Transthoracic Impedance Accurately Estimates Pulmonary Wedge Pressure in Patients With Decompensated Chronic Heart Failure

Routine cardiac catheterization to assess pulmonary capillary wedge pressure (PCWP) is not recommended in heart failure (HF), and various noninvasive tools have been proposed. The authors evaluated the reliability of echocardiography, brain natriuretic peptide (BNP), and thoracic electrical bioimpedance (TEB) in predicting PCWP in 29 patients (72±4 years, New York Heart Association class 3.5±0.9, ejection fraction 28%±6%) who underwent hemodynamic evaluation for worsening HF. Echocardiography was performed immediately before the hemodynamic study. During clinical stability, PCWP, plasma BNP, and TEB were simultaneously assessed. Among TEB variables, thoracic conductance (thoracic fluid content [TFC]=1/kΩ) was used. PCWP was related with E/E' obtained with mitral Doppler and mitral annulus tissue Doppler imaging echocardiography ( R=0.55, P<.005), with BNP levels (R=0.43, P<.01) and TFC values (R=0.69, P<.001). For detection of PCWP ≥15 mm Hg, TFC ≥35/kΩ had high specificity (97%) and sensitivity (86%) and negative (92%) and positive (97%) predictive value, while E/E' and BNP levels had poorer specificity. After infusion of the inodilator levosimendan, changes in TFC and PCWP were of the same order of magnitude and mutually related. In worsening HF, TEB could help avoid right heart catheterization, since it may estimate PCWP better than BNP or echocardiography. Moreover, TFC could be used for noninvasive assessment of drugs' effect.