Injury to descending autonomic (sympathetic) pathways is common after high-level spinal cord injury (SCI) and associated with abnormal blood pressure and heart rate regulation. In individuals with high-level SCI, abnormal sympathovagal balance (such as during autonomic dysreflexia; paroxysmal hypertension provoked by sensory stimuli below the injury) is proarrhythmogenic. Exercise training is a key component of SCI rehabilitation and management of cardiovascular disease risk, but it is unclear whether exercise training influences susceptibility to cardiac arrhythmia. We aimed to evaluate: (i) whether susceptibility to arrhythmia increases in a rodent-model of SCI; (ii) the impact of the sympathomimetic drug dobutamine (DOB) on arrhythmia risk; (iii) whether exercise training ameliorates arrhythmia risk. Twenty-one Wistar rats were divided into 3 subgroups: T2-contusive SCI (T2, n = 7), T2-contusive SCI completing passive hindlimb cycling training (PHLC, n = 7), and T10-contusive SCI (T10, n = 7). Known electrocardiographic arrhythmia markers and heart rate variability parameters were evaluated before (PRE), 1-week (POST) and 5-weeks post-SCI (TERM) at baseline and during DOB infusion (30 μg/kg/min). Baseline markers of arrhythmia risk were increased in both T2 and T10 animals. DOB decreased R-R interval (p < 0.001), and increased markers of risk for ventricular arrhythmia, particularly in high-level (T2) animals (p < 0.05). Exercise training blunted the exacerbation of markers of arrhythmia risk in the presence of DOB. Markers of risk for cardiac arrhythmia are increased in experimental SCI, and DOB further increases arrhythmia risk in high-level SCI. Exercise training did not improve markers of arrhythmia risk at rest, but did ameliorate markers of arrhythmia risk during sympathetic stimulation.

在高水平脊髓损伤 (SCI) 后，下行自主神经（交感神经）通路的损伤很常见，并且与血压和心率调节异常有关。在患有高水平 SCI 的个体中，异常的交感迷走神经平衡（例如在自主神经反射异常期间；由损伤下方的感觉刺激引起的阵发性高血压）是促心律失常的。运动训练是 SCI 康复和心血管疾病风险管理的关键组成部分，但尚不清楚运动训练是否会影响心律失常的易感性。我们旨在评估：（i）在 SCI 啮齿动物模型中对心律失常的易感性是否增加；(ii) 拟交感神经药物多巴酚丁胺 (DOB) 对心律失常风险的影响；(iii) 运动训练是否能改善心律失常风险。21 只 Wistar 大鼠分为 3 个亚组：T2-挫伤性 SCI（T2，n = 7）、T2-挫伤性 SCI 完成被动后肢自行车训练（PHLC，n = 7）和 T10-挫伤性 SCI（T10，n = 7）。已知的心电图心律失常标志物和心率变异性参数在基线和 DOB 输注期间 (30 μg/kg/min) 在 SCI 前 (PRE)、1 周 (POST) 和 SCI 后 5 周 (TERM) 进行评估。T2 和 T10 动物的心律失常风险基线标志物均增加。DOB 降低了 RR 间期 (p < 0.001)，并增加了室性心律失常风险的标志物，尤其是在高水平 (T2) 动物中 (p < 0.05)。在 DOB 存在的情况下，运动训练可以减缓心律失常风险标志物的恶化。心律失常风险标志物在实验性 SCI 中增加，和 DOB 进一步增加高水平 SCI 的心律失常风险。运动训练并未改善静息时的心律失常风险标志物，但确实改善了交感神经刺激期间的心律失常风险标志物。