News Column

"Pacing Configuration for an Implantable Medical Device" in Patent Application Approval Process

September 11, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- A patent application by the inventors RENESTO, Fabrizio (Borgofranco d'lvrea, IT); GIORGIS, Lionel (Saint Brieuc, FR), filed on April 28, 2014, was made available online on August 28, 2014, according to news reporting originating from Washington, D.C., by VerticalNews correspondents.

This patent application has not been assigned to a company or institution.

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to 'active implantable medical devices' as defined by the 20 Jun. 1990 Directive 90/385/EEC of the Council of the European Communities, and more particularly to those devices that continuously monitor a patient's heart rhythm and deliver to the heart, if necessary, electrical pulses for joint and permanent stimulation of the left and the right ventricles, so as to resynchronize them, said technique being known as Cardiac Resynchronization Therapy ('CRT') or Bi-Ventricular Pacing ('BVP').

"Cardiac resynchronization is known whereby a patient is implanted with a device equipped with electrodes to stimulate various sites in both ventricles (often called a CRT device or CRT pacemaker). The CRT device typically applies between the respective moments of stimulation of the left and right ventricles a delay that is called an 'interventricular delay' (VVD) which VVD is adjusted to resynchronize the contraction of both ventricles to optimize the patient's hemodynamic status.

"A CRT pacemaker is for example disclosed in EP 1108446 A1 and its counterpart U.S. Pat. No. 6,556,866 (both assigned to Sorin CRM S.A.S., previously known as ELA Medical), which describes a CRT device for applying between the two ventricular pacing sites a variable VVD, adjusted to resynchronize the contractions of the ventricles with a fine optimization of the patient's hemodynamic status. The VVD may be zero (meaning that the left and right ventricles are stimulated essentially simultaneously), positive (meaning that the left ventricle is stimulated after the right ventricle) or negative (meaning that the right ventricle is stimulated after the left ventricle).

"Clinical studies have often observed a dramatic improvement in results for patients diagnosed with heart failure that is not improved by conventional therapy, because the parameters of the CRT therapy have been precisely adjusted according to the patient and to the nature of the patient's disorder.

"But the implementation of CRT devices remains a very delicate intervention for the practitioner, because of the many choices that must be made. First, it must be determined for each of the leads the best stimulation site. The physical locations of the pacing electrodes for each lead relative to the myocardial tissue are called 'pacing sites'; generally, these pacing sites can only be selected at implantation, by appropriate positioning of the electrodes. It is important to verify the effectiveness of the selected pacing sites, due to the possible influence of long-term efficacy of the resynchronization therapy. In some cases, the CRT device has several multi-site electrodes placed in the same cavity, and a change of pacing site(s) for delivering stimulation pulses in this cavity is possible by internal switching of the device.

"In any case, during the intervention, the practitioner tests several possible pacing sites by successive repositioning of the lead to find the one that he believes is the most appropriate.

"Another aspect of the development of these CRT devices is the increasing number of electrodes, especially for 'multisite' devices that allow selecting the pacing sites used for the delivery of stimulation pulses and detection of myocardial potentials (e.g., from spontaneous cardiac events) and optimizing the operation of the CRT device.

"The increasing number of electrodes can also result from the presence at the same level of the lead of several sectorial electrodes (electrodes specifically directed in a radial direction relative to the lead, at the pacing site), with the possibility to select one or the other of these sectorial electrodes to optimize the delivery of pulses to the selected pacing site. This is particularly true for leads implanted in the coronary venous system, for indirect stimulation of a left cavity: with several sectorial electrodes, it is possible to select one that is turned towards the epicardium wall facing the cavity in contact with this wall.

"Second, with the development of implantable medical devices for stimulation of more than two ventricular sites, it is necessary to determine whether this * * * 'tri-ventricular' or 'multi-ventricular' mode of stimulation is or is not preferable to a conventional 'bi-ventricular' pacing mode.

"Thus, the practitioner may be faced with a choice between a standard mode of bi-ventricular pacing (right and left ventricles), a tri-ventricular pacing mode (simultaneous stimulation by three electrodes, with an additional electrode in the right or left cavity), or even multi-ventricular (with multi-electrode leads for which multiple electrodes of the same lead are used concurrently). By appropriate switching, the practitioner can choose the most appropriate stimulation mode, but the number of possible configurations increases very rapidly with the increase of the electrodes, making the task all the more difficult for the practitioner, faced with a choice between a large number of different configurations.

"Third, the device should be set properly, including the atrioventricular delay (AVD) and interventricular delay (VVD).

"The many opportunities arising from these various choices are referred to as 'pacing configurations.'

"Indeed, it appears that today, even with full implementation of procedures, there are approximately 30% of patients who do not respond to CRT therapy, with serious consequences that can be imagined in terms of quality of life, hospitalizations for heart failure and reduced life expectancy.

"Most studies now focus on methods to treat this refractory patient population by testing new stimulation configurations, and seeking to optimize the stimulation setting, during the implantation as well as on an ongoing basis, by periodic reassessments.

"There is thus a real need for a technique to evaluate, according to a simple, rapid, automated and precise method, the impact of the choice of the stimulation sites and of the parameters of CRT therapy, especially the AVD and VVD, so as to optimize the patient's hemodynamic status.

"The reference technique for the adjustment of CRT stimulation parameters is an assessment by echocardiography with estimation of the characteristic delays of the systole, in particular the delay of opening of the aortic valve. This procedure, which must be implemented in hospitals and by qualified personnel, is time consuming and expensive and cannot be applied as often as would be useful or necessary. In addition, it is not easy to perform ultrasound measurements during the implantation procedure, as the sterile field does not allow easy access to the patient's chest with the ultrasound probe.

"Other techniques have been proposed to evaluate the effectiveness of the choice of stimulation pacing sites and of the setting of CRT therapy parameters. Thus, EP 1736203 A1 and its US counterpart U.S. Pat. No. 7,664,547 (both assigned to Sorin CRM S.A.S, previously known as ELA Medical) describe a CRT device that uses for this purpose the parameters related to endocardial acceleration (hereinafter 'EA') to determine an optimal pacing configuration, at the time of implantation or thereafter.

"Indeed, it may be necessary to reassess these choices later, after the initial implantation, and eventually readjust the settings. The benefits provided by CRT therapy can ultimately lead to change the initial configuration and setup of the stimulation.

"Indeed, several clinical studies have shown that endocardial acceleration is a parameter that accurately and in real-time reflects phenomena related to the movements of the heart chamber, and can therefore provide comprehensive information on the mechanical heart, both in the case of normal operation and in the case of a deficient operation. Endocardial acceleration is for example measured by an accelerometer integrated into an endocardial lead, as described for example in EP 0515319 A1 and its US counterpart U.S. Pat. No. 5,304,208 (both assigned to Sorin Biomedica Cardio SpA).

"WO 2006/049538 A1 (St. Jude Medical AB) describes a known technique to evaluate a physiological parameter that reflects the hemodynamic performance of the heart for a given stimulation configuration, from various sensors (pressure, acceleration, acoustic) placed on one or more leads, some of them being possibly repositioned; thus the signal delivered by these sensors depends on the current position of the lead and cannot be a reliable reference. However, the proposed technique has a number of drawbacks, including the fact that the optimization is based on the analysis of a single physiological parameter (e.g., cardiac output, stroke volume). However, some patients may be more or less sensitive to either of these parameters, which is not always the same from one patient to another because of the specific response of the patient, his pathology and the evolution of it. Further, the analyzed parameter is not necessarily the most relevant relatively to the changes in the stimulation configuration."

In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventors' summary information for this patent application: "It is, therefore, an object of the present invention to propose a system or apparatus that can help the practitioner find the pacing configuration that is the most appropriate, especially to enable the practitioner to evaluate the effectiveness of modifications to pacing configurations due to repositioning of the lead and, where appropriate, selections of additional leads (bi-ventricular, tri-ventricular or multiventricular pacing) or switching of electrodes in the case of a multi-electrode lead.

"It is another object of the present invention to provide a technique for evaluating the pacing configuration with an increased sensitivity and specificity compared to what has been proposed to date, including the EP 1736203 A1 cited above, particularly with respect to changes of position of the pacing electrodes.

"It is another object of the present invention to define indexes of cardiac hemodynamic performance of the patient, to optimize the positioning of the leads and the choice of configurations of the CRT pacemaker during the implantation procedure, and the possible reprogramming of any parameter after the CRT device implantation.

"Another object of the present invention is to provide complete equipment, made available to the implanting practitioner, which is specifically adapted to the selection of stimulation pacing sites during the process of implantation of the leads and of a bi-ventricular, tri-ventricular or multi-ventricular device.

"To this end, the present invention is broadly directed to a system for seeking an optimal pacing configuration for an active medical device (implantable cardiac prosthesis or external device used temporarily) implementing CRT by bi-, tri- or multiventricular pacing, this system including, as taught by and disclosed in EP 1736203 A1 cited above, to which one skilled in the art is referred: means for ventricular pacing, able to deliver stimulation pacing pulses to be applied to electrodes located respectively at least at one right ventricular pacing site and at least at one left ventricular pacing site according to a predetermined pacing configuration that is current and modifiable; an acceleration sensor for delivering an endocardial acceleration (EA) signal representative of cyclical contractions and relaxations of the heart, and means for isolating and preprocessing in the EA signal during a given cardiac cycle between two successive ventricular events: (i) an EA1 component corresponding to the first peak of endocardial acceleration associated with the isovolumetric ventricular contraction, and (ii) an EA2 component corresponding to the second peak of endocardial acceleration associated with the isovolumetric ventricular relaxation.

"It is another aspect of the present invention to assess the efficiency of stimulation based on a 'performance index' compiled from parameters from a signal delivered by an endocardial acceleration sensor, including: the amplitude of the first endocardial acceleration peak, the duration of this peak, and the duration of systole (i.e., the interval between the first and second peaks of endocardial acceleration).

"Preferably, a system in accordance with the present invention further includes means for evaluating the effectiveness of the current pacing configuration, including: means for extracting at least two parameters from the isolated and preprocessed EA1 and EA2 components: means for combining said at least two parameters in a composite index representative of the effectiveness of that current pacing configuration; means for determining a plurality of values of said composite index for a corresponding plurality of different pacing configurations, and means for determining a preferred pacing configuration from said plurality of values of said composite index by searching for an optimum of that composite index.

"In a preferred embodiment, said at least two parameters characteristic of the EA1 and EA2 components are parameters selected from among the group consisting of: PEA1=value of the peak-to-peak EA1 component; TstEA1=duration of occurrence of the beginning of the EA1 component represented by the time interval between i) a temporal marker of the beginning of the cardiac cycle and ii) the crossing of an energy envelope threshold of the EA1 component; LargEA1=time interval between i) said crossing of the energy envelope threshold, and ii) the instant of the peak of said energy envelope of the EA1 component; and Syst=duration of systole, represented by the time interval between the beginning of the EA1 component and the beginning of the EA2 component.

"In one embodiment, the composite index is an index selected from among the group consisting of:

"Ind1=(TstEA1.times.LargEA1)/(Syst.times.PEA1);

"Ind2=(TstEA1.times.LargEA1)/[(Syst-LargEA1).times.PEA1];

"Ind3=(TstEA1.times.LargEA1)/(Syst); and/or

"Ind4=(TstEA1)/(PEA1),

"said optimum being a minimum of the indexes.

"The system advantageously comprises an atrial lead carrying the endocardial acceleration sensor, and left and right ventricular leads with their distal electrode respectively defining the pacing site(s) for right and left ventricular pacing according to the current pacing configuration. It may also include an additional, right or left, ventricular lead carrying at its distal end electrodes for definition of at least one additional pacing site for ventricular pacing, defining the current pacing configuration in combination with the right and left ventricular pacing site(s).

"Another embodiment of the present invention is directed to a system including: An implantable active medical device capable of delivering CRT by bi-, tri- or multi-ventricular stimulation; An atrial lead carrying an endocardial acceleration sensor; Right and left ventricular leads respectively carrying distal electrodes for definition of the right and left ventricular pacing sites according to a current pacing configuration; Optionally an additional, right or left, ventricular lead carrying at its distal end electrodes for definition of at least one additional ventricular pacing site, defining the current pacing configuration in combination with the right and left ventricular pacing site(s); An external device for providing cardiac detection/stimulation for a patient; An interface unit comprising means for processing an EA signal, provided by said EA sensor, and means for coupling the external equipment to the atrial and ventricular leads; and External programmer means, coupled to the interface housing for reception of the processed EA signal, including the means for evaluating the effectiveness of the pacing configuration.

"One embodiment relates to a memory device having instructions stored thereon that, when executed by a processor of an implantable medical device, cause the implantable medical device to perform operations. The operations include generating, using an acceleration sensor of the implantable medical device, an endocardial acceleration (EA) signal representative of activity of a patient's heart. The operations further include identifying within the EA signal a first EA signal component corresponding to a first peak of endocardial acceleration and a second EA signal component corresponding to a second peak of endocardial acceleration. The operations also include extracting from at least one of the first EA signal component and the second EA signal component at least two characteristic parameters, the at least two characteristic parameters relating to at least two different types of characteristics of the at least one of the first EA signal component and the second EA signal component. The at least two different types of characteristics to which the at least two characteristic parameters relate are selected from among the following: a peak-to-peak amplitude (PEA1) of the first EA signal component; a first time interval (TstEA1) between a beginning of a cardiac cycle and a beginning of the first EA signal component; a second time interval (LargEA1) between the beginning of the first EA signal component and a peak associated with the first EA signal component; or a third time interval (Syst) representative of a duration of a systole, the third time interval between the beginning of the first EA signal component and a beginning of the second EA signal component. The operations may further include generating a composite index based on a combination of the at least two characteristic parameters, wherein the composite index is selected from among the following:

"Ind1=(TstEA1.times.LargEA1)/(Syst.times.PEA1);

"Ind2=(TstEA1.times.LargEA1)/[(Syst-LargEA1).times.PEA1];

"Ind3=(TstEA1.times.LargEA1)/(Syst); or

"Ind4=(TstEA1)/(PEA1);

"The operations may further include determining a plurality of values of the composite index for a plurality of pacing configurations. The operations may further include selecting a current pacing configuration for the implantable medical device from among the plurality of pacing configurations based on the plurality of values of the composite index.

DRAWINGS

"FIG. 1 is a series of three timing diagrams illustrating various signals characterizing the cardiac activity during a given cycle;

"FIG. 2 illustrates, in more detail, the shape of the endocardial acceleration signal during a given cardiac cycle, with the various parameters used for the implementation of the invention;

"FIG. 3 schematically illustrates the various elements of a preferred embodiment of the present invention in the form of functional block diagrams, of the equipment available to the practitioner at the time of implantation for the selection of the pacing sites of the invention;

"FIG. 4 illustrates a diagram displayed by the interface of FIG. 3 for selection of the pacing sites;

"FIG. 5 is a flow chart describing the various stages of a preferred method of implementing the elements of the present invention; and

"FIG. 6 is a flow chart describing the various stages of the long-term patient's monitoring by analysis of the evolution of one or more of the indexes calculated according to a preferred embodiment of the present invention."

URL and more information on this patent application, see: RENESTO, Fabrizio; GIORGIS, Lionel. Pacing Configuration for an Implantable Medical Device. Filed April 28, 2014 and posted August 28, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=1444&p=29&f=G&l=50&d=PG01&S1=20140821.PD.&OS=PD/20140821&RS=PD/20140821

Keywords for this news article include: Cardio Device, Cardiology, Cardiovascular Physiological Phenomena, Cardiovascular Physiological Processes, Hemodynamics, Medical Devices, Myocardial Contraction, Pacemakers, Patents, Systole, Therapy.

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