Mortality is classified in Table 4 according to the basis of the operation and LVEF. Three of the 4 patients (75%) with post-MI angina and cardiogenic shock died after emergency surgery. The other 6 patients with poor LVEF (not in cardiogenic shock) and unstable angina un-responsive to intravenous therapy, had a good outcome from emergency CABG. Mortality was 2.3% (7/300) for male patients and 2.1% (1/48) for female. Mortality for patients over 60 years of age was 4.8% (6/125).
All patients were followed up for 4 to 6 weeks post-operatively and every 3 months subsequently. Those from East Malaysia were seen by physicians there who were then contacted by telephone. There were 5 late deaths: 2 from presumed cardiac events at 1 month and 10 months postoperatively; 2 from complications related to cere-brovascular accidents; and 1 in a patient known to have late-onset asthma who died from an acute asthmatic attack. Of the surviving 335 patients, follow-up was 97% complete (10 lost to follow-up). There was early recurrence of angina in 9 patients at 1 week to 10 months after surgery; 3 had early vein graft occlusion that was successfully treated by percutaneous coronary angioplasty, 4 had normal graft studies (3 with good and 1 with poor distal run-off), and 2 are presently well controlled with antianginal medication. All 9 patients with early recurrence of angina were of Indian origin. Currently, 316 patients are angina-free. The 335 survivors were followed up for a mean of 14.9 ± 8 months (range, 1 to 30 months). Freedom from angina was 98.3% with 95% confidence intervals (CI) of 96% to 99% at 6 months, 97% (95% CI, 94% to 98%) at 12 months, and 97% (95% CI, 94% to 98%) at 24 months. The overall survival was 96.7% (95% CI, 94% to 98%) at 6 months, 95.8% (95% CI, 93% to 97%) at 12 months, and 94.4% (95% CI, 90% to 96%) at 24 months. There were significant differences (p < 0.05) in survival according to basis of operation (elective, urgent, or emergency) and LVEF (good, moderate, or poor). The highest mortality was associated with emergency operation and poor LVEF (Table 4
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Discussion
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The age of this population was younger than that reported in Western series. There was also a high prevalence of multiple risk factors and almost half of the patients had a history of previous MI, with more than 10% suffering MI less than 6 weeks prior to CABG. A high incidence of left main stem disease (known to be high in Asians) and a majority of patients in Canadian Cardiovascular Society angina class III and IV was reflected in both a high percentage of urgent and emergency operations and a mean preoperative hospital stay of 3.7 days. Poor patient compliance in the management of diabetes also contributed to the preoperative stay. Poor patient compliance in the treatment of hypertension was reflected in the high prevalence of left ventricular hypertrophy.
Improved operative morbidity and mortality after CABG as a result of contemporary strategies and the successful management of single and double-vessel coronary artery disease by interventional cardiology, have resulted in increased referral of patients with diffusely diseased coronary arteries for CABG. In this center, coronary endarterectomy was only performed on occluded or nearly occluded vessels that had long multiple flow-limiting stenosis extending distally, or in vessels with small (
1 mm in diameter) distal vessels. As in most studies, the right coronary artery was most frequently endarterec-tomized (Table 2).7 It is our practice to avoid performing endarterectomy of the left anterior descending and circumflex vessels, except in situations where it is essential for technical reasons.
Despite concern about repeated crossclamping of the aorta to perform distal graft anastomoses and partial clamping of the aorta to perform proximal anastomoses, the incidence of transient and permanent stroke was low and comparable with other reports.1,5 Musumeci and colleagues8 showed that the incidences of perioperative cerebral emboli and neuropsychological disturbance up to 6 months postoperatively were similar with either the single-clamp technique or intermittent ischemic arrest for elective CABG. Our study did not exclude patients with clinically palpable atherosclerotic plaque in the ascending aorta. In 2 patients with diffuse aortic disease, CABG was performed with femoral artery cannulation and intermittent fibrillatory arrest without the application of an aortic crossclamp. In patients with localized plaques, both the aortic crossclamp and side-biting clamp were applied away from these plaques.
Bonchek and colleagues1 showed that CABG using intermittent fibrillatory arrest was suitable for high-risk cases; in 290 consecutive patients with LVEF < 30%, operative mortality was 6.2%. Patients undergoing redo coronary surgery who already have patent vein grafts to critical areas of the myocardium, are probably not suitable for intermittent fibrillatory arrest because the aortic partial occlusion clamp that is necessary for new proximal anastomoses must almost always incorporate the old proximal anastomoses to grip the aorta reliably.2 With increased manipulation in this area, the risk of embo-lization from diseased grafts is increased. Cardioplegia given in a retrograde manner can theoretically reduce this risk. Nevertheless, there are surgeons who use intermittent ischemic fibrillatory arrest in redo CABG with good results. Since 1982, there have been a number of clinical trials comparing cardioplegia with ischemic arrest in a prospective randomized manner.3,4,9–12 None showed significant superiority of cardioplegia over intermittent ischemic fibrillatory arrest.
There are disadvantages with intermittent aortic cross-clamping in CABG. Perfusion of the subendocardium is impaired during cardiopulmonary bypass in fibrillated hypertrophied hearts and myocardial oxygen uptake is higher than with cardioplegia.13 However, the oxygen debt incurred during the brief episode of ischemia is quickly repaid. The effects of brief ischemic intervals under mild hypothermia are rapidly reversible by adequate reperfusion in the decompressed heart even during ventricular fibrillation.14 It is contraindicated in patients with extensive atheromatous disease of the aorta where repeated aortic clamping might precipitate embolization of debris or cause dissection. Because of a greater pressure for relatively speedy completion of distal anastomoses with intermittent ischemic fibrillatory arrest, this technique is not ideal for the training of junior cardiac surgeons.
A substantial minority of cardiac surgeons in the United States, Europe, and the Indian subcontinent still use intermittent aortic crossclamping for myocardial protection during CABG, mainly because it is more versatile and flexible. Usually, no venting of the heart is required, thereby minimizing the chance of air embolism. The order of grafting can be decided and it allows the surgeon to restore flow promptly to the most ischemic territories and progressively improve the state of the heart. Preconditioning of the myocardium during CABG has been shown to result in better preservation of adenosine triphosphate during subsequent periods of ischemia.15 The heart is allowed to beat between grafts and the electrocardiogram and left ventricular and segmental contraction of the heart can be assessed. Blood, a physiologic solution that does not contain high levels of potassium, perfuses the heart between episodes of aortic crossclamping. Iatrogenic myocardial edema has been shown to occur with potassium cardioplegia.16 The opportunity of the heart to beat on circulatory support is also important as myocardial contraction supports myocardial lymphatic function, resulting in minimal myocardial edema, associated with less impairment of left ventricular performance.17 Thus, allowing the heart to beat between periods of ischemic fibrillatory arrest can theoretically lessen myocardial edema. The results of this study reassured us that this method of myocardial protection for CABG provided excellent operating conditions for patients with coronary artery disease in our population. We consider that other methods of myocardial protection in CABG, particularly in the clinical setting, have not been shown to be superior to hypothermic intermittent ischemic fibrillatory arrest of the heart.
Presented at the 7th Annual Meeting of The Asian Society for Cardiovascular Surgery, Singapore, May 28–31, 1999.
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Acknowledgments
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We would like to thank the Director General of Ministry of Health Malaysia for allowing us to publish this data and Dr. Lim Teck Onn, Department of Nephrology, Kuala Lumpur General Hospital, for help with the statistical analyses. We would also like to thank the Medical Records Department, Ong Eng Khin, and nurses Kamariah Mohd Tap, Fauziah Sulaiman, and Habibah Hassan at Sultanah Aminah Hospital for their help in retrieving data for this study.
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References
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Abstract
Introduction
