St. Jude Medical Ab

Berit Larsson

Nils Holmström

Sven-Erik Hedberg

Karin Järverud

Martin Obel

Peter Andersson

Åsa Uhrenius

Feresteh Shojaei

Asa Uhrenius

Goran Budgifvars

Göran Budgifvars

Magnus Öhman

&angst;sa Uhrenius

G&ouml;ran Budgifvars

Feresteh Shojael

G&ouml;ran Budgivars

An implantable cardiac stimulator, such as a cardioverter defibrillator, is operable in an autocapture mode. Following the delivery of a defibrillation or cardioversion shock, the stimulator switches from the autocapture mode to a post-shock mode, in which predetermined pacing pulse parameter settings are used for the delivery of pacing pulses. Following the expiration of a predetermined time interval, which may be extendable, the stimulator switches back to the autocapture mode.

Implantable cardioverter defibrillator with automatic switching to a pre-set pacing mode following delivery of a shock

A heart stimulator has a pulse generator which emits stimulation pulses of different amplitudes, which are delivered to a patient's heart via a lead connected to the pulse generator. The pulse generator is controlled by a control unit, in a procedure for determining a stimulation threshold value, to emit stimulation pulses of successively unidirectionally changing amplitudes. Each stimulation pulse is followed by a test pulse having a predetermined high, constant amplitude delivered in a period corresponding to the refractory period after the preceding stimulation pulse. Each test pulse has an amplitude sufficient to capture a non-refractory heart. A measurement unit is connected to the electrode lead, and measures a signal picked up by the lead after each test pulse. The measured signals are supplied to a comparator, which compares the signals following the test pulses with each other. A significant change in the measured signal after the test pulses indicates that the amplitude of the stimulation pulses has passed the threshold value.

Heart stimulator with evoked response detector and an arrangement for determining the stimulation threshold

The invention relates to an implantable dual chamber heart stimulator comprising a stimulation threshold detector arranged to activate a stimulation threshold search algorithm to perform a stimulation threshold search at predetermined time intervals in order to determine a stimulation threshold of heart tissue. The heart stimulator comprises an AV-interval generator adapted to generate an AV-interval and a controller arranged to temporarily shorten the AV-interval to a threshold search AV-interval when this threshold search is performed. The heart stimulator further comprises AR/PR-interval measure adapted to measure the actual AR/PR conduction time in which this threshold search AV-interval is set by the AV-interval generator and the controller to the measured AR/PR-interval shortened by a predetermined time.

Implantable dual chamber heart stimulator

An implantable heart stimulator has an AV-interval generator which generates a variable AV-interval and which is provided with a predetermined basic AV-interval. The heart stimulator has a counter that counts the number of times the AV-interval is changed in response to a fusion avoidance algorithm or a stimulation threshold search algorithm during a predetermined time period. The basic AV-interval is changed if the number of times counted by the counter is greater than a predetermined value.

Implantable heart stimulator

A heart stimulator has a pulse generator which emits stimulation pulses for delivery to the heart of a patient through a lead connected to the pulse generator and introduced into the heart. The heart stimulator has an evoked response detector which includes a measuring unit for measuring electrode signals picked up by the lead. An averaging unit is supplied with the electrode signals and forms an average value of the amplitude of the respective electrode signals for each heartbeat. A comparator in the evoked response detector compares the average value for each heartbeat with two predetermined limit values and emits a signal indicating that the electrode signal results from a fusion beat if the average values are between the two limit values.

Evoked response detector, averaging the value of the amplitude of the picked-up electrode signal

An implantable heart stimulator has a control and detection circuit which operates a pulse generator which emits stimulation pulses which are delivered to cardiac tissue via at least one electrode lead adapted for insertion in the heart of a patient. The electrode lead has an electrode surface which is intended to be in contact with heart tissue. The control and detection circuit performs a microinstability test by causing the pulse generator to emit a predetermined number of stimulation pulses, each having the same stimulation energy. The control and detection circuit determines a microinstability test value, representing a measure of the contact between the electrode surface and the heart tissue, as a ratio of a number of stimulation pulses, within said predetermined number of stimulation pulses, for which capture is detected, and the predetermined number of stimulation pulses.

Implantable heart stimulator with microinstability testing for electrode contact with tissue

A heart stimulator has an evoked response detector which determines evoked response in the presence of polarization. To determine the magnitude of the polarization for different stimulation amplitudes, the electrode signals picked up by a lead after the delivery of a stimulation pulse having a selected amplitude are measured. A polarization signal is obtained from the picked up signals, and this polarization signal, with modification, is subtracted from signals picked up following subsequently emitted stimulation pulses. Dependent on the subtraction result, a determination is made as to whether an evoked response has occurred.

Heart stimulator having an evoked response detector

A heart stimulator has an evoked response detector for determining evoked response in the presence of polarization. The heart stimulator produces stimulation pulses of different amplitudes via a lead introduced to the heart of the patient. The evoked response detector measures an electrode signal picked up by the lead after each stimulation pulse. In order to set an evoked response threshold value, the pulse generator of the stimulator is controlled to deliver at least two stimulation pulses with different amplitudes, at least one of these stimulation pulses having a high amplitude that exceeds the stimulation threshold value. A measuring unit in the evoked response detector measures the picked up electrode signals, and a calculating unit in the evoked response detector calculates the polarization for the high stimulation amplitude and identifies a measured electrode signal for the lowest possible stimulation amplitude from the measured electrode signals. The evoked response detector also has an analyzing unit which sets a threshold value for the measured electrode signal from the calculated polarization and lowest possible stimulation amplitude.

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Danderyd, Sweden

Berit Larsson