Intracellular diffusion in the presence of mobile buffers. Application to proton movement in muscle.

Junge and McLaughlin (1987) derived an expression for the apparent diffusion constant of protons in the presence of both mobile and immobile buffers. Their derivation applies only to cases in which the values of pH are considerably greater than the largest pK of the individual buffers, a condition that is not expected to hold in skeletal muscle or many other cell types. Here we show that, if the pH gradients are small, the same expression for the apparent diffusion constant of protons can be derived without such constraints on the values of the pK's. The derivation is general and can be used to estimate the apparent diffusion constant of any substance that diffuses in the presence of both mobile and immobile buffers. The apparent diffusion constant of protons is estimated to be 1-2 x 10(-6) cm2/s at 18 degrees C inside intact frog twitch muscle fibers. It may be smaller inside cut fibers, owing to a reduction in the concentration of mobile myoplasmic buffers, so that in this preparation a pH gradient, if established within a sarcomere following action potential stimulation, could last 10 ms or longer after stimulation ceased

Safety and success of transvenous lead extraction using excimer laser sheaths: A meta-Analysis of over 1700 patients

Aims: While numerous studies have demonstrated favourable safety and efficacy of the excimer laser sheath for transvenous lead extraction (TLE) in smaller cohorts, comprehensive large-scale investigations with contemporary data remain scarce. This study aims to evaluate the safety and performance of laser-Assisted TLE through a meta-Analysis of contemporary data. Methods and results: A systematic literature search was conducted to identify articles that assessed the safety and performance of the spectranetics laser sheath (SLS) II and GlideLight Excimer laser sheaths in TLE procedures between 1 April 2016 and 31 March 2021. Safety outcomes included procedure-related death and major/minor complications. Performance outcomes included procedural and clinical success rates. A random-effects, inverse-variance-weighting meta-Analysis was performed to obtain the weighted average of the evaluated outcomes. In total, 17 articles were identified and evaluated, including 1729 patients with 2887 leads. Each patient, on average, had 2.3 ± 0.3 leads with a dwell time of 7.9 ± 3.0 years. The TLE procedural successes rate was 96.8% [1440/1505; 95% CI: (94.9-98.2%)] per patient and 96.3% [1447/1501; 95% CI: (94.8-97.4%)] per lead, and the clinical success rate per patient was 98.3% [989/1010, 95% CI: (97.4-99.0%)]. The procedure-related death rate was 0.08% [7/1729, 95% CI: (0.00%, 0.34%)], with major and minor complication rates of 1.9% [41/1729; 95% CI: (1.2-2.8%)] and 1.9% [58/1729; 95% CI: (0.8-3.6%)], respectively. Conclusion: This meta-Analysis demonstrated that excimer laser sheath-Assisted TLE has high success and low procedural mortality rates. It provides clinicians with a reliable and valuable resource for extracting indwelling cardiac leads which require advanced extraction techniques