Asian Cardiovasc Thorac Ann 2007;15:14-18
© 2007 Asia Publishing EXchange Ltd
Surgical Coronary Revascularization in Severe Left Ventricular Dysfunction
Chee Fui Chong, FRCSEd (CTh),
Ali Akbar Fazuludeen, MBBS,
Christie Tan, FMAS,
Mark Da Costa, FRCSI,
Poo Sing Wong, FRCS (CTh),
Chuen Neng Lee, FAMS (CTh)
Department of Cardiac, Thoracic and Vascular Surgery, National University Hospital, Singapore
For reprint information contact: Chee Fui Chong, FRCSEd (CTh) Tel: 65 6772 5214 Fax: 65 6776 6475 Email: chong_chee_fui{at}hotmail.com, Department of Cardiac, Thoracic and Vascular Surgery, National University Hospital, 5 Lower Kent Ridge Road, 119074 Singapore.
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ABSTRACT
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Surgical revascularization in patients with coronary artery disease and severe left ventricular dysfunction is a common practice and poses a surgical challenge. From September 2002 to May 2004, 50 patients (47 men and 3 women; mean age, 59 ± 9 years) with a mean preoperative ejection fraction of 19.7% ± 3.2% underwent surgical revascularization. The mean EuroSCORE was 7.2 ± 3.4. Indications for surgery were congestive heart failure in 8 patients (16%), angina in 20 (40%), ventricular arrhythmias in 4 (8%), and critical left main stem disease in 12 (24%). Twenty-two patients (44%) had emergency surgery for critical anatomy and unstable symptoms. The number of grafts per patient was 3.7 ± 0.8. Seventeen patients (34%) required intra-aortic balloon pump support, 16 (32%) needed pacing, and 48 (96%) had inotropic support postoperatively. Morbidity included re-operation for bleeding (2%), acute renal failure (10%), hemodialysis (4%), and fatal multiorgan failure (4%). Postoperative (4.9 ± 3.7 months) 2-dimentional echocardiography was available in 18 patients of whom 11 (61%) showed improved left ventricular function (range, 5% to 45%). Thirty-day hospital mortality was 8%. These data indicate that surgical revascularization can be performed safely with acceptable hospital mortality in high-risk patients with severe left ventricular dysfunction.
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INTRODUCTION
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Patients with coronary artery disease and severe left ventricular (LV) dysfunction, defined as LV ejection fraction (LVEF) < 25%, have a poor long-term prognosis, with survival < 25% at 3 years on medical therapy alone.1,2 Most will ultimately succumb to fatal cardiac events such as myocardial infarction, congestive heart failure, or ventricular arrhythmias.3 Up to the early 1990s, transplantation was the only surgical option for this group because of the significant mortality associated with surgical revascularization.4,5 With the shortage of donor organs, only 10% of eligible patients actually underwent successful transplantation, whilst the majority died while on the waiting list.6 Thus, despite being a good solution, transplantation is not a viable option for most patients with severe LV dysfunction. In the last decade, they have been increasingly referred for surgical revascularization, and operative mortality has significantly decreased due to improvements in anesthesia, myocardial protection with blood cardioplegia, cardiopulmonary bypass, and postoperative support.7,8 Recent studies suggest low hospital mortality with 5-year freedom from sudden death of 91%.9 Various LV remodeling operations such as the Dor procedure, surgical anterior ventricular endocardial restoration, partial left ventriculectomy, and mitral annuloplasty have been applied in combination with coronary revascularization for treating dilated cardiomyopathy.10–13 We reviewed our experience in managing this group of patients to evaluate risk factors that might predict early mortality after coronary artery bypass grafting (CABG) and to determine late survival in our Asian population.
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PATIENTS AND METHODS
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From September 2002 to May 2004, 731 patients underwent CABG in our unit. All patients had preoperative 2-dimensional (2D) echocardiographic assessment of cardiac and valvular function; 50 (6.8%) had LVEF < 25%. Data from these 50 patients were retrieved from our database and also from the clinical notes. These included preoperative demographics, LVEF, nuclear cardiac viability studies, history of myocardial infarction (MI) or ventricular arrhythmias, angina pattern, risk factors, priority of surgery, and use of an intra-aortic balloon pump (IABP). The operation was designated elective or emergency with an acutely unstable patient or with significant left main stem stenosis. Operative variables collected included the number of grafts, cardioplegia, concomitant procedures, off-pump surgery, cross clamp and bypass times. Cardiac catheterization was performed in all patients prior to surgery to determine the extent and anatomy of the coronary artery disease. Left ventricular ejection fraction was estimated by a dedicated echocardiographer using 2D-echocardiography. Coronary artery narrowing > 50% was considered significant.
A combination of midazolam, fentanyl citrate, and etomidate was used for induction of anesthesia, with isoflurane for maintenance. Cardioplegia techniques were based on the individual consultant’s preference but essentially consisted of initial antegrade delivery of warm blood cardioplegia (St. Thomas’ Hospital II cardioplegic solution) until cardiac arrest was achieved, or for 2 min, followed by cold blood cardioplegia for 2–4 min and intermittent doses every 20 min or after each distal anastomosis. Use of retrograde blood cardioplegia was based on significant left main stem stenosis, diffuse coronary artery disease, chronically occluded coronary arteries, or the surgeon’s preference. Topical cold saline was used in all cases. Body temperature was generally cooled to 32°C during the cross clamp period. After completion of all distal anastomoses, a hot shot was delivered routinely by two surgeons. Proximal vein anastomoses were carried out using a Cobra side-biting clamp. Endarterectomies were performed when necessary, particularly in severely diffuse disease.
Operative mortality was defined as death within 30 days of operation or during hospital stay. A postoperative stroke was diagnosed if a persistent neurological deficit was present at the time of discharge. Wound status was assessed at discharge and during clinic review. Sternal wound infection was diagnosed if there was a sternal discharge with positive bacteriological culture. Postoperative arrhythmias were considered significant if they required treatment for > 24 hr and were classified as atrial (fibrillation or flutter) or ventricular arrhythmias (paroxysmal ventricular ectopics, ventricular tachycardia or fibrillation). Each patient’s status on 31 December 2004 was ascertained by telephone contact and from outpatient clinic interview. Follow-up was achieved in all patients, and a definite cause of death was obtained from the Registry for Births and Deaths. Postoperative LVEF was assessed by 2D-echocardiography and the results were retrieved from our Computerized Patient Service System database.
Predictors of early mortality were determined by both univariate and multivariate analysis using SPSS software (SPSS, Inc., Chicago, IL, USA). For univariate analysis, discrete data were analyzed with the chi-squared test or Fisher’s exact test, as appropriate. Continuous variables such as age, preoperative LVEF, and creatinine were analyzed using the Mann-Whitney test for continuous variables. Variables that were significant on univariate analysis were entered into the multivariate analysis by Cox regression. Statistical significance was assumed when the p value was < 0.05. Kaplan-Meier survival curves were also constructed.
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RESULTS
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The demographic profile of the 50 patients is shown in Table 1
. All except 9 patients had a history of MI, of whom 10% underwent emergency CABG within 24 hr of developing acute MI, and 36% had their operation within 21 days of MI. The primary indications for CABG were unstable angina in 40% (10% had post-MI angina), congestive heart failure in 16%, ventricular arrhythmias in 8%, critical left main stem anatomy in 24%, and cardiogenic shock in 6%. Operative details are shown in Table 2. Complete revascularization was achieved in all patients. For on-pump cases, cold blood cardioplegia was delivered antegradely with a combination of retrograde infusions or direct infusion into grafts after each anastomosis or every 20 min. All except 2 patients required inotropic support in the form of dopamine with or without adrenaline on coming off cardiopulmonary bypass. Ventricular pacing was necessary in 8 patients (16%). Mean duration of ventilation was 31.9 ± 57.9 hr. Blood products to control early bleeding disorders were used in 30 patients (60%).
The 30-day hospital mortality was 8%; 3 patients died of multiorgan failure resulting from low output syndrome, and 1 suffered sudden cardiac death 2 weeks after discharge. Postoperative complications were observed in 23 patients: repeat sternotomy for bleeding in 1; leg wound infection in 2; renal failure in 5, of whom 2 required temporary hemodialysis; atrial arrhythmias in 11; ventricular arrhythmias in 3; and pulmonary complications in 4.
By univariate analysis, only cardiogenic shock and preoperative ventricular tachyarrhythmias were significant risk factors for early mortality (Table 3). Patients in cardiogenic shock undergoing CABG were 45-times more likely to die compared to those without shock, and those with preoperative ventricular tachyarrhythmias were 31.5-times more likely to die. By multivariate logistic regression analysis, only cardiogenic shock was a significant predictor of death within 30 days of surgery (Table 4).
The mean follow-up period was 16.4 ± 6.2 months (range, 7.6–27.6 months). There were 3 (6.5%) late deaths; 2 were sudden cardiac deaths, and 1 was due to lung cancer. Actuarial survival was 92%, 88%, and 83% at 3 months, 1 and 2 years respectively (Figure 1). Two patients were diagnosed with malignant disease during follow-up (colon and pancreatic carcinoma), 2 had recurrent angina and were on medical therapy, one was in New York Heart Association functional class II, and the others were all well. Postoperative 2D-echocardiography at a mean of 4.9 ± 3.7 months after surgery was available in 18 patients. Of these, 11 had improvements in LVEF, ranging from 5% to 45%. Worsening of LVEF by 2% to 10% was seen in 6 patients.
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Figure 1. Early and midterm actuarial survival curve of patients with severely depressed left ventricular function at 7.6–27.6 months after coronary artery bypass.
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DISCUSSION
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As in Western countries, the number of patients in Asia with severely depressed LV function being considered for surgical revascularization is increasing annually. With improvements in anesthesia, myocardial protection, cardiopulmonary bypass, and postoperative support, operative mortality in this group has decreased significantly to 2.4% – 11%.9,14–17 Our 30-day mortality of 8% is comparable to previous reports and supports coronary revascularization surgery for patients with severely depressed LV function. Early and midterm survival rates were also satisfactory and comparable to those reported previously in Western populations.9,16,17 These survival rates are also comparable to the results achieved with heart transplantation.18
On multivariate analysis, only cardiogenic shock was a significant predictor of early hospital death. Age was not found to be a significant risk factor for early death in our series, which may be due to the small sample size. Age > 70 years was shown to be a significant predictor of decreased survival by Mickleborough and colleagues.9 Intra-aortic balloon pump use either preoperatively or perioperatively also did not significantly reduce early mortality; 3 of the 4 deaths were in patients who had IABP support for hemodynamic instability. Use of the left internal mammary artery (LIMA) was lower than expected (62%). Most cases in which the LIMA was not used were emergencies requiring cardiopulmonary bypass due to hemodynamic instability; hence, there was insufficient time to harvest the LIMA. In elective cases, LIMA was not used in elderly patients, but this was based on the individual surgeon’s preference. We avoid using radial artery in this group as most require inotropic support postoperatively, which may cause radial artery vasospasm.
Improvements in LVEF were seen in 61% of patients who had postoperative 2D-echocardiography; the other 39% had no improvement or worsening of their LVEF. This variation in postoperative LVEF may reflect the degree of viable or hibernating myocardium at the time of surgery.19 A larger amount of viable but hibernating myocardium may lead to a greater degree of improvement in postoperative LVEF. Reversible ischemia or myocardial thickening on echocardiography are generally accepted as indicators of myocardial viability. Suggested markers of reversible ischemia include clinical symptoms such as persistent angina responsive to nitrates, and redistribution on thallium or positron-emission scanning.20 Only 26% of patients had undergone preoperative Tc-99m scanning to assess myocardial viability and of these, 10 (77%) had significant amounts of viable myocardium. Only 8/13 patients had postoperative 2D-echocardiography, of whom 7 showed improved LVEF. With 39% of our patients not benefiting from surgical revascularization, myocardial viability studies should be considered in all patients with severely depressed LV function being considered for surgical revascularization. However, this will only be possible in elective cases. Clinical symptoms of reversible ischemia, such as persistent angina relieved by nitrates or systolic myocardial thickening with regional wall motion abnormalities on 2D-echocardiography, may suffice in emergency cases.
These findings support the use of surgical revascularization in patients with severely depressed LV function. Myocardial viability should be assessed in this group as those with evidence of reversible ischemia or myocardial viability will benefit the most, with expected improvements in postoperative LV function. Those in preoperative cardiogenic shock are at high risk and should only be considered if there is evidence of reversible ischemia.
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ACKNOWLEDGMENTS
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Thanks to Associate Professor Eugene Sim for advice on the manuscript, Professor Reida El-Oakley, and our Database Administrator, Ms Chien Pei Gen, for helping to retrieve data for the project, as well as the Clinical Research Committee, National University Hospital for statistical analysis of the data.
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ABSTRACT
INTRODUCTION
