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PRE-CLINICAL RESEARCH

Ambulatory Monitoring of Congestive Heart Failure by Multiple Bioelectric Impedance Vectors

Dirar S. Khoury, PhD^_*,_*, Mihir Naware, MS, Jeff Siou, BS, Andreas Blomqvist, MS, Nilesh S. Mathuria, MD, Jianwen Wang, MD, PhD^_*, Hue-Teh Shih, MD, Sherif F. Nagueh, MD^_* and Dorin Panescu, PhD

^_* Department of Cardiology, Methodist DeBakey Heart and Vascular Center, Methodist Hospital Research Institute, Houston, Texas
Cardiac Rhythm Management Division, St. Jude Medical, Inc., Sylmar, California
Section of Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas
Center for Cardiac Arrhythmias, Houston, Texas

Manuscript received July 21, 2008; revised manuscript received November 17, 2008, accepted December 15, 2008.

^_* Reprint requests and correspondence: Dr. Dirar S. Khoury, Methodist Hospital Research Institute, 6565 Fannin Street, F764, Houston, Texas 77030 (Email: dkhoury{at}tmhs.org).

Objectives: This study was designed to investigate the properties of multiple bioelectric impedance signals recorded during congestive heart failure (CHF) by utilizing various electrode configurations of an implanted cardiac resynchronization therapy system.

Background: The monitoring of CHF has relied mainly on right-side heart sensors.

Methods: Fifteen normal dogs underwent implantation of cardiac resynchronization therapy systems using standard leads. An additional left atrial (LA) pressure lead sensor was implanted in 5 dogs. Continuous rapid right ventricular (RV) pacing was applied over several weeks. Left ventricular (LV) catheterization and echocardiography were performed biweekly. Six steady-state impedance signals, utilizing intrathoracic and intracardiac vectors, were measured through ring (r), coil (c), and device Can electrodes.

Results: Congestive heart failure developed in all animals after 2 to 4 weeks of pacing. Impedance diminished gradually during CHF induction, but at varying rates for different vectors. Impedance during CHF decreased significantly in all measured vectors: LV_r–Can, –17%; LV_r–RV_r, –15%; LV_r–RA_r, –11%; RV_r–Can, –12%; RV_c–Can, –7%; and RA_r–Can, –5%. The LV_r–Can vector reflected both the fastest and largest change in impedance in comparison with vectors employing only right-side heart electrodes, and was highly reflective of changes in LV end-diastolic volume and LA pressure.

Conclusions: Impedance, acquired by different lead electrodes, has variable responses to CHF. Impedance vectors employing an LV lead are highly responsive to physiologic changes during CHF. Measuring multiple impedance signals could be useful for optimizing ambulatory monitoring in heart failure patients.

Key Words: cardiac resynchronization therapy • hemodynamic monitoring • pulmonary edema

Abbreviations and Acronyms   CHF = congestive heart failure   CRT = cardiac resynchronization therapy   LA = left atrial   LV = left ventricle/ventricular   RA = right atrial   RV = right ventricle/ventricular

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J. Am. Coll. Cardiol. 2009 53: A26. [Full Text] [PDF]