Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0033—Features or image-related aspects of imaging apparatus, e.g. for MRI, optical tomography or impedance tomography apparatus; Arrangements of imaging apparatus in a room
  • A61B5/004—Features or image-related aspects of imaging apparatus, e.g. for MRI, optical tomography or impedance tomography apparatus; Arrangements of imaging apparatus in a room adapted for image acquisition of a particular organ or body part
  • A61B5/0044—Features or image-related aspects of imaging apparatus, e.g. for MRI, optical tomography or impedance tomography apparatus; Arrangements of imaging apparatus in a room adapted for image acquisition of a particular organ or body part for the heart
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
  • A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
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  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/316—Modalities, i.e. specific diagnostic methods
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/316—Modalities, i.e. specific diagnostic methods
  • A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
  • A61B5/346—Analysis of electrocardiograms
  • A61B5/349—Detecting specific parameters of the electrocardiograph cycle
  • A61B5/35—Detecting specific parameters of the electrocardiograph cycle by template matching
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
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  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/316—Modalities, i.e. specific diagnostic methods
  • A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
  • A61B5/346—Analysis of electrocardiograms
  • A61B5/349—Detecting specific parameters of the electrocardiograph cycle
  • A61B5/366—Detecting abnormal QRS complex, e.g. widening
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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  • A61B5/48—Other medical applications
  • A61B5/4887—Locating particular structures in or on the body
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  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
  • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
  • G01R33/323—Detection of MR without the use of RF or microwaves, e.g. force-detected MR, thermally detected MR, MR detection via electrical conductivity, optically detected MR
• • G—PHYSICS
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• • G—PHYSICS
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  • G06F2218/12—Classification; Matching
  • G06F2218/16—Classification; Matching by matching signal segments
• • G—PHYSICS
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  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F2218/00—Aspects of pattern recognition specially adapted for signal processing
  • G06F2218/22—Source localisation; Inverse modelling
• • G—PHYSICS
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  • G06T2207/00—Indexing scheme for image analysis or image enhancement
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  • G06T2207/20112—Image segmentation details
  • G06T2207/20152—Watershed segmentation
• • G—PHYSICS
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  • G06T2207/30004—Biomedical image processing
  • G06T2207/30048—Heart; Cardiac
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  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
  • G06V2201/00—Indexing scheme relating to image or video recognition or understanding
  • G06V2201/03—Recognition of patterns in medical or anatomical images
  • G06V2201/031—Recognition of patterns in medical or anatomical images of internal organs

Definitions

• the present invention relates to a method and system for identifying an isthmus in three-dimensional mapping. It finds a particularly interesting application in the field of disorders of the heart rhythm, during a ventricular tachycardia, for example.
• interventional rhythmologists take charge of rhythm disorders that are more and more complex in terms of their mechanism, and this first dimension adds the need for a precise representation in the space of the positioning of the ablation catheter and finally the integration of spatial and temporal data to identify the arrhythmogenic substrate.
• 3D mapping systems associated with magnetic resonance imaging are a very important tool for the interventional rhythmologist. These systems are a great help in identifying complex arrhythmogenic substrates that require "tailored” ablations for a given patient.
• the aid provided by his systems is not only relevant to understanding and locating the arrhythmogenic substrate in space, but also to accurately positioning the ablation catheter.
• Another element of the progress concerns the reduction of X-ray exposure time, both for the patient and also for the electrophysiology team, because these systems do not use X-rays in their own technology.
• atria of the heart In normal operation, the atria of the heart impose the rhythm of beat to the ventricles. The latter receive blood from the atria and contract in a synchronized manner to eject the blood either to the lungs or to other organs of the body. These are electrical impulses in the atria that allow this contraction.
• Ventricular tachycardia occurs when the electrical pulse originates in the muscle of one of the two ventricles, not the atria.
• Ventricular tachycardia VT is a fast arrhythmia, that is to say a very fast acceleration of the heart beyond 180 beats per minute for example. The heart can no longer fill, the heart pump then beats in a vacuum. This malfunction can escalate into another arrhythmia, ventricular fibrillation that can lead to cardiac arrest if it is not treated successfully quickly.
• ECG electrocardiogram
• the purpose of the ECG is to collect on several leads (pairs of electrodes) simultaneously, the overall electrical activity of the heart (cardiac vector): propagation in time and space.
• the leads correspond to the pairs of electrodes present during the recording.
• Each lead gives a unidirectional image of the cardiac activation vector. This image corresponds to the projection of the vector on the derivation.
• a standard ECG records cardiac activity on 12 to 18 leads, which fall into two categories:
• Precordial derivations The plot must have at least 12 main derivations, ie, in order: the three standard derivations (DI, D II, D III), the three unipolar derivations of the limbs (aVR, aVL, aVF ), and the six precordial derivations from VI to V6.
• a 12-lead ECG is a set of 12 curves each presenting particular shapes such as a hump for a P wave or a rapid variation for a QRS complex.
• a QRS complex corresponds to the depolarization of the ventricles. It has an average duration of about 0.08sec.
• an automatic defibrillator implanted in the patient can be used to generate electrical impulses in the event of arrhythmia onset.
• Medication can also be used to reduce the number of seizures.
• radiofrequency ablation can be performed for arrhythmia related to the reentry mechanism.
• This arrhythmogenic substrate also called isthmus
• isthmus can be determined during electrophysiological exploration, the patient being in ventricular tachycardia. It can be cauterized and circumscribed by a probe whose end is heated by a radio frequency current. The examination is assisted by a three-dimensional mapping system of the heart. This technique has a good efficiency but the risk of recurrence is not eliminated and does not allow, as a rule, to dispense with the implantation of a defibrillator.
• Such a post-infarction isthmus ablation technique is known in which surface ECGs are performed and compared to a reference ECG recorded during ventricular tachycardia.
• Such a technique is described in the document "Localizing the critical isthmus of postinfarct ventricular tachycardia: the value of pace-mapping during sinus rhythm", by Chillou et al, Heart Rhythm; 2014 Feb; ll (2): 175-81.
• the present invention aims at a new method of determining the isthmus quickly.
• Another object of the invention is an identification of the isthmus completely preventatively even for patients who are not able to withstand a ventricular tachycardia, in particular caused.
• At least one of the above-mentioned objectives is achieved with a method of identifying an isthmus in a three-dimensional mapping of a heart chamber, by means of a processing unit configured to perform the following steps:
• each stimulated point being represented by a set of signals obtained following a surface electrocardiography (ECG), excluding ventricular tachycardia, in sinus rhythm for example,
• ECG surface electrocardiography
• the invention may relate to a method of identifying a watershed in a three-dimensional mapping of a heart chamber, by means of a processing unit configured to perform the following steps:
• each stimulated point being represented by a set of signals obtained following a surface electrocardiography (ECG), excluding ventricular tachycardia, in sinus rhythm for example,
• ECG surface electrocardiography
• off ventricular tachycardia is a clear expression for those skilled in the art which means that the ECG is acquired at a basic rhythm that is not ventricular tachycardia (VT). It is known to those skilled in the art that the off-TV rhythm can be a sinus rhythm in most of the time, but it can also be in atrial fibrillation, electro-driven by a pacemaker ... The watershed corresponds to a sharp variation in correlations between close neighbors.
• a reference electrocardiography is not used which is generally a ventricular tachycardia electrocardiography, the latter has the disadvantage of being slow to perform and placing the patient in hazardous conditions.
• the stimulated points are areas of the heart of a patient that are stimulated to collect electrocardiography. These points can be chosen randomly throughout the volume of the heart chamber, but they can also be methodically determined.
• step a) a step of constituting several overlapping volumes in the 3D cartography is carried out, these volumes containing all the stimulated points, step a) being realized between stimulated points of each of the volumes.
• the invention does not stimulate the entire heart cavity equitably.
• it is preferable to carry out at least one iteration of steps a) and b); at each iteration, new stimulated points are added near the watershed identified in the previous iteration.
• a maximum correlation coefficient calculation is carried out around the watershed, which is the zone that makes it possible to precisely identify the isthmus. Other areas may have very few points stimulated.
• the realization of the iterations makes it possible firstly to carry out rough identifications up to more and more precise identifications; the criterion for stopping the iterations can be the duration, number of points stimulated or a predetermined number of iterations.
• said signals may correspond to the 12 leads of a surface ECG.
• the correlation is performed on QRS complexes derived from said signals.
• a first can be the identification of the QRS complexes in the signals. This improves the speed of calculations and therefore the speed of the entire process of identification of the isthmus.
• the correlation can be implemented according to the so-called “template matching” BARD algorithm or correspondence diagram.
• template matching BARD algorithm or correspondence diagram. This is a method described in particular in the document “Quantitative Comparison of Spontaneous and Paced 12-Lead Electrocardiogram During Right Ventricular Outflow Tract Ventricular Tachycardia", Gerstenfeld EP et al. J Am Coll Cardiol 2003; 41: 2046-53.
• the aim is to compare the morphology of 12-lead ECG complexes.
• the Bard method defines a numerical calculation that makes it possible to compare by objective criteria two twelve-lead electrocardiograms.
• CORR where X and Y are vectors of length n representing the two signals to be compared.
• the correlation coefficient CORR generally varies from -1 for a completely opposite waveform to + 1 for identical signals.
• step a) further comprises a step of identifying groups of points stimulated as a function of the level of correlation between these stimulated points.
• the first distribution by family is a distribution only geographical, here we use as criterion the level of the coefficient of correlation.
• the identification of groups is performed by displaying on a display screen, with an identical color, the set of stimulated points of the same group. A color code is determined to display a group having a high correlation coefficient between them. This can easily identify an isthmus visually.
• a system for identifying an isthmus in a three-dimensional mapping of a heart chamber which system comprises:
• an electrocardiograph for generating electrocardiography by stimulating several points of a body
• - processing unit configured to perform the following steps:
• each stimulated point being represented by a set of signals obtained following a surface electrocardiography (ECG), excluding ventricular tachycardia,
• ECG surface electrocardiography
• This system may advantageously further comprise an ablation catheter.
• FIG. 1 is a three-dimensional representation of a heart chamber with an illustration of an electrical circuit in case of ventricular tachycardia
• FIG. 2 is a simplified schematic view of the reentrant electrical circuit revealing the isthmus to be identified
• Figures 3 to 5 are schematic views of a set of points stimulated in the heart chamber, these different are illustrating different stages of correlation two by two between the different points stimulated to form a density map to operate groupings between strongly correlated stimulated points,
• FIG. 6 is a schematic view illustrating the ventricular tachycardia circuit with visualization of the area to be ablated across the isthmus;
• FIG. 7 is a schematic view of two electrocardiograms to undergo a correlation operation
• FIG. 8 is a very simplified schematic view of a system for implementing the method according to the invention.
• the present invention uses a 3D mapping system to have a three-dimensional representation of the heart as can be seen in Figure 1.
• left ventricle 1 This is a map of amplitude of the left ventricle of a patient with a history of anterior myocardial infarction.
• the healthy zones appear globally outside the circuit 2 drawn on the map and the sequela of infarction globally inside this circuit 2.
• the circuit 2 is more clearly represented in FIG. 2.
• This circuit represents the path of a depolarization front during a tachycardia episode.
• All ventricular tachycardias can be represented by a reentrant circuit 2 in the form of a double loop forming an "8", the two loops 3 and 4 being the seat of a depolarization front flowing in opposite directions around barriers 5 and 6 delimiting the isthmus.
• the isthmus is the central area 7 that forms the arrhythmogenic substrate of the mapped arrhythmia.
• Treatment of ventricular tachycardia is equivalent to ablation of the isthmus. More precisely it is a question of burning by radiofrequency wave a part of the isthmus so as to make a cut of it and thus avoid the propagation of the depolarization wave.
• the invention is notably remarkable in that the ablation zone is determined without resorting to an ECG of a prior ventricular tachycardia.
• FIG. 2 illustrates a random distribution of these points.
• a priori the circuit 2 which is shown in Figures 2 to 6 is not known. It is simply represented for the sake of understanding.
• the distribution of points can be random but it can also be obtained in a methodical manner, including predetermined, so for example to cover fairly a surface or a volume. The distribution can therefore be homogeneous or well defined according to physiological criteria.
• each group is a family of points that are geographically close to each other. In FIG. 3, for example, there are four families 13, 14, 15 and 16.
• a correlation coefficient is determined for each pair of a family. For this, we use the Bard method taking into account the twelve derivations associated with each stimulated point. We thus establish a map of densities of the links between different stimulated points, as can be seen very schematically in Figure 4 with regard to the family 16. In each family, techniques can be implemented. allowing to gradually determine the correlation coefficients without computationally compute this coefficient for all the couples of the family.
• Points are then identified having substantially the same density, that is, points that are strongly related to each other independently of the families constituted above. Thus, groups of points strongly connected to one another are formed as shown in FIG. 5 for groups 17 and 18.
• the watershed 8 is the area to be burned.
• the isthmus is the area substantially perpendicular to the watershed 8. The ablation to cut the isthmus can also be performed at any other place different from the watershed.
• FIG. 8 schematically illustrates a system for implementing the present invention.
• a processing unit 9 equipped with at least one microprocessor, memory spaces, communication cards to external devices, input / output components and a display means.
• This unit of The treatment is connected to a mapping device 10 comprising a catheter 11, one end of which may be placed at different locations in the heart chamber of a patient.
• the mapping device 10 is also connected to electrodes (not shown) for the development of 3D maps and the elaboration of twelve-lead ECG.
• the catheter can stimulate any point in the heart chamber. It also allows radiofrequency ablation.
• electromagnetic emission sources are placed at the apex of a triangular frame, itself positioned under the examination table on which the patient is installed.
• One of the electromagnetic sensors (the spatial reference) is incorporated in a cutaneous patch positioned under fluoroscopy opposite the cardiac shadow on the patient's back.
• the other sensor is incorporated at the distal end of the ablation catheter that will be moved at different points at the endocardial surface of the heart chamber that will be mapped during the examination. The displacement of this catheter can be observed in real time on a control screen. At each new position of the catheter in a given heart chamber, this position can be acquired as a point that will appear on the monitor screen.
• the points thus acquired will be automatically connected to each other by the computer program which will create a virtual surface between the different points and, with the accumulation of these, we will obtain a three-dimensional geometrical shape that will exactly match the endocardial contours of the mapped cardiac cavity.
• the catheter is equipped with electrodes for the collection of the bipolar and unipolar endocavitary signal at each of the points that form the virtual reconstruction of the heart chamber. It is therefore possible, using a color coding correlated to the bipolar or unipolar amplitude of the signal collected, to obtain an amplitude map of the examined cardiac cavity.
• the present invention may consist of a treatment unit receiving, as input, a 3D map of a heart chamber, possibly supplemented by magnetic resonance imaging, as well as sinus rhythm ECGs of a set of stimulated points.
• the output of the treatment unit may be an image of the cardiac cavity on which is displayed superimposed the line e water division. This watershed can be represented as a set of spatial coordinates that can be used for ablation.
• the method according to the invention advantageously makes it possible to identify the isthmus of a post-infarction ventricular tachycardia independently of the availability of a 12-lead ECG during ventricular tachycardia. Preventive radiofrequency ablation treatments can now be performed with a catheter for a large number of post-infarction patients.

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