Abstract: A new model is provided for understanding and exploiting impedance or admittance values measured by implantable medical devices, such as pacemakers or cardiac resynchronization devices (CRTs.) The device measures impedance along vectors extending through tissues of the patient between various pairs of electrodes. The device then converts the vector-based impedance measurements into near-field individual electrode-based impedance values. This is accomplished, in at least some examples, by converting the vector-based impedance measurements into a set of linear equations to be solved while ignoring far-field contributions to the impedance measurements. The device solves the linear equations to determine the near-field impedance values for the individual electrodes, which are representative of the impedance of tissues in the vicinity of the electrodes.

Abstract: Techniques are provided for assessing left atrial pressure (LAP) based on atrial electrocardiac signal parameters, particularly intra-atrial conduction delay (IACD) and P-wave duration. In one example, a pacemaker or other implantable device senses an intracardiac electrogram (IEGM) or a subcutaneous electrocardiogram (ECG), from which IACD and P-wave duration are derived. The device tracks changes, if any, in the parameters. A significant increase in either IACD or P-wave duration is associated with an increase in LAP. In some examples, conversion factors are calibrated for use with a particular patient to relate IACD and/or P-wave duration values to LAP values to provide an estimate of actual LAP. The conversion factors are pre-calibrated using LAP measurements obtained using a wedge pressure sensor. In other examples, IACD and P-wave duration are instead used to confirm the detection of an elevation in LAP initially made using impedance signals. Other confirmation parameters are described as well.

Abstract: In specific embodiments, a method to monitor left atrial pressure and/or intra-thoracic fluid volume of a patient, comprises (a) monitoring posture of the patient using a posture sensor implanted within the patient, and (b) using portions of an impedance signal, obtained using implanted electrodes, to monitor the left atrial pressure and/or intra-thoracic fluid volume of the patient. Each portion of the impedance signal used to monitor the left atrial pressure and/or intra-thoracic fluid volume of the patient corresponds to a period after which the patient has maintained a predetermined posture for at least a predetermined period of time, and during which the patient has remained in the predetermined posture.

Abstract: In specific embodiments, a method to monitor pulmonary edema of a patient, comprises (a) detecting, using an implanted posture sensor, when a posture of the patient changes from a first predetermined posture to a second predetermined posture, (b) determining an amount of time it takes an impedance signal to achieve a steady state after the posture of the patient changes from the first predetermined posture to the second predetermined posture, where the impedance signal is obtained using implanted electrodes and is indicative of left atrial pressure and/or intra-thoracic fluid volume of the patient, and (c) monitoring the pulmonary edema of the patient based on the determined amount of time it takes the impedance signal to achieve the steady state after the posture of the patient changes from the first predetermined posture to the second pre-determined posture.

Abstract: A magnetically self balancing pen and base includes a base member housing a disk magnet and a concentric ring magnet having a predetermined inside diameter. The pen assembly has a barrel, an elongated ink cartridge with a magnetically attractable tip, and an annular magnet disposed inside the barrel and around the elongated ink cartridge. The annular magnet is located proximal but separated from the magnetically attractable tip with the end proximal the tip having a polarity equal to that of an upper surface of the ring magnet in the base.