Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Tom Reilly Building, Byrom Street, Liverpool L3 3AF, United Kingdom.
Hypertension. 2011 Jul;58(1):51-6. doi: 10.1161/HYPERTENSIONAHA.111.171512. Epub 2011 May 31.
Diminished baroreflex sensitivity in the morning negatively influences morning coronary blood flow and blood pressure control in hypertensive patients. Our aim was to determine the contribution of the mechanical and neural components of the cardiac baroreflex to diurnal variation in blood pressure control. In 12 healthy participants, we used the modified Oxford method to quantify baroreflex sensitivity for rising (G(up)) and falling (G(down)) pressures in the morning (7:00 am) and afternoon (4:00 pm). Beat-to-beat blood pressure, R-R intervals, and carotid artery diameter measurements were recorded. Integrated sensitivity was determined by plotting R-R intervals against systolic blood pressure. The mechanical component was carotid artery diameter plotted against systolic blood pressure, and the neural component was R-R intervals plotted against carotid artery diameter. Linear mixed models were used to compare the integrated, mechanical, and neural sensitivities between morning and afternoon. We found significant diurnal variation in integrated sensitivity, with an attenuated response in the morning (G(up)=13.0±0.6; G(down)=6.3±0.4 ms/mm Hg) when compared with the afternoon (G(up)=15.1±0.6; G(down)=12.6±0.4 ms/mm Hg). For rising pressures, the diminished integrated sensitivity in the morning was caused by a reduction in mechanical sensitivity, whereas for falling pressures it was caused by a reduction in neural sensitivity. Our findings explicate the mechanisms underlying diurnal variation in baroreflex function. Pharmacological and lifestyle interventions targeted specifically at the diminished component of the cardiac baroreflex in the morning may lead to better management of hypertension.
清晨的压力反射敏感性降低会对高血压患者的清晨冠状动脉血流和血压控制产生负面影响。我们的目的是确定心脏压力反射的机械和神经成分对血压控制的昼夜变化的贡献。在 12 名健康参与者中，我们使用改良的牛津方法来量化清晨（7:00 am）和下午（4:00 pm）的上升（G(up)）和下降（G(down)）压力的压力反射敏感性。记录了逐拍血压、R-R 间隔和颈动脉直径测量值。通过绘制 R-R 间隔与收缩压来确定综合敏感性。机械成分是颈动脉直径与收缩压的关系，神经成分是 R-R 间隔与颈动脉直径的关系。线性混合模型用于比较清晨和下午的综合、机械和神经敏感性。我们发现综合敏感性存在明显的昼夜变化，与下午相比，清晨的反应减弱（G(up)=13.0±0.6；G(down)=6.3±0.4 ms/mm Hg）。对于上升压力，清晨综合敏感性的降低是由于机械敏感性的降低引起的，而对于下降压力，则是由于神经敏感性的降低引起的。我们的发现阐明了压力反射功能昼夜变化的机制。针对清晨心脏压力反射敏感性降低的药理学和生活方式干预可能会更好地管理高血压。
