FIELD OF THE INVENTION

This invention relates generally to electrophysiological potentials, and specifically to identification of tissue having abnormal electrophysiological potentials.

BACKGROUND OF THE INVENTION

A standard method for cardiac investigation comprises producing maps of local activation times (LATs) of chambers of a beating heart. A “normal” heart, operating in sinus rhythm, produces well-defined LAT maps for the different chambers. A deviation from these maps allows a physician inspecting a map to identify possible problematic regions of the chambers. However, such identification may not be immediately obvious from the LAT map itself.

SUMMARY OF THE INVENTION

An embodiment of the present invention provides apparatus, including a catheter that is configured to be inserted into a chamber of a heart and that has one or more electrodes configured to contact myocardial tissue at multiple locations in the chamber and to receive electrical signals responsive to a conduction wave traveling through the tissue.

The apparatus also has a display, and a processor that is configured to receive the electrical signals from the catheter and to render to the display, responsively to the electrical signals, a map of the chamber including an indication of local times of occurrence of the conduction wave at the multiple locations. The processor also calculates, responsively to the local times of occurrence, a velocity of the conduction wave between the locations and marks on the map one or more areas of the chamber in which the velocity is below a preset threshold.

In a disclosed exemplary embodiment, the processor is configured to calculate interpolated local times of occurrence at respective positions between the multiple locations, and to mark on the map at the respective positions an indication of the interpolated local times of occurrence. Typically, the processor is configured to not mark on the map the indication of the interpolated local times of occurrence at the one or more areas.

In a further disclosed exemplary embodiment the processor is configured to divide the chamber into contiguous surfaces, each surface surrounding a respective one of the multiple locations, and the one or more areas are located at a border between two contiguous surfaces.

The processor may be configured to divide the chamber into the contiguous surfaces by forming a surface of the chamber as a set of voxels, and, for each given location of the multiple locations, iteratively and simultaneously adding an immediately neighboring voxel to a previous voxel, the previous voxel initially comprising a local originating voxel corresponding to the given location, so as to form a given contiguous surface.

The processor may also be configured to calculate the velocity of the conduction wave at a region on the border by finding a sum of the distances of the region to the respective locations of the two contiguous surfaces and dividing the sum by a time difference between the local times of occurrence at the respective locations.

In a yet further disclosed exemplary embodiment the electrical signals include electrocardiograph (ECG) signals, and the local times of occurrence correspond to local activation times (LATs) derived from the ECG signals. Typically, the processor is configured to incorporate into the map colors from a color scale having respective colors in a one-to-one correspondence with values of the LATs. The processor may be configured to color the one or more areas in a different color from colors of the color scale.

In an alternative embodiment the preset threshold is between 0.01 mm/ms and 1 mm/ms.

In a further alternative exemplary embodiment, the preset threshold is 0.1 mm/ms.

In a yet further alternative exemplary embodiment the catheter includes a position sensor configured to provide signals indicative of the multiple locations to the processor. Typically, the position sensor includes one or more coils which provide the signals in response to magnetic fields traversing the coils.

Another exemplary embodiment of the present invention provides a method, including:

inserting a catheter into a chamber of a heart, the catheter having one or more electrodes configured to contact myocardial tissue at multiple locations in the chamber and to receive electrical signals responsive to a conduction wave traveling through the tissue;

providing a display;

receiving the electrical signals from the catheter;

rendering to the display, responsively to the electrical signals, a map of the chamber including an indication of local times of occurrence of the conduction wave at the multiple locations;

calculating, responsively to the local times of occurrence, a velocity of the conduction wave between the locations; and

marking on the map one or more areas of the chamber in which the velocity is below a preset threshold.

