The assignee for this patent application is Sorin Crm S.a.s.
Reporters obtained the following quote from the background information supplied by the inventors: "The present invention relates to 'implantable medical devices' such as those defined by the
"ATP therapy is indicated to treat certain arrhythmias caused by disturbances of the action potentials in the atrium. Therapy by stimulation of the atrium can be applied in case of detection of an abnormal fast heart rhythm of atrial origin (atrial fibrillation or other atrial arrhythmia). It will be called hereinafter 'antitachycardia atrial pacing' (also referred to as 'ATP-A').
"Overall, the decision to apply antitachycardia therapy, and the choice of this therapy (whether an application of a defibrillation shock, or an ATP therapy or a similar type antitachycardia stimulation) is made by an algorithm for detecting and classifying different tachyarrhythmias based on several discrimination criteria. These criteria include, for example, the ventricular rate, the stability of ventricular intervals (namely, RR intervals), the analysis of the atrioventricular association revealed by the stability of the PR interval, and the start-up mode of the tachycardia (presence of an abrupt acceleration and identity of the cavity of origin, ventricular or atrial).
"Some of these tachycardias can be treated by activating an antitachycardia atrial pacing (ATP-A).
"However, when an antitachycardia pacing in the atrium therapy is delivered, the device is unable to detect ventricular events. This is because the duration of the post atrial pacing ventricular refractory periods, relative to the interval between two consecutive atrial stimulations, effectively blocks any detection of any ventricular depolarization.
"Further, ventricular contractions during these arrhythmia episodes can be very irregular or even non-existent, causing the onset of ventricular pauses. It is therefore important to maintain a detection of the ventricular activity during the application of antitachycardia atrial pacing so as, if necessary, to stimulate the ventricle if no spontaneous ventricular event is detected. As will be discussed below, the term 'antibradycardia ventricular pacing' refers to this conditional stimulation of the ventricle.
"More specifically, disturbances of the atrium and/or ventricle action potentials can cause ventricular arrhythmias. These are generally classified as Supraventricular Tachycardias (SVT) or Ventricular Tachycardias (VT). The SVT is characterized by an abnormal rhythm in the atrium or at the atrioventricular node. The most common SVTs are atrial flutters and atrial fibrillations:
"During atrial flutters, the action potentials have a circular atrial path, causing an acceleration of the rate of contraction of the atrium with atrioventricular intermittent conduction (2:1 or 3:1, for example);
"As for atrial fibrillation, these are common arrhythmias that correspond to uncontrolled atrial depolarization, leading to a sometimes rapid and often irregular activity of the ventricles thereby reducing the hemodynamics efficiency of the ventricular contraction.
"During these atrial arrhythmias, the patient may experience palpitations and complain of malaises, dyspnoea and chest pains. It can be important to treat these arrhythmias in some cases, and the application of antitachycardia pacing is one treatment option.
"However, in the presence of a stimulation of the atrium--and thus, especially during the application of an antitachycardia atrial pacing therapy--the electrical detection of the ventricular activity by the device can be masked by the atrial post-stimulation refractory periods.
"One solution to this masking problem is to always deliver a ventricular pacing for the duration of the antitachycardia atrial pacing therapy. However, such a ventricular stimulation will always be an asynchronous pacing, because of the refractory periods subsequent to the stimulation and the blanking periods, corresponding to the disconnection of the detection circuits of the amplifier to allow the discharge of the stored energy in the heart at the heart/electrode inter face after stimulation. Because of this asynchrony, there is a risk of stimulating a T wave, with the possible consequence of triggering ventricular arrhythmias."
In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventor's summary information for this patent application: "It is therefore an object of the present invention to overcome these difficulties by proposing a new technique for the detection of ventricular activity during an application of antitachycardia atrial pacing, whereby, if necessary, an antibradycardia pacing stimulation is applied to the ventricle, during the duration of an ATP-A therapy, in a controlled manner (i.e., applied only where needed) and a synchronous manner, so as to minimize any risk of triggering ventricular arrhythmias.
"Broadly, the present invention proposes to detect the contraction, or lack of contraction, of the ventricle by detecting a mechanical activity of the ventricle through an acceleration signal produced by a sensor that is responsive to the mechanical activity of the ventricle. In one embodiment, the acceleration signal is an endocardial acceleration signal delivered by an implanted endocardial accelerometer sensor. Such an endocardial acceleration sensor may be present on the ventricular lead, or on another lead, said lead being placed directly into the ventricle (namely, an endocardial lead) or in another position, e.g., in the atrium, to collect the endocardiac acceleration (EA) signal representative of the ventricular contractions. Although the invention will be discussed in the context of an endocardial acceleration sensor, it should be understood that any sensor that allows measuring the mechanical activity of the ventricle may be used, e.g., a pressure responsive sensor, a bio-impedance sensor.
"In one particular embodiment, the invention is directed to methods and apparatus for using, during antitachycardia pacing of the atrium, a functional signal (e.g., the EA signal) representative of the mechanical contraction of the ventricle. The mechanical activity signal is used instead of a signal that has originated from the electrical propagation of the depolarization wave. The detection of the ventricular mechanical activity will thus replace the detection of the electrical cardiac activity for the duration of the antitachycardia atrial therapy.
"One aspect of the invention is thus directed to an active implantable medical prosthesis that is able to provide cardiac stimulation, resynchronization and/or defibrillation. One suitable device is an improvement of the known type, such as the one disclosed in international publication WO95/03086 A1, having circuits and logic control for atrial and ventricular detection, namely able to detect the occurrence of spontaneous atrial events and spontaneous ventricular events; antitachycardia atrial pacing, able to deliver sequences of low energy atrial pacing pulses at a higher frequency than that of the patient' s sinus rhythm in case of a detected atrial arrhythmia; a calculator that can calculate a ventricular escape interval; and antibradycardia ventricular pacing, able to deliver a conditional ventricular stimulation pulse in the absence of a spontaneous ventricular event detected by the ventricular detection circuits at the end of a ventricular escape interval. In accordance with the present invention, the device also includes a sensor responsive to mechanical activity of the myocardium (herein also called a 'mechanical activity sensor'), able to deliver a mechanical activity signal representative of the mechanical movements produced by the contractions of the ventricular cavity; and ventricular detection, able to detect the mechanical activity of the ventricle, including: a primary detection means, able to detect a spontaneous ventricular depolarization electrical potential ®, and an auxiliary detection means, able to recognize and isolate in the mechanical activity signal delivered by the sensor a component associated to a ventricular contraction.
"In a manner characteristic of the present invention, the antitachycardia pacing is provided by the circuits that produce atrial pacing, and the auxiliary detection means are implemented in response to an initiation of an antitachycardia atrial pacing stimulation therapy, in order to supplement, and more preferably replace, the primary detection means during the presence of post-atrial pacing refractory periods that might block the detection of a ventricular electrical activity ® by the primary detection means. In addition, the escape interval calculator includes: means for calculating a first escape interval value (IE.sub.RR) from the successive moments of occurrence of the spontaneous ventricular depolarization potentials ® detected by the primary detection means; means for calculating a second escape interval value (IE.sub.PEA) from the successive moments of occurrence of said ventricular contractions detected by the auxiliary detection means; and means to select the second escape interval value in response to an activation of the antitachycardia atrial stimulating means.
"In calculating the second escape interval value, the escape interval calculator preferably limits the escape interval value to a predetermined minimum value, and also averages a plurality of successive escape interval values identified during successive cycles.
"The mechanical activity sensor of the myocardium is preferably an acceleration sensor able to deliver an endocardiac acceleration (EA) signal, the auxiliary detection means thus being able to recognize and isolate the endocardiac acceleration signal component that corresponds to a peak of endocardiac acceleration associated with said ventricular contraction. This acceleration sensor may be an endocardial sensor, an epicardial sensor, or a myocardium wall motion sensor.
"Alternatively, the mechanical activity sensor may be a pressure sensor or an intracardiac impedance sensor. A combination of one or more of the foregoing sensors (with or without correlation of their signals) may be used.
BRIEF DESCRIPTION OF THE DRAWINGS
"Further features, advantages and characteristics of the present invention will now be described in accordance with the following detailed description of a preferred embodiment of the present invention, made with reference to the drawings annexed, in which the same numerical references designate items that are identical or functionally similar from one figure to the next, and in which:
"FIG. 1 illustrates an example of an endocardiac acceleration signal EA collected during three successive cardiac cycles;
"FIG. 2 is a series of three timing diagrams illustrating various signals characterizing the cardiac activity during a given cycle;
"FIG. 3 illustrates endocardiac acceleration and electrogram signals over five successive cardiac cycles representing how the invention manages ventricular pacing on the basis of an endocardiac acceleration signal during the duration of an atrial stimulation; and
"FIG. 4 is a flow chart illustrating exemplary steps for ventricular pacing management; and
"FIG. 5 is a block diagram of an example implantable device."
For more information, see this patent application: Elodie, Vincent. Active Implantable Medical Device Having Antitachycardia Atrial and Antibradycardia Ventricular Pacing. Filed
Keywords for this news article include: Therapy, Cardiology, Tachycardia, Heart Disease, Cardiovascular, Sorin Crm S.a.s, Cardiac Arrhythmias.
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