Validity of hemodynamic monitoring using inert gas rebreathing method in patients with chronic heart failure and those implanted with a left ventricular assist device.

Abstract Objective The present study assessed agreement between resting cardiac output estimated by inert gas rebreathing (IGR) and thermodilution methods in patients with heart failure and those implanted with a left ventricular assist device (LVAD). Methods and results : Haemodynamic measurements were obtained in 42 patients: 22 with chronic heart failure and 20 with implanted continuous flow LVAD (34 males; aged 50 ± 11 years). Measurements were performed at rest using thermodilution and inert gas rebreathing methods. Cardiac output derived by thermodilution and IGR were not significantly different in LVAD (4.4±0.9 vs 4.7±0.8 l/min; P=0.27) or heart failure patients (4.4±1.4 vs 4.5 ± 1.3 l/min; P=0.75). There was a strong relationship between thermodilution and IGR cardiac index (r=0.81, p=0.001) and stroke volume index (r=0.75, p=0.001). Bland-Altman analysis showed acceptable limits of agreement for cardiac index derived by thermodilution and IGR i.e. mean difference (lower and upper limits of agreement) for heart failure patients -0.002 (-0.65 - 0.66) l/min/m2, and -0.14 (-0.78 - 0.49) l/min/m2 for patients with LVAD. Conclusion Inert gas rebreathing is a valid method for estimating cardiac output and should be used in clinical practice to complement evaluation and management of chronic heart failure and LVAD patients.