Ablation Electrode Phase Measurement for Reliable Tissue Contact
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Solution Overview
Problem
Existing methods for verifying electrode contact with cardiac tissue during ablation procedures are often unreliable, particularly due to binary impedance-based contact indications that are sensitive to changes in skin impedance, which can lead to inconsistent and ineffective ablation results.
Innovation Solution
A method involving a catheter with an ablation electrode that measures the phase of an electrical current between the electrode and a body-surface electrode before and during tissue contact, using a reference waveform to iteratively determine the completion of ablation based on phase shifts, ensuring precise energy application and termination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If binary impedance-based contact indication is used, then the device complexity is reduced, but the reliability of contact verification deteriorates due to sensitivity to skin impedance changes
Solution Approach 1:
The patent transitions from measuring impedance magnitude alone to measuring the phase angle of impedance, which is a different parameter that is not affected by skin impedance changes. This parameter change allows reliable contact detection without increasing device complexity, as the phase angle measurement can be obtained from the same impedance measurement circuit.
Solution Approach 2:
The patent introduces a reference waveform as an intermediary to compare against the measured impedance waveform. By comparing the phase relationship between the reference waveform and the impedance waveform, the system can reliably determine contact status without being influenced by variations in skin impedance, thus improving reliability without adding significant complexity.
2Reliability
If phase measurement is used for contact verification, then the reliability of contact verification is improved, but the device complexity increases due to additional measurement and processing requirements
Solution Approach 1:
The patent makes the existing impedance measurement circuit perform an additional function by analyzing the phase angle of the impedance signal. Instead of requiring a separate contact detection system, the same circuit that measures impedance magnitude is used to extract phase information, thereby improving reliability without proportionally increasing device complexity.
Solution Approach 2:
The system continuously monitors the phase angle of impedance during the ablation procedure and provides real-time feedback on contact status. This feedback mechanism allows for reliable contact verification and automatic adjustment of ablation parameters, with the processing requirements managed through efficient algorithms that analyze phase relationships between waveforms.
3Measurement precision
If iterative phase determination is performed during ablation, then the precision of ablation monitoring is improved, but the productivity of the procedure decreases due to increased measurement frequency
Solution Approach 1:
The system performs a pre-contact determination of the phase angle before actual tissue contact is made. This preliminary measurement establishes a baseline that allows for more lenient termination criteria during ablation, reducing the need for frequent iterative measurements and thereby maintaining productivity while still achieving precise monitoring through comparison against the baseline phase value.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a sensitive and reliable verification of tissue contact and progress of ablation, ensuring effective lesion formation by accurately measuring phase shifts between the electrode and tissue, thereby improving the consistency and completeness of the ablation process.
Implementation Method 1
measuring a pre-contact determination of a phase of an electrical current passing between the ablation electrode and another electrode
Implementation Method 2
applying a dosage of energy via the ablation electrode to the target tissue for ablation thereof
Data Source
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AI summary
Methods and systems achieve tissue ablation, which is carried out by inserting a probe having an ablation electrode into a body of a living subject, and while the ablation electrode is in a non-contacting relationship to a target tissue, making a pre-contact determination of a phase of an electrical current passing between the ablation electrode and another electrode. The ablation electrode is placed in contact with the target tissue, and while the ablation electrode is in the contacting relationship, a dosage of energy is applied via the ablation electrode to the target tissue for ablation thereof. Iterative intra-operative determinations of the phase of the electrical current are made. When one of the intra-operative determinations satisfies a termination criterion, the energy application is terminated.