Abstract: A processor is configured to construct a baseline impedance model (BIM) that models a portion of a heart of a subject as a collection of three-dimensional cells, each of which corresponds to a respective volume within the heart, at least some of the cells being designated as baseline-impedance cells, for each of which the BIM specifies a respective baseline impedance, to ascertain, based on a signal received via an electrical interface, an impedance between a catheter electrode, which is within the heart, and an external electrode that is externally coupled to the subject, to identify one of the baseline-impedance cells as a reference cell, to ascertain that the catheter electrode is within a threshold distance of tissue of the heart, by comparing the ascertained impedance to the baseline impedance that is specified for the reference cell, and to update a map of the tissue in response to the ascertaining.

Abstract: A system includes an electrical interface and a processor. The electrical interface is configured for communicating with a probe inserted into a heart of a patient. The processor is configured to receive, via the electrical interface, (i) a first indication of an electrical impedance measured by the probe at a given location on an inner surface of the heart, and (ii) a second indication of a quality of mechanical contact between the probe and the inner surface of the heart during measurement of the electrical impedance. The processor is further configured, based on the first and second indications, to classify tissue at the given location as scar tissue.

Abstract: Apparatus and method for detecting metal disturbance during a medical procedure includes a probe having an insertion tube, a joint and a joint sensor, contained within the probe, for sensing a position of the insertion tube. The joint sensor has first and second subassemblies that are magnetic transducers. A processor is used for measuring force using the joint sensor, and has a threshold field value stored therein. The processor compares a sensed field value to the threshold field value and identifies a presence metal when the sensed field value is greater than the threshold field value.

Abstract: A processor is configured to construct a baseline impedance model (BIM) that models a portion of a heart of a subject as a collection of three-dimensional cells, each of which corresponds to a respective volume within the heart, at least some of the cells being designated as baseline-impedance cells, for each of which the BIM specifies a respective baseline impedance, to ascertain, based on a signal received via an electrical interface, an impedance between a catheter electrode, which is within the heart, and an external electrode that is externally coupled to the subject, to identify one of the baseline-impedance cells as a reference cell, to ascertain that the catheter electrode is within a threshold distance of tissue of the heart, by comparing the ascertained impedance to the baseline impedance that is specified for the reference cell, and to update a map of the tissue in response to the ascertaining.

Abstract: Described embodiments include a method for use with a catheter that includes at least one flexible arm to which are coupled a plurality of electrodes. The method includes calculating, by a processor, respective estimated locations of the electrodes while the catheter is within a portion of a body of a subject, fitting a model of the catheter, which models the flexible arm as a piecewise-linear element that includes a plurality of linear segments, to the estimated locations, ascertaining for each of the electrodes, based on respective orientations of one or more of the linear segments per the fitting, whether the electrode is in contact with tissue of the subject, and updating a map of the portion of the body of the subject, in response to ascertaining that at least one of the electrodes is in contact with the tissue. Other embodiments are also described.

Abstract: Described embodiments include a method for use with a catheter that includes at least one flexible arm to which are coupled a plurality of electrodes. The method includes calculating, by a processor, respective estimated locations of the electrodes while the catheter is within a portion of a body of a subject, fitting a model of the catheter, which models the flexible arm as a piecewise-linear element that includes a plurality of linear segments, to the estimated locations, ascertaining for each of the electrodes, based on respective orientations of one or more of the linear segments per the fitting, whether the electrode is in contact with tissue of the subject, and updating a map of the portion of the body of the subject, in response to ascertaining that at least one of the electrodes is in contact with the tissue. Other embodiments are also described.

Abstract: Described embodiments include an apparatus, including a display and a processor. The processor is configured to navigate a catheter to a particular location within a body of a subject, using each one of a plurality of electrodes coupled to the body of the subject. The processor is further configured to identify, subsequently, from a signal that represents an impedance between a given pair of the electrodes, that a phrenic nerve of the subject was stimulated by a pacing current passed from the catheter into tissue of the subject at the particular location, and to generate an output on the display, in response to the identifying. Other embodiments are also described.

Abstract: A medical catheter has an inflatable balloon assembly on its distal portion and a plurality of ablation electrodes disposed on the surface of the balloon assembly. Conductors extending through the shaft supply the ablation electrodes with electrical power when connected to a power source. A plurality of thermistors on the balloon assembly are connected to the conductors to form a resistive network, and a plurality of access points on the conductors are provided for obtaining electrical measurements and analyzing the measurements to determine respective resistances of the thermistors.

Abstract: Described embodiments include apparatus for use with a catheter. The apparatus includes a sheath configured for insertion into a body of a subject, and a sensor, coupled to the sheath, configured to detect an electric current passing through the catheter, when the catheter passes through the sheath and into the body of the subject. Other embodiments are also described.

Abstract: A method, consisting of modeling physical parameters representative of a probe in proximity to body tissue during an ablation procedure performed by the probe. The method also includes measuring a subgroup of the physical parameters during a non-ablation stage of the ablation procedure so as to generate measured non-ablative values of the subgroup, and measuring the subgroup of the physical parameters during an ablation stage of the ablation procedure so as to generate measured ablative values of the subgroup. In response to the modeling, the method includes generating calculated non-ablative values of the subgroup for the non-ablation stage, and generating calculated ablative values of the subgroup for the ablation stage. The method compares the measured non-ablative values with the calculated non-ablative values, and compares the measured ablative values with the calculated ablative values, so as generate optimal values of the physical parameters.

Abstract: A method, consisting of modeling physical parameters representative of a probe in proximity to body tissue during an ablation procedure performed by the probe. The method also includes measuring a subgroup of the physical parameters during a non-ablation stage of the ablation procedure so as to generate measured non-ablative values of the subgroup, and measuring the subgroup of the physical parameters during an ablation stage of the ablation procedure so as to generate measured ablative values of the subgroup. In response to the modeling, the method includes generating calculated non-ablative values of the subgroup for the non-ablation stage, and generating calculated ablative values of the subgroup for the ablation stage. The method compares the measured non-ablative values with the calculated non-ablative values, and compares the measured ablative values with the calculated ablative values, so as generate optimal values of the physical parameters.

Abstract: A method, including calculating locations of first sensors attached to a probe that has been inserted into a human patient, and calculating positions of second sensors attached to a sheath via which the probe is inserted. The method also includes calculating respective shapes of the probe and the sheath, to achieve a best fit to the calculated probe sensor locations and sheath sensor positions, while restricting the probe to pass through the sheath. The calculated respective shapes of the probe and the sheath are used to present an image of the sheath aligned with the probe.

Abstract: Described embodiments include a catheter, which includes a plurality of splines at a distal end of the catheter, and a plurality of helical conducting elements disposed on the splines. Other embodiments are also described.

Abstract: Described embodiments include an apparatus that includes an expandable structure, configured for insertion into a body of a subject, and a plurality of conducting elements coupled to the expandable structure. Each of the conducting elements comprises a respective coil and has an insulated portion that is electrically insulated from tissue of the subject, and an uninsulated portion configured to exchange signals with the tissue, while in contact with the tissue. Other embodiments are also described.

Abstract: Apparatus, consisting of a probe, configured to be inserted into a body cavity, and an electrode having an outer surface and an inner surface connected to the probe. The apparatus also includes a temperature sensor, protruding from the outer surface of the electrode, which is configured to measure a temperature of the body cavity.

Abstract: A method for performing a medical procedure, includes, coupling a probe to tissue in an organ of a patient. Ablation energy is applied to the tissue using the probe. A model of an evolution of steam pressure in the tissue, caused by the ablation energy, as a function of time is estimated. Based on the model, an occurrence time of a steam pop event caused by the steam pressure is predicted, and the predicted occurrence time of the steam pop event is indicated to an operator.

Abstract: A method includes positioning body-electrodes in galvanic contact with a body of a patient and positioning a mapping-tool, having a mapping-electrode, in a plurality of regions in the body. The method further includes tracking the mapping-tool at different positions in each of the regions using a location-measuring system, and for each region, generating a respective set of calibration-currents between the body-electrodes and the mapping-electrode at the different positions in the region. A respective relation is derived for each region between the respective set of the calibration-currents and the different positions, and is used in determining the location of an investigation-tool in response to the different respective relations and investigation-tool-currents.

Abstract: A method for performing a medical procedure, includes, coupling a probe to tissue in an organ of a patient. Ablation energy is applied to the tissue using the probe. A model of an evolution of steam pressure in the tissue, caused by the ablation energy, as a function of time is estimated. Based on the model, an occurrence time of a steam pop event caused by the steam pressure is predicted, and the predicted occurrence time of the steam pop event is indicated to an operator.

Abstract: A method includes positioning body-electrodes in galvanic contact with a body of a patient and positioning a mapping-tool, having a mapping-electrode, in a plurality of regions in the body. The method further includes tracking the mapping-tool at different positions in each of the regions using a location-measuring system, and for each region, generating a respective set of calibration-currents between the body-electrodes and the mapping-electrode at the different positions in the region. A respective relation is derived for each region between the respective set of the calibration-currents and the different positions, and is used in determining the location of an investigation-tool in response to the different respective relations and investigation-tool-currents.

Abstract: A medical apparatus, including a reference probe having a flexible insertion tube with a distal end for insertion into a body cavity, a pair of isolated electrodes fixedly attached to the distal end, and a position sensor fixedly located in the distal end. The apparatus also includes a supplementary probe having an electrode fixed thereto. The apparatus further includes a processor, configured to inject respective alternating currents into the pair of isolated electrodes so as to generate an electrical field therefrom, to measure a potential generated at the electrode of the supplementary probe in response to the electrical field, and to evaluate a location of the supplementary probe with respect to the reference probe in response to the measured potential and in response to a position of the distal end indicated by the position sensor.