Method and apparatus for controlling cardiac resynchronization therapy using cardiac impedance
First Claim
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1. A system for monitoring a heart having first and second ventricles, the system comprising:
- a device including;
an impedance measurement circuit, including terminals configured to be coupled to electrodes in association with the first ventricle to measure a first impedance signal that is substantially indicative of a volume of the first ventricle as the first ventricle expands and contracts during a cardiac cycle of the heart and in association with the second ventricle to measure a second impedance signal that is substantially indicative of a volume of the second ventricle as the second ventricle expands and contracts during the cardiac cycle; and
a processor, coupled to the impedance measurement circuit to receive information about the first and second impedance signals over the cardiac cycle, the processor configured to perform instructions to detect a first peak of the first impedance signal during the cardiac cycle, detect a second peak of the second impedance signal during the cardiac cycle, determine a first type point on the first impedance signal, the first type point being a function of the first peak, determine a second type point on the second impedance signal, the second type point being a function of the second peak, compute a first slope of the first impedance signal at the first type point on the first impedance signal, compute a second slope of the second impedance signal at the second type point on the second impedance signal, and produce a first resynchronization parameter using a difference between the first slope and the second slope, the first resynchronization parameter indicative of a degree of cardiac mechanical synchrony or asynchrony between the first and second ventricles.
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Abstract
This document discusses, among other things, systems, devices, and methods for measuring cardiac impedances and producing one or more resynchronization index parameters each indicative of a cardiac synchrony or asynchrony using the measured cardiac impedances. In one example, the one or more resynchronization index parameters are used to adjust one or more pacing parameters of a cardiac resynchronization therapy.
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Citations
20 Claims
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1. A system for monitoring a heart having first and second ventricles, the system comprising:
a device including; an impedance measurement circuit, including terminals configured to be coupled to electrodes in association with the first ventricle to measure a first impedance signal that is substantially indicative of a volume of the first ventricle as the first ventricle expands and contracts during a cardiac cycle of the heart and in association with the second ventricle to measure a second impedance signal that is substantially indicative of a volume of the second ventricle as the second ventricle expands and contracts during the cardiac cycle; and a processor, coupled to the impedance measurement circuit to receive information about the first and second impedance signals over the cardiac cycle, the processor configured to perform instructions to detect a first peak of the first impedance signal during the cardiac cycle, detect a second peak of the second impedance signal during the cardiac cycle, determine a first type point on the first impedance signal, the first type point being a function of the first peak, determine a second type point on the second impedance signal, the second type point being a function of the second peak, compute a first slope of the first impedance signal at the first type point on the first impedance signal, compute a second slope of the second impedance signal at the second type point on the second impedance signal, and produce a first resynchronization parameter using a difference between the first slope and the second slope, the first resynchronization parameter indicative of a degree of cardiac mechanical synchrony or asynchrony between the first and second ventricles. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system for monitoring a heart having first and second ventricles, the system comprising:
a device comprising; an impedance measurement circuit, including terminals configured to be coupled to electrodes in association with the first ventricle to measure a first impedance signal that is substantially indicative of a volume of the first ventricle as the first ventricle expands and contracts during a cardiac cycle of the heart and in association with the second ventricle to measure a second impedance signal that is substantially indicative of a volume of the second ventricle as the second ventricle expands and contracts during the cardiac cycle; a depolarization detector to detect a first ventricular depolarization of the first ventricle and a second ventricular depolarization of the second ventricle during the cardiac cycle; and a processor, coupled to the impedance measurement circuit to receive information about the first and second impedance signals over the cardiac cycle, the processor configured to perform instructions to detect a first peak of the first impedance signal during the cardiac cycle, detect a second peak of the second impedance signal during the cardiac cycle, measure a first time interval between the first ventricular depolarization and the first peak, measure a second time interval between the second ventricular depolarization and the second peak, and produce a first resynchronization parameter using a difference between the first time interval and the second time interval, the first peak being a first point at which the first impedance signal reaches a first maximum value, the second peak being a second point at which the second impedance signal reaches a second maximum value, the first resynchronization parameter indicative of a degree of cardiac mechanical synchrony or asynchrony between the first and second ventricles. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
Specification