Method and system for determining fluid status based on a dynamic impedance surrogate for central venous pressure

Abstract

A method and system are provided for determining fluid status with a central venous system of a heart. Dynamic impedance (DI) data and static impedance (SI) data are collected over multiple cardiac cycles (CC) for a persistent time period of interest (POI). The DI and SI data are collected along a central venous (CV) vector that extends through a superior vena cava (SVC). The DI and SI data are analyzed to obtain DI long-term variation (LTV) information and SI LTV information, respectively, and to detect whether the DI LTV information and the SI LTV information include decreasing persistent trends in the DI and SI data. When decreasing persistent trends are detected in the DI and SI data, an overload output is generated to indicate that the heart is experiencing a volume overload state. The DI and SI data represent a surrogate for central venous pressure.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is related to U.S. patent application Ser. No. 13 / 841,184, filed Mar. 15, 2013, titled “METHOD AND SYSTEM FOR CHARACTERIZING CARDIAC FUNCTION BASED ON DYNAMIC IMPEDANCE.”FIELD OF THE INVENTION[0002]Embodiments of the present invention generally relate to determining fluid status, and more particularly to methods and systems that utilize dynamic impedance as a surrogate for central venous pressure to determine fluid status.BACKGROUND OF THE INVENTION[0003]Implantable medical devices (IMDs) exist today that are used to monitor venous volume status. These conventional IMDs utilize an impedance measurement taken along a RV vector between the RV-tip electrode and the CAN electrode and along a vector between the RV coil to CAN electrodes. The duration and magnitude of decreases in impedance measured along the RV-tip—CAN and RV-coil to CAN vectors is used to detect volume overload. These RV vectors use weighted combinations of i...

AI Technical Summary

Problems solved by technology

However, in patients with heart disease, significant changes in the DC component may take place over longer periods of time, such as over several hours, days or weeks.

However, conventional IMDs have not been able to determine fluid status in the central venous system.

Yet, the overall DC impedance does not exhibit satisfactory specificity or sensitivity as an indicator of the presence of volume overload.

However, the echocardiography evaluation is time consuming and has high variations.

Yet, a comprehensive echocardiography evaluation assessment is time consuming.

Also, when the parameters of a pacemaker are set to a preferred setting, while a patient is in the clinic, the same parameter settings may not reflect the best parameter settings for the patient when the person is ambulatory and active.

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