M. Dupuis

Determination of Cardiac Output in Pulmonary Hypertension Using Impedance Cardiography

Background: Cardiac output (CO) is a prognostic factor in pulmonary hypertension (PH). Right heart catheterisation using the direct Fick method or thermodilution (TD) is the reference technique for CO measurement. Impedance cardiography (IPc) is a known non-invasive method of measuring CO. Objectives: In our study, we assume that the measurement of CO by IPc using the PHYSIOFLOW® system is as accurate as TD or using the direct Fick method in patients with PH in group 1 or group 4. Methods: A total of 75 patients were enrolled in a prospective study carried out at the hypertension reference centre of Toulouse University Hospital. Right heart catheterisation was performed for the diagnosis or follow-up of the disease. CO was measured using the Fick method, TD, and IPc simultaneously. A Bland-Altman analysis was plotted. Results: CO was 5.7 ± 1.9 L/min as measured by the Fick method, 5.4 ± 1.5 L/min by TD, and 5.5 ± 1.7 L/min by IPc. The bias between CO measurements by IPc and the direct Fick method was 0.149 L/min (95% CI, –0.298 to 0.596). The bias between CO measurements by IPc and the TD method was –0.153 L/min (95% CI, –0.450 to 0.153). The correlation decreased with the more extreme CO values (< 3 L/min or > 7 L/min). A few factors changed the agreement between measurements (BMI or membership in group 4). Conclusion: To conclude, this study shows that the measurement of CO by IPc in PH patients is reliable compared to the direct Fick method and TD obtained by right heart catheterisation. This accuracy decreases for extreme CO values.

Accuracy of impedance cardiography to measure cardiac output at rest in pulmonary hypertension

Introduction: Cardiac output (CO) is one of the most important prognostic factor in PH and is required for the assessment of treatment response. CO is measured invasively by right heart catheterization by thermodilution or the Fick method. Impedance cardiography (IP) measures CO and is noninvasive, simple and provides immediate results. Objectives: The main objective of this feasibility study was to assess the accuracy of of CO measures performed IP compared to the Fick method in selected patients treated for PH (Group 1 or 4). Secondary objectives were to evaluate the accuracy of CO evaluation by IP compared to thermodilution and to determine the factors that may affect the measures. Methods: Patients were recruited from the cohort of the Competence Center PH of Midi-Pyrenees, France. The three techniques (Fick, thermodilution and IP) were realized at the same time during right heart catheterization performed in the patient follow up. All patients had confirmed PH from Group 1 or group 4. Results: We had recruited 37 subjects in the study. (31 patients group 1 and 6 patients group 4). The CO measured by IP correlates with the CO measured by the Fick method: ρ=0.62 CI 95% [0.3064; 0.8124] (P Conclusion: This pilot study validates the measurement of CO by IP in patients with PH (group 1 or 4). This suggests a potential role of the non-invasive IP in the follow up of PH patients.