Medtronic, Inc.

Diederick M Keizer

Mattias Rouw

Peter M Van Dam

Peter Oosterhoff

Jos P A Smit

The invention is directed to sensing techniques that can be executed by an implantable medical device (IMD). The sensing techniques exploit the fact that useful information can be sensed during the periods where the sympathetic and vagal tone balance changes in a patient's nervous system. This balance generally changes when a patient is falling asleep or waking up from sleep. In accordance with the invention, sensed information is recorded specifically during the times where a patient is either falling asleep or waking up. The IMD can be designed to sense or identify when a patient is falling asleep or waking up, and can record the useful sensed information specifically during those times.

Sensing techniques for implantable medical devices

The invention is directed to methods and apparatus for automatically changing from bi-ventricular pacing, in which an implantable medical device (IMD) applies pacing stimuli to both ventricles of a heart during a cardiac cycle, to single-ventricle pacing, in which the IMD paces one ventricle and inhibits pacing of the other. An IMD applying the techniques of the invention automatically changes from bi-ventricular pacing to single-ventricle pacing, or vice versa, as a function of the reliability of left ventricular pacing. Exemplary techniques for determining the reliability of left ventricular pacing include impedance measurement, capture testing, capture threshold testing, or any combination thereof.

Bi-ventricular and single-ventricle pacing

The invention presents a medical device system and method for determining the degree of heart failure of a patient, utilizing information representative of dynamic variations in patient QT, or segments of QT, over time. The dynamic variations in QT that are measured relate to characteristics of the variation of QT with rate when rate is increasing and when it is decreasing. The dynamic variations include QT dynamic range, QT hysteresis, and QT directrix, each providing important information relating to the patient's variation of QT with heart rate, or QT(RR). QT and dynamic variations of QT can be measured in both left and right ventricles, and taken over the patient's normal rate range. The dynamic data is measured and stored periodically and compared with historical data to determine progression toward heart failure. In another embodiment, the QRST signals are divided into segments, namely QRS width; ST segment; and T wave width, and variations of these segments are analyzed to provide additional information indicative of the patient's heart condition. Preferably the system utilizes a microprocessor programmed to carry out an algorithm that weighs detected variations in QT, QT segments and/or QT dynamic parameters with time to track cardiac changes.

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Elst, Netherlands

Diederick M Keizer