Telectronics N.v.

Other

Robert H Whigham

Tibor A Nappholz

John R Hamilton

James C Hansen

An implantable pacemaker receives electrical signals from a patient's heart through an electrode, the signals being either intrinsic cardiac signals or repetitive noise signals, due for instance to electromagnetic inference. The pacemaker includes circuitry for determining if the signals from the electrode are cardiac in origin or not by extracting certain signal characteristics from the signals. For example, the noise signals produced by EMI are repetitive, i.e., they have a fairly constant amplitude except for the initial peak. On the other hand cardiac signals have at most three peaks of decreasing amplitudes. These characteristics are used by the determined circuitry to differentiate between cardiac and noise signals. While this determination is taking place, the received signals are stored or delayed. Signals identified as cardiac signals are processed. The processed signals are compensated for the delay caused by the noise detection circuitry.

EMI detection in an implantable pacemaker and the like

A pacemaker which generates a triphasic stimulus; the first and third phases are positive pulses, and the second is the negative stimulus. After-potentials are so low that reliable sensing of evoked signals are possible. The rapidity of the charge balancing is not affected by the stimulus amplitude because the relative amplitudes of the three phases are maintained independent of the stimulus amplitude.

Pacing pulse compensation

A noise rejection circuit for an implantable pacemaker. During re-triggerable relative refractory periods following a heartbeat, the peak noise level is sensed; the relative refractory period is re-started whenever the input signal exceeds the previous peak. Following a time-out of the relative refractory period, the peak value detected, representing the noise level, is added to the programmed threshold value; the sum is used as the threshold value during sensing.

Pacemaker noise rejection system

An implantable pacemaker which stores in memory the representation of an ECG signal by compressing the data. Whenever the input signal changes by a threshold amount from the last time data was recorded, a representation of the time interval which has elapsed is recorded. In a maximimally efficient system, the only information which must be stored are the successive elapsed times, along with indications of when the input signal changes slope.

Storage in a pacemaker memory

An implantable pacemaker in which the sensitivity is automatically controlled. The peak value of each R wave is measured, and a long-term average is derived. The gain of the sense channel is adjusted automatically in accordance with the average of the measured peak values.

Automatic sensitivity control for a pacemaker

A combined pacemaker delta modulator and bandpass filter which requires only one active device. The sense signal is applied through a conventional delta modulator capacitor to the minus input of a differential amplifier, and the conventional current sources are connected to the minus input. Instead of simply connecting the plus input to a reference potential, however, it is also coupled, through a resistor, to the input signal, and an RC network is connected across the two inputs.

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Aurora, CO, United States of America

Robert H Whigham