Abstract 17467: Development and Validation of an Accurate Predictive Equation for Oxygen Consumption in Congenital Heart Disease
Objectives: To improve the accuracy of hemodynamic data in patients with congenital heart disease (CHD), we sought to identify factors associated with inaccurate predicted oxygen consumption (VO2) and to develop and validate a new predictive equation for VO2.
Methods: Retrospective review of 502 consecutive CHD patients undergoing cardiac cath with a validated VO2 measurement (M-VO2; GE CARESCAPE™ B850). M-VO2 was compared to VO2 from the LaFarge equation (LF-VO2) in patients < 3 yrs (Group 1) and ≥ 3 yrs (Group 2). Logistic regression identified factors associated with an inaccurate LF-VO2 (≥ 20% difference from M-VO2). Multivariate predictors with a p-value ≤ 0.1 were incorporated into a new predictive equation. The new equation was validated prospectively in the next 100 patients using Pearson correlation and Bland-Altman (B-A) analysis.
Results: In the retrospective cohort, median age was 4.4 yrs (0 - 59.4). Compared to M-VO2, LF-VO2 was inaccurate in 42% of Group 1 (n = 201) and 13% of Group 2 (n = 301). Multivariate predictors of inaccurate LF-VO2: age (OR 0.41, p = 0.01) and single ventricle (OR 2.98, p = 0.03) in Group 1 and anemia in Group 2 (OR 0.84, p < 0.001). Critical-illness was borderline significant in Group 1 (OR 2.0, p = 0.07) and Group 2 (OR 2.48, p = 0.08). The new equation:
VO2 = 242.1 + [9.7 х ln(Age)] - [34 х ln(Weight)] - [9.6 х Single Ventricle] - [11.2 х Critical-illness]
VO2 from the new equation was highly correlated with M-VO2 (r = 0.45, p < 0.001), whereas LF-VO2 was not (r = 0.096, p = 0.34). B-A analysis comparing M-VO2 to VO2 from the new equation (Fig A) and M-VO2 to LF-VO2 (Fig B) demonstrates superiority of the new equation (mean bias 2.5 vs. -5.0 mL/min/m2; 95% CI -51.6, 56.5 vs. -82.1, 72).
Conclusions: Estimates of VO2 derived from the LaFarge equation are frequently inaccurate in CHD, and will lead to erroneous hemodynamic calculations. Using M-VO2, we developed and prospectively validated a novel predictive equation that is highly accurate in the CHD population.
- © 2013 by American Heart Association, Inc.