The authors reply
First, we agree with them that having data on the course of patients between onset of shock and extracorporeal membrane oxygenation (ECMO) would have been interesting. Unfortunately, we do not have these data: indeed, 47% of them were referred from other hospital (cardiology department or ICU) to our ICU to discuss heart transplantation because of refractory cardiogenic shock and were implanted at admission. Data on clinical course before ECMO are not retrievable for these patients. Furthermore, although we agree that a decrease in Sequential Organ Failure Assessment (SOFA) score and/or blood lactate level is associated with good outcome, we are not sure that: 1) our patients will have improvement in those variables from hospital admission to ECMO start (all had refractory cardiogenic shock, defined by absence of improvement or degradation despite maximal treatment) and 2) that this could predict good outcome better than pre-ECMO SOFA score. In fact, patients with cardiogenic shock who improved during stay are rarely candidate for ECMO. And, such improvement is often (if not always) accompanied with improvement of blood lactate levels and SOFA score. However, as discussed in our article (2), it could be interesting to look at these variables during hospital stay in patients with cardiogenic shock, before the need for circulatory support. It is highly probable that blood lactate (and/or SOFA score) decrease during treatment of cardiogenic shock could predict no need for ECMO. We think that this would be interesting to evaluate and should be investigated in future studies.
We agree with their second comment: 1-year mortality was nearly the same that of 3-month mortality. As suggested by Kyo et al (1), we ran a Cox regression analysis with ICU mortality as the dependent variable and found the same results (as compared to our primary analysis evaluating 1-year mortality); pre-ECMO SOFA score greater than 11 (odds ratio [OR], 3.4; 95% CI, 1.4–8.3), duration of pre-ECMO cardiac disease greater than 2 years (OR, 2.7; 95% CI, 1.1–6.5), and pre-ECMO blood lactate greater than 4 mmol/L (OR, 3.4; 95% CI, 1.4–8.3) were independently associated with ICU mortality. However, we disagree with Kyo et al (1); we think that 1-year mortality is more meaningful than 3-month mortality for these patients: many of the survivors were transplanted, and evaluating 3-month mortality in such a population may lead to false conclusion. Nevertheless, as expected by the Kaplan-Meier analysis, short- and long-term mortalities share the same risk factors.
Last, Kyo et al (1) asked for the rationale for calculating cutoff values for the SOFA score. As they assumed, we defined the optimal cutoff value using the receiver operating characteristics curve. Best cutoff value was 11, the one used in the multivariable analysis (2). Then, we split the SOFA values of our population into quartiles and calculated the mortality rate for each quartile. The meaning was to help clinicians faced to such patients: as shown in our article (2), patients with pre-ECMO SOFA score greater than or equal to 14 had the highest mortality. In those patients, futility of ECMO should be discussed. The SOFA score is easy to calculate, and we think that it should be included in the treatment discussion of every patient with refractory cardiogenic shock, whatever the cause of cardiogenic shock. As underlined by Kyo et al (1), it has been previously demonstrated, by us and others in different settings, that high pre-ECMO SOFA scores were associated with high mortality (2–5).