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

<b>Background:</b> 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. <b>Methods:</b> 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. <b>Results:</b> 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, <i>p</i> = 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 (<i>p</i> = 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, <i>p</i> = 0.003). <b>Conclusions:</b> 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.