Implementation of a human in vitro assay to evaluate tissue specificity during irreversible electroporation cardiac ablation
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Contributing OfficeCenter for Devices and Radiological Health
Abstract
Background
Atrial fibrillation (AF) is an arrhythmia initiated in the atria of the heart. AF is one of the most common heart arrhythmia in the USA, affecting 2.7 to 6.1 million people. This condition can last for several years or become permanent. In addition, AF carries severe risks that significantly increases the probability of blood clots, strokes, and heart failures. Consequently, patients that are unresponsive to drug treatments for AF are good candidates for cardiac ablation therapy. To date, the state-of-the-art technology for cardiac ablation is based on thermal approaches, where either heat or cold is applied to the cardiac tissues responsible for AF. Thermal ablation is non-invasive and considered relatively safe and effective. However, some of the disadvantages of thermal ablation are long procedure times, high reoccurrence rates, and rare, but serious adverse effects relating to involuntarily damage of surrounding tissues, such as phrenic nerve and the esophagus. Recently, cardiac ablation devices based on pulse electric fields (PEF) have been designed to treat AF. PEF ablation is a non-thermal approach that causes cell death by creating irreversible damages to the plasma membrane of the cells, a phenomenon known as irreversible electroporation (IRE). IRE ablation has been shown to decrease treatment times and minimize the chances of off target-tissue damages. Nevertheless, there is a lack of systematic studies to inform the optimal PEF parameter selection for cardiac ablation, which significantly slows device development and the regulatory review processes.
Objective
As part of a larger effort in developing a standard laboratory protocol for IRE cardiac ablation characterization, this study will investigate tissue specificity for IRE treatments. We will expose human induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) and human esophageal smooth muscle cells (HESMC) to various PEF parameters and evaluate lesion extensions to assess the safety of the treatment in vitro.
Methods
hiPSC-CMs (iCell Cardiomyocytes2, Fujifilm Cellular Dynamic, Inc.) and HESMC (ScienCell Research Laboratories) were cultured in monolayer format on 96-well NanoFiber plates. Seven days after plating, cells were exposed to PEF treatment. Pulses were delivered by an FID pulse generator (FID GmbH, Germany) connected to two needle electrodes (2-mm interelectrode distance). Our study included the following pulse parameters for tissue specificity assessment: amplitude - 0 (sham) to 600 V, duration - 1 to 5 µs and pulse number - 50 and 100. The reversible and irreversible lesions were quantified at 4 hours post treatment with YO-PRO-1 (YP1) and Propidium iodide (Pr) florescence dyes, respectively.
Results
Preliminary results showed that for a treatment of 100 unipolar pulses delivered at 1kHz repetition frequency, 3 µs pulse duration, and 250-350 V, the area of IRE lesion in hiPSC-CM is approximately twice that of HESMC.
Conclusion
Our data suggests that the esophageal tissue has a higher IRE threshold than the cardiac tissue. Future work will focus on extending our investigation to a wide set of PEF parameters to assess safety of cardiac ablation devices.