Mixed Venous Oxygen Saturation during the Transcatheter Aortic Valve Replacement—A Prospective Cohort Study

Purpose: Patients scheduled to undergo the transcatheter aortic valve replacement (TAVR) are usually octogenarians with severe co-morbidities and an increased risk of surgery-associated complications. The aim of this study was to determine the incidence of insufficient oxygen delivery as measured by mixed venous oxygen saturation (SvO2) via invasive continuous cardiopulmonary monitoring and the low cardiac output syndrome (LCOS) in patients undergoing the TAVR procedure. The second objective was to examine how these hemodynamic measurements would change during critical events, such as rapid ventricular pacing (RVP) during this procedure. Methods: This prospective, observational study, examined twenty patients undergoing TAVR under general anesthesia. Hemodynamic variables, SvO2 and the continuous cardiac output (CO) were assessed using pulmonary artery catheter (PAC) and a Vigilance® monitor. Insufficient oxygen delivery was defined as a SvO2 value under 58% and LCOS as a cardiac index (CI) under 2 L/min/m2. Total intravenous anesthesia and hemodynamic management protocol were standardized. RVP was induced twice during the procedure at a frequency of 180 - 200/min. Predefined clinical endpoints were assessed during the procedure and hemodynamic values were analyzed before and after twelve critical events. Results: The data of twenty patients with a mean age of 80 ± 4 years and EuroSCORE 18 ± 10 were analyzed. Fourteen (70%) of the TAVR procedures were performed transapically, the other six (30%) transfemorally. The SvO2 value under 58% (mean 54 ± 6) and the CI under 2 L/min/m2 (mean 1.6 ± 0.2) were detected in 60% of patients (n = 12) before the use of RVP. All of these patients received perioperative inotropic medication and required norepinephrine infusion for maintenance of adequate blood pressure. The SvO2, CO and CI were significantly decreased after the use of RVP (P 2 reverted rapidly to the same level as before the application of RVP (1 min), CO, and CI 10 min later. At the end of the operation SvO2 values were at same level as before RVP and CO and CI were higher than before RVP. Conclusion: A high incidence of insufficient oxygen delivery and low cardiac output syndrome were detected in patients undergoing TAVR procedures. Nonetheless, all hemodynamic values returned rather rapidly to the same level as before the use of the RVP and were at the optimal level at the end of the procedure. According to the current study, the most hemodynamically hazardous steps during TAVR are the use of RVP sequences, the induction of anesthesia and the initiation of surgery.