Total Arterial Revascularization versus Conventional Coronary Artery Bypass Grafting; A Comparative study

INTRODUCTION

Coronary artery bypass grafting (CABG) is the most commonly performed cardiac surgical procedure.¹ Moreover, CABG remains the most effective revascularization strategy for severe coronary atherosclerotic disease² and in patients with diabetes, left main and three vessels disease.³ The debate about the optimal conduit for CABG is still going on, and choosing the proper graft affects CABG's short and long-term outcomes. Graft patency is related to the smooth postoperative course and enhances patients' survival and freedom from coronary reintervention.

Long saphenous vein graft has been the preferred conduit for a long time; however, progressive vein graft failure negatively affects the long-term outcomes after CABG.⁴ Total arterial revascularization has emerged as an alternative solution to improve the long-term outcomes after CABG.⁵ The superiority of total arterial revascularization over conventional methods is a subject of continuous debate.

Therefore, we aimed to compare early surgical and hospital outcomes of the total artery and conventional revascularization strategies in patients undergoing CABG.

PATIENTS AND METHODS

Design and patients

This retrospective cohort research comprised 60 patients who underwent primary CABG at Cardiothoracic Surgery Departments, Faculty of Medicine, Al-Azhar University, between 2018 and 2020. We included patients who had elective on-pump CABG. Patients who underwent emergency CABG,  or those with poor left ventricular ejection fraction (EF˂ 35%), redo CABG, concomitant procedure, and end-organ dysfunction or previous stroke were excluded. Patients were grouped according to the revascularization strategy into two groups. Group 1 included patients who had conventional revascularization using left internal mammary artery (LIMA) and vein grafts (n= 30), and group 2 included patients who had total arterial coronary revascularization (TACR) (n= 30). Patients were assigned to each group according to the surgeons' preferences and experience.

The study was approved by the local Ethical Committee, and the need for patients' consent was waived because of the retrospective design.

Data and outcomes

All patients were subjected to full history taking, preoperative laboratory tests, chest x-ray, ECG, echocardiography, and coronary angiography. Operative data included the number of anastomoses, graft, coronary size, anastomosis technique, and operative, cardiopulmonary bypass (CPB), and cross-clamp times. Intraoperative events included using inotropes, defibrillator, intra-aortic balloon pump, and mortality. Postoperative outcomes included cardiac output, cardiac index, postoperative inotropes, blood loss, blood transfusion, hospital complications, length of intensive care unit stay (ICU), and hospital stay and mortality. Patients were followed for six months after surgery at the outpatient clinic. Follow-up data included angina and dyspnea status, EF, and wall motion index. Wall motion index was evaluated in echocardiography in 16 segments. Segmental wall motion was classified into normal (= 1), hypokinetic (=2), akinetic (= 3), and dyskinetic (=4).⁶

Operative techniques

All patients had surgery via median sternotomy. Arterial cannulation was performed through the ascending aorta and venous cannulation through the right atrium. In patients with conventional CABG, LIMA was anastomosed to the left anterior descending artery (LAD) and saphenous vein to other targets. In the TACR group, LIMA was used for LAD, and the right internal mammary (RIMA) or radial artery was used for other grafts. The patency of the grafts was assessed using a transient time flow meter (TTFM), and the mean flow (MF) and pulsatile index (PI) were reported.

Statistical analysis

A normality test, the Kolmogorov-Smirnov test, was used to measure the data distribution. Accordingly, a comparison between normally distributed variables in the two groups was performed using an unpaired t-test. A comparison between non-normally distributed variables was performed using the Mann-Whitney test. Continuous data were expressed as mean and standard deviation, and categorical data as numbers and frequencies. Statistical Package for Social Sciences (SPSS) computer program (version 19 windows, IBM Corp, Armonk, NY, USA) was used for data analysis. A P value of ˂0.05 was considered significant.

RESULTS

Preoperative data

Patients who underwent TACR were significantly younger (P= 0.003). There were no differences in gender, weight, and height between groups. Dyspnea class III and hypertension were more prevalent in patients in the TACR group, with no difference in angina class or other comorbidities between groups. Preoperative antiplatelets were significantly higher in patients who underwent TACR, with a significantly higher prevalence of stable angina. There was no difference in ejection fraction between groups; however, left ventricular end-diastolic diameter was significantly higher in patients in the TACR group. (Table 1)

(AHA: American Heart Association; CCS: Canadian Cardiovascular Society; LEVEDD: left ventricular end-diastolic diameter; LVESD: left ventricular end-systolic diameter; NYHA: New York Heart Association)

(Continuous data were presented as mean and standard deviation and categorical data as numbers and frequencies)

Table 1: Comparison of the preoperative data between patients who had conventional versus total arterial revascularization (Group 1: conventional coronary artery bypass grafting; Group 2: total arterial revascularization)

Operative data

The number of distal anastomoses was significantly higher in patients with conventional CABG (P˂ 0.001). The most common graft conduit used in the total arterial revascularization group was pedicled LIMA (46.9%), followed by radial artery (26.6%), then pedicled RIMA (20.3%), and skeletonized RIMA (6.2%). In comparison, long SV was the most common graft used in the conventional group (63%), followed by pedicled LIMA (34.6%) and pedicle RIMA (2.5%).

The most common graft site in the TACR group was the LAD (46.9%), followed by first obtuse marginal branches (OM1) (26.6%), then the right coronary artery (RCA) (20.3%), and ramus site (6.2%). Similarly, LAD was the most common graft site used in the conventional group (37.0%), followed by RCA (29.6%), OM1 (23.5%), and first diagonal branch (D1) (9.9%). The side-to-side anastomosis was done in six cases (9.4%) in the TACR group, while all patients in the conventional group had an end-to-side anastomosis (P<0.01). The mean flow and coronary size were significantly higher in the TACR group compared to the conventional group.

Cardiopulmonary bypass and ischemic times were significantly longer in patients with conventional CABG, while there was no difference between groups in the operative time. (Table 2)

Table 2: Comparison of the operative data between patients who had conventional versus total arterial revascularization (Group 1: conventional coronary artery bypass grafting; Group 2: total arterial revascularization)

Postoperative outcomes

There were no differences in cardiac output and index between groups. There was lower blood loss and fewer fresh frozen plasma and platelets units used in the TACR group compared to the conventional group. Duration of mechanical ventilation, ICU, and hospital stay were significantly longer in the conventional group. (Table 3) We did not report sternal wound infection or hospital mortality in our cohort.

Table 3: Comparison of the postoperative data between patients who had conventional versus total arterial revascularization (Group 1: conventional coronary artery bypass grafting; Group 2: total arterial revascularization)

Follow-up data

After six months, angina and dyspnea classes were significantly better in the total revascularization group. There was no difference in EF between groups, and the wall motion index was significantly lower in the TACR group. (Table 4)

Table 4: Comparison of the 6-months follow-up data between patients who had conventional versus total arterial revascularization (Group 1: conventional coronary artery bypass grafting; Group 2: total arterial revascularization)