Impact of Catheterization Lab Computer Software Settings on Hemodynamic Assessment of Aortic Stenosis

Accurate assessment of Cardiac Output (CO) is a critical measurement in the calculation of aortic valve area (AVA). Due to the known inaccuracy of estimated Fick calculations, many measure thermodilution (TD) CO as well due to previous studies showing better correlation with the gold standard direct CO. Previous studies showed suboptimal correlation between both methods. Most physicians assume that the TD CO is chosen by catheterization laboratory software for AVA evaluation. Our study was performed to check which CO method is assigned by our popular computer software system [Philips Xper Connect (XIM)] for the AVA calculation and the impact of that on clinical decision.

We studied one hundred consecutive patients who underwent right and left heart catheterization from 2009 to 2012 for assessment of AVA and who had both estimated Fick and TD CO calculated. Correlation of direct continuous VO2, assumed VO2 and TD based CO measurements were assessed by linear regression analysis and by variance component analysis.

We found that whichever CO calculation was entered first to the software system became the determinative output used to calculate the AVA appearing on the final report. This was the estimated Fick method in 32 patients and TD in 68 patients. The CO used for the final report depended solely on the timing of the oxygen saturation samples. The Correlation between AVA based on both methods correlated poorly (Pearson R=0.73, Intra-Class Correlation (ICC) =0.72). This discrepancy affects recommendation for surgery (AVA <1.0 cm2) in 18 cases (18% of patients).

Our widely used software has an arbitrary method of selecting the determinative CO to calculate the final AVA. For TD CO to 'trump' the Fick CO a complex series of computer commands needs to be performed. None of the physicians or technicians was aware of this software selection process, which affects critical treatment decisions.