Immediate electrical physiological damage dependence of myocardial cells on irradiance and photosensitizer concentration

We studied the dependence of immediate myocardial cell response on irradiance and photosensitizer concentration by an extracellular photosensitization reaction. We have proposed a new methodology for tachyarrhythmia treatment using the extracellular photosensitization reaction. Immediate cell response is needed in the tachyarrhythmia treatment since electrical physiological diagnosis is performed during the operation to judge the treatment effect. Intracellular Ca²⁺ during and after the reaction was measured using a confocal microscope and Fluo-4 AM as Ca²⁺ dye. The photosensitizer concentration, irradiance, and radiant exposure were varied 10-30 μg/ml, 30-293 mW/cm², and 10-40 J/cm², respectively. We found that the necrosis occurrence timing after the laser irradiation beginning was decreased with the photosensitizer concentration and irradiance increasing. The minimum necrosis occurrence timing was 209 s with 30 μg/ml in photosensitizer concentration and 293 mW/cm² in irradiance.