Patient population

Eighty-four isolated CABG patients with acute coronary syndrome who operated in our hospital between June 2021 and April 2022 were included in this study. Exclusion criteria included the following basis: (a) patients younger than 20 and older than 80 years old; (b) patients who had preoperative arrhythmia; (c) no arterial graft usage; (d) accompanying other intrathoracic surgeries; (e) having preoperative thyroid disease; (f) previous myocardial infarction.

Patients grouped as single ITA or BITA were used. Graft choice was made based on the patient's age, the severity of coronary artery lesions, native coronary vasculatures, body structures, comorbidities, and graft qualities. Preoperative demographic data, laboratory results, comorbidities, ECG, and TTE measurements of patients were recorded. Patients were observed prospectively over the post-operative period. Preoperative, post-operative 1. hour, 1. day, and 1. week ECG recordings documented. Extra ECG recordings are for symptomatic patients with dyspnea, hypotension, or palpitation. Routine post-operative 1. week TTE measurements were made. Newly onset arrhythmias were recorded. AF was defined according to current guidelines [6].

All patients who developed AF rhythm were classified according to their hemodynamic stability. As initial treatment, amiodarone was administered as a rapid infusion of 300 mg to hemodynamically stable patients, followed by a 24-h maintenance infusion of 900 mg. After 24 h, IV treatment was terminated, and oral amiodarone administration was started. No additional medication was administered to patients whose rhythm and rate were controlled. In patients whose rate control could not be achieved (> 110/min), oral metoprolol (50 mg) was additionally given. In patients with hemodynamic instability, cardioversion was performed accompanied by amiodarone infusion. All AF patients were determined as first diagnosed paroxysmal AF and were converted to sinus rhythm within seven days.

Data gathering

Preoperative medications, comorbidities, and demographic data were recorded by face-to-face anamnesis. Laboratory results and intraoperative data were noted.

All ECG measurements are obtained from semiautomatic analyses of standard 12-lead ECG (25 mm/s, 10 mm/mV) converted to digital images and amplified 6–10 × by EP Calipers software version 3.6.1. P wave duration, morphology, and amplitude were measured from preoperative ECGs. The presence of interatrial block (IAB) was investigated. All patients were classified by MVP ECG risk score.

TTE studies were acquired on a GEVivid E95 unit (GE Healthcare; Vingmed Ultrasound, Horten, Norway) equipped with an M5S probe (frequency: 1.5–4.6 MHz).

MVP ECG Risk score

MVP ECG Risk Score examines three factors. Each factor has points for specific situations. Eventually, the sum of points determines the AF risk of patients.

a

P Wave Morphology

P wave elongation is accepted as evidence for atrial depolarization transmission delay and is valuable for atrial arrhythmia development. Elongation in the P wave (≥ 120 ms) is defined as partial IAB; either the P wave is regular in shape or notched. The biphasic pattern in the P wave is classified as severe IAB. P wave morphology is examined in inferior derivations of standard 12-lead ECG (Fig. 1) [7].

Fig. 1

Technique of measurement of P‐wave indices. P‐wave duration is measured from the first upward deflection of the P wave to return of the waveform to the isoelectric line in leads II, III, and aVF. P‐wave voltage is measured from the peak of the P wave to the isoelectric line of the T‐P interval in lead I

b

P Wave Amplitude (Voltage)

P wave amplitude is the measurement of the height of the P wave peak point from the isoelectric line (Fig. 1). Its unit is denoted as mV. Attenuation of P wave amplitude is considered related to weakened atrial transmission patterns [7].

iii.

P Wave Duration

The first upward mark from the isoelectric line is accepted as the beginning of the P wave, and returning to the isoelectric line is defined as the end [8]. Measurement of this period is called P wave duration and is noted as ms (Fig. 1). P waves, which are longer than 120 ms, are an independent risk factor for AF development in many populations [9]. The longer the P wave duration, the higher the risk of AF development [10].

All Scoring system was detailed in Table 1.

Table 1 Morphology‐Voltage‐P‐wave duration (MVP) ECG risk score for atrial fibrillationOperative technique

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 0.2 ml/kg was used every 20 min for maintenance under cross-clamp (CC). Myocardial protection was supported by systemic hypothermia (28-32º C).

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. No other arterial grafts were used. Other stenotic coronary arteries were grafted with saphenous vein grafts.

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

Statistical methods

All statistical analyses were done using SPSS software, IBM, version 21.0. The Kolmogorov–Smirnov test was performed to test if the variables were normally distributed and if the sample size > 50. The Shapiro–wilk test was used if the sample size < 50 The data were presented as median (interquartile range) for continuous parameters, while the data were provided as percentage and number values for categorical parameters. The independent t-test was performed to determine the difference between the groups of continuous parameters with normal distribution. All continuous variables showed skewed distributions and were compared using the Mann–Whitney U test. For categorical variables, the Chi-square test was used. To determine the predictors of postoperative atrial fibrillation, we first performed a univariate analysis. The variables with a significance of p < 0.1 in the univariate analysis were used in the multivariate analysis in order to detect independent predictors of postoperative atrial fibrillation.Cut-off values of MVP ECG risk score with a highest sensitivity and specificity was calculated by nonparametric receiver-operating characteristics (ROC) curve analysis. The level of statistical significance was established at p value ≤ 0.05. The effect size (Cohen’s d) and power value (1- β) for MVP ECG risk score, compared between post-operative atrial fibrillation (-) and post-operative atrial fibrillation ( +), were calculated using G*Power software (version 3.1.9.2.) The alpha level used for this analysis was < 0.05. The effect size and power value were 0.554 and 0.922 for MVP ECG risk score.