Left main coronary artery (LMCA) supplies more than 80% of the left ventricle, and significant disease of this artery carries a high mortality unless intervened surgically. However, the influence of coronary artery bypass grafting (CABG) surgery on patients with LMCA disease on morbidity intensive care unit (ICU) outcomes needs to be explored. However, the impact of CABG surgery on the morbidity of the ICU population with LMCA disease is worth exploring.

To determine whether LMCA disease is a definitive risk factor of prolonged ICU stay as a primary outcome and early morbidity within the ICU stay as secondary outcome.

Retrospective descriptive study with purposive sampling analyzing 399 patients who underwent isolated urgent or elective CABG. Patients were divided into 2 groups; those with LMCA disease as group 1 (75 patients) and those without LMCA disease as group 2 (324 patients). We correlated ICU outcome parameters including ICU length of stay, post-operative atrial fibrillation, acute kidney injury, re-exploration, perioperative myocardial infarction, post-operative bleeding in both groups.

Patients with LMCA disease had a significantly higher prevalence of diabetes (43.3% vs 29%, P = 0.001). However, we did not find a statistically significant difference with regards to ICU stay, or other morbidity and mortality outcome measures.

Post-operative performance of Patients with LMCA disease who underwent CABG were comparable to those without LMCA involvement. Diabetes was more prevalent in patients with LMCA disease. These findings may help in guiding decision making for future practice and stratifying the patients’ care.

Defining the intensive care unit (ICU) outcome predictors after cardiac surgery remains an optimum goal[1]. Prolonged ICU stay is associated with increased costs and adverse patient outcome[2]. Age, congestive cardiac failure, peripheral vascular disease, higher perioperative serum creatinine, and prior cardiac surgery had been identified by Hammermeister et al[3], as potential risk factors for adverse outcome after cardiac surgery. Although the risk of mortality after cardiac surgery has been identified in several studies through various scoring systems, there is a growing need to identify morbidity predictors and factors influencing the ICU length of stay in the cardiac surgery setting[4]. Time in blood glucose range[5], elevated perioperative troponin[6], and acute kidney injury (AKI) have been identified as individual risk factors for morbidity in cardiac surgery ICU[7].

The left main coronary artery (LMCA) supplies 80% of the blood demands of the left ventricle. Obstructive lesions of the LMCA carries high mortality with medical treatment[8], but improves markedly with surgical treatment[9]. Some authors do not consider LMCA occlusion as a risk for early and late mortality[10]. The challenges associated with LMS disease had been explored in previous work of El-Menyar et al[10] to include lesion location to outcome relation, subacute thrombosis potential, left ventricular function and patient comorbidities on overall outcome; and the risk-benefit ratio of coronary artery bypass graft surgery vs stenting. In a cross-sectional study conducted in Qatar, isolated LMCA obstruction was 4-fold higher in women, with high prevalence of distal and proximal lesions. The authors found that renal failure was independent predictor of left main stem (LMS) disease. The mortality over one-year was higher in patients with LMS disease[11].

To the best of our knowledge no previous studies have addressed the short-term morbidity based on the ICU outcome; hence LMS morbidity measures need to be explored further.

Of the 421 patients screened, 399 patients were enrolled in this study; the remaining 22 patients met the exclusion criteria. The mean age was 51.9 ± 11.3 years. The rest of the baseline descriptive data are highlighted (Table 1). The predominant gender in this study were males, accounting for 245 patients (82.2%). The high prevalence of diabetes was noted in our study where 141 patients (47.3%) were diabetics. Patients were divided based on the association of LMS disease into 2 groups. Both groups were matched regarding the age, gender, association of hypertension, Euro score, baseline ejection fraction (EF), baseline creatinine and need for elective surgery (Table 2). We noted that diabetes was significantly more prevalent in LMS group (53% vs 44.4%, P = 0.05). The usage of IABP was significantly higher percentage among LMS group (P = 0.05).

There was no significant difference between both groups regarding inotropic and vasopressors demands. We did not encounter significant differences between the groups in terms of anesthesia, CPB and ACC times as well as number of grafts. The postoperative lengths of mechanical ventilation, ICU stay, and hospital stay did not show any significant differences between both groups (Table 3). Post-operative complications, including POAF, AKI, hospital-mortality, ventilator associated pneumonia, need for VA-ECMO, vasoactive inotrope score (VIS), re-admission to ICU, surgical re-exploration, major bleeding and PMI did not make significant differences between groups.

The salient findings of this work were: (1) The primary outcome which was the LOS_ICU was not different between the studied groups; (2) The secondary outcome measures did not show any significant differences; (3) Need for IABP support for LMS group was significantly higher than the group without LMS: and (4) Diabetes was more prevalent in patients with LMS.

To the best of our knowledge, this is the first study to address the ICU outcome of LMS disease after CABG. Chaitman et al[15] have highlighted the high morbidity and mortality of LMS disease and its frequent association with multi-vessel disease.

LMS disease patients comprised 18.7% of the patients in our study, compared with 30% in the Keogh et al[16] database. According to the guidelines of the American College of Cardiology/American Heart Association (ACC/AHA), CABG is a class I one recommendation for LMS stenosis in asymptomatic patients[17]. The most important coronary lesion in prognosis prediction is LMS, the latter is diagnosed in 5%-7% of patients who underwent coronary angiography[18]. The mortality in our LMS group was 2.7%. Conley and colleagues pointed to the contributing factors in LMS mortality to include age, diabetes, left ventricular function and dyslipidemia[19]. Su et al[20] in their review observed a mortality of 3.4% with conventional CABG in patients having LMS disease. Lower mortality in our series may be related to younger age.

In our study, patients with LMS disease were older and having higher prevalence of diabetes compared to those without LMS disease, but this did not attain statistical significance. Older patients may have more advanced form of CAD[21]. Usage of IABP was significantly higher in patients with LMS. In a meta-analysis of randomized controlled trials Rampersad et al[22] concluded that preoperative utilization of IABP reduced the early mortality in high-risk patients undergoing elective CABG. The IABP has been the most widely used mechanical circulatory support device. In cardiac surgery, the placement of the IABP was indicated when post-cardiotomy cardiogenic shock or mechanical complications appeared. Although preoperative IABP is frequently used by some clinicians in high-risk patients undergoing cardiac surgery, its effectiveness has not been confirmed[23].

In our study, patients with LMS had significantly more IABP utilization than the other group. IABP is the most commonly used mechanical circulatory device, and it is used in some centers as preoperative prophylaxis for high-risk CABG surgeries, although this practice is debatable[24]. In our study we followed an earlier study that supported the use of IABP preoperatively when 2 of the following factors were associated with LMS ejection fraction EF below 35%, re-do CABG, LMS stenosis more than 70%, unstable angina in the preoperative period[25]. Pilarczyk et al[26] mentioned that utilization of IABP in high risk patients could help the intra-operative hemodynamic management with trend towards clinical stability and better prognosis. The authors found that usage of IABP in the preoperative period could reduce ICU and hospital lengths of stay as well as death within the hospital. Similarly, Christenson et al[25] found reduction in mortality, postoperative ICU and hospital stay with use of IABP. Our study is a retrospective data review. Our institutional preference is to insert IABP prophylactically after induction in patients with high risk LMCA disease. Takaro et al[27] mentioned that stenosis greater than 75% especially in the presence of left ventricular dysfunction is considered a high risk.

The assumption that LMS disease portends higher risk is due to the fact that 75% to 100% of myocardial territory is at risk when dominance of the left system is associated. Revascularization is recommended when more than 50% LMS disease is present, regardless of the symptoms or other ischemic association. CABG is recommended according to the American guidelines - when surgical bypass is feasible and SYNTAX score is more than 33, which define complexity of the multi-vessel disease[13]. The primary outcome in our study was the ICU length of stay, which was not significantly different in both groups (65.9 ± 4 6.1 vs 63.4 ± 43.9, P = 0.6). Many studies have showed LMS disease as a risk factor for surgery. In a systemic review over 172000 patients after cardiac surgery, the authors found LMS to be predictive of short-term adverse outcome[28].

In our study urgent procedures in the LMS group was 40%, which was not significantly different from patients without LMS 36.4% (Table 2). Sher-I-Murtaza et al[29] conducted a single center study and found the ICU length of stay to be higher in patients with LMS disease. The LMS population in this study was older and had more cases done on urgent basis. This was not the case in our study where both groups were matched regarding the age, Euro score and urgency. In our institution, LMS involvement alone does not warrant urgent surgical intervention. This probably has accounted for the difference in the ICU length of stay compared to Sher-I-Murtaza et al’s[29] study.

According to the SYNTAX trial, the postoperative outcome is related to the burden of atherosclerosis of the native coronary vessels where percutaneous coronary revascularization strategy is adopted but not if CABG is applied[30]. In our study, the postoperative lengths of mechanical ventilation, ICU stay, and hospital stay did not show any significant differences between both groups (Table 3). Post-operative complications, including POAF, AKI, hospital-mortality, ventilator-associated pneumonia, need for VA-ECMO, re-admission to ICU, surgical re-exploration and PMI did not make significant differences between groups. The in-hospital mortality after CABG range from 1%-3% and its related to age, female gender, re-do surgery, low EF, degree of LMS stenosis and other coronary vessel involvement[31]. Mortality was equal in our studied groups, the low mortality in our patient population did not allow us to analyze the predictive factors beyond mortality. Both our groups were matched regarding the ACC, CPB, VIS, anesthesia time. Some authors refer the outcome to the type of cardioplegia used and the length of ACC[32]. All our patients underwent on-pump CABG, we used the same cardioplegia. Sher-I-Murtaza et al[29] reported worse outcome with LMS when compared to non LMS groups with regard to length of ventilation, mortality and need for inotropic support. This can be explained by the older age and the association of other lesions in their population while we operated on younger population. Blood consumption rate was not different among the two groups. This may be due to timely stoppage of antiplatelet therapy with appropriate bridging and use of antifibrinolytics in high risk patients.

Finally, we noted that diabetes was significantly more prevalent in LMS group (53% vs 44.4%, P = 0.05). Diabetes is known to increase the cardiovascular disease risk[33].

Study limitations: This study had the following limitations: (1) Being retrospective and conducted in a single center; (2) The revascularization strategy was based on the physician discretion; (3) Difficulty in doing long term follow up. Our study conclusions should be confirmed with larger randomized trials to better define mortality and morbidity variation in LMS patients in relation to the others; and (4) Low sample size.

Patients with LMS disease showed similar outcome as those without LMS in this study. Diabetes was more prevalent in patients with LMS. We observed that patients with LMS had significantly more IABP utilization. These findings may help in guiding decision making for future practice and stratifying the patients’ care.