Assessing the Relative Integrity of Formed Cardiac Linear Lesions by Recording Both Focal Monophasic Action Potentials and Contact Forces: A Technical Brief

Contact Forces Required to Record Monophasic Action Potentials: A Complement to Catheter Contact Force Measurement

OBJECTIVE

The ability to monitor catheter contact force (CF) plays a major role in assessing radiofrequency ablation, impacting lesion size and arrhythmia recurrence, and dictating ablation duration and/or overall patient safety. Our study sought to determine the relative CFs required to elicit reproducible monophasic action potential (MAP) recordings.

METHODS

The study utilized four swine in which: first, median sternotomies were performed and MAPs were collected from seven ventricular locations on the epicardial surface of each heart; and second, a subset of endocardial signals was recorded from a reanimated heart. In these studies, the initial elicitation and then loss of stable MAP waveforms were recorded, as were their associated catheter CFs (n = 371).

RESULTS

Mean CF at the onset of stable MAP recordings was 14.2 ± 2.9 g for epicardial and 16.6 ± 2.5 g for endocardial locations. Across epicardial locations, no significant differences in CF were required to elicit MAPs. Additionally, endocardial and epicardial CFs for MAPs did not significantly differ for respective locations, i.e., right ventricular septum endocardial versus epicardial. In our study, the catheter CFs required to elicit MAPs were within optimal ranges previously reported for eliciting clinically viable radiofrequency ablations.

CONCLUSION

We believe that MAP recordings could complement CF measurements with electrical data, providing additional clinical feedback for physicians performing cardiac ablation.

SIGNIFICANCE

If applied clinically, MAP recordings could potentially improve ablation outcomes in patients with cardiac arrhythmias.

The Ability to Reproducibly Record Cardiac Action Potentials From Multiple Anatomic Locations: Endocardially and Epicardially, In Situ and In Vitro

OBJECTIVE

For cardiac arrhythmia mapping and ablation procedures, the ability to record focal cardiac action potentials could aid in precisely identifying lesions, scarred tissue, and/or arrhythmic foci. Our study objective was to validate the electrophysiologic properties of a routinely employed large mammalian in vitro working heart model.

METHODS

Monophasic action potentials (MAPs) were recorded from 18 swine hearts during viable hemodynamic function both in situ (postmedian sternotomy) and in vitro (using Visible Heart methodologies). We placed specially designed mapping catheters in epicardial and endocardial locations. High-quality MAP signals were recorded for up to 2 h, and MATLAB was utilized to evaluate relative duration and temporal/regional changes in waveform morphology.

RESULTS

MAPs were reproducibly recorded from both epicardial and endocardial locations in situ and in vitro. No significant differences were noted in right atrial endocardial, right ventricular endocardial, right ventricular epicardial, or left atrial epicardial waveforms, when baseline recordings were compared to all other in situ and in vitro time points. Furthermore, MAP duration between right ventricular endocardial and epicardial waveforms was not significantly different, in situ or in vitro.

CONCLUSION

The use of in vitro models like the Visible Heart is considered invaluable for the study of cardiac arrhythmias, the development of novel therapies, and/or preclinical testing of future cardiac mapping catheters and systems.

SIGNIFICANCE

Preclinical studies assessing in situ and/or in vitro recorded cardiac monophasic action potentials could be critical for the future development and validation of cardiac devices.

The Visible Heart® project and methodologies: novel use for studying cardiac monophasic action potentials and evaluating their underlying mechanisms

INTRODUCTION

This review describes the utilization of Visible Heart® methodologies for electrophysiologic studies, specifically in the investigation of monophasic action potential (MAP) recordings, with the aim to facilitate new catheter/device design and development that may lead to earlier diagnosis, treatment, and ultimately a higher quality of life for patients with atrial fibrillation.

AREAS COVERED

We describe the historically proposed mechanisms behind which electrode is responsible for the MAP recording, new catheters for recording these signals, and how Visible Heart methodologies can be utilized to develop and test new technologies for electrophysiologic investigations.

EXPERT OPINION

When compared to traditional electrogram recordings, MAP waveforms provide clinical information vital to the understanding, diagnosis, and treatment of cardiac arrhythmias. New catheters and ablation technologies are routinely being assessed on reanimated large mammalian hearts (swine and human) in our laboratory. These abilities, combined with continued enhancements in imaging modalities and computational systems for electrical mapping, are being applied to the MAP catheter design process. Through this testing we are hopeful that the time from concept to product can be reduced, and that an array of MAP catheters can be placed in the hands of physicians, where they will improve patient outcomes.