Lehmann H Immo, Deisher Amanda J, Takami Mitsuru, Kruse Jon J, Song Limin, Anderson Sarah E, Cusma Jack T, Parker Kay D, Johnson Susan B, Asirvatham Samuel J, Miller Robert C, Herman Michael G, Packer Douglas L
From the Mayo Clinic Translational Interventional Electrophysiology Laboratory (H.I.L., M.T., K.D.P., S.B.J., S.J.A., D.L.P.) and Department of Radiation Oncology (A.J.D., J.J.K., L.S., S.E.A., J.T.C., R.C.M., M.G.H.), Mayo Clinic, Rochester, MN; and Texas Center for Proton Therapy, Irving (L.S.).
Circ Arrhythm Electrophysiol. 2017 Apr;10(4). doi: 10.1161/CIRCEP.116.004304.
This study sought to investigate external photon beam radiation for catheter-free ablation of the atrioventricular junction in intact pigs.
Ten pigs were randomized to either sham irradiation or irradiation of the atrioventricular junction (55, 50, 40, and 25 Gy). Animals underwent baseline electrophysiological evaluation, cardiac gated multi-row computed tomographic imaging for beam delivery planning, and intensity-modulated radiation therapy. Doses to the coronary arteries were optimized. Invasive follow-up was conducted ≤4 months after the irradiation. A mean volume of 2.5±0.5 mL was irradiated with target dose. The mean follow-up length after irradiation was 124.8±30.8 days. Out of 7 irradiated animals, complete atrioventricular block was achieved in 6 animals of all 4 dose groups (86%). Using the same targeting margins, ablation lesion size notably increased with the delivered dose because of volumetric effects of isodose lines around the target volume. The mean macroscopically calculated atrial lesion volume for all 4 dose groups was 3.8±1.1 mL, lesions extended anteriorly into the interventricular septum. No short-term side effects were observed. No damage was observed in the tissues of the esophagus, phrenic nerves, or trachea. However, histology revealed in-field beam effects outside of the target volume.
Single-fraction doses as low as 25 Gy caused a lesion with interruption of cardiac impulse propagation using this respective target volume. With doses of ≤55 Gy, maximal point-doses to coronary arteries could be kept <7Gy, but target conformity of lesions was not fully achieved using this approach.
本研究旨在探讨体外光子束辐射用于完整猪房室结无导管消融的效果。
将10头猪随机分为假照射组或房室结照射组（55、50、40和25 Gy）。动物接受基线电生理评估、用于射束传输规划的心脏门控多排计算机断层成像以及调强放射治疗。优化了冠状动脉的剂量。在照射后≤4个月进行有创随访。目标剂量照射的平均体积为2.5±0.5 mL。照射后的平均随访时长为124.8±30.8天。在7只接受照射的动物中，所有4个剂量组的6只动物（86%）实现了完全性房室传导阻滞。使用相同的靶向边界，由于靶体积周围等剂量线的体积效应，消融灶大小随所给予的剂量显著增加。所有4个剂量组的平均宏观计算心房灶体积为3.8±1.1 mL，病灶向前延伸至室间隔。未观察到短期副作用。在食管、膈神经或气管组织中未观察到损伤。然而，组织学检查显示在靶体积之外存在野内射束效应。
使用该特定靶体积，低至25 Gy的单次剂量即可造成心脏冲动传导中断的病灶。剂量≤55 Gy时，冠状动脉的最大点剂量可保持<7 Gy，但使用该方法未完全实现病灶的靶区适形性。
