Occlusion of canine atrial appendage using an expandable silicone band.

OBJECTIVE: Because the left atrial appendage is thought to be a major source of stroke in patients with atrial fibrillation, a new device and technique were developed for thoracoscopic isolation of the left atrial appendage. METHODS: The left and right atrial appendages were approached from an 11.5-mm port in the left thorax in 15 canines. With an atraumatic grasper for appendage positioning, expandable silicone bands covered with polyester fabric were placed at the base of the left and right atrial appendages. The location of the bands was marked with radiopaque clips to assess migration, and radiopaque dye was injected to confirm occlusion. The animals were killed at 1 week (n = 3), 2 weeks (n = 6), or 12 weeks (n = 6). RESULTS: The bands were deployed on 30 appendages without complications. The appendages were 100% occluded, and there was no migration of any bands at death. There was no indication of bleeding, rupture, or systemic emboli in any of the 15 animals. Following complete occlusion, the appendages became necrotic and were replaced by scar tissue. The healed atrial surface was consistently smooth and devoid of thrombus. There was evidence of mild-to-moderate inflammation associated with a foreign body-type reaction to the fabric material but no pericarditis. CONCLUSIONS: Permanent occlusion of the left atrial appendage is feasible via a thoracoscopic epicardial approach with this novel silicone band. As the atrial tissue becomes necrotic, the silicone band continues to constrict, ensuring that the appendage remains isolated. Band occlusion of the left atrial appendage could potentially improve overall treatment outcome in patients at high risk of atrial thrombus formation.

Band occlusion of the atrial appendage.

OBJECTIVES: A new device has been developed for occlusion of the left atrial appendage (LAA). Previous investigations have been in the canine model. The canine atrial appendage does not vary in size and shape as much as the human. The goal of this study was to investigate band occlusion of right atrial appendages in the pig model, which are more broad based. METHODS: The right atrial appendages of six pigs were approached through a right thoracotomy. An expandable polyester fabric-covered silicone band was placed on the appendage. The animals were evaluated at the time of band placement with fluoroscopy, contrast injection, and in three animals, echocardiography. After one week, the animals were again evaluated with fluoroscopy. The animals were sacrificed at 12 weeks. RESULTS: Bands were placed without complication at the base of all six appendages. All appendages were effectively occluded and all bands remained at the appendage base. The healed atrial surface was consistently smooth and devoid of thrombus. CONCLUSIONS: Occlusion of a broad-based appendage as seen with human LAA is feasible with this novel band technique.

Cardiac ablation via electroporation.

Thermal-based ablation for the treatment of arrhythmias is known to cause issues (e.g. heat loss due to blood perfusion, mechanical damage of the tissue from excessive heat, etc.) that hamper the success of the treatment. A novel technique termed "electroporation" is a process that leads to pore formation in cell membranes. These pores may cause cellular death without inducing negative thermal effects. We successfully developed a system, tools, and methodology to operate this new ablation technique. Preliminary in vivo acute animal studies (ovine) suggest distinct lesion morphology. High transmurality success rates also suggest the possibility of applying this new ablation modality to cardiac ablation. A long term study confirming lesion durability is necessary to warrant the successful adoption of this technique.

Exit vs. entrance block testing for cardiac lesion assessment.

Cardiac lesions are created to act as barriers which prohibit the transmission of cardiac myocyte contractile activity from one side of the lesion to the other. Testing for conduction block is the main way to acutely confirm the effectiveness of this therapy. There are two general methods used to test for conduction block. These methods are called: 1) "exit block testing" and 2) "entrance block testing." In this study, two different devices were used on n = 5 swine to determine if the method of lesion assessment (exit vs. entrance block testing) affected the ability to correctly identify if acute conduction block was achieved. No significant difference was found between conclusions drawn from either method of lesion assessment. However, the most robust lesion assessment will occur when both methods are employed so that the physician has the most information available for analysis.

Irrigated radiofrequency-biophysics and application to surgical ablation.

Surgical ablation has become a routine procedure in many institutions and is a nearing standard of care for certain conditions. A variety of energy sources are available to the surgeon to induce cell death and create a line of conduction block. This article provides a brief review of the biophysics of irrigated radiofrequency and its application to monopolar and bipolar ablation.