Value of impedance cardiography in patients studied for pulmonary hypertension

The aim of this study was to evaluate the accuracy and precision of impedance cardiography as a method for noninvasive hemodynamic evaluation of patients with pulmonary hypertension (PH). We performed a prospective and blinded study of patients who underwent right heart catheterization (RHC) for evaluation of known or presumed PH at the University of Florida from August 2009 to March 2010. The cohort consisted of a total of 39 patients (age = 57 ± 14 years, 87% women) with presumed (23%) or confirmed PH (77%) of different etiologies. Patients underwent RHC and impedance cardiography using the PhysioFlow PF-05. The PhysioFlow PF-05 measures cardiac output (CO) and LV end-diastolic volume (LVEDV), among other parameters. The median pulmonary artery pressure was 36 (IQR 26-56) mmHg. The CO (mean ± SD) by thermodilution (CO-T) and by impedance cardiography (CO-IC) was 5.9 ± 2.2 and 5.6 ± 1.5 L/min, respectively. Bland-Altman analysis of CO-T versus CO-IC revealed a mean of 0.3 L/min (95% LoA: -2.2 to +2.8). In patients with PH, the correlation of CO-T and CO-IC had a mean of 0.4 L/min (95% LoA: 2.9 and -2.2). Pulmonary artery occlusion pressure (PAOP) correlated with LVEDV (R (2) = 0.2, p = 0.005). By ROC analysis, EDV ≥ 200 ml had a sensitivity of 53% and a specificity of 86% for PAOP > 15 mmHg (AUC = 0.78). In patients with PH, impedance cardiography had good accuracy and fair precision for CO determination when compared with thermodilution. Impedance cardiography may provide information about the preload status and has the potential to become a cost-effective and noninvasive method for the follow-up of patients with PH.