Abstract 807: Directly Assessed Pulmonary Fluid Overload in Acute Cardiac Decompensation Shows a Strong Correlation with Device-Based Measurement of Intrathoracic Impedance

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Introduction : Heart failure (HF) is often associated with hospitalizations due to pulmonary congestion resulting in cardiogenic lung edema (LE). Implant-based monitoring of intrathoracic impedance as a surrogate measure of thoracic fluid status provides the chance to detect early stages of cardiac decompensation. Previously pulmonary fluid congestion has been related to clinical or preload parameters. In this study we tested for the first time the correlation between changes in intrathoracic impedance (Z) and directly measured intrathoracic fluids during LE induction as well as LE recovery. Methods : 20 anesthetized sheep were studied, 3 served as controls, in 17 acute pulmonary fluid overload was induced by hypervolemia in combination with gradually increasing peripheral arterial resistance, in 5 sheep restitution of pulmonary fluid overload was attempted. Hemodynamics were continuously monitored including LVEDP. A transpulmonary thermodilution system was used to determine intrathoracic blood volume (ITBV) and extravascular lung water (EVLW). Z was measured between the coil of a right ventricular ICD lead and an implanted device case. Results : All variables remained stable for the control group, whereas pulmonary fluid accumulation was observed in the LE group, confirmed by mean increases of LVEDP (4 to 28 mmHg), ITBV (1464 to 2273 ml) and EVLW (954 to 1267 ml). There was a concomitant decrease in intrathoracic impedance Z (−15%). Regarding LE recovery, intensified diuresis resulted in restitution of pulmonary fluid overload and a decrease in ITBV (−22%) paralleled by an increase of Z (+6%). Significant inverse correlations between Z and LVEDP (r=−0.84), ITBV (r=−0.85) and EVLW (r=−0.77) were calculated. Conclusions : Here we show for the first time that changes of intrathoracic impedance show a strong inverse correlation with changes in directly assessed intrathoracic fluids and preload parameters during formation of and recovery from lung edema. Therefore, implants capable of long term monitoring of intrathoracic impedance will have the potential to enhance therapy management in HF patients. A combination of these device-based features with existing telemedicine concepts has a tremendous potential to improve outpatient HF management.

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