Thirty-five patients who underwent CABG surgery by our surgical team at our hospital between June 2021 and April 2022 were included in the study. The inclusion criteria for the study were determined as being between the ages of 20 and 80, having an isolated CABG operation, and having a single ITA or BITA used. Exclusion criteria are being under 20 years old and older than 80, having no arterial graft used, and having aortic or valve surgery accompanying CABG.

The patients were divided into two groups according to the graft types (single ITA-BITA). Graft selection was made according to the patient's age, coronary lesion severity, coronary vasculature, body structures, comorbidities, and graft structures. Demographic, operative, and postoperative data of the patients were recorded. Preoperative and postoperative 1st-week TTE measurements of the patients were recorded. Strain and 3D EF data in preoperative and postoperative TTE controls were compared according to graft preference.

The patients’ demographic data were obtained by verbatim anamnesis, and the peroperational data were recorded.

All TTE recordings in our study were made with the GEvivid E95 TTE device (GE Healthcare; Vingmed Ultrasound, Horten, Norway) and 4Vc probe (frequency: 1.5–4.6 MHz). From these records, systolic strain and 3D EF values were calculated using the 2D STE analysis method using the EchoPAC version 202 program.

Strain means disruption created by a force. Myocardial strain is the percentage change in the length of myocardial fibers at the end of the diastole and systole phases [3]. Positive values indicate increased myocardial fiber length in that segment, and negative values indicate a shortening. Lower negative values (fiber shortenings with smaller amplitudes) express impairment in ventricular functions [2].

LV myocardium consists of 3 layers of muscle tissue: deep, middle, and superficial. The superficial layer is located obliquely. The middle layer is arranged circumferentially, and contraction occurs in that direction. The deep layer is placed in the form of longitudinal fibers extending from the base of the heart to the apex [6]. Global, circumferential, radial, and longitudinal strain values can be calculated by determining the movements of the muscle fibers of each layer in different planes [2]. Global Longitudinal Ventricular Strain (GLVS) is the most used value, showing the contraction of longitudinal, subendocardial, and subepicardial fibers. In our study, we used GLVS measurements as a basis to evaluate LV functions in the best way.

In our study, three apical images were recorded when calculating GLVS. Myocardial segments in the images of 2 Chambers (2CH), 4 Chambers (4CH), and Apical Long Axis (APLAX) planes were marked semi-automatically with the help of software. The computer software calculated strain values from the segmental movements of each plane, and finally, global longitudinal strain values were obtained (Fig. 1). 3D EF measurements were calculated via semi-automatic software (Fig. 2).

GLVS Measurements. GLVS: Global Longitudinal Ventricular Strain

3D EF Measurements. 3D EF: 3 Dimension Ejection Fraction

Many studies have investigated average values of strain measurements, but very different results have been obtained, and no certainty has yet been achieved. However, in a recent meta-analysis, longitudinal strain values measured with EchoPAC software were reported as endocardial − 23.9 ± 0.62%, mid myocardial − 20.73 ± 1.11%, and epicardial − 18.1 ± 1.54% [7]. Since our study aimed to compare the decrease/increase in preoperative and postoperative values between the groups using single ITA and BITA, a specific reference value was not accepted.

Standardized anesthesia method used for all patients (2–2.5 mg/kg intravenous (IV) propofol, 2.5–5 mg/kg IV fentanyl and 0.6 mg/kg IV rocuronium for induction; 6–10 mg/kg/h propofol, 2 mg/kg/h fentanyl and 0.03 mg/kg/h rocuronium IV infusion for maintenance).

All patients operated with median sternotomy. After sternotomy, LITA and RITA (in one group) flaps were prepared with heparin administration. ITA flaps were kept in a tepid saline solution with local 0.05 papaverine administration. All operations were performed on the pump. A routinely arterial cannula was implanted in the ascending aorta, and two staged venous cannula were in the right atrial appendage. For cardioplegia and venting, a cannula was placed in ascending aorta. Antegrade cold blood cardioplegia was used for all patients, and 2–3 ml/kg was used every 20 min for maintenance under aortic CC. Myocardial protection was supported by systemic hypothermia (28–32 ºC).

Following cardiac arrest, distal anastomoses were completed. RITA was our first choice for LAD anastomosis according to length, flow dynamics, and distance to the LAD position. In unsuitable cases, RITA flaps were divided as free grafts and anastomosed to the best-developed, stenotic left coronary system artery. In this group of patients, LITA was anastomosed to LAD, and the proximal edge of the free RITA graft was sewn on the LITA flap. Other stenotic coronary arteries were grafted with saphenous vein grafts (SVG).

Proximal anastomoses were completed under aortic CC. Extracorporeal life support was applied one-third of the aortic CC time for all patients after the removal of aortic CC.

SPSS 25.0 (SPSS, Inc., Chicago, USA) program was used to analyze the data obtained within the scope of the research. It is given with descriptive statistics (frequency, percentage, mean, standard deviation). Pearson chi-square test was used to analyze categorical variables, and Student's t-test was used to analyze continuous variables. A dependent samples t-test was used to compare the preoperative and postoperative measurements. P < 0.05 was accepted for statistical significance.