Impedance based metric of tissue coupling

An apparatus for use in ablation of cardiac tissue by irreversible electroporation, the apparatus comprising:

• a graphical display;
• and
• one or more controllers configured to:
• generate and display, on the graphical display, an anatomical model of a cardiac chamber and a graphical representation of an electrode assembly of an ablation catheter, the electrode assembly including one or more electrodes;
• determine a proximity of the electrode assembly to the cardiac tissue surface;
• generate a model of an electric field generated in response to delivery of a pulse waveform to the one or more electrodes;
• generate and display, on the graphical display, a graphical representation of a predicted ablation zone on the anatomical model of the cardiac chamber based on one or both of the model of the electric field and the determined proximity of the electrode assembly to the cardiac tissue surface;
• and
• generate and display, on the graphical display, one or more visual indicators of tissue coupling responsive to the determined proximity of the electrode assembly to the cardiac tissue satisfying a pre-determined criteria.

A method of graphically representing an ablation procedure on a graphical display, the method comprising:

• generating and displaying, on the graphical display, an anatomical model of a cardiac chamber and a graphical representation of an electrode assembly of an ablation catheter, the electrode assembly including one or more electrodes;
• determining a proximity of the electrode assembly to the cardiac tissue surface;
• generating a model of an electric field generated in response to delivery of a pulse waveform to the one or more electrodes;
• generating and displaying, on the graphical display, a graphical representation of a predicted ablation zone on the anatomical model of the cardiac chamber based on one or both of the model of the electric field and the determined proximity of the electrode assembly to the cardiac tissue surface;
• and
• generating and displaying, on the graphical display, one or more visual indicators of tissue coupling responsive to the determined proximity of the electrode assembly to the cardiac tissue satisfying a pre-determined criteria.