摘要:
An implantable cardiac stimulation device, e.g., a pacemaker or an implantable cardioverter defibrillator (ICD), is provided which prolongs the atrial refractoriness of a heart. The implantable cardiac stimulation device includes a generator that delivers pacing pulses to an atrium of a heart and a detector that detects atrial activations of the heart. An inhibitor is coupled to the detector that inhibits the generator when an atrial activation is detected within an escape interval. A generator control coupled to the generator causes the generator to deliver a primary pacing pulse to the atrium at the end of the escape interval, absent an atrial activation being detected within the escape interval, and causes the generator to deliver a secondary pacing pulse to the atrium a delay time after an atrial activation is detected within the escape interval or the delivery of a primary pacing pulse to the atrium.
摘要:
Preemptive tachyarrhythmia pacing is provided in an implantable cardiac-stimulation device, such as an implantable pacemaker or defibrillator, by modifying the operation of the implantable device in a way that minimizes the likelihood of occurrence of a tachyarrhythmia. The behavior modification is achieved through the use of an appropriate preemptive tachyarrhythmia pacing control routine stored within the memory of the device. Depending upon the needs of the patient, preemptive tachyarrhythmia pacing is invoked continuously or on demand. If invoked on demand, Preemptive tachyarrhythmia pacing is triggered only upon the sensing of one or more conditions suggest that the onset of a tachyarrhythmia is imminent. When thus invoked, preemptive tachyarrhythmia pacing remains invoked only for as long as the onset-of-a-tachyarrhythmia-is-imminent conditions persist. Various preemptive tachyarrhythmia pacing control routines are contemplated, including those based on overdrive pacing, pacing with randomicity, and mode switching. Overdrive pacing, when used, is based on an automatically-determined diurnal rate, an automatic stepped increase over the average atrial rate, or a rate set by a cycle-to-cycle negative hysteresis. Conditions which suggest the imminency of the onset of a tachyarrhythmia include, but are not limited to, a sudden change in the patient's cardiac cycle from a previously-determined normal cardiac cycle.
摘要:
An implantable cardiac stimulation device, such as a pacemaker or an implantable cardioverter-defibrillator, that includes an accelerometer-based activity sensor that processes one or more signals from the activity sensor to obtain parameters that are indicative of the heartbeat of the patient. The implantable cardiac stimulation device determines when the patient is at rest and the activity sensor provides a signal that corresponds to the acceleration of the sensor due to the heartbeat of the patient. This acceleration signal is integrated over time once to provide a contractility parameter, which is indicative of the contractility of the heart and is integrated over time twice to provide a displacement parameter, which is indicative of the displacement of the heart wall during the heartbeat. This displacement parameter is thereby indicative of the volume of blood pumped by the heart. A microprocessor uses either the contractility parameter, the displacement parameter or both to modify the delivery of therapeutic stimulation pulses to the heart.
摘要:
A single-pass A-V lead for cardiac pacing comprises a lead body having an atrial electrode and a right ventricular outflow tract (RVOT) electrode. Preformed bends in the lead body are configured such that the atrial and RVOT electrodes are biased against walls of the right atrium and the RVOT respectively. Biasing forces generated by the preformed bends help to maintain the atrial and RVOT electrodes in their respective positions following implantation. The lead advantageously permits ventricular stimulation in the RVOT, resulting in an improved sequence of ventricular activation and a corresponding increase in cardiac output. Branched and unbranched embodiments of the lead are disclosed.
摘要:
A system and method for a pacemaker are provided, for using cardiac wall motion sensor signals to provide hemodynamically optimal pacing therapy to patient at rest, and for providing rate-responsive pacing therapy. The cardiac wall motion sensor signals are provided by an implantable lead that incorporates an accelerometer for measuring cardiac mechanical activity. The cardiac wall motion sensor signals are processed to derive cardiac wall velocity signals and cardiac wall displacement signals. The derived signals are further processed to derive physiologic parameters indicative of cardiac performance, including stroke volume, contractility, pre-ejection period, and ejection time. The physiological parameters, in turn, are used by the pacemaker to provide hemodynamically optimal pacing therapy at rest, and rate-responsive pacing therapy.
摘要:
An implantable dual-chamber pacemaker programmed to operate primarily in an atrial tracking mode is provided, where the pacemaker includes an atrial rate smoothing filter for producing a filtered atrial rate from an intrinsic atrial rate, and where the pacemaker automatically switches its mode of operation from the atrial tracking mode to a non-atrial tracking mode in the event the filtered atrial rate exceeds a prescribed upper rate limit. The pacemaker switches from a primary set of operational parameter settings for the primary mode, to an alternate set of operational parameters for the alternate mode when the mode is switched from the primary mode to the alternate mode. The pacemaker also includes the capability of recording and storing mode switching events and data pertaining to the mode switching events.
摘要:
A rate-responsive pacemaker measures a patient's level of activity and stores the results in an activity level histogram. The patient's average level of activity is maintained as a running average. Based on a prescribed base pacing rate, a prescribed maximum pacing rate, the average level of activity, and the measured levels of activity stored in the activity level histogram, the rate-responsive pacemaker automatically calculates the slope of the pacemaker transfer function. An activity deviation histogram is also maintained. Analysis of the activity deviation histogram allows the pacemaker to determine if the patient was usually inactive for an extended period of time, and to inhibit an automatic slope calculation under such conditions. If a patient desires to reach a prescribed target heart rate during exercise, the slope may be calculated using the target heart rate and a prescribed fraction of time each week that the patient devotes to exercise.
摘要:
A leadless intra-cardiac medical device senses cardiac activity from multiple chambers and applies cardiac stimulation to at least one cardiac chamber and/or generates a cardiac diagnostic indication. The leadless device may be implanted in a local cardiac chamber (e.g., the right ventricle) and detect near-field signals from that chamber as well as far-field signals from an adjacent chamber (e.g., the right atrium).
摘要:
Techniques are provided for use with an implantable medical device for detecting and assessing heart failure and for controlling cardiac resynchronization therapy (CRT) based on impedance signals obtained using hybrid impedance configurations. The hybrid configurations exploit right atrial (RA)-based impedance measurement vectors and/or left ventricular (LV)-based impedance measurement vectors. In one example, current is injected between the device case and a ring electrode in the right ventricle (RV) or RA. RA-based impedance values are measured along vectors between the device case and an RA electrode. LV-based impedance values are measured along vectors between the device case and one or more electrodes of the LV. Heart failure and other cardiac conditions are detected and tracked using the measured impedance values. CRT delay parameters are also optimized based impedance. In this manner, multiple hybrid impedance measurement configurations are exploited whereby different vectors are used to inject current and measure impedance.