Department of Clinical Medicine, Burrell College of Osteopathic Medicine, Las Cruces, NM, USA.
Departments of Biomedical Sciences, Burrell College of Osteopathic Medicine, Las Cruces, NM, USA.
J Osteopath Med. 2021 Feb 18;121(4):349-359. doi: 10.1515/jom-2020-0213.
Management of atrial fibrillation includes either rhythm control that aims at establishing a sinus rhythm or rate control that aims at lowering the ventricular rate, usually with atrioventricular nodal blocking agents. Another potential strategy for ventricular rate control is to induce a negative dromotropic effect by augmenting cardiac vagal activity, which might be possible through noninvasive and nonpharmacologic techniques. Thus, the hypothesis of this study was that occipitoatlantal decompression (OA-D) and transcutaneous auricular vagus nerve stimulation (taVNS) not only increase cardiac parasympathetic tone as assessed by heart rate variability (HRV), but also slow atrioventricular conduction, assessed by the PQ-interval of the electrocardiogram (EKG) in generally healthy study participants without atrial fibrillation.
To test whether OA-D and/or transcutaneous taVNS, which have been demonstrated to increase cardiac parasympathetic nervous system activity, would also elicit a negative dromotropic effect and prolong atrioventricular conduction.
EKGs were recorded in 28 healthy volunteers on three consecutive days during a 30 min baseline recording, a 15 min intervention, and a 30 min recovery period. Participants were randomly assigned to one of three experimental groups that differed in the 15 min intervention. The first group received OA-D for 5 min, followed by 10 min of rest. The second group received 15 min of taVNS. The intervention in the third group that served as a time control group (CTR) consisted of 15 min of rest. The RR- and PQ-intervals were extracted from the EKGs and then used to assess HRV and AV-conduction, respectively.
The OA-D group had nine participants (32.1%), the taVNS group had 10 participants (35.7%), and the CTR group had nine participants (32.1%). The root mean square of successive differences between normal heartbeats (RMSSD), an HRV measure of cardiac parasympathetic modulation, tended to be higher during the recovery period than during the baseline recording in the OA-D group (mean ± standard error of the mean [SEM], 54.6 ± 15.5 vs. 49.8 ± 15.8 ms; p<0.10) and increased significantly in the taVNS group (mean ± SEM, 28.8 ± 5.7 vs. 24.7 ± 4.8 ms; p<0.05), but not in the control group (mean ± SEM, 31.4 ± 4.2 vs. 28.5 ± 3.8 ms; p=0.31). This increase in RMSSD was accompanied by a lengthening of the PQ-interval in the OA-D (mean ± SEM, 170.5 ± 9.6 vs. 166.8 ± 9.7 ms; p<0.05) and taVNS (mean ± SEM, 166.6 ± 6.0 vs. 162.1 ± 5.6 ms; p<0.05) groups, but not in the control group (mean ± SEM, 164.3 ± 9.2 vs. 163.1 ± 9.1 ms; p=0.31). The PQ-intervals during the baseline recordings did not differ on the three study days in any of the three groups, suggesting that the negative dromotropic effect of OA-D and taVNS did not last into the following day.
The lengthening of the PQ-interval in the OA-D and taVNS groups was accompanied by an increase in RMSSD. This implies that the negative dromotropic effects of OA-D and taVNS are mediated through an increase in cardiac parasympathetic tone. Whether these findings suggest their utility in controlling ventricular rates during persistent atrial fibrillation remains to be determined.
心房颤动的管理包括节律控制，旨在建立窦性节律，或速率控制，旨在降低心室率，通常使用房室结阻滞药。另一种潜在的心室率控制策略是通过增强心脏迷走神经活动来诱导负性变时作用，这可能通过无创和非药物技术来实现。因此，本研究的假设是，寰枢减压（OA-D）和经皮耳迷走神经刺激（taVNS）不仅通过心率变异性（HRV）评估增加心脏副交感神经张力，而且还通过心电图（EKG）的 PQ 间期评估减慢房室传导，通常在没有心房颤动的健康研究参与者中。
测试 OA-D 和/或 taVNS 是否会产生负性变时作用并延长房室传导，这些方法已经证明可以增加心脏副交感神经系统的活动。
在连续 3 天的 30 分钟基线记录、15 分钟干预和 30 分钟恢复期内，记录 28 名健康志愿者的 EKG。参与者被随机分配到三个实验组中的一个，这三个实验组在 15 分钟的干预中有所不同。第一组接受 5 分钟的 OA-D，然后休息 10 分钟。第二组接受 15 分钟的 taVNS。第三组作为时间对照组（CTR）的干预包括 15 分钟的休息。从 EKG 中提取 RR 和 PQ 间期，然后分别用于评估 HRV 和 AV 传导。
OA-D 组有 9 名参与者（32.1%），taVNS 组有 10 名参与者（35.7%），CTR 组有 9 名参与者（32.1%）。OA-D 组的 RR 间期差值的均方根（RMSSD），一种 HRV 测量心脏副交感神经调节的指标，在恢复期比基线记录时倾向于更高（平均值±标准误差[SEM]，54.6±15.5 vs. 49.8±15.8 ms；p<0.10），并且在 taVNS 组中显著增加（平均值±SEM，28.8±5.7 vs. 24.7±4.8 ms；p<0.05），但在对照组中没有增加（平均值±SEM，31.4±4.2 vs. 28.5±3.8 ms；p=0.31）。RMSSD 的增加伴随着 OA-D（平均值±SEM，170.5±9.6 vs. 166.8±9.7 ms；p<0.05）和 taVNS（平均值±SEM，166.6±6.0 vs. 162.1±5.6 ms；p<0.05）组 PQ 间期的延长，但在对照组中没有（平均值±SEM，164.3±9.2 vs. 163.1±9.1 ms；p=0.31）。在任何一组中，在三个研究日的基线记录中，PQ 间期都没有差异，这表明 OA-D 和 taVNS 的负性变时作用不会持续到第二天。
OA-D 和 taVNS 组的 PQ 间期延长伴随着 RMSSD 的增加。这意味着 OA-D 和 taVNS 的负性变时作用是通过增加心脏迷走神经张力介导的。这些发现是否表明它们在控制持续性心房颤动期间的心室率有用，仍有待确定。
