INTRODUCTION

Cardiac reoperations have been associated with high mortality and morbidity due to technical difficulties^[1,2]. Although surgical technique and postoperative care have advanced during the last two decades, the need for cardiac reoperations is still a risk factor for both short-term and long-term mortality^[3]. The main technical concern during resternotomy is the possibility of iatrogenic fatal injuries to the mediastinal structures below the sternum. In cardiac reoperations, central cannulation is performed after mediastinal adhesion lysis and exposure of cannulation sites. Whereas peripheral cannulation can be done before resternotomy and initiated in case of a major bleeding and hemodynamic instability to decompress the heart^[4]. So, peripheral cannulation may be a reasonable approach for some surgeons^[4-6]. Although there are different series in the literature about the outcomes of reoperation regarding coronary or valve procedures^[3,7,8], there are still limited data in terms of the outcomes of cannulation strategies and postoperative mortality in cardiac reoperations^[4-6,9]. The aim of our study is to compare the early mortality and morbidity rates after use of peripheral and central cannulation techniques in cardiac reoperations using a propensity score matching (PSM) analysis.

METHODS

Statistical Analysis

All statistical analyses were performed on R version 4.0.3 (R Foundation for Statistical Computing). Descriptive statistics are reported as percentage for categoric variables and mean standard deviation (SD) for continuous variables. Categorical variables were compared by a chi-squared analysis or Fisher’s exact test. Normal and abnormal continuous variables were compared by Student’s t-test and the Mann-Whitney U test. Normally distributed continuous data were presented as mean and SD. Abnormally distributed continuous data were presented as median and interquartile (Q1-Q3). Statistical tests were two-sided, and P-values < 0.05 were considered statistically significant.

Considering the cannulation technique selection criteria especially for different cardiac operation types cannot be completely random, we applied the PSM method to balance the effect of selection bias and potential confounding factors. PSM analysis was based on the logistic regression model^[10]. For the purposes of this model, operation types were grouped into four main groups to increase interpretability (“isolated coronary artery bypass grafting [CABG] surgery”, “valve, adult congenital, or intracardiac mass surgery”, “combined CABG and valve surgery”, and “aortic surgery”). The propensity score was calculated according to the patients baseline characteristics (age, sex, ejection fraction, pulmonary artery pressure, New York Heart Association Classes 3 and 4, hypertension, diabetes mellitus, atrial fibrillation, renal failure, obstructive lung disease, infective endocarditis, cerebrovascular disease, emergency operative status, recurrent cardiac operation, and reoperation time < one year), first cardiac operation types ( “isolated CABG surgery”, “valve, adult congenital, or intracardiac mass surgery”, “combined CABG and valve surgery”, and “aortic surgery”), and current cardiac reoperation types (“isolated CABG surgery”, “valve, adult congenital, or intracardiac mass surgery”, “combined CABG and valve surgery”, and “aortic surgery”). Groups were derived using 1:1 matching with a caliper of 0.2. Eventually, a total of 178 patients were matched using PSM analysis. Figure 1 shows that patient flow diagram used in PSM.

Fig. 1 - Patient flow diagram used in propensity score matching.

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Fig. 1 - Patient flow diagram used in propensity score matching.

RESULTS

After PSM, the mean age of the patients in Group 1 was 53.0±15.9 years, and in Group 2, it was 52.1±13.9 years (P=0.68). There was no statistical difference between the two groups in terms of the baseline characteristics of the patients (Table 1). The rate of patients who had reoperated cardiac reoperation in Group 1 was 13.5%, in Group 2 it was 15.7% (P=0.83). In Group 1, nine patients had 2^nd time redo sternotomies, and three patients had 3^rd time redo sternotomies. In Group 2, six patients had 2^nd time redo sternotomies, three patients had 3^rd time redo sternotomies, one patient had 4^th time redo sternotomies, and one patient had 5^th time redo sternotomies.

Table 1 - Baseline characteristics of the patients in Group 1 (central cannulation) and Group 2 (peripheral cannulation) according to propensity score matching (PSM).

Before PSM, there were statistically more patients whose first cardiac operation was aortic surgery in Group 2 (P=0.03). There were statistically more patients who underwent isolated CABG in Group 1 (P=0.02). In addition, there were statistically more patients who underwent aortic surgery at reoperation in Group 2 (P=0.02). We applied the PSM method to balance the effect of cannulation technique selection bias and potential confounding factors for different types of cardiac operations. After PSM, there was no statistically significant difference among the operation types between the two groups. Operation types for all and propensity-matched cohorts (central vs. peripheral cannulation) are summarized in Table 2.

Table 2 - Operation types for all and propensity-matched cohorts (central vs. peripheral cannulation).

Before and after PSM, statistically significant differences were found between Group 1 and Group 2 in terms of CPB time (P=0.02 vs. P=0.03, respectively). There was no statistically significant difference between the groups in early mortality in all cohort and propensity-matched cohorts. Early mortality was observed in 24 (13.5%) of 178 patients in propensity-matched cohorts. Before PSM, prolonged ventilation (P=0.03) and the development of acute renal failure (P=0.04) were statistically less frequent in Group 1. For propensity-matched cohorts, prolonged ventilation (P=0.16) was not statistically significant different between the two groups. After PSM, the development of acute renal failure (P=0.02) was statistically less frequent in Group 1. Table 3 shows comparison of the perioperative data for propensity-matched cohorts.

Table 3 - Comparison of the operative and postoperative data for all and propensity-matched cohorts.

In group 1, four major cardiac injuries occurred. One was in the ascending aorta, two were in the right ventricle, and one was in the right atrium. Two of the injuries occurred during resternotomy, one during pre-pump dissection, and other one during CPB. In Group 2, three major cardiac injuries occurred. One was in the superior vena cava, one was in the right ventricle, and the other was in main pulmonary artery. All injuries occurred during CPB before aortic cross-clamping. There was no statistically significant difference between the groups in terms of major cardiac injury. No complications related to jugular venous cannulation developed in the clinical follow-ups of the peripheral cannulation group. Wound infection was observed in two patients, and seroma developed in three patients in the femoral region.

DISCUSSION

With the significant improvement of surgical techniques, mortality rates of reoperations are higher than of first operations^[3]. Injuries during resternotomy are the most common cause of mortality and morbidity^[11]. Surgeons have been trying to develop some preventive strategies since compensatory recovery methods for undesirable adverse events may not always be successful^[1]. One of the preventive methods is to set-up peripheral cannulation technique before resternotomy. This strategy can be used as a safe approach in a case of emergency to save the patient’s life. There are different series in the literature about the cannulation strategies in cardiac reoperations^[4-6,9]. After applying PSM to balance the effect of selection bias and the effect of potential confounding factors, we observed that performing CPB via peripheral cannulation increases acute renal failure in cardiac reoperations. Therefore, prolonged CPB was the main factor that increases postoperative acute renal failure in cardiac reoperations via peripheral cannulation.

Prior studies have identified heterogeneous data on the impact of cannulation techniques on the development of postoperative acute renal failure in cardiac reoperations. Luciani et al.^[4] reported that peripheral cannulation reduced postoperative acute renal failure in the postoperative period. In this study, detailed preoperative demographic characteristics that may affect postoperative acute renal failure were not given and it was not clearly discussed why acute renal failure was less common in the peripheral cannulation group. Other studies by Ata et al.^[5], Kuralay et al.^[6], and Kindzelski et al.^[9] found no difference between the central cannulation and the peripheral cannulation technique in terms of postoperative acute renal failure. To the best of our knowledge, this is the first study to demonstrate that performing CPB via peripheral cannulation increases acute renal failure during cardiac reoperations. Previous studies have identified prolonged CPB time as a risk factor for postoperative acute renal failure^[12-14]. Kumar et al.^[15] have examined the relationship between postoperative acute renal failure and CPB time using meta-analysis techniques. They concluded that the mean duration of CPB was 25 minutes longer in patients with postoperative acute renal failure. In our study, in which we applied PSM, the only preoperative and operative difference between the groups was CPB time.

Hamid et al.^[16] reported that the in-hospital mortality rate of re-entry injury in cardiac reoperations was 26%. Contrary to the studies in the literature, our study observed that using the peripheral cannulation technique did not have a reducing effect on major cardiac injury^[4,6]. Most injuries in the central cannulation group occurred during the pre-pump dissection stage. Roselli et al.^[1] demonstrated that injuries occurring in the pre-pump dissection cause poor outcome. When cardiac injury occurs in a decompressed heart with the peripheral cannulation technique, early mortality is thought to be less because the repair is easier and faster.

In the whole cohort and propensity-matched cohorts, there was no difference in early mortality between the groups. Like our study, Ata et al.^[5], Luciani et al.^[4], and Kuralay et al.^[6] found no difference between central cannulation technique and peripheral cannulation technique in terms of early mortality. However, Brown et al. found higher mortality in the peripheral cannulation group. But the rate of use of the peripheral cannulation technique in this study is only 5.5%^[17].

In this cohort, peripheral cannulation is mostly preferred in patients with aortic surgery first cardiac operation and reoperation. The injury that may occur during resternotomy is difficult to repair, especially if the aortic grafts are dangerously close to the sternum or accompanied by aortic pseudoaneurysm, which suggests that resternotomy under CPB with peripheral cannulation is preferred in these patients. Central cannulation technique was generally preferred in the patient group whose reoperation was to undergo isolated CABG. It may be that surgeons want to avoid complications due to prolongation of CPB time by not using the peripheral cannulation technique, especially in CABG patients who are planned to internal mammary artery harvesting. In the study, PSM was performed to avoid selection bias of choosing different cannulation techniques according to these operation types.

CONCLUSION

We observed that performing CPB via peripheral cannulation increases acute renal failure in cardiac reoperations. In contrast, peripheral or central cannulation have similar early mortality rate in cardiac reoperations.