We experimentally studied the correlation between myocardial damage depth due to the extracellular photosensitization
reaction (PR) using talaporfin sodium and fluorescence-fall amount (FA), which is calculated from the measured
backscattering fluorescence intensity via a manipulatable 7 Fr. laser catheter during the PR operation in vivo to establish
treatment depth predictor for a non-thermal tachyarrhythmia treatment. The PR was performed to left and/or right
ventricle in the open-chest canine heart. The laser irradiation of 663±2 nm in wavelength via the laser catheter was
operated 15 min after the intravenous administration of talaporfin sodium with concentration of 36.2±8.0 μg/ml in plasma. The irradiation was operated with irradiance of 5, 10, 20 W/cm2, and duration of 5, 10, 20 s. Backscattering
fluorescence of 710±2 nm in wavelength was measured via the laser catheter during the PR. The FA was calculated
multiplying the irradiation duration by the fluorescence-fall, which is subtraction of the fluorescence intensity at the
kickoff and end of the irradiation. The canine heart was extracted 1 week after the PR and HE stained specimen was
histologically evaluated. The correlation of the myocardial damage depth and FA was investigated. We found that FA
obtained a logarithmic relation to the myocardial damage depth. We think that the FA might be available to predict the
PR induced myocardial damage depth for the application of tachyarrhythmia treatment under catheterization in vivo.
We studied photosensitization reaction progress in a cell culture well by oxygen partial pressure distribution measurement along the well depth direction with a high concentration of talaporfin sodium solution. The talaporfin sodium solution of 20 μg/ml in concentration with 2.8 mm thickness in the well was irradiated from the well bottom by 663 nm excitation laser with 0.29 W/cm2. A small Clark-type oxygen electrode was used to measure oxygen partial pressure during the photosensitization reaction with approximately 200 μm resolution. Corrections against solution temperature change and direct light irradiation were applied to the electrode output. The oxygen partial pressures at various depths were decreased uniformly from the atmospheric oxygen partial pressure with the photosensitization reaction progress up to the irradiation of 1.0 J/cm2 in radiant exposure. In the case of photosensitization reaction over 1.0 J/cm2 in radiant exposure, the oxygen partial pressure distribution along the well depth was non-uniform. In the case of photosensitization reaction with 40 J/cm2 in radiant exposure in the solution without cells, there was pressure gradient of 2.8×104 mmHg/m from 0.5 to 1.0 mm in depth from the solution surface. In this case, there was no pressure gradient near the bottom of the well. In contrast, with myocardial cells at the bottom, oxygen partial pressure gradient of 7.5×103 mmHg/m from 1.5 to 2.0 mm in the depth was appeared after irradiation with 40 J/cm2 in radiant exposure. Consequently, we found that oxygen partial pressure distribution along the depth in the well with high concentration of talaporfin sodium solution was dynamically changed with time of the photosensitization reaction using the laser irradiation from the bottom. We think this dynamic pressure change in the well might be useful to understand the photosensitization reaction progress in the well experiment system in vitro corresponding to the extracellular PDT.
We detected near-infrared luminescence from singlet oxygen in photosensitization reaction with talaporfin sodium rich condition excited by CW laser in vitro. The applicability of our singlet oxygen luminescence measurement system to in vivo is suggested.
We investigated electrophysiological and histological effect on canine anatomical isthmus in right atrium by photosensitization reaction (PR) of talaporfin sodium operated via a manipulative 7 Fr. laser catheter to establish a nonthermal tachyarrhythmia treatment. We continuously administrated talaporfin sodium via a left femoral vein to maintain photosensitizer concentration of 25-35 μg/ml in blood plasma, which is within the range of clinical use in human. Fifteen-minute after kickoff of the photosensitizer administration, a 663 nm laser was irradiated via the laser catheter for 30 s/point with irradiance of 10 W/cm2. After 17 times irradiations, a 23 ms delay of the electrical signal propagation along tricuspid annulus was observed. This result might demonstrate the acute electrical conduction delay induced by PR. The canine heart was extracted 10 days after PR and Azan staining specimen was histologically evaluated to investigate the myocardial damage by PR. The transmural fibrosis in anatomical isthmus was found. We demonstrated the PR-induced electrical conduction delay in acute phase in vivo using continuous photosensitizer dosed canine model, which maintain the clinical photosensitizer concentrat
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