Non-thermal photodynamic therapy: a radical and reliable approach to cardiac catheter ablation

Abstract

Purpose: Radiofrequency (RF) catheter ablation was revolutionary a decade ago, but operators still face the limitations to ablate arrhythmogenic foci because of ineffective heat conduction to deep tissue, high impedance, and the blood flow effect. A high output is then often required and may result in steam pop. Therefore, we aimed to determine a proper condition for photodynamic therapy (PDT), which induces a non-thermal oxidative injury only to an irradiated area. Methods: We developed a 1.4mm catheter which emits an irradiating laser from the distal tip (a). In 27 canines prepared with an open chest surgery, we commenced infusion of the photosensitizer (talaporfin sodium) and the laser was then irradiated to the heart. Canines were survived for 2 weeks and lesion depth was measured by HE stain to compare each condition; at a photosensitizer dose of 0, 2.5, and 5mg/kg, and laser output of 5, 10, and 20W/cm2 for duration of 0, 5, 10, 20, 30, 40, and 60sec (b). Catheter tip temperature was measured and compared with an open irrigated RF catheter. Results: A positive correlation was exhibited between lesion depth, photosensitizer concentration, laser output, and irradiation time. An output of 10W/cm2 under 5mg/kg of the photosensitizer for 60sec successfully created a lesion depth of 8.2±0.2mm (c). PDT catheter tip temperature rose to only 5.2±0.5oC without irrigation, whereas 23.3±8.9oC in RF ablation at 35W for 30sec with a 50oC cut-off under 27ml/min of saline irrigation. A maximum lesion depth of 8.7±0.8mm was acquired by 20W/cm2 for 60sec under 5mg/kg without a gross tissue edema. ![Figure][1] Figure 1 Conclusions: PDT mediated ablation proved to be a reliable non-thermal method to create a sufficient cardiac lesion, positively depending on photosensitizer concentration, laser output, and irradiation time. [1]: pending:yes