Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, Mississippi;
Am J Physiol Heart Circ Physiol. 2013 Oct 1;305(7):H1080-8. doi: 10.1152/ajpheart.00464.2013. Epub 2013 Aug 2.
The sensitivity of baroreflex control of heart rate is depressed in subjects with obesity hypertension, which increases the risk for cardiac arrhythmias. The mechanisms are not fully known, and there are no therapies to improve this dysfunction. To determine the cardiovascular dynamic effects of progressive increases in body weight leading to obesity and hypertension in dogs fed a high-fat diet, 24-h continuous recordings of spontaneous fluctuations in blood pressure and heart rate were analyzed in the time and frequency domains. Furthermore, we investigated whether autonomic mechanisms stimulated by chronic baroreflex activation and renal denervation-current therapies in patients with resistant hypertension, who are commonly obese-restore cardiovascular dynamic control. Increases in body weight to ∼150% of control led to a gradual increase in mean arterial pressure to 17 ± 3 mmHg above control (100 ± 2 mmHg) after 4 wk on the high-fat diet. In contrast to the gradual increase in arterial pressure, tachycardia, attenuated chronotropic baroreflex responses, and reduced heart rate variability were manifest within 1-4 days on high-fat intake, reaching 130 ± 4 beats per minute (bpm) (control = 86 ± 3 bpm) and ∼45% and <20%, respectively, of control levels. Subsequently, both baroreflex activation and renal denervation abolished the hypertension. However, only baroreflex activation effectively attenuated the tachycardia and restored cardiac baroreflex sensitivity and heart rate variability. These findings suggest that baroreflex activation therapy may reduce the risk factors for cardiac arrhythmias as well as lower arterial pressure.
肥胖型高血压患者的心率压力反射敏感性降低，这会增加心律失常的风险。其机制尚未完全阐明，也没有治疗方法可以改善这种功能障碍。为了确定高脂肪饮食喂养的犬渐进性体重增加导致肥胖和高血压的心血管动力学效应，我们对血压和心率的自发性波动进行了 24 小时连续记录，并在时频域进行了分析。此外，我们还研究了慢性压力反射激活和去肾神经支配（目前用于治疗难治性高血压的方法，这些患者通常肥胖）刺激自主神经机制是否可以恢复心血管动力学控制。体重增加到对照的 150%左右，会导致在高脂肪饮食 4 周后平均动脉压逐渐升高 17±3mmHg（对照值为 100±2mmHg）。与动脉压的逐渐升高相反，在高脂肪饮食摄入的 1-4 天内就会出现心动过速、变时性压力反射反应减弱和心率变异性降低，达到 130±4 次/分钟（对照值为 86±3 次/分钟）和分别约为对照水平的 45%和<20%。随后，压力反射激活和去肾神经支配都消除了高血压。然而，只有压力反射激活才能有效减轻心动过速，并恢复心脏压力反射敏感性和心率变异性。这些发现表明，压力反射激活疗法可能降低心律失常的风险因素，并降低动脉压。
