ABSTRACT
OBJECTIVE: Cardiac catheter cryoablation is a safer alternative to radiofrequency ablation for arrhythmia treatment, but electrophysiological (EP) effects during and after freezing are not adequately characterized. The goal of this study was to determine transient and permanent temperature induced EP effects, during and after localized tissue freezing. METHODS: Conduction in right (RV) and left ventricles (LV) was studied by optical activation mapping during and after cryoablation in paced, isolated Langendorff-perfused porcine hearts. Cryoablation was performed endocardially (n=4) or epicardially (n=4) by a cryoprobe cooled to -120 °C for 8 minutes. Epicardial surface temperature was imaged with an infrared camera. Viability staining was performed after ablation. Motion compensation and co-registration was performed between optical mapping data, temperature image data, and lesion images. RESULTS: Cryoablation produced lesions 14.9 +/- 3.1 mm in diameter and 5.8 +/- 1.7 mm deep. A permanent lesion was formed in tissue cooled below -5 +/- 4 °C. Transient EP changes observed at temperatures between 17 and 37 °C during cryoablation surrounding the frozen tissue region directly correlated with local temperature, and include action potential (AP) duration prolongation, decrease in AP magnitude, and slowing in conduction velocity (Q10=2.0). Transient conduction block was observed when epicardial temperature reached <17 °C, but completely resolved upon tissue rewarming, within 5 minutes. CONCLUSION: Transient EP changes were observed surrounding the permanent cryo lesion (<-5 °C), including conduction block (-5 to 17 °C), and reduced conduction velocity (>17 °C). SIGNIFICANCE: The observed changes explain effects observed during clinical cryoablation, including transient increases in effective refractory period, transient conduction block, and transient slowing of conduction. The presented quantitative data on temperature dependence of EP effects may enable the prediction of the effects of clinical cryoablation devices.
ABSTRACT
PURPOSE OF REVIEW: The institutional development award (IDeA) program was created to increase the competitiveness of investigators in states with historically low success rates for National Institutes of Health (NIH) research funding applications. IDeA states have high numbers of rural and medically underserved residents with disproportionately high rates of infant mortality, obesity, and poverty. This program supports the development and expansion of research infrastructure and research activities in these states. The IDeA States Pediatric Clinical Trials Network (ISPCTN) is part of the environmental influences on child health outcomes program. Its purpose is to build research capacity within IDeA states and provide opportunities for children in IDeA states to participate in clinical trials. This review describes the current and future activities of the network. RECENT FINDINGS: In its initial year, the ISPCTN created an online series on clinical trials, initiated participation in a study conducted by the pediatric trials network, and proposed two novel clinical trials for obese children. Capacity building and clinical trial implementation will continue in future years. SUMMARY: The ISPCTN is uniquely poised to establish and support new pediatric clinical research programs in underserved populations, producing both short and long-term gains in the understanding of child health.