Abstract: According to the invention methods and structures for determining whether impingement of x-ray radiation upon potentially vulnerable discrete components, circuits and/or circuit pathways of an implantable medical device (IMD) causes modifications or damage thereto. The invention includes structures for deflecting impingement of x-ray radiation from said potentially vulnerable components, circuits and/or circuit pathways. The x-ray radiation can be generated by various imaging modalities or unknown sources. Myriad IMDs can utilize the teaching of the present invention, including for example, a pacemaker, a drug delivery pump, a nerve stimulation device, a muscle stimulation device, an implantable cardioverter-defibrillator, a subcutaneous defibrillator, a deep brain stimulator or the like.

Abstract: An implantable medical device (IMD) includes a detector for detecting the presence of x-ray radiation, where the presence of x-ray radiation is detected in response to the strength of the x-ray radiation exceeding a first threshold. In one embodiment, the IMD includes a processor for adjusting a cardiac stimulation rate IMD in response to determining that the strength of the detected x-ray radiation exceeds a second threshold. The second pre-selected x-ray radiation threshold is greater than the first pre-selected x-ray radiation threshold. In another embodiment, the implantable device includes a detector for detecting the presence of any amount x-ray radiation and a processor for adjusting a stimulation rate provided by the IMD in response to detected x-ray radiation to reduce the chance of over-sampling artifacts or inappropriate therapy delivery.

Abstract: An implantable medical device (IMD) includes a detector for detecting the presence of x-ray radiation, where the presence of x-ray radiation is detected in response to the strength of the x-ray radiation exceeding a first threshold. In one embodiment, the IMD includes a processor for adjusting a cardiac stimulation rate IMD in response to determining that the strength of the detected x-ray radiation exceeds a second threshold. The second pre-selected x-ray radiation threshold is greater than the first pre-selected x-ray radiation threshold. In another embodiment, the implantable device includes a detector for detecting the presence of any amount x-ray radiation and a processor for adjusting a stimulation rate provided by the IMD in response to detected x-ray radiation to reduce the chance of over-sampling artifacts or inappropriate therapy delivery.

Abstract: An implantable medical device (IMD) includes a detector for detecting the presence of x-ray radiation, where the presence of x-ray radiation is detected in response to the strength of the x-ray radiation exceeding a first threshold. In one embodiment, the IMD includes a processor for adjusting a cardiac stimulation rate IMD in response to determining that the strength of the detected x-ray radiation exceeds a second threshold. The second pre-selected x-ray radiation threshold is greater than the first pre-selected x-ray radiation threshold. In another embodiment, the implantable device includes a detector for detecting the presence of any amount x-ray radiation and a processor for adjusting a stimulation rate provided by the IMD in response to detected x-ray radiation to reduce the chance of over-sampling artifacts or inappropriate therapy delivery.

Abstract: The invention presents techniques for processing an atrial electrogram. An atrial electrogram senses atrial events, but may also sense a ventricular event, causing a far field R-wave to be present in the atrial electrogram signal. A far field R-wave is an undesired artifact. The invention provides techniques for estimating the far field R-wave and subtracting the far field R-wave from the atrial electrogram signal.

Abstract: The invention presents techniques for processing an atrial electrogram. An atrial electrogram senses atrial events, but may also sense a ventricular event, causing a far field R-wave to be present in the atrial electrogram signal. A far field R-wave is an undesired artifact. The invention provides techniques for estimating the far field R-wave and subtracting the far field R-wave from the atrial electrogram signal.

Abstract: A system and method is provided to view an anatomical structure such as a blood vessel in high contrast with its surrounding tissue. The system and method may be used to produce an image of an anatomical structure using reflected electromagnetic radiation singularly scattered from target tissue. The system and method may also provide same-side illumination and detection of reflected electromagnetic radiation in a convenient integral imaging device. The system and method may also provide helmet mounted imaging technology in a single integral helmet which allows the wearer to view an anatomical structure located within a patient such that the image is continuously oriented according to the orientation of the helmet wearer's head. The system and method may also be used in the performance of venipuncture. The system and method may provide for improved contrast between any anatomical structure and its surrounding tissue for use in any imaging system.

Abstract: An implantable cardiac pacemaker and a method of its operation. The pacemaker delivers pacing pulses to a first chamber of a patient's heart and senses depolarizations of a second chamber of the patient's heart. The amplifier for sensing depolarizations of the second chamber of the patient's heart defines a base sensing threshold and, responsive to delivery of a pacing pulse to the first chamber of the patient's heart for defines an increased sensing threshold greater than the base sensing threshold. The increased sensing threshold persists for a defined period of time following delivery of a pacing pulse to the first chamber of the patient's heart and thereafter gradually decreases from the increased sensing threshold to the base sensing threshold.

Abstract: A rate-responsive cardiac pacemaker comprising a minute ventilation circuit and an activity circuit. The minute ventilation circuit computes a first target pacing rate as a function of measurements of the patient's pleural blood impedance, and the activity circuit computes a second target pacing rate as a function of measured levels of patient activity. A rate control function establishes a rate-responsive pacing rate based on the first and second target pacing rates. The minute ventilation circuit delta-modulates an analog impedance waveform and maintains short-term and long-term weighted averages of delta-modulator output counts. Variations in the difference between the short-term and long-term weighted average values are determinative of the first target pacing rate. Variations in an activity sensor output signal are determinative of the second target pacing rate.