Surgical Outcome of Coronary Artery Bypass Graft in Patients with Previous Coronary Stenting

INTRODUCTION

Patients presenting to coronary artery bypass grafting (CABG) became older and had multiple co-morbidities, which could be attributed to the advancement of percutaneous coronary interventions (PCI).¹ Many patients may be managed with coronary stenting and present to surgery at a later stage with in-stent restenosis or progression of the native coronary disease.²

The impact of previous coronary stenting on the outcome after CABG is still debated.^3,4 Patients with coronary stenting are prone to stent occlusion before surgery because of the discontinuation of anti-platelets and the use of coagulants during surgery.

The expanding indications for stenting had affected the practice of coronary revascularization. Many patients are still referred for surgery due to the occurrence of stent restenosis, which occurs with an average frequency of 20–30%.⁵

There is a paucity of the studies on the effect of prior coronary stenting on the outcomes of CABG. The aim of the study was to evaluate the surgical outcome of coronary artery bypass graft in patients with previous coronary stenting.

PATIENTS AND METHODS

This is a prospective cohort study conducted between February 2016 and June 2017. Fifty patients with previous coronary stents who underwent CABG are included in this study. We excluded patients with concomitant surgical procedure, emergence, and re-operative surgery and patients with severe end-organ dysfunction and with ejection fraction less than 30%. The local Ethical Committee approved the study, and the patients’ consent was obtained prior to enrollment.

All patients had routine preoperative laboratory investigations, 12-lead ECG, trans-thoracic echocardiography, and cardiac catheterization. The carotid duplex was performed in patients with a left main disease, history of stroke or transient ischemic attack or in patients with audible carotid bruit.

All patients had surgical intervention under general anesthesia with endotracheal intubation.  The surgical approach was via median sternotomy, the pericardium was opened, and theinternal thoracic artery (ITA) was harvested. All patients had aortic and right atrial cannulation with a two-stage venous cannula. Antegrade cardioplegia was used in all patients. In some patients with in-stent stenosis, the stent was opened, and a patch was done to the left anterior descending artery or other native coronaries. The reversal of heparin action was achieved with protamine sulfate at a ratio of 1 mg for each 100 IU heparin. After obtaining medical and surgical hemostasis, the sternum was closed, and the patient was transported mechanically ventilated to the intensive care unit (ICU). We reported the cardiopulmonary bypass and ischemic times, number of grafts, and the need for mechanical support.

Postoperative data included the duration of mechanical ventilation, the use of intra-aortic balloon pump (IABP), postoperative bleeding, arrhythmias, organ dysfunction, and length of ICU stay. Postoperative echocardiography was done before discharge and after six months.

Statistical analysis:

Recorded data were analyzed using the statistical package for social sciences, version 20.0 (SPSS Inc., Chicago, Illinois, USA). Quantitative data were expressed as mean ± standard deviation (SD). Qualitative data were expressed as frequency and percentage. Unpaired-samples t-test was used when comparing between two independent means. The paired sample t-test was used when comparing two related means. The Chi-square test was used to compare two proportions. The confidence interval was set to 95%, and the margin of error accepted was set to 5%.

RESULTS

Thirty-eight patients were males (76%), and the mean age was 57.66±8.81 years.  Echocardiography was routinely performed preoperatively to assess the left ventricular function, valves, pulmonary artery pressure. The EF ranged from 30-50, with amean of 41.43±9.25%.

Forty-six patients (92%) had previous one stent, and 4 patients (8%) had 2 stents in different coronary arteries.Nineteen patients had in-stent restenosis (ISR) (38%), and 31 patients had new lesions (62%). Seven patients had lesions distal to the site of the stent (14%), and 24 patients had lesions not related to the location of the stent (48%).

The mean cardiopulmonary bypass time was 102.66±25.34 minutes. (Table 1) In all patients, pedicled LIMA was used for anastomosis to LAD, long saphenous vein for other targets.

Table 1: Cardiopulmonary bypass time and aortic cross-clamp time (minutes) presented as range and (mean and standard deviation)

All patients required postoperative mechanical ventilation, and no patient was extubated in the operating theatre. Twenty-five cases needed postoperative inotropic support.  Two patients required an intraoperative intra-aortic pump (4%), and four cases had IABP in ICU (8%).

We had 5 patients (10%) who developed acute myocardial infarction; three cases (6%) were treated with nitroglycerine, morphine, oxygen, and increased dosage of inotropes until their condition was stabilized. The other two patients were unstable even after adjustment of inotropes, and IABP was used.

Operative mortality occurred in 4 patients (8%); one patient (2%) had acute renal failure not responding to treatment or dialysis, and the other 3 patients (6%) had ventricular arrhythmias.

A comparison of the echocardiographic study preoperative and pre-discharge revealed that patients had a decrease in their ejection fraction from 41.43±9.25% to 36.52±8.29%; P= 0.002. Echocardiographic study 6 months post-discharge showed that patients had an increase in their ejection fraction to 44.78±6.99%, P= 0.013.

There was no significant difference in demographic data between survivors and non-survivors. (Table 2) Mortality occurred more frequently in patients with IABP and in patients who had MI and renal failure. (Table 3) Mortality was not associated with in-stent stenosis. (Table 4)

    Table 2: The characteristics of the survivors and non-survivors. Continuous variables are presented as mean    

    and standard deviation and categorical variables as number and percent.

    Table 3:Relation between mortality and complications (Data are presented as number and percent)

   Table (4): Comparison between survivors and non-survivors according to the lesion of the study group. (ISR: in   

    tent restenosis)