# CO2 Gap Alone Is Not a Prognostic Marker for 28-Day Survival of Patients Undergoing a Transcatheter Aortic Valve Replacement

## TL;DR

The study found that the CO2 gap is not a reliable predictor of 28-day survival in patients undergoing TAVR.

## Contribution

This study challenges the use of CO2 gap as a prognostic marker in TAVR patients.

## Key findings

- The CO2 gap was higher in non-survivors but showed limited prognostic value for 28-day survival.
- No significant difference in CO2 gap was found between cardiac and non-cardiac groups.
- CO2 content was significantly higher in survivors at one time point.

## Abstract

Background: The venous-to-arterial difference in partial pressure of carbon dioxide (CO2 gap) has been suggested as a marker of cardiac output and clinical outcomes. This study aimed to evaluate the CO2 gap as a prognostic indicator for 28-day survival in patients undergoing transcatheter aortic valve replacement (TAVR) and to explore its relationship with cardiac function and lactate levels. Methods: In this prospective cohort study, 50 TAVR patients were stratified based on their left ventricular ejection fraction (LV-EF) and survival status. Central venous and arterial blood samples were collected at five time points to measure blood gas parameters. The primary endpoint was the prognostic value of the CO2 gap for 28-day survival. Secondary endpoints included group differences in the CO2 gap, its correlation with lactate levels, and CO2 content analysis. Results: ROC analysis indicated limited prognostic value for 28-day survival. The CO2 gap was higher in non-survivors than in survivors (11.1 mmHg vs. 6.8 mmHg, p = 0.039), but showed no significant difference between individual time points. The CO2 gap between cardiac (LV-EF ≤ 50%) and non-cardiac (LV-EF > 50%) groups showed no significant difference. Lactate and CO2 gap showed no correlation, except at T2 in the cardiac group (p = 0.039, r = 0.525). CO2 content showed no significance, except at T5, where it was significantly higher in survivors (5.3 mL/dL vs. 1.1 mL/dL, p = 0.003). Conclusions: The CO2 gap did not emerge as a reliable prognostic marker for 28-day survival in TAVR patients. Further studies are needed to explore its clinical relevance.