Abstract 16671: Thermodilution Underestimates Cardiac Output During Exercise Leading to Frequent Erroneous Diagnoses of Exercise-induced Pulmonary Hypertension
Introduction: Recent interest in establishing a definition of exercise-induced pulmonary hypertension (EiPH) has resulted in two potential criteria: mean pulmonary artery pressure/cardiac output (mPAP/CO) slope >3 mmHg*min*L-1 and peak exercise total pulmonary resistance (TPR) >3 Wood units (WU) with a mPAP ≥30 mmHg. Despite the importance of accurately measuring exercise CO for both criteria, there is significant variability in the CO method used throughout the literature and among institutions.
Hypothesis: We hypothesized that use of direct Fick CO (DFCO) versus thermodilution cardiac output (TDCO) would significantly alter EiPH diagnoses.
Methods: We performed a single-center retrospective analysis of invasive cardiopulmonary exercise testing data (supine bicycle ergometer) to compare TDCO and DFCO exercise measurements. TDCO and mixed venous oxygen saturations were recorded at rest and every 2 minutes during graded exercise; gas exchange was measured via metabolic cart (Medical Graphics, St. Paul, MN). Hemodynamics were measured at end-expiration at rest and averaged over the respiratory cycle during exercise. Patients were excluded if less than three CO data points were recorded.
Results: Over two years, 27 patients (18 with resting mPAP <25 mmHg and 9 with mPAP ≥25 mm Hg) had both DFCO and TDCO measured during exercise. Bland-Altman comparison (Figure) revealed that TDCO underestimated DFCO, especially at higher CO. Regardless of EiPH definition used, TDCO led to excess diagnoses: 7 excess diagnoses (18/27 vs. 11/27) when using mPAP/CO slope >3 mmHg*min*L-1 and 5 excess diagnoses (21/27 vs. 16/27) when using TPR >3 WU. This discrepancy was magnified further when considering only those with mPAP <25 mm Hg.
Conclusions: TDCO systematically underestimates output during exercise when compared to DFCO, leading to an excess of EiPH diagnoses. These findings have important implications in the ongoing assessment of new EiPH diagnostic criteria and methodology.
Author Disclosures: S.B. Brusca: None. S. Hsu: None. P.S. Rhodes: None. R.J. Tedford: None.
- © 2016 by American Heart Association, Inc.