Abstract: Embodiments of the present invention are directed to implanted systems, and methods for use therewith, that can monitor a cardiac condition. Pressure in sensed in a left chamber of the heart and a right chamber of the heart. A pressure differential is determined between the sensed pressure in the left chamber and the sensed pressure in the right chamber. A cardiac condition is monitored based on the pressure differential. By determining pressure differentials, as opposed to absolute pressures, calibrations/adjustments for changes in weather, altitude or similar pressure affecting factors are not necessary, since the pressure in the left and right chambers should both be equally affected by such changes. Accordingly, with embodiments of the present invention, an external (i.e., non-implanted) pressure sensor is not needed for measuring ambient pressure.

Abstract: A method for monitoring the progression of the hemodynamic status of a patient by tracking autonomic tone. For example, the method may be applied to patients suffering from heart failure, diabetic neuropathy, cardiac ischemia, sleep apnea and hypertension. An implantable or other ambulatory monitor senses a pulse amplitude signal such as a vascular plethysmography signal. Variations of the signal amplitude on a scale greater than the heartbeat to heartbeat scale are indicative of variations in autonomic tone. A significant reduction in pulse amplitude and pulse amplitude variability are indicative of a heart failure exacerbation or other disease state change. This information may be used to warn the patient or healthcare providers of changes in the patient's condition warranting attention.

Abstract: Cardiac performance associated with a current set of N pacing parameters is improved by adjusting the cardiac pacing parameters until optimal or substantially optimal cardiac performance is achieved. The cardiac performance associated with the current set of N pacing parameters is determined. An incrementing step, a determining step, and a increment updating step, are repeated for i=1 to N, where i represents which of the N pacing parameter is being adjusted. The incrementing step includes incrementing an ith pacing parameter in the current set of N pacing parameters based on a corresponding ith increment value, to thereby produce an ith set of test pacing parameters. The determining step includes determining a cardiac performance associated with the ith set of test pacing parameters. The increment updating step includes updating the ith increment value based on the cardiac performance associated with the ith set of test pacing parameters.

Abstract: A time-varying modulating signal is used as a plethysmography signal, rather than a time-varying detected optical power. The time-varying detected optical power is used (e.g., in a feedback loop) to adjust the source intensity. Light is transmitted from a light source, wherein an intensity of the transmitted light is based on a light control signal. A portion of the light transmitted from the light source is received at a light detector, the portion having an associated detected light intensity. A feedback signal is produced based the portion of light received at the light detector, the feedback signal indicative of the detected light intensity. The feedback signal is compared to a reference signal to produce a comparison signal. The light control signal is then adjusted based on the comparison signal, wherein at least one of the comparison signal and the light control signal is representative of volume changes in blood vessels.

Abstract: A method for monitoring the condition of a heart failure patient using respiration patterns is provided. An implantable or other ambulatory monitor senses the patient's respiratory patterns to identify the presence of periodic breathing or Cheyne-Stokes respiration. In a first embodiment, mechanical changes of the thorax due to breathing are detected and this data is used to recognize hyperventilation and apnea or hypoventilation. In a second embodiment of the invention, Cheyne-Stokes respiration is recognized by detecting changes in blood or tissue pH or CO2 concentration and partial pressure. In another embodiment of the invention, changes in pulse amplitude associated with Cheyne-Stokes respiration are detected. Alternating loss and return of respiration-induced amplitude modulation or pulse-interval variation may also be used to identify the presence of Cheyne-Stokes respiration.

Abstract: The heart failure (HF) status of a patient is determined based on the morphology of a signal representative of arterial pulse pressure. The signal can be a plethysmography signal that is produced by a implantable sensor or a non-implanted sensor. The signal can be produced by a chronically implantable sensor. In one embodiment, a time derivative signal is produced based on a signal representative of arterial pulse pressure. The time derivation signal can be used to determine maximum and minium peaks of,the signal representative of arterial pulse pressure. Alternatively, HF status can be assessed directly from the time derivative signal.

Abstract: An implantable cardiac stimulation device and method optimizes pacing effectiveness of a patient's heart. A pulse generator delivers right and left pacing pulses to corresponding right and left chambers of the heart with a selected pacing delay between the right pacing pulse and the left pacing pulse wherein the selected pacing delay is within a continuum from left chamber pacing only, to simultaneous right and left chamber pacing, and to right chamber pacing only. A sensor senses a parameter, such as ventricular pressure, associated with pacing effectiveness. A control circuit selects the pacing delay, which maximizes the sensed parameter.

Abstract: The heart failure (HF) status of a patient is determined based on the frequency characteristics of a signal representative of arterial pulse pressure. The signal can be a plethysmography signal that is produced by a implantable sensor or a non-implanted sensor. The signal can be produced by a chronically implantable sensor.

Abstract: A method for monitoring the progression of the disease of a heart failure patient is provided. An implantable or other ambulatory monitor senses acoustic signals including heart and lung sounds within the patient. Significant changes in the energy content of either the heart or lung sounds is indicative of a heart failure exacerbation. This information may be used to warn the patient or healthcare providers of changes in the patient's condition warranting attention.

Abstract: Cardiac performance associated pacing parameters is improved by applying evolutionary algorithms that maintain a plurality of sets of pacing parameters for pacing a heart. An initial plurality of sets of pacing parameters are determined. A cardiac performance value is determined for each of the plurality of sets of pacing parameters. At least one set of pacing parameters is selected from the plurality of sets of pacing parameters based on the cardiac performance values. An updated plurality of sets of pacing parameters is then created based on the selected at least one set of pacing parameters. These steps (except for determining the initial plurality of sets of pacing parameters) are repeating a plurality of times, wherein each time the steps are repeated, the updated plurality of sets of pacing parameters most recently created are used.

Abstract: An implantable medical device such as a pacemaker or implantable cardioverter defibrillator or stand-alone hemodynamic monitor that uses optical plethysmography responsive to variations in arterial pulse amplitude to detect the hemodynamic status of a patient. A light source and light detector are positioned for a reflected-light configuration on a device housing and coupled to electronic circuitry in the housing via a hermetic feedthrough. In one embodiment, the light source and detector are positioned in a recess in a wall of the device housing and surrounded by an encapsulant. The source and detector are positioned for a reflected-light configuration and are preferably an infrared (IR) LED and photodiode, respectively. The source and detector may be placed in a single recess that is created when the device housing is manufactured. An opaque optical barrier is place between the source and detector, which ensures that no light passes between them without first interacting with the overlying tissue.

Abstract: A method for monitoring the progression of the hemodynamic status of a heart failure patient. An implantable or other ambulatory monitor senses the patient's electrocardiogram (ECG) and calculates R-R intervals. The R-R intervals are used to calculate a measure of heart rate variability (HRV). Significant excursions from the average of the HRV measure are indicative of a heart failure exacerbation. Alternatively, vascular plethysmography provides a measure of pulse amplitude. Significant reduction in pulse amplitude and pulse amplitude variability are indicative of a heart failure exacerbation. This information may be used to warn the patient or healthcare providers of changes in the patient's condition warranting attention.

Abstract: An implantable medical device such as a pacemaker or implantable cardioverter defibrillator or stand-alone hemodynamic monitor that uses an acoustic transducer responsive to heart sounds to detect the hemodynamic status of a patient. A hermetic housing encloses the device electronics and the device housing includes at least one substantially planar face configured to act as a diaphragm in response to acoustic waves. A transducer positioned inside the device housing provides an output signal to the device electronics responsive to vibration of the diaphragm. Embodiments of the transducer include a piezoelectric element and laser interferometer. The hemodynamic information may be used in various ways including arrhythmia discrimination and pacing and sensing optimization.

Abstract: A method and apparatus for monitoring the hemodynamic status of a patient is provided. It comprises an implantable monitor with one or a plurality of sensors configured for extravascular placement, electronic circuitry that is coupled to the sensors and processes their output, a transmitter/receiver for conveying information between the monitor and an external unit, and a patient alert which notifies the patient if medical attention should be sought. The extravascular sensors include vascular plethysmography, heart and lung sounds, thoracic impedance, and ECG. In the preferred embodiment, the radio frequency transmitter/receiver provides for the automatic telemetry of data, without requiring the active participation of the patient or clinician. Thus data can be conveyed routinely and automatically, allowing more computationally demanding analysis to be done by an external device, or allowing human review at a central location. The monitor is particularly applicable to patients with heart failure.

Abstract: A method for detecting or classifying cardiac arrhythmias using interval irregularity. The method includes the steps of detecting a patient's cardiac activity and looking at a first selected criterion such as the patient's heart rate exceeding a preset rate threshold to determine if a tachycardia is present. When the first criterion is met, a window of N successive cardiac intervals is selected for analysis. A selected number of the shortest and longest intervals are ignored and the difference between the remaining longest and shortest intervals is calculated to provide a measure of interval irregularity indicative of the origin of the cardiac rhythm. In one embodiment, a parameter n is set such that 0.ltoreq.n<N/2, and the intervals in the window are ordered from shortest to longest with the shortest being interval 1 and the longest being interval N.

Abstract: A method for characterizing the degree of similarity between phase space representations of trajectories of different dynamical systems. This method provides a computationally efficient technique for comparing different dynamical systems, or different dynamics exhibited by the same system. A first trajectory is designated as a template against which other trajectories are compared. A test trajectory is characterized by providing a measure based on determining the smallest distance between each point of the test trajectory to the template and then determining the largest of these smallest distances. The similarity of the two trajectories is quantified by establishing a lattice or grid for the phase space. For each lattice point, the distance, as given by a metric defined for the space, is calculated to the nearest point of the template trajectory. The minimum distance is retained and associated in a memory for each lattice point.

Abstract: A method of discriminating among cardiac rhythms of supraventricular and ventricular origin by exploiting the differences in their underlying dynamics reflected in the morphology of the waveform. A phase space representation of the dynamics of a waveform is obtained from the electrogram signal amplitude by using the technique of delay embedding. A first cardiac rhythm electrogram of known origin is sensed and a phase space representation or trajectory is generated for use as a template. A second or test cardiac rhythm electrogram is sensed and a phase space representation is generated from the detected waveform complex. This second phase space representation is compared to the template to distinguish between the origins of the first and second cardiac rhythms. If a test trajectory is sufficiently different from the template trajectory, the test complex is deemed to have different dynamics, and therefore be from a different origin than the template.