|Year : 2017 | Volume
| Issue : 2 | Page : 162-166
Outcome of coronary artery bypass graft surgery in patients with low ejection fraction
Avinash K Inamdar1, Shweta Pralhad Shende1, Sanjeevini A Inamdar2
1 Department of Cardiovascular and Thoracic Surgery, B.J. Medical College, Pune, Maharashtra, India
2 Department of Cardiac Anaesthesia, B.J. Medical College, Pune, Maharashtra, India
|Date of Web Publication||14-Mar-2017|
Shweta Pralhad Shende
Flat No. 2, Neel Ganga Vaibhav Society, Subhash Nagar, Chinchpokli (West), Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
Background: Patients with low ejection fraction (EF) are at high risk for postoperative complication and mortality. Our aim was to assess the effect of low EF on clinical outcome after surgery. Objective: The present study evaluates our experience with coronary artery bypass grafting in patients with low EF. Materials and Methods: We analyzed the data of 35 patients with EF <35%. All participants were assessed preoperatively with respect to patient characteristics, risk factors, and preoperative two dimension echocardiography (2D ECHO). Depending on findings of 2D ECHO patients were divided into three groups: in Group 1, we included patients with EF 30%–35%, Group 2 comprised patients with EF of 25%–30%, and Group 3 consisted of patients with EF <25%. Patients were operated by off-pump coronary artery bypass grafting; only three patients were operated by on-pump beating heart surgery. We noted a mean number of grafts required, use of intra-aortic balloon counterpulsation (intra-aortic balloon pump) intraoperatively and postoperatively, postoperative complication, mortality, mean hospital stay, postoperative improvement in EF, and postoperative control of angina and symptomatic improvement. Results: Hospital mortality rate in present series was 11%. Mean grafts were 3.02 per patient. Fourteen (40%) patient had a postoperative complication. EF improved in 78% of patients. Canadian Cardiovascular Society Angina class improved in 42% of patients. Conclusion: In patients with coronary artery disease and low EF, CABG can be performed safely, and improvement in left ventricular function can be achieved with this procedure improving the quality of life.
Keywords: Coronary artery bypass surgery, low ejection fraction, stunned myocardium
|How to cite this article:|
Inamdar AK, Shende SP, Inamdar SA. Outcome of coronary artery bypass graft surgery in patients with low ejection fraction. Med J DY Patil Univ 2017;10:162-6
|How to cite this URL:|
Inamdar AK, Shende SP, Inamdar SA. Outcome of coronary artery bypass graft surgery in patients with low ejection fraction. Med J DY Patil Univ [serial online] 2017 [cited 2017 May 26];10:162-6. Available from: http://www.mjdrdypu.org/text.asp?2017/10/2/162/202107
| Introduction|| |
Despite the improvement in medical therapies and surgical techniques, the management of patients with coronary artery disease with low ejection fraction (EF) remains challenging. Patients with low EF are at higher risks of sudden death, ventricular arrhythmia, and worsening heart failure due to recurrent ischemia.
Left ventricular dysfunction in patients with coronary artery disease is not always an irreversible process related to previous myocardial infarction since left ventricular function improves substantially in many patients and may even normalize after coronary artery bypass grafting.
In these patients with low EF, coronary artery bypass grafting has been shown to be superior to medical therapy alone, resulting in significant clinical improvement and improving long-term survival. Advances in preoperative management, refinements in surgical techniques, use of off-pump coronary artery bypass grafting, and advances in cardiac anesthesia with improvement in intensive postoperative care all have resulted in a decrease in the mortality rate in patients with low EF operated by off-pump coronary artery bypass surgery.
The present study evaluated the outcome of patients with coronary artery disease with low EF with respect to long-term survival, mortality, complications, improvement in EF, and quality of life.
| Materials and Methods|| |
All 35 patients of coronary artery disease with low EF, operated in our center, by coronary artery bypass grafting during a 4-year period (2008–2012), were included in this study. After admission for coronary artery bypass grafting, detailed history recording, clinical examination, and relevant investigations were carried out. History included past episodes of myocardial infarction, thrombolytic medication if any in the past, comorbidity, and personal history regarding addiction to alcohol and tobacco. One patient had a history of coronary angioplasty done in 2001 and presented with stent block and critical triple vessel disease. Another patient was with single vessel disease, in which cardiologist had tried stenting, but since stent could not be negotiated due to tight stenosis was referred for surgery. All patients were investigated with respect to kidney function test, liver function test, creatinine phosphokinase-MB (CPK-MB), and two-dimensional echocardiography (2D ECHO). We operated only those patients with CPK-MB within normal range. EF was determined by calculation with 2D-ECHO through the biplane apical method and modified Simpson's rule. We categorized those patients with low EF, i.e., EF <35% into three categories. The categories were EF 31%–35%, EF 25%–30%, and EF <25%. All those patients, whose EF was <25%, are further evaluated for myocardial viability by thallium scanning.
After patients were hemodynamically stable and fit for anesthesia, they were posted for surgery. In our setup, we prefer off-pump coronary artery bypass grafting in all patients, except those patient who show hemodynamic deterioration after lifting up heart by positioner were converted to on pump beating heart surgery. After midline sternotomy and half dose heparinization for off-pump coronary artery bypass surgery, left internal mammary artery was harvested. If found to be of good caliber and flow then it was anastomosed to left anterior descending coronary artery (LAD). Other conduits used were radial artery after doing Allen's test and Doppler study of radial and ulnar arteries of that hand and saphenous vein graft. Additional maneuvers were used during cardiac exposure to maintain hemodynamics including opening of the pleural spaces and the use of pericardial retraction suture. Anastomoses were facilitated by the use of suction stabilizer. In all cases, we used intracoronary shunt to provide distal flow while doing anastomosis to prevent myocardial ischemia. The visualization of target vessels while doing anastomoses was aided by instillation of saline with a blower and mister. Revascularization of obtuse marginal artery and posterior descending artery was performed by lifting up the heart with the help of apical positioner device (starfish). We usually perform LAD graft first in cases of critical triple vessel disease and allow heart to rest for some time and recover before moving on the next graft. Distal grafting was followed immediately by proximal anastomoses. Proximal anastomoses using 6-0 Prolene were performed using a partial occlusion side-biting clamp. Site selection was performed by ascending aorta palpation. Those patients who showed hemodynamic deterioration during positioning of heart were converted to on-pump beating heart surgery after full heparinization. Aortic arterial and two-stage venous cannulation were done to establish cardiopulmonary bypass.
Postoperatively, outcomes evaluated were mortality, postoperative complications, use of intra-aortic balloon pump (IABP), hospital stay, control of angina, and long-term survival. Mortality was defined as any death occurring within 30 days after surgery in or out of hospital or after 30 days during the same hospitalization subsequent to the operation as recommended by European Association of Cardiothoracic Surgeon. Stroke was defined as a new focal deficit or a comatose state lasting more than 24 h. Acute myocardial infarction was defined as elevated serum creatine kinase-MB >30 IU/L, the presence of new electrocardiographic changes indicative of necrosis, or new akinetic segments revealed by echocardiography (ECHO). Acute renal failure was defined as a postoperative creatinine level >2.0 mg/dL (with a history of prior normal renal function). Respiratory failure was defined as unable to wean off from ventilator support for more than 72 h.
We routinely did 2D ECHO before operation, before discharge, and same ECHO report was continued till further follow-up, for comparison to evaluate the improvement after surgery. All patients were called for follow-up 1 month after discharge, 3 monthly thereafter for 6 months, and then 6 monthly. During follow-up, a detailed history was taken with respect to angina and breathlessness, and review 2D ECHO was done.
| Results|| |
The important characteristics of the study subjects are shown in [Table 1].
In addition to this, history of smoking was present in 19 (54.28%) patients. History of chronic obstructive pulmonary disease was present in three patients. History of peripheral vascular disease was present one patient. Six (17.14%) patients gave a history of alcoholism. Five (15%) patients gave a history of both smoking and alcoholism. Other laboratory investigations of these patients were normal except for high values of kidney function test in two patients with diabetes mellitus.
All patients depending on estimated EF by 2D ECHO were divided into three groups. Group I – EF: 31%–35% included 17 (48%) patients, Group II - EF: 25%–30% 13 patients (37.14%), and Group III - EF: <25% 5 patients (14.28%). Three patients of Group III were treated successfully with coronary artery bypass grafting. All those patients, whose EF was <25%, were further evaluated by positron emission tomography thallium scan. Two out of five patients show no peri-infarct viability in right coronary artery territory and other in left circumflex artery territory artery. Both patients died postoperatively.
We planned those patients for coronary artery bypass surgery who were hemodynamically stable and fit for anesthesia. In our setup, we prefer off-pump coronary artery bypass grafting in all patients except those who showed hemodynamic deterioration after lifting up heart, underwent on-pump beating heart surgery. Thus, three patients (8.5%) were done on-pump beating heart surgery and 91.5% were off-pump beating heart surgery. Left internal mammary artery was harvested in 32 patients (91.42%) but used as a conduit in thirty patients (85.75%). In one patient, it was of very poor caliber and flow, and in other patient, there was intimal flap dissection. Thus, in those patients, great saphenous vein was used as conduit. Radial artery was used as a conduit in three patients (8.57%). Reverse great saphenous vein graft was used as a conduit in all patients. A total number of grafts in our study were 103, and an average number of grafts per patient was 2.942. Some patients mainly with diabetes mellitus had diffuse nongraftable coronary arteries. Six (17.43%) patients required IABP support. In two patients, intra-aortic balloon insertion (IABP) was done immediately before closure of sternum and in four patients postoperatively. Out of these six patients, four patients did not survive the procedure. Of the 2 who survived, one died due to septicemia 15 days postoperatively.
These are highlighted in [Table 2]. There were 4 (11%) mortalities in this study group. One patient was with EF 35% operated by on-pump beating heart surgery; this patient deteriorated even after insertion of IABP and went in low cardiac output state. Two patients develop renal failure postoperatively. Other patient was 70 years diabetic male patient who had low cardiac output and respiratory failure. He eventually develops septicemia and succumbed. Total 7 (20%) patients had a postoperative complication. One patient had sternal instability and was operated by sternal rewiring. Two (5.6%) patients were reexplored for left-sided hemothorax. One patient had complication of ventricular fibrillation with prior ECG changes of acute myocardial infarction. Two patients had a postoperative myocardial infarction. One patient developed atrial fibrillation. One patient had sudden cardiac arrest, after intracardiac massage and IABP support, he could be revived. A mean hospital stay of all these patients was 10.2 days.
All patients were followed for 2 years. Three out of 31 surviving patients were lost to follow-up. All patients were evaluated regarding any residual symptoms and with respect to Canadian Cardiovascular Society Angina Classification. Twenty (57.14%) patients had no symptom of angina. Two patients had mild chest discomfort. Five (14.28%) patients who initially had Class 2 angina now presented with Class 1 angina. One patient had severe chest pain but was hemodynamically stable. ECG shows no fresh ST, T wave changes. All patients were reassessed by 2D ECHO to evaluate EF. Out of the three patients with low EF <25%, one showed improvement in EF to 35% while the other two improved to 40%. Others also showed improvement in EF up to 40% in 20 (78.57%) and 45% in 5 (17.85%). Thus, there was definitely increase in EF in patients who were successfully operated.
| Discussion|| |
Coronary artery bypass grafting enables longer survival and better quality of life than does the medical therapy. Improvements in preoperative management, operative techniques, and optimum postoperative management have substantially reduced the negative impact of severely depressed left ventricular function on early outcome. Careful preoperative selection and operative management including optimal strategies of myocardial preservation are essential in patients with low EF undergoing cardiac surgery.
The patient with low EF, as studied from 2D-ECHO findings, had regional wall motion abnormalities, with hypokinesia or akinesia. Because of the presence of these regional wall motion abnormalities, patients have depressed ventricular function. Stunned or hibernating myocardium represents these regional wall motion abnormalities. Following the recognition and correct definition of stunned and hibernating myocardium, the possibility of reversal of ventricular dysfunction has been accepted with heightened interest. “Hibernating myocardium” is chronically hypocontractile tissue due to persistently low flow with the potential to improve function after restoration of blood supply. Hibernating myocardium might represent adaptation to both impaired coronary flow reserve (repetitive ischemia and stunning) and reduced resting coronary blood flow. Stunning is contractile dysfunction in viable myocardium resulting from transient ischemia, followed by restoration of perfusion. Pathogenesis likely involves oxyradicals and calcium. Dysfunction might persist from hours to days but generally improves with time. An exception is “repetitive stunning,” defined as repeated episodes of ischemia producing prolonged postischemic contractile dysfunction, which is similar to hibernation in that revascularization has the potential to improve contractile function. Thus, in patients of left ventricular dysfunction in the presence of stunned myocardium, after revascularization, there is return of viable myocardium, improvement in EF which provides relief of symptom and offer survival >60% at more than 5 years. The other predictor of outcome of these patients is operative technique. With the use of conventional on-pump surgery which is associated with release of inflammatory mediators and potential induction of multiple organ dysfunction, with significant myocardial edema and ischemia, which further depresses myocardial function resulting in high mortality and morbidity. Hence, on-pump coronary artery bypass grafting is not the solution for patients with low EF. An intermediatory approach between conventional and off-pump bypass was studied by Perrault et al. They found that using cardiopulmonary bypass without cross-clamping and cardioplegic arrest with beating heart is associated with less myocardial edema and ischemia. In a study performed by Rastan et al. using on-pump beating heart surgery among patients with normal EF, they found increase incidence of myocardial injury when compared to off–pump surgery.
In the present study, we used off-pump coronary artery bypass grafting in 91.5% of patients. There was no technical difficulty with acceptable mortality rate. Mortality rate in the present study was 11%. Di Carli et al. had operative mortality of 9.3% in patient with low EF. Christakis et al. recorded operative mortality of 9.8% with an EF of <20%. Carr et al. reported 11% perioperative mortality rate.
The other benefit of on-pump surgery, as per literature, is to achieve complete revascularization. In the present study, there was no difficulty while grafting obtuse marginal artery and posterior descending artery, due to availability of suction stabilizer and positioner, and hence no compromise with revascularization. In the present study, mean grafts were 3 per patient comparable with Di Carli et al. study which also reported mean grafts of 3 per patient. Number of complications was also less in the present study. During follow-up of patients, symptoms of angina were significantly decreased further improving the quality of life.
Thus, in patients of left ventricular dysfunction in the presence of stunned myocardium, after revascularization, there is return of viable myocardium to normal functional state and increase in EF as seen with all our patients which can be determined objectively. Postoperative angina is also relieved symptomatically.
| Conclusion|| |
In patients with coronary artery disease and low EF off-pump, CABG can be performed relatively safely and is a safe procedure. It results in good medium-term survival, improves left ventricular function, and enhances overall quality of life.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]