Outcome of Coronary Artery Bypass Graft Surgery with Coronary Endarterectomy

Background: Coronary Endarterectomy (CE) is the expulsion of the atheromatous plaque, and isolating the outer media and adventitia layers of arterial wall. Objective of this study was to review the consequences of coronary endarterectomy (CE) with coronary artery bypass grafting (CABG), and demonstrate the outcomes of this surgical technique for patients with diffuse coronary artery disease in a single surgeon’s practice. Methods: Retrospectively outcome of 1473 endarterectomised coronary artery in 1189 patients with diffuse coronary artery disease (CAD) was reviewed, who have had experienced CE with OPCABG in the year of 2007 to 2016. CE was performed in multi-segmental diffuse CAD, or when a calcified or extremely thick plaque making anastomosis troublesome. Results: Approximately 75.0% coronary endarterectomy were performed in the left coronary territory and most commonly left anterior descending artery was endarterectomized (42.83%). An average of 1.2 coronary endarterectomies performed per patient. Post-operative ICU and 30-days mortality rate was 2.2%, and 0.6% respectively in CE group. Post-operative atrial fibrillation, acute MI, neurological complication, and blood transfusion were significantly higher in CE group. Following CE, Kaplan–Meier cumulative survival rate was 89.5%, and about 85% patients were free from angina at follow-up of 5 years. Conclusion: Coronary endarterectomy with OPCABG is attainable, and accomplishes surgical revascularization in patients; when there is no other alternative for total myocardial revascularization.


Introduction
Ischaemic heart disease (IHD) patients, who are referred for coronary artery bypass graft (CABG) surgery are progressively getting more complex with multiple comorbidities, and subsequently, this group of patients have diffuse coronary artery disease, which has made complete surgical revascularization more difficult. 1In the late 1957, coronary endarterectomy was at first presented as a surgical option for myocardial revascularization by Bailey et al. 2 Coronary Endarterectomy (CE) is the expulsion of the atheromatous plaque, and isolating the outer media and adventitia layers of arterial wall. 2,3Initial results for coronary endarterectomy with CABG surgery was downhearted due to greater incidence of perioperative mortality and morbidity.Furthermore, the adverse effects are even more disastrous when endarterectomy is performed on a coronary artery that are highly pivotal to achieve optimum myocardial revascularisation especially left anterior descending (LAD) artery, where incomplete myocardial revascularisation may results in an awful clinical outcome. 4,5nadequate myocardial revascularizations do not influence the early death rate, but rather the occurrence of restenosis which influences the long term cardiac dysfunction.These patients have more prominent repeated attacks of angina, and more noteworthy work absence rate and require a higher number of re-interventions following CABG. 2,4,6ronary endarterectomy is frequently important to perform optimal myocardial revascularization during CABG surgery, or to encourage anastomosis of severely calcified and diffusely diseased coronary arteries. 3,7The principle indication for CE technique is the presence of diffuse coronary artery disease with leaping lesion, that are not feasible to achieve distal bypass grafting.However, coronary endarterectomy *Correspondence: Redoy Ranjan, Department of Cardiac Surgery, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh; e-mail: redoy_ranjan@yahoo.comORCID: https://orcid.org/0000-0003-1927-5023  can be performing safely in all territories, but few authors stated that endarterectomy in left anterior descending artery may be exceptionally tricky. 8herefore, most of the surgeons performed LAD endarterectomy in a highly selective manner, where there are no other options exist. 9Atherosclerotic plaques in LAD artery is hard and fragile in contrast to right coronary or circumflex artery, thereby increasing the incidence of plaque disruption.Moreover, branches of LAD artery like diagonal and septal artery arises in two different planes and have the chance of shearing-off the branches during extraction of the atheromatous plaque in either direction. 9,10e fundamental concept of coronary endarterectomy in complex coronary artery disease is to extract the total atheromatous plaque, and achieve a good distal run off in diseased coronary arteries. 11However, it is disputable that the difference in positive outcomes between concurrent CE with CABG and only CABG procedure is due to the complexity of the coronary lesion.][10] Research data from the last two decades observe better long term survival rates following coronary endarterectomy in diffuse IHD patient's. 11,12However, many cardiac surgeons are still unenthusiastic to do coronary endarterectomy due to the absence of authentic guidelines as well as varying results from different cardiac centers.The aim of this retrospective study was to evaluate the both early and long term outcomes following coronary endarterectomy with coronary artery bypass graft surgery in a single surgeon's practice and to provide details regarding treatment strategies for patients having diffuse coronary artery disease.

Materials and Methods
Between the years 2007 to 2016, a retrospective analysis of total 2647 number of patients were submitted to CABG procedure with or without CE in a single surgeon's practice.This study was carried out at the department of cardiac surgery, Bangabandhu Sheikh Mujib Medical University and was approved by the institutional review board (IRB) of the University.A purposive sampling methods utilized to select study population, and patients were divided into 2 study groups according to types of surgery: Group-I includes combined CE with CABG, and Group-II consist of isolated CABG surgery.Inclusion criteria for CE procedure were distal diffuse coronary artery lesion, multi-segmental lesion; or when a calcified or extremely thick plaque burst, making anastomosis troublesome or hindering the distal stream.Patient's with short segment coronary artery lesion were not included in CE procedure.The decisiveness to perform coronary endarterectomy was based on the findings of preoperative coronary angiograms, and majority of the endarterectomy were plan before surgery.However, the conclusive decision to have a CE procedure was made according to per-operation findings of the vessel conditions as well as the surgeon's preference.
Surgical technique: All procedures were performed through a standard median sternotomy and a CPB circuit was kept on standby for all cases.Heparin was used just before completing LIMA harvest to maintain an ACT (Activated clotting time) more than 350 seconds.Almost all the operations were performed off pump CABG and a few cases required the assistance of cardiopulmonary bypass (CPB).Mechanical stabilisers like suction type and the compression type were utilised, to immobilize the target coronary artery during grafting.A conclusive decision to endarterectomise a vessel is made peroperatively. 5,7Coronary endarterectomies were performed manually by utilizing the closed methods-"slow sustain and continuous traction" of atheromatous plaque with the aid of delicate Ring Forceps, followed by reproduction of distal anastomosis with pre-planned graft.The arteriotomy incision was roughly 8-10mm long, however that was stretched out for another 5mm in few cases.Much consideration was provided to the entire expulsion of the distal segment, but complete proximal endarterectomy avoided due to the danger of competitive flow loss between the graft and the native artery. 7,11,12To ensure complete expulsion, the atheromatous plaque carefully inspected for a smooth distal tapper end.2][13] In this study, longest atheroma (14 cm in size) was removed from RCA and also another 10cm atheromatous plaque extracted from LAD during OPCABG (figure 1).
Anticoagulation therapy: In early post-operative period, every patient received heparin infusion bridging to warfarin from the first post-operative day for next 3-6 months.Heparin was used (usually 5000IU subcutaneously 8 hourly) in the early postoperative period, usually 3-4 hours following surgery, followed by oral warfarin (5-10mg) till 3 rd post-operative day.From 4 th post-operative day to onwards, warfarin was used at a dose of 2.5 to 5mg for next 3 to 6 months and dose was adjusted according to INR (targeted INR was 1.5-2.5).In this study, a combination of clopidogrel with aspirin (75 mg) also used to anticipate acute thrombosis at the graft and also in the endarterectomies native artery for life long from 1 st post-operative day.

Study endpoints and follow-up:
The primary endpoint of this study was LV function and post-procedural graft patency rate at five year follow up.LV function were classified as (a) Good LV function (EF >50%), (b) Moderate dysfunction (EF 30-50%), (c) Poor LV function (EF <30%).Furthermore, graft patency rate was classified as (a) Grade A: excellent patency rate (≤50% stenosis), (b) Grade B: moderate graft stenosis (> 50% lesion), and (c) Grade O: total graft occlusion.The patients underwent a TTE (Transthoracic Echocardiography) and CT (Computer tomography) angiogram to evaluate LV function and the degree of in-graft stenosis respectively.Moreover, the secondary study endpoint was the incidence of major adverse cardiac and cerebrovascular events (MACCE), defined as allcause death, non-fatal myocardial infarction and also cerebrovascular event during the 5-year clinical follow-up.During this study, every patient was reached either during outpatient department visit (OPD) or by phone call and data was noted to data sheet.
Statistical analysis: All statistical analyses were performed with Statistical Package for the Social Sciences.Continuous variables were expressed as mean ± standard deviation and categorical variables as percentages.Categorical variables were compared using Pearson's chi-square and are expressed as a percentage of the group of origin.Cumulative survival rate were evaluated with the Kaplan-Meier estimation method.All reported p values are two-sided, and p values of ≤ 0.05 were considered statistically significant.

Results
A total of 2647 patients were undergone surgical revascularization in this review.However, 1189 patients underwent CE with CABG (Group-I), and 1458 patients underwent isolated CABG (Group-II) surgery.In Group-I 1473 coronary endarterectomies were performed, that is an average of 1. 24

Discussion
This study evaluated the outcomes of coronary endarterectomy in CABG surgery having diffuse coronary artery disease (CAD) and shown that the complete revascularization of diffuse CAD enhanced the early and late post-operative outcomes following CABG.The mean age of study population was 61.25 ± 5.5 and 59.75 ± 2.5 in endarterectomy and only CABG group respectively.In this study, 1.24 endarterectomies required per patient in CE group.Out of total endarterectomies, two third endarterectomy was done in Left coronary territory, and mean graft number were 3.21 ± 0.25 and 3.02 ± 0.15 in CE Group and only CABG Group respectively.There were only 13.29% and 3.84% cases required cardiopulmonary bypass support in two groups respectively.Post-operative ICU mortality and 30 day's mortality rate was minimum in both study group, and all of the patients were belongs to poor LV function (EF<30%) group.In this study, a mean of more blood was transfused postoperatively in CABG with endarterectomy group (p value <0.05).At median follow-up of 5 years, most of the patients were angina free in both group, however, the incidence of post-operative MI and atrial fibrillation rate was higher in endarterectomy group (p < 0.05).
1][12] In a study, Jones et al. observed that complete myocardial revascularization appeared to be a most critical component influencing perioperative outcome, ventricular function, early and late postoperative morbidity and mortality. 13][10]14 In this study, approximately 75% of the coronary endarterectomy was performed in the left coronary territory and outcome was satisfactory.In a review, Eryilmaz et al. described that coronary endarterectomy technique as well as management yet a matter of controversy. 153][14][15][16] But the potential dangers are inadequate expulsion of the plaque and the "snowplow effect," means shearing-off of the plaque in the side branches.[8]16 Postoperative anticoagulation therapy plays a crucial role in preventing perioperative myocardial infraction following CE procedure.In a study, Papakonstantinou et al. observed that postoperative strict antiplatelet and anticoagulation management with systemic heparin infusions followed by warfarin therapy for several months provides better graft patency rate. 18Moreover, the systematic infusion of heparin is continued until warfarin is become effective with a target international normalized ratio between 2.0 and 2.5 which is similar this study results.In another recent study by Qiu et al. also observed that in diffuse coronary disease, CE is a safe and feasible procedure for a select group of patients with excellent mid-term survival rates as well as graft patency rates. 24CE provides better overall outcomes when performed on the LAD artery, and grafted over with the LIMA conduit.0][21][22][23] In a study Naseri et al. demonstrate higher incidence of completely blocked or significant stenosis in graft and endarterectomized artery on CT angiogram and a higher incidence of (6.8%) postoperative MI rate. 252][23][24] This superiority of graft patency rate in this study may be due to fixed management protocol with combined antiplatelet and anticoagulant therapy.
It was observed that, only CABG surgery is not sufficient to provide total revascularization in presence of complex CAD with diffuse lesion, stent restenosis, and LV dysfunction, where need to do concurrent coronary endarterectomy in addition to CABG to achieved good distal run-off and better postoperative outcome.However, surgical skills and postoperative anticoagulation therapy remains the key stream in our study and CE was not found to be independently associated with mortality in the analysis for the predictors of mortality.

Conclusion
Coronary endarterectomy is feasible and a good surgical option for total myocardial revascularization in patients with diffuse coronary artery disease with excellent long-term survival rates and graft patency rates.Furthermore, CE provides optimal myocardial revascularization resulting improvement of postoperative left ventricular function as well as NYHA functional class.However, surgical skill, patient's selection criteria, and postoperative anticoagulation therapy are the key words for better outcome following CE with CABG surgery.Altogether, endarterectomy should not take the place of CABG procedure, but this technique is an adjunctive to CABG surgery in diffuse calcified coronary artery disease, and CE is not expedient for every IHD patient undergoing coronary artery bypass surgery.

Figure 2 :
Figure 2: Kaplan-Meier survival curve demonstrates long term survival benefits between combined coronary endarterectomy with CABG group versus isolated CABG group.Time (Years) Cum Servival Rate (%) CE + CABG CABG Used conduit for LAD graft was LIMA in 100% cases for CE with CABG group, and 99.25% in only CABG group.Mean number of graft were 3.21 ± 0.25 in CE with CABG group, and 3.02 ± 0.15 in only CABG group.There were 13.3% conversions to on-pump CABG using cardiopulmonary by pass in CE with CABG Group but only 3.84% conversions in only CABG Group.table II.

Table II :
Operative data of study population Note: LAD-Left Anterior Descending, OM-Obtuse Marginal, RCA-Right Coronary Artery, PDA-Posterior Descending Artery.There were no intra-operative mortalities in this study, however post-operative ICU mortality rate was 2.19% in Group -1, and 1.44% in Group -II.Kaplan-Meier survival estimates in the combined CE with CABG group and isolated CABG group at 5 years were 89.48% and 91.02% respectively (figure2).The rest of the postoperative outcome variables are listed in table III and table IV.

Table III :
Early post-operative variables of study population

Table IV :
Long term outcome variables of study population