Concurrent initiation of intra-aortic balloon pumping with extracorporeal membrane oxygenation reduced in-hospital mortality in postcardiotomy cardiogenic shock

We consecutively included 152 adult subjects ( ≥ 18 years) who received veno-arterial VA-ECMO for refractory PCS in Fuwai Hospital from January 1, 2005 to December 31, 2017 in the study. We retrospectively collected clinical variables for all the subjects from their clinical records. Our study complies with the Declaration of Helsinki. The Ethical Committee of the Fuwai Hospital approved this study. As this was a retrospective chart review study, requirement of informed consent was waived.

Primary indication for VA-ECMO was intra-operative circulatory instability during or immediately after weaning from cardiopulmonary bypass when the primary surgery procedure was finished. Secondary indications included delayed PCS for progressive heart failure, post-operative cardiac arrest. The decision and the optimum time to initiate VA-ECMO and IABP support was made by the surgical team, which was independent of the study. The clinical criteria of VA-ECMO institution for PCS were defined as follows: hypotension with systolic arterial pressure < 80 mm Hg and mean arterial pressure (MAP) < 60 mm Hg; signs of renal failure (urinary volume < 20 mL/h), anaerobic metabolism and metabolic acidosis (pH < 7.3, lactate level > 3.0 mmol/L), despite optimized supportive measures such as IABP, inotropes, nitric oxide and phosphodiesterase inhibitors. Hemodynamic criteria were cardiac index (CI) < 30 mL/s/m² and pulmonary capillary wedge pressure ≥ 20 mmHg.

In our center, the surgical team evaluated the patient to decide when the ECMO was indicated according to inclusion criteria mentioned above. The ECMO circuit consisted of a centrifugal pump console (Bio-Medicus BP-550, Medtronic, Minneapolis, MN, USA, or RotaFlow RF-32, Maquet Cardiopulmonary AG, Hirrlingen, Germany) in conjunction with a microporous membrane oxygenator (Carmeda coating Affinity NT or Maxima PRF Plus, Medtronic) or a polymethylpentene oxygenator with a plasma-tight diffusion membrane (Quadrox D, Maquet Cardiopulmonary AG) with integrated heat exchanger and adapted tube. All components were heparin bonded and connected by the shortest possible tubing system. All patients had peripheral ECMO via the cannulae of the femoral vein and artery. An additional 16Fr intravenous needle casing was inserted distally into the femoral artery to prevent leg ischemia.

The ECMO system was implanted under full heparinization, and activated clotting time (ACT) was kept longer than 300 s. Half of the heparin was antagonized with protamine when full ECMO flow was established, aiming for an ACT of 140–180 s unless there was ongoing coagulopathy with hemorrhage. During the first 24–48 h, ECMO blood flow was adequately adjusted to maintain cardiac index of 40 mL/s/m², with an aim to keep mixed venous oxygen saturation (SvO₂) around 70%, and mean artery pressure of 60–65 mmHg. The oxygenator was examined twice a day for early detection of thrombus formations. After 48 h, cardiopulmonary recovery was daily assessed by hemodynamic, clinical and echocardiographic measurements to define the optimal time of weaning. Weaning was cautiously begun when SvO₂ ≥ 70%, hematocrit of 30–35%, absence of bleeding, tamponade or left heart distension, left ventricular ejection fraction (LVEF) ≥ 35% and normal blood lactate levels. Flow rate was reduced stepwise to approximately 1 L/min under continuous monitoring of hemodynamic and respiratory variables. When signs of insufficient perfusion occurred during ECMO weaning, the flow was increased again to full, allowing prolonged ECMO support. When the patients were hemodynamically stable on the minimal ECMO flow with satisfactory recovery of myocardial function evaluated by echocardiograph, patients were weaned off of ECMO support and IABP was retained for further evaluation.

The primary care surgeon made the decision of IABP initiation. IABP (Datascope System 98, Datascope Corporation, Fairfield, NJ or AutoCAT2 wave, Teleflex Incorporated, Hilversum, The Netherlands) was inserted through a femoral sheath and with the tip located near the second rib with a 30 or 40 mL IABP balloon, which was judged according to the patient’s height. The support was initiated at a 1:1 inflation–deflation to cardiac cycle ratio, triggering by the R wave of the electrocardiogram. The weaning criteria of IABP were the systolic blood pressure above 100 mmHg without inotropic agent after removal of ECMO. The support was decreased at a 1:3 inflation–deflation to cardiac cycle ratio when weaning program was initiated, and the patients were weaned off of IABP if the hemodynamic condition was stable.

The normality was tested by Shapiro–Wilk test. Continuous variables with normal distribution were expressed as mean ± standard deviation and compared by Student’s t test, while those that were not normally distributed were reported as medians (first and third interquartile range) and compared by Mann–Whitney U test. Categorical variables were expressed as percentages and compared by Chi-square test. Logistic regressions were used to analyze the predictors for in-hospital mortality. The multivariate logistic regression was performed to identify independent factors using an “Enter” method. P values were two sided, and values < 0.05 were considered statistically significant. SPSS statistical software (version 22, IBM Corp., Armonk, NY) was used for the analyses.

Baseline characteristics of all subjects in our study are shown in Table 1. The mean age of the subjects was 49.5 ± 14.1 years, and males accounted for 73.7%. Among all subjects, 57 (37.5%) suffered coronary artery disease with 8 (5%) acute myocardial infarction, 37 (24.3%) cardiomyopathy, 32 (21.1%) valvular heart disease, 23 (15.1%) congenital heart disease (CHD) and 12 (7.9%) aortic disease. The original surgery procedures mainly included 49 (32.2%) heart transplantation, 26 (17%) coronary artery bypass graft (CABG) alone, 18 (11.8%) valvular surgery alone, 10 (6.6%) CABG combined with valvular surgery, 14 (9.2%) CHD surgeries and 12 (7.9%) aortic surgery. VA-ECMO was implanted for primary indication in 85 (55.9%) subjects and secondary indications in 67 (44.1%) subjects. IABP was applied in 77 (50.7%) subjects, among whom IABP was implanted concurrently with VA-ECMO in 49 (32.2%) subjects and sequentially in 28 (18.4%) subjects.

There were 86 (56.6%) subjects successfully weaned from VA-ECMO, among which 73 (48.0%) survived to discharge. Mean VA-ECMO and IABP support time was 4.8 ± 2.7 days and 6.6 ± 4.2 days, respectively. Characteristics of the survivors and non-survivors were compared as listed in Table 1. Compared to non-survivors, survivors had less hypertension morbidity (15.1% vs. 35.4%, p = 0.004), more heart transplantation procedures (45.2% vs. 20.3%, p = 0.001), lower rate of secondary thoracotomy before ECMO initiation (19.2% vs. 39.2%, p = 0.007) and pre-ECMO cardiac arrest/ventricular fibrillation (11.0% vs. 34.2%, p = 0.001). However, we found subjects in survivor group had a lower LVEF (43.3% vs. 53.0, p = 0.001) and a larger left ventricular end-diastolic diameter (LVEDD, 60.4 mm vs. 53.8 mm, p = 0.015) than those in non-survivor group. Interestingly, we detected much less subjects initiated VA-ECMO by bedside (11.0% vs. 41.8%, p < 0.001) among survivors than that among non-survivors. Although both groups had a similar rate of IABP implantation, concurrent initiation of IABP with ECMO was significantly higher in survivors (41.1% vs. 24.1%, p = 0.025). Multivariate logistic regression analysis was performed to analyze relevant factors that might affect in-hospital mortality (Table 2). The result indicated concurrent initiation of IABP with VA-ECMO was an independent protective factor for in-hospital mortality (OR = 0.375, p = 0.041, 95% CI 0.146–0.963).

Complications are shown in Table 3. Renal failure being the most common complications was detected in 68 (44.7%) subjects, followed by neurological complications in 29 (19.1%) subjects. Compared to subjects who received VA-ECMO alone, subjects concurrently received IABP with VA-ECMO had less need for continuous renal replacement therapy (30.6% vs. 49.3%, p = 0.039) and neurological complications (8.2% vs. 22.7%, p = 0.035), but more thrombosis complications (18.4% vs. 2.7%, p = 0.007).

As a single-center retrospective study, this study is subject to all limitations of a non-randomized study. Our findings need to be further confirmed in a larger multicenter cohort or a randomized controlled trial.