Pacesetter, Inc.

Siemens-pacesetter, Inc.

Jonathan A Kleks

Raymond J Wilson

Gene A Bornzin

John W Poore

Brian M Mann

Alan B Vogel

Ali Enayat Zadeh

Stuart W Buchanan

Methods and apparatus are provided for classifying cardiac events with an implantable cardiac device. Cardiac signals are stored in a buffer. When a significant cardiac event is confirmed, a corresponding segment of the stored cardiac signals is processed to generate a set of feature values. The set of feature values is compared to various sets of reference values. Each set of reference values preferably corresponds to a separate type of cardiac event, so that the cardiac device may classify the significant cardiac event by matching its set of feature values to a set of reference values. Feature values include the maximum positive and negative slew rates exhibited by the cardiac signal during the segment, the maximum positive and negative signal amplitudes, the times to reach the maximum positive and negative signal amplitudes, the area under the cardiac signal curve, the area under the cardiac signal curve above zero as compared to the area below zero, and the number of zero crossings made by the cardiac signal. Additional feature values are generated by simultaneously processing the cardiac signals measured along two different vector directions in the heart.

Methods and apparatus for classifying cardiac events with an implantable

A micropower analog-to-digital converter (ADC) for use in an implantable medical device is disclosed. The ADC achieves a high conversion speed at micropower levels through a number of timing and circuit improvements over the conventional implementation of the successive approximation ADC architecture. The ADC includes a digital-to-analog converter (DAC) that preferably is implemented as a binary-weighted, switched capacitor array that employs top plate charging and performs bipolar conversion. The DAC provides an analog output signal representing array charge to a comparator. During a comparator latch phase, the DAC asynchronously determines a bit of the ADC digital output signal in response to the comparator output, and initiates a test of the next least significant bit during the same latch phase. Further, the DAC analog output signal is timed to settle during the latch phase in response to both the bit update and the next bit test. In conjunction with increasing conversion speed, the DAC reduces power requirements by using a power gated buffer that selectively increases the power of the ADC input signal only when necessary to drive the ADC conversion circuitry. Further, the comparator includes a precharged static memory cell to avoid crossover currents. Finally, the ADC includes a digital offset correction DAC that corrects not only the cumulative offset voltage generated by components of the ADC, but also the offset voltage of any device that provides the ADC input.

Method and apparatus for micropower analog-to-digital conversion in an

An autocapture system within an implantable pulse generator automatically maintains the energy of a stimulation pulse at a level just above that which is needed to effectuate capture. The electrical post-stimulus signal of the heart following delivery of a stimulation pulse is compared to a polarization template, determined during a capture verification test. A prescribed difference between the polarization template and the post-stimulus signal indicates capture has occurred. Otherwise, loss of capture is presumed, and a loss-of-capture routine is invoked that increases the energy a prescribed amount to obtain capture. Periodically, and/or at programmed intervals or events, the capture verification test is performed. During the capture verification test, the pulse generator determines a polarization template for a particular stimulation energy and for each of a plurality of sensitivity or threshold settings. A determination is also made as to which sensitivity settings yield capture. An autocapture routine extends the capture verification test data to a wide range of stimulation energies. An autothreshold routine automatically sets the energy of the stimulation pulse a specified level above the energy at which capture is first lost.

Autocapture system for implantable pulse generator

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Northridge, CA, United States of America

Jonathan A Kleks