Environmental Impedance and Ablation Lesions Introduction The electrical conductivity of the environment surrounding a catheter electrode may affect radiofrequency (RF) current. A higher impedance environment enveloping a catheter tip can be insulating and thus direct RF preferentially into targeted cardiac tissue. We sought to evaluate whether different environmental impedances will affect RF lesions. Methods An ex vivo model using bovine myocardium, load cell, and 4 mm ablation catheter was tested using a circulating bath of normal (0.9%; NS) and half normal (0.45%; HNS) saline. Ablations were performed at 50 W. In addition, using a porcine thigh prep model, warmed heparinized blood was circulated at 350 mL/min. Prior to ablation, circulating bath impedance was altered with NS and HNS. RF was applied at 30 W with a force‐sensing, open irrigated catheter. Results Ex vivo RF with a 4 mm catheter using an HNS bath led to larger lesions, 286.7 ± 64 mm³ versus 198.9 ± 61 mm³ (P < 0.001), compared to an NS bath. In the porcine thigh prep, for RF in the high impedance (HNS) bath, initial and final impedances were higher, and the measured impedance reductions during ablation were larger, compared to RF in the low impedance (NS) bath. In vivo ablation within a higher impedance bath created larger lesion sizes, compared to a lower impedance bath, 222.4 ± 63.4 mm3 versus 135.4 ± 61.7 mm3 (P < 0.001). Conclusions A higher impedance surrounding an RF catheter can facilitate more effective RF and thereby increase lesion size. This may have implications for RF safety and efficacy, especially in the epicardium where pericardial fluid can be altered with infusion of ionic solutions.

Background: Concern exists that the clinical trial populations differ from respective cancer populations in terms of their age distribution affecting the generalizability of the results, especially in underrepresented minorities. We hypothesized that the clinical trials that do not report race are likely to suffer from a higher degree of age disparity. Methods: Food and Drug Administration (FDA) drug approvals from July 2007 to June 2019 were reviewed to identify oncology approvals, and trials with age details were selected. The outcomes studied were the weighted mean difference in age between the clinical trial population and real-world population for various cancers, the prevalence of race reporting and association of age and race reporting with each other. Results: Of the 261 trials, race was reported in 223 (85.4%) of the trials, while 38 trials (14.6%) had no mention of race. Race reporting improved minimally over time: 29 (85.3%) in 2007–2010 vs. 49 (80.3%) in 2011–2014 vs. 145 (85.4%) during the period 2015–2019 (p-value = 0.41). Age discrepancy between the clinical trial population and the real-world population was higher for studies that did not report race (mean difference −8.8 years (95% CI −12.6 to −5.0 years)) vs. studies that did report it (mean difference −5.1 years, (95% CI −6.4 to −3.7 years), p-value = 0.04). Conclusion: The study demonstrates that a significant number of clinical trials leading to cancer drug approvals suffer from racial and age disparity when compared to real-world populations, and that the two factors may be interrelated. We recommend continued efforts to recruit diverse populations.

Background: Concern exists that the clinical trial populations differ from respective cancer populations in terms of their age distribution affecting the generalizability of the results, especially the underrepresented minorities. We hypothesized that the clinical trials that do not report race are likely to suffer from a higher degree of age disparity as well and the issue should be addressed in conjunction with each other. Methods: Food and Drug Administration (FDA) drug approvals from 7/2007-6/2019 were reviewed to identify oncology approvals, and trials with age details were selected. The primary outcome was the weighted mean difference in age between the clinical trial population and realworld population for various cancers. The secondary outcomes were the prevalence of race reporting and association of age and race reporting with each other. Group comparisons for proportions were performed using the χ2 test while continuous variables were compared using multiple analysis of variance (MANOVA) test or students t-test as appropriate. P values &lt; .05 were considered significant. Results: Of the 261 trials, the race was reported in 223 (85.4%) of the trials while 38 trials (14.6%) had no mention of race. Race reporting improved minimally over time – 29 (85.3%) in 2007-2010 vs. 49 (80.3%) in 2011-2014 vs. 145 (85.4%) during 2015-2019 (p-value=0.41). No significant association between type of cancer and race reporting was noted – 147 (86.5%) of solid cancer trials vs. 76 (83.5%) of hematological cancer trials reported race (p-value=0.52). Age discrepancy between the clinical trial population and the real-world population was present for several cancer types. The discrepancy was higher for studies that did not report race, mean difference - 8.8 years 4 (95% CI -12.6 to -5.0 years) vs. studies that did report the race, mean difference -5.1 years, (95% CI -6.4 to -3.7 years), p-value=0.04. Conclusion: The study demonstrates that a significant number of clinical trials leading to cancer drug approvals suffer from racial and age disparity when compared to real-world populations and that the two factors may be interrelated. We recommend continued efforts to recruit diverse populations. In the meantime, reporting these characteristics for these crucial trials should be mandated. Citation Format: Thejus Jayakrishnan, Sonikpreet Aulakh, Mizba Baksh, Kianna Nguyen, Meghna Ailawadhi, Ayesha Samreen, Ricardo Parrondo, Taimur Sher, Vivek Roy, Rami Manochakian, Aneel Paulus, Asher Chanan-Khan, Sikander Ailawadhi. Disparity in race and age reporting in landmark cancer clinical trials: Underrepresentation of the traditionally underserved U.S. population [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-104.

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