Material and methods
Patients
We retrospectively analyzed 50 consecutive patients (44 male and 6 females, mean age 65 ± 8 years) who underwent off-pump coronary artery bypass grafting (OPCAB) in our department in 2018. There were 19 (38%) patients with a body mass index (BMI) over 30kg/m2(obese group – OB), and 31 (62%) with a BMI below this value (non-obese group – nOB) The mean follow-up was 897 +/- 123 days.
Patients were qualified for surgery based on coronary angiography results. Twenty-nine patients (58%) were diagnosed with the left main disease. All patients underwent arterial revascularization including left and right internal mammary artery and left radial artery. Prevalence of concomitant diseases in both groups is outlined in Table 1.
On the day of admission, blood samples for complete blood count and biochemical tests were collected. Special attention was paid to platelets and white blood cells count along with their fractions. Then, PLR and NLR were calculated for both groups. In addition, transthoracic echocardiography (M+2D+Doppler) was performed.
All patients signed written informed consent for routine surgery for CAD. Blood samples analysis and blood flow measurements were performed with standard of care. The study received positive agreement of the Local Ethics Committee.
Surgical technique
All the procedures were performed via complete median sternotomy on the beating heart, without cardiopulmonary bypass support (OPCAB). The only applied grafts were arterials including left and right internal mammary and left radial artery. Upon completion of graft harvesting, heparin in an initial dose of 2mg/kg was administered to achieve the therapeutic range of activating clotting time (ACT) (exceeding 400s; in our group 488±37 s). To facilitate distal anastomoses of the aorto-coronary bypass grafts, the deep pericardial stitch to elevate the beating heart and tissue stabilizer (Octopus III, Medtronic, USA) to immobilize segment of the recipient coronary artery, were used. All the anastomoses were performed with a continuous monofilament 7-0 suture following application of intraluminal shunts (Medtronic, USA). The size was chosen individually on the base of coronary artery diameter and wall quality to allow blood flow (and, consequently, distal myocardial perfusion) and to limit bleeding (diameters of shunts used in both groups and with respect to the target artery are presented in Table 2). After final anastomosis heparin action was reversed by two doses of protamine administered under ACT guidance to achieve its baseline value (in our group, the final ACT was 132±36s).
Blood flow measurements
The graft blood flow measurements were routinely performed in every surgical revascularization procedure in our department. In every case, they were performed following the second dose of protamine when patient was hemodynamically stable. Ultrasonography equipped with a 6.5MHz linear transducer (Verify Q, USA) was used.
Measurements were performed for left and right internal mammary arteries (LIMA and RIMA) approximately 10cm from its origins from subclavian arteries, while for radial artery (RA) - 5cm from the proximal anastomosis to the ascending aorta.
Postoperative period
Following the surgery, all patients were transferred to the postoperative intensive care unit (ICU) where their vital functions were carefully monitored. Electrocardiography (ECG) was carried out immediately upon their admission to the ICU, and then on a daily basis. Serum concentrations of troponin-I were measured every 12 hours for 3 days following the surgery and maximal values were recorded for a further statistical analysis. Upon discharge, all patients were referred the outpatient clinic follow-up.
Statistical analysis
Continuous variables were reported as mean ± standard deviation (SD) when data followed a normal distribution; otherwise, the data were presented as medians and interquartile range [Q1-Q3], where Q1 is lower and Q3 upper quartile, respectively. The differences between groups were calculated by means of unpaired Student’s t-test (normally distributed) or the Mann-Whitney U test (the rest, eg. shunt diameters or troponin-I concentrations). Categorical variables were reported as numbers (n) with percentages (%) and then compared by test for proportions. Moreover, the strengths of association between the selected blood morphology-derived ratios (PLR, NLR) and body mass index (BMI) were estimated using Pearson’s parametric correlation (r) method. All tests were considered significant at p<0.05. The analysis was performed using Statistica 13 statistical package (TIBCO Software Inc. (2017), Statistica (data analysis software system), version 13. http://statistica.io.).