ABSTRACT
OBJECTIVE: This study examined the effectiveness of a recently developed non-thermal technology, nanosecond pulse field ablation (nsPFA), for surgical ablation of the atria in a beating heart porcine model. METHODS: Six pigs underwent sternotomy and ablation using an nsPFA parallel clamp. The ablation electrodes (53 mm long) were embedded in the jaws of the clamp. Nine lesions per pig were created in locations chosen to be representative of the Cox-Maze procedure. Four lesions were intended to electrically isolate parts of the atrium: the right atrial appendage, left atrial appendage, right pulmonary veins, and left pulmonary veins. For these lesions, exit block testing was performed both after ablation and before euthanasia; the time between the two tests was 3.3±0.5 hours (range 2 to 4 hours). Using purse string sutures, five more lesions were created up to the superior vena cava, down to the inferior vena cava, across the right atrial free wall, and at two distinct locations on the left atrial free wall. The clamp delivered a train of nanosecond duration pulses, with a total duration of 2.5 s, independent of tissue thickness. The heart tissue was stained with 1% triphenyltetrazolium chloride (TTC) after a dwelling period of two hours. Subsequently, each lesion was cross sectioned at 5 mm intervals to assess the ablation depth and transmurality. In some sections, transmurality could not be established on the basis of TTC staining alone; for these lesions, Gomori-trichrome stains were used, and the histological sections were evaluated for transmurality. RESULTS: The ablation time was 2.5 seconds per lesion, for a total of only 22.5 seconds ablation time to create 9 lesions. A total of 53 lesions were created, resulting in 388 separate histological sections. Transmurality was established in 386 sections (99.5%). Mean tissue thickness was 3.1±1.5 mm (range of 0.2 mm to 8.6 mm). Exit block was confirmed in 23 of the 24 lesions (96%) post-ablation and 23/24 (96%) pre-euthanasia. Over the course of the procedure, neither pulse-induced arrhythmias nor any other complications were noted. CONCLUSIONS: The novel nsPFA clamp device was effective in creating acute conduction block and transmural lesions in both the right and left atria in an acute porcine model. This non-thermal energy source has great potential to both shorten procedural time and enable effective ablation in the beating heart.
