To our knowledge, this study is one of the largest cohorts reporting the outcome of cardiac catheterization performed after congenital heart surgery for patients receiving ECMO support. This study did not include patients who had cardiomyopathy or myocarditis, unlike previous studies. Patients with cardiomyopathy/myocarditis and connected to ECMO support has a better prognosis compared to other patients with congenital heart disease [2, 3, 5].
In this cohort, approximately half of our patients had single ventricle physiology with RACHS 1socre of 4–6. This proportion is relatively larger compared to other reports[1, 5]. Other studies reported a similar proportion of patients with univentricular heart [3].
Cardiac catheterization
Echocardiography plays an important role in the management of patients with critical illness especially those connected to ECMO. The role of echocardiography is not only to evaluate the cardiac functions and cardiac recovery, but it can also be used for identification of residual cardiac lesions of hemodynamic significance after congenital heart surgery[12, 13]. Identification of residual cardiac lesions by echocardiography for ECMO patients might be very difficult due to poor acoustic windows associated with opened sternum and poor cardiac pulsations that might underestimate lesion severity [7]. As residual lesions after congenital heart surgery might carry a high risk for poor outcome, cardiac catheterization could provide a detailed evaluation of residual lesions and then a proper decision could be considered for either further intervention during the same catheterization procedure or referral for redo surgery [3, 11, 14].
Based upon information obtained from cardiac catheterization, 65% of our patients underwent further interventional procedures either in the form of interventional catheterization during the same procedure (48%), subsequent redo surgery (16%) or both (2 patients, 3%). Among this cohort one-third of patients underwent diagnostic cardiac catheterization proceeded to redo surgery which might emphasis that not all residual lesions are amenable by cardiac catheterization.
Interventional catheterization might be associated with better survival compared to diagnostic catheterization or redo surgery [3]. Among this report, although patients underwent interventional catheterization had better survival compared to other patients, in multivariate analysis, interventional catheterization had no impact on successful decannulation from ECMO. The explanation of this finding might be related to the fact that 8 out of 9 patients who failed decannulation among the interventional group had severe cardiac dysfunction. Kato el reported similar results [1].
In the present study, early cardiac catheterization had a great impact on the clinical outcome. Interestingly, patients who underwent early cardiac catheterization spent less time on ECMO support, had a lower incidence of pulmonary injury and reported more successful decannulation and survival compared to other patients. This may be attributed to the early detection and correction of significant residual lesions causing cardiovascular compromise before irreversible cardiac or end-organ damage as reported by previous studies[1, 3, 15]. Agarwal el reported better ECMO decannulation rate and survival with detection of residual lesions within 3 days from starting ECMO support[7]. Despite better outcome was reported in patients underwent early cardiac catheterization, these findings should be interpreted cautiously. These results could be biased being in patients who had early catheterization the decision for catheterization might be considered after correctable lesions were detected by echocardiography[1]. This also may explain why univariate logistic regression analysis revealed higher odds for successful decannulation in patients with early catheterization while in multivariate regression analysis early catheterization had no impact on successful decannulation. Moreover, a large proportion of early catheterization group had biventricular cardiac anatomy the condition that favour successful decannulation in univariate logistic regression analysis.
There was no reported mortality during patients transfer from PICU to catheterization laboratory or during catheterization procedure like previous reports[2, 4, 5, 12]. Most of the reported complications after cardiac catheterization were related to vascular access. Femoral venous and arterial thrombosis was reported in 6 and 5 patients respectively. All vascular complications were mild and managed conservatively. The rate of serious complications related to catheterization procedures is variable in previous reports[1, 3, 5, 15].
ECMO support
After congenital cardiac surgery, ECMO is usually used in the setting of low cardiac output status, extracorporeal cardiopulmonary resuscitation and failure of weaning from cardiopulmonary bypass. According to previous reports ECMO is used in approximately 1.5-5% of cases undergoing congenital cardiac surgery[17–19]. As cardiovascular compromise ended by ECMO support can impair systemic perfusion leading to multiorgan dysfunction, prolonged use of ECMO can also lead to adverse effects to various body organs. ECMO related complications are variable among literatures [1, 4, 9, 15, 20, 21].
Regarding ECMO complications, the bleeding tendency was the most frequent complications. Moreover, in univariate regression, patients with bleeding tendency had a high risk for unsuccessful decannulation while in multivariate regression analysis complications related to ECMO had no effect on successful weaning from ECMO unlike previous reports[1, 9].
Predictors of successful ECMO decannulation and survival
Predictors of outcome and survival for patients receiving ECMO supported had been widely discussed in previous literature. Predictors associated with better survival commonly reported with myocarditis/cardiomyopathy, biventricular physiology, low inotropic score, absence of associated complications (renal failure, lung injury, neurological complications, bleeding tendency), good lactate clearance, duration of ECMO less than 5 days, and early cardiac catheterization[1, 3, 5, 19, 22–25]. Like previous reports, patients with biventricular physiology, early catheterization, absence of bleeding tendency or lung injury and those with a shorter duration on ECMO ≤ 6 days had higher odds for successful decannulation in the univariate regression model. In the multivariate regression model, only patients with a shorter duration on ECMO support had higher odds for successful decannulation.
Kaplan Meier survival analysis showed better survival in patients with Biventricular physiology, early cardiac catheterization and those received ECMO support for ≤ 6 days. Our results were comparable to previously published reports[1, 3, 5, 10, 15].
In this cohort successful decannulation was reported in 57% of patients while survival to hospital discharge was reported in 36% of patients. Recent cohorts reported a higher percentage of successful decannulation and survival, this discrepancy might be related to different complexities of cardiac lesions, the inclusion of a significant proportion of myocarditis/cardiomyopathy patients who had better prognosis in addition to the unavailability of programs for ventricular assisted device and heart transplantation in our institutions for patients who could not be weaned from ECMO support [3, 5, 15].