Highlighting Recent Research: Impact of Minimally Invasive Extracorporeal Circuits on Octogenarians Undergoing CABG

Research published recently in the European Journal of Cardio-Thoracic Surgery analyzed the outcomes of elderly cardiac surgery patients to evaluate whether minimally invasive extracorporeal circuits (MiECCs) conferred a benefit over conventional cardiopulmonary bypass (cCPB) (El-Essawi, 2017). The minimal design of these circuits reduces the contact between blood and nonbiological surfaces and requires a lower volume of priming solution, alterations that lead to a more moderate inflammatory response and a smaller reduction in hematocrit (Baikoussis, 2014; Curtis, 2010). Because of these differences, MiECCs are thought to better preserve a patient’s physiological reserves, but the extent of clinical benefit attributable to this is debated. Some analyses find that this results in a broad array of improved short-term outcomes (Anastasiadis, 2013), while others find more narrow benefits for MiECC (Wang, 2016). In order to look more specifically at patients for whom small differences in the preservation of physiological reserves might have major effects on outcomes after cardiac surgery, Aschraf El-Essawi and colleagues focused on patients who were 80 years old and older. “We thought that if the philosophy of minimal invasiveness were true, then [an MiECC] should have its highest impact in patients in whom these reserves have been depleted,” said Dr El-Essawi, the first author of the study.  “Hence, [an MiECC] may have its impact on mortality [in such patients], and mortality is the only definite outcome that leaves no place for arguments.”

The authors retrospectively analyzed records for 324 octogenarians who had undergone coronary artery bypass surgery (CABG) at their institution over eight years (El-Essawi, 2017). The two groups had similar EuroSCOREs, 16 ± 13 and 14 ± 11 for MiECC and cCPB, respectively. The group that underwent CABG on MiECC had a greater proportion of patients with reduced left ventricular ejection fraction, a higher incidence of renal dysfunction, a lower incidence of unstable angina, and was older than the group who underwent surgery with cCPB. After propensity matching to account for these differences, 30-day mortality in patients who had MiECC was 2.4%, significantly lower than 9.5% for matched patients who had cCPB (p = 0.02). More surprising to the authors, however, was that this survival benefit was apparent prior to propensity matching: 3.5% with MiECC versus 9.0% with cCPB (p = 0.04). “We interpreted this finding as follows,” said Dr El-Essawi, “the minimal invasive concept has the potential to compensate even for an unbalanced distribution of [preoperative] risk factors, which we see as a strong argument for the validity of the concept.” Also prior to matching, no patients in the MiECC group had low cardiac output after surgery, whereas seven patients (5.6%) did in the cCPB group. Finally, transfusion rates and red blood cell transfusion quantity per patient were significantly lower in the MiECC group, both before and after matching.

The authors plan to continue their research to provide evidence for a broader application of MiECCs. “We will continue trying to identify other groups of patients that are expected to profit most from the concept,” says Dr El-Essawi. “Our goal is to increase the evidence for a shift in concept, in which the MiECC is the standard approach for extracorporeal circulation and conventional systems are the exception, [used only] for specific indications.”

Visit the European Journal of Cardio-Thoracic Surgery to read the full article: Impact of minimally invasive extracorporeal circuits on octogenarians undergoing coronary artery bypass grafting. Have we been looking in the wrong direction?

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References

Anastasiadis K, Antonitsis P, Haidich AB, Argiriadou H, Deliopoulos A, Papakonstantinou C. Use of minimal extracorporeal circulation improves outcome after heart surgery; a systematic review and meta-analysis of randomized controlled trials. Int J Cardiol. 2013;164(2):158-169.

Baikoussis NG, Papakonstantinou NA, Apostolakis E. The "benefits" of the mini-extracorporeal circulation in the minimal invasive cardiac surgery era. J Cardiol. 2014. Jun;63(6):391-396.

El-Essawi A, Breitenbach I, Haupt B, Brouwer R, Baraki H, Harringer W. Impact of minimally invasive extracorporeal circuits on octogenarians undergoing coronary artery bypass grafting. Have we been looking in the wrong direction? Eur J Cardiothorac Surg. 2017;52(6):1175-1181.

Wang C, Hua K, Yin L, Wang Y, Li W. A Meta-Analysis of Miniaturized Versus Conventional Extracorporeal Circulation in Valve Surgery. Ann Thorac Surg. 2016;102(6):2099-2108.