FIELD OF THE INVENTION

The present invention relates generally to representing data graphically, and specifically to mapping of three-dimensional parameters that are changing with time.

BACKGROUND OF THE INVENTION

Intra-cardiac ECG (electrocardiograph) signals may be used to track the progress of a cardiac procedure, such as a ablation procedure. Typically, the signals are acquired by inserting a catheter with one or more electrodes into the heart undergoing the procedure. The electrodes acquire electropotentials developed in the heart, at the positions where the electrodes contact the heart, as the heart beats. The signals may then be analyzed, and results of the analysis may be used to inform a medical professional performing the procedure of the progress of the procedure.

The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.

SUMMARY OF THE INVENTION

An embodiment of the present invention provides a method, including:

acquiring an initial set of electrical signals from selected positions in a heart of a subject;

computing, based on the electrical signals in the initial set, respective initial local values of a signal propagation metric at the selected positions;

spatially interpolating the initial local values of the signal propagation metric between the selected positions to compute initial interpolated values of the signal propagation metric at intermediate positions, between the selected positions;

acquiring a subsequent set of electrical signals from the selected positions;

computing, based on the electrical signals in the subsequent set, respective subsequent local values of the signal propagation metric at the selected positions;

spatially interpolating the subsequent local values of the signal propagation metric between the selected positions to compute subsequent interpolated values of the signal propagation metric at the intermediate positions;

generating and displaying a map of the signal propagation metric, including the subsequent interpolated values at the intermediate positions; and

when the subsequent interpolated values exceed a bound defined with respect to the initial interpolated values, providing an indication on the map that the bound has been exceeded.

In a disclosed embodiment the signal propagation metric includes a local activation time of the heart.

In a further disclosed embodiment there are no intervening sets of electrical signals between the subsequent set and the initial set.

In a yet further disclosed embodiment the method includes:

acquiring a prior set of electrical signals from the selected positions prior to the initial set;

computing, based on the electrical signals in the prior set, respective prior local values of the signal propagation metric at the selected positions;

spatially interpolating the prior local values of the signal propagation metric between the selected positions to compute prior interpolated values of the signal propagation metric at the intermediate positions, and wherein the bound is defined with respect to the initial interpolated values and to the prior interpolated values.

Typically, there are no intervening sets of electrical signals between the prior set and the initial set.

In an alternative embodiment the signal propagation metric includes a local activation time (LAT) of the selected positions. If there is a time ΔT between the initial set and the subsequent set, the bound may be exceeded when a difference between the LAT at a given selected position of the initial set and the LAT at the given selected position of the subsequent set exceeds ΔT.

In a further alternative embodiment the signal propagation metric cycles in a preset temporal direction, and the bound is exceeded when the subsequent interpolated values cycle with respect to the initial interpolated values in a direction counter to the preset temporal direction.

There is further provided, according to an embodiment of the present invention, apparatus, including:

a screen configured to display a map of a signal propagation metric; and

a processing unit, configured to:

acquire an initial set of electrical signals from selected positions in a heart of a subject,

compute, based on the electrical signals in the initial set, respective initial local values of a signal propagation metric at the selected positions,

spatially interpolate the initial local values of the signal propagation metric between the selected positions to compute initial interpolated values of the signal propagation metric at intermediate positions, between the selected positions,

acquire a subsequent set of electrical signals from the selected positions,

compute, based on the electrical signals in the subsequent set, respective subsequent local values of the signal propagation metric at the selected positions,

spatially interpolate the subsequent local values of the signal propagation metric between the selected positions to compute subsequent interpolated values of the signal propagation metric at the intermediate positions;

generate and display on the screen the map of the signal propagation metric, including the subsequent interpolated values at the intermediate positions, and

when the subsequent interpolated values exceed a bound defined with respect to the initial interpolated values, provide an indication on the map that the bound has been exceeded.

The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which:

