News Column

Patent Issued for Automatic Modulation of Pacing Timing Intervals Using Beat to Beat Measures

July 7, 2014

By a News Reporter-Staff News Editor at Cardiovascular Week -- Cardiac Pacemakers, Inc. (St. Paul, MN) has been issued patent number 8761879, according to news reporting originating out of Alexandria, Virginia, by NewsRx editors (see also Cardiac Pacemakers, Inc.).

The patent's inventors are Hopper, Donald L. (Maple Grove, MN); Yu, Yinghong (Shoreview, MN); Shuros, Allan C. (Saint Paul, MN); Arcot-Krishnamurthy, Shantha (Vadnais Heights, MN); Carlson, Gerrard M. (Champlin, MN); Stahmann, Jeffrey E. (Ramsey, MN).

This patent was filed on June 11, 2013 and was published online on June 24, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "When functioning normally, the heart produces rhythmic contractions and is capable of pumping blood throughout the body. The heart has specialized conduction pathways in both the atria and the ventricles that enable the rapid conduction of excitation impulses (i.e. depolarizations) from the SA node throughout the myocardium. These specialized conduction pathways conduct the depolarizations from the SA node to the atrial myocardium, to the atrioventricular node, and to the ventricular myocardium to produce a coordinated contraction of both atria and both ventricles.

"The conduction pathways synchronize the contractions of the muscle fibers of each chamber as well as the contraction of each atrium or ventricle with the opposite atrium or ventricle. Without the synchronization afforded by the normally functioning specialized conduction pathways, the heart's pumping efficiency is greatly diminished. Patients who exhibit pathology of these conduction pathways can suffer compromised cardiac output.

"Cardiac rhythm management devices have been developed that provide pacing stimulation to one or more heart chambers in an attempt to improve the rhythm and coordination of atrial and/or ventricular contractions. Cardiac rhythm management devices typically include circuitry to sense signals from the heart and a pulse generator for providing electrical stimulation to the heart. Leads extending into the patient's heart chamber and/or into veins of the heart are coupled to electrodes that sense the heart's electrical signals and for delivering stimulation to the heart in accordance with various therapies for treating cardiac arrhythmias.

"Pacemakers are cardiac rhythm management devices that deliver a series of low energy pace pulses timed to assist the heart in producing a contractile rhythm that maintains cardiac pumping efficiency. Pace pulses may be intermittent or continuous, depending on the needs of the patient. There exist a number of categories of pacemaker devices, with various modes for sensing and pacing one or more heart chambers.

"Pacing therapy has been used in the treatment of heart failure (HF). HF causes diminished pumping power of the heart, resulting in the inability to deliver enough blood to meet the demands of peripheral tissues. HF may cause weakness, loss of breath, and build up of fluids in the lungs and other body tissues. HF may affect the left heart, right heart or both sides of the heart. For example, HF may occur when deterioration of the muscles of the heart produce an enlargement of the heart and/or reduced contractility. The reduced contractility decreases the cardiac output of blood and may result in an increased heart rate. In some cases, HF is caused by unsynchronized contractions of the left and right heart chambers, denoted atrial or ventricular dysynchrony. Particularly when the left or right ventricles are affected, the unsynchronized contractions can significantly decrease the pumping efficiency of the heart.

"Pacing therapy to promote synchronization of heart chamber contractions to improve cardiac function is generally referred to as cardiac resynchronization therapy (CRT). Some cardiac pacemakers are capable of delivering CRT by pacing multiple heart chambers. Pacing pulses are delivered to the heart chambers in a sequence that causes the heart chambers to contract in synchrony, increasing the pumping power of the heart and delivering more blood to the peripheral tissues of the body. In the case of dysynchrony of right and left ventricular contractions, a biventricular pacing therapy may pace one or both ventricles. Bi-atrial pacing or pacing of all four heart chambers may alternatively be used."

Supplementing the background information on this patent, NewsRx reporters also obtained the inventors' summary information for this patent: "Embodiments are directed to systems and methods for automatic adjustment of pacing intervals. One embodiment is directed to a method for delivering pacing therapy to a heart. For each cardiac cycle, one or both of an atrioventricular (A-V) timing interval and an atrial (A-A) timing interval are modulated to oppose beat-to-beat ventricular (V-V) timing variability. Pacing therapy is delivered using the modulated timing intervals.

"In some implementations, a sensor indicated pacing rate may be determined based on the patient's physiological status and the timing intervals of the indicated pacing rate may be modulated to oppose beat-to-beat ventricular (V-V) timing variability. Physiological status is determined, for example, by sensing metabolic need, autonomic tone and/or hemodynamic status.

"In addition to modulating the A-V and A-A intervals, one or more of an interventricular delay interval, an intraventricular delay interval, an interatrial delay interval, or an intraatrial delay interval may also be modulated to improve cardiac function.

"Modulation of the timing intervals may be effected to produce optimal stroke volume for each beat. As the base pacing rate is varied to produce physiologic respiratory sinus arrhythmia, the timing intervals may also be modulated based on respiration. An amount or degree of the modulation may be a function of exertion level or heart rate. Independent modulation of the timing intervals may be based on one or more parameters that affect heart function. The parameters may include, for example, one or more of stroke volume, blood pressure, blood flow, cardiac contractility, baroreflex, chemoreflex and/or other parameters.

"One implementation involves sensing a physiological parameter of a right heart chamber during a cardiac cycle. The timing intervals are independently modulated for a next cardiac cycle based on the sensed right heart chamber parameter.

"The timing intervals can be initially determined using an algorithm designed to optimize the pacing intervals for a particular type of disorder experienced by the patient, such as heart failure. For example, modulating the timing intervals may involve modulating an atrioventricular interval and/or interventricular delay interval and/or other timing intervals to provide cardiac resynchronization therapy.

"Another embodiment is directed to a cardiac rhythm management device. The device includes a sensor system configured to sense one or more physiological parameters. For each cardiac cycle, a therapy control processor independently modulates one or more of atrial (A-A) timing interval and an atrioventricular (A-V) timing interval to oppose ventricular (V-V) timing variability based on the sensed physiological parameters. A therapy delivery system delivers pacing to the heart using the independently modulated timing intervals. The sensor system may include, for example, a respiration sensor and the therapy control processor may control deliver of pacing based on respiration cycle phase to mimic natural respiratory sinus arrhythmia. Modulation of the pacing timing intervals may also occur based on respiration cycle phase.

"According to one aspect, the therapy control processor is configured to modulate the A-A and A-V timing intervals to cancel fluctuations in the V-V intervals within one beat at elevated heart rates. In addition, the therapy control processor may be further configured to modulate one or more of an interventricular timing interval, an intraventricular timing interval, an interatrial timing interval, and an intraatrial timing interval.

"In one implementation, the sensor system is configured to sense a physiological parameter of a right heart chamber during a cardiac cycle. The therapy control processor independently modulates the timing intervals of the indicated pacing rate for a next cardiac cycle based on the sensed right heart chamber parameter. Rate dependent modulation of the pacing timing intervals may be used to produce optimal stroke volume for each cardiac beat at elevated heart rates.

"In certain configurations, the therapy control processor is configured to control delivery of non-excitory electrical stimulation to alter myocardial contractility. The therapy delivery system is configured to deliver the non-excitory electrical stimulation under control of the therapy control processor.

"The above summary is not intended to describe each embodiment or every implementation of the present disclosure. Advantages and attainments, together with a more complete understanding of the embodiments, will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings."

For the URL and additional information on this patent, see: Hopper, Donald L.; Yu, Yinghong; Shuros, Allan C.; Arcot-Krishnamurthy, Shantha; Carlson, Gerrard M.; Stahmann, Jeffrey E.. Automatic Modulation of Pacing Timing Intervals Using Beat to Beat Measures. U.S. Patent Number 8761879, filed June 11, 2013, and published online on June 24, 2014. Patent URL:

Keywords for this news article include: Therapy, Cardiology, Heart Failure, Cardiac Pacemakers Inc..

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Source: Cardiovascular Week

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