Surgical Ablation Energy Sources
A surgical ablation energy source is used in the Maze surgical ablation and the minimally-invasive mini maze procedure. The energy source creates a conduction block of scar tissue to isolate the pulmonary veins and stop the chaotic electrical signals that disrupt the heart. Research has proven that surgical ablation is nearly as effective as cut-and-sew surgeries, but is much faster to accomplish.
In the earliest surgeries, surgeons had to estimate the time required for ablation, which varied by patient due to such variations as heart wall thickness. Newer devices now measure the conductivity and determine when a "transmural" (completely through the tissue) conduction block is achieved.
Clinical testing is underway to find energy sources and tools that are reliable and effective, regardless of heart wall thickness, size of the atrium, tissue consistency, or blood flow in the beating heart, and that do not damage adjacent tissues.
A variety of surgical ablation energy sources may be used:
- Microwave — uses electromagnetic radiation to produce the heat that creates the conduction block. Microwave ablation is claimed to provide the greater tissue penetration that makes transmural ablation more likely and to produce no charring of surface tissue, thus reducing blood clots.
- Cryoablation (cryothermy) — uses very cold temperatures to freeze the tissue, which also produces no charring or vaporization of tissue. Ice spreading has been reported as a problem, but without reported consequences.
- High intensity focused ultrasound (HIFU) — uses focused ultrasound (acoustic energy) to heat the tissue and create the conduction block.
- Laser — uses light energy to create the conduction block. Laser energy is claimed to produce transmural lesions with a relatively low temperature and without vaporizing tissue.
- Non-irrigated (dry) bipolar radiofrequency — uses a clamp that delivers radiofrequency (RF) energy and measures the transmurality of the lesion to determine when conduction block at the pulmonary veins is achieved. Bipolar devices are more effective than unipolar ones, with transmurality that has approached 100% in numerous studies. Bipolar devices are generally larger and just slightly more invasive than unipolar ones.
- Irrigated (wet) bipolar radiofrequency — uses radiofrequency (RF) energy and adds saline to cool the surface and let heat go deeper into the tissue. There is a research study indicating a 100% rate of transmurality.
- Non-irrigated unipolar radiofrequency — unipolar devices are smaller and more flexible, but are not as thorough in creating transmural lesions and have been involved in some injuries to the esophagus.
- Irrigated unipolar radiofrequency.