US-12622598-B2 - Decreasing IEGM hazards in time division multiplexed system

US12622598B2US 12622598 B2US12622598 B2US 12622598B2US-12622598-B2

Abstract

In one embodiment, a medical system includes a catheter interface comprising electrode lines configured to be electrically connected to respective electrodes of a catheter, and a signal generation apparatus configured to generate signal pulses, each of the signal pulses comprising a carrier frequency and having a non-rectangular signal envelope, the signal generation apparatus being configured to time multiplex the signal pulses among the electrode lines.

Inventors

Michael Levin
Alek Vilensky
Amit Yarimi
Rami Rozen
Yavgeny Bonyak

Assignees

BIOSENSE WEBSTER (ISRAEL) LTD.

Dates

Publication Date: 20260512
Application Date: 20221220

Claims (8)

1 . A medical system, comprising: a catheter interface comprising: electrode lines electrically connected to respective electrodes of a catheter and body surface electrodes, the catheter being inserted into a cardiac chamber of a patient and the electrodes emitting signal pulses dedicated for sensing positions of each of the electrodes and concurrently sensing intracardiac electrogram (IEGM) signals; and a signal generation apparatus generating the signal pulses, each of the signal pulses comprising a carrier frequency and having a non-rectangular signal envelope, the signal generation apparatus time multiplexing the signal pulses among the electrode lines; and a position tracking system configured to sense the signal pulses on the body surface electrodes and track positions of each of the electrodes based on the signal pulses sensed, wherein the electrodes of the catheter emit the signal pulses responsively to the time multiplexed signal pulses generated by the signal generation apparatus; wherein the signal generation apparatus generates the non-rectangular signal envelope with a gradual increase in a peak-to-peak amplitude of the envelope over time to a maximum peak-to-peak amplitude and then after a given time period a gradual reduction in the envelope over time to a zero peak-to-peak amplitude, and wherein the gradual increase in the peak-to-peak amplitude of the envelope is based on an error function (ERF), and the gradual reduction is based on a complementary error function (ERFC) thereby reducing or eliminating signal spikes in IEGM signals sensed currently with generating the signal pulses.
2 . The system according to claim 1 , wherein the signal generation apparatus further comprises a memory storing a digital signal pulse representation, processing circuitry and a digital-to-analog converter, the processing circuitry configured to retrieve the digital signal pulse representation from the memory and provide the digital signal pulse representation to the digital-to-analog converter, which converts the digital signal pulse representation into an analog signal including one of the signal pulses.
3 . The medical system of claim 1 further comprising an ablation energy generator, wherein the ablation energy generator is configured to conduct ablation energy to one or more of the electrodes, wherein the ablation energy generator generates one or more of radio frequency energy or pulsed field ablation energy configured for ablating tissue in the cardiac chamber.
4 . The medical system of claim 1 further comprising: body surface electrocardiogram (ECG) electrodes mounted on skin of the patient and electrically coupled to the catheter interface; wherein the catheter interface is further configured to receive and process ECG signals from the ECG electrodes concurrently with sensing the signal pulses and the IEGM signals; and a display configured to display the ECG signals and the IEGM signals as processed.
5 . A computer-implemented method comprising: generating signal pulses by a signal generation apparatus, each of the signal pulses comprising a carrier frequency and having a non-rectangular signal envelope; and time multiplexing the signal pulses among electrode lines electrically connected to respective electrodes of a catheter, the catheter inserted into a cardiac chamber of a patient and the electrodes emitting the signal pulses responsively to the time multiplexed signal pulses generated by the signal generation apparatus, sensing the signal pulses emitted by the electrodes on body surface electrodes mounted on skin of the patient; tracking position of each of the electrodes based on the signal pulses sensed; and sensing intracardiac electrogram (IEGM) signals on the electrodes concurrently with sensing the signal pulses among electrode lines, wherein the non-rectangular signal envelope has a gradual increase in a peak-to-peak amplitude of the envelope over time to a maximum peak-to-peak amplitude and then after a given time period a gradual reduction in the envelope over time to a zero peak-to-peak amplitude, and wherein the gradual increase in the peak-to-peak amplitude of the envelope is based on an error function (ERF), and the gradual reduction is based on a complementary error function (ERFC), thereby reducing or eliminating signal spikes in the IEGM signals.
6 . The method according to claim 5 , further comprising: sensing electrocardiogram (ECG) signals from ECG electrodes mounted on the skin of the patient concurrently with sensing the IEGM signals and the signal pulses; and displaying on a display device, activation sequences compiled from IEGM signals and the ECG signals.
7 . The method according to claim 5 , further comprising: receiving electro-anatomical signals from the electrodes via the electrode lines; and processing the received electro-anatomical signals.
8 . The method according to claim 5 , further comprising: storing a digital signal pulse representation; retrieving the stored digital signal pulse representation; and converting the digital signal pulse representation into an analog signal including one of the signal pulses.

Description

FIELD OF THE DISCLOSURE The present disclosure relates to medical systems, and in particular, but not exclusively to, signal generation. BACKGROUND A wide range of medical procedures involve placing probes, such as catheters, within a patient's body. One medical procedure in which these types of probes or catheters have proved extremely useful is in the treatment of cardiac arrhythmias. Cardiac arrhythmias and atrial fibrillation in particular, persist as common and dangerous medical ailments, especially in the aging population. Diagnosis and treatment of cardiac arrhythmias include mapping the electrical properties of heart tissue, especially the endocardium and the heart volume, and selectively ablating cardiac tissue by application of energy. Catheters are inserted into the heart chamber and optionally around the heart chamber during such procedures. In most procedures, multiple catheters are inserted into the patient. Catheters may include mapping, ablation, temperature sensing and image sensing catheters. Some catheters are dedicated for placement in specific parts of the anatomy, e.g., coronary sinus, esophagus, atrium, ventricle. The catheters have multiple electrical channels, some more than others depending on the number of sensors and electrodes included in each catheter. The number and type of catheters depends on the procedure and on the physician preferred workflow. BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will be understood from the following detailed description, taken in conjunction with the drawings in which: FIG. 1 is a pictorial view of a catheter-based electrophysiology mapping and ablation system constructed and operative in accordance with an exemplary mode of the present disclosure; FIG. 2 is a block diagram view of a patient interface unit in the system of FIG. 1; FIG. 3 is a flowchart including steps in a method of operation of the system of FIG. 1; and FIG. 4 is an example signal pulse for use in the system of FIG. 1. DESCRIPTION OF EXAMPLES Overview One method to track the position of a catheter is based on catheter electrodes transmitting position signals at different unique frequencies. The signals may be detected by body surface patches and processed by a processor, for example, based on a distribution of currents or impedances over the body surface patches, to compute the position of the catheter and/or the electrodes. In today's generation of catheters, the number of electrodes has sharply increased. This increase would lead to an increase in the number of different unique frequency position signals, an increase in the frequency band to accommodate all the unique frequencies, and an increase in the number of frequency generators to generate these signals. To solve this problem, signals may be transmitted using time division multiplexing (TDM) so that the same signal frequency may be used for a number of electrodes while directing the signal to different ones of the electrodes during different time periods, e.g., transmit from electrode 1 during time period A, and from electrode 2 during time period B, and so on. In this manner, electrodes may be divided into groups that transmit at the same group-frequency and one electrode per group transmits at any one time. In this manner, the number of different frequencies and frequency generators is reduced. Each TDM signal per time period is typically a signal pulse with a rectangular envelope. The same electrodes which transmit position signals also detect intracardiac electrogram (IEGMs). The transmitted TDM signal pulses, due to the non-linear surface impedance between the metal electrode and the blood pool, induce artifacts (e.g., signal spikes) in the detected IEGMs corresponding to the start and end points of the TDM bursts. A direct current (DC) signal component is also imposed on the IEGM signals throughout the TDM signal pulses. Therefore, in accordance with an exemplary mode of the present disclosure, the TDM signal pulses are generated with non-rectangular signal envelopes thereby reducing or eliminating signal spikes in the detected IEGMs. The signal pulses are time multiplexed among electrode lines to different catheter electrodes. The non-rectangular signal envelope may be generated with a gradual increase in a peak-to-peak amplitude of the envelope over time to a maximum peak-to-peak amplitude and then after a given time period a gradual reduction in the envelope over time to a zero (or other minimum) peak-to-peak amplitude. The gradual increase in the peak-to-peak amplitude of the envelope may be based on an error function (ERF) or other suitable function. The gradual reduction in the peak-to-peak amplitude of the envelope may be based on a complimentary error function (ERFC) or other suitable function. In some exemplary modes, a digital signal pulse representation is retrieved from memory by a processor such as a field-programmable gate array (FPGA), which provides the retrieved digital signal pulse rep