Rate adaptive cardiac rhythm management device using transthoracic impedance

US6161042A · kind A · utility

Assignee

• Cardiac Pacemakers, Inc. · US

Inventors

• Jesse W. Hartley · Lino Lakes, US
• Marc Cohen · Silver Spring, US
• Nicholas J. Stessman · Minneapolis, US
• Scott A. Reedstrom · Vadnais Heights, US
• Steven D. Check · Eden Prairie, US
• James P. Nelson · Lino Lakes, US

Key dates

• Filing date: May 21, 1999
• Grant date: Dec 12, 2000
• Expiry date: May 21, 2019

Classification

• Technology area (CPC A): Human Necessities
• CPC primary: A61N1/36521
• WIPO field: Medical technology
• WIPO sector: Instruments

Abstract

A cardiac rhythm management (CRM) device detects transthoracic impedance, extracts ventilation or other information, and adjusts a delivery rate of the CRM therapy accordingly. A four-phase sequence of alternating direction current pulse stimuli is periodically delivered to a patient's thorax. A transthoracic impedance signal is extracted using a weighted demodulation. Signal processing extracts ventilation information and removes cardiac stroke information using an adaptive lowpass filter. The adaptive filter cutoff frequency is based on the patient's heart rate; a higher cutoff frequency is provided for higher heart rates. Peak/valley detection indicates tidal volume, which is integrated to extract minute ventilation (MV). Short and long term averages are formed and compared to establish a MV indicated rate. Rate adjustment ignores MV information when a noise-measurement exceeds a threshold. An interference avoidance circuit delays delivery of the stimuli when telemetry pulses or other interfering signals are detected.