Department of Anesthesia, Heart Institute, University of Sao Paulo , Sao Paulo , Brazil.
Department of Neurosurgery, Hospital das Clinicas, University of São Paulo , São Paulo , Brazil.
Am J Physiol Heart Circ Physiol. 2018 Aug 1;315(2):H254-H261. doi: 10.1152/ajpheart.00727.2017. Epub 2018 Apr 13.
The incidence of neurological complications, including stroke and cognitive dysfunction, is elevated in patients with heart failure (HF) with reduced ejection fraction. We hypothesized that the cerebrovascular response to isometric handgrip (iHG) is altered in patients with HF. Adults with HF and healthy volunteers were included. Cerebral blood velocity (CBV; transcranial Doppler, middle cerebral artery) and arterial blood pressure (BP; Finometer) were continuously recorded supine for 6 min, corresponding to 1 min of baseline and 3 min of iHG exercise, at 30% maximum voluntary contraction, followed by 2 min of recovery. The resistance-area product was calculated from the instantaneous BP-CBV relationship. Dynamic cerebral autoregulation (dCA) was assessed with the time-varying autoregulation index estimated from the CBV step response derived by an autoregressive moving-average time-domain model. Forty patients with HF and 23 BP-matched healthy volunteers were studied. Median left ventricular ejection fraction was 38.5% (interquartile range: 0.075%) in the HF group. Compared with control subjects, patients with HF exhibited lower time-varying autoregulation index during iHG, indicating impaired dCA ( P < 0.025). During iHG, there were steep rises in CBV, BP, and heart rate in control subjects but with different temporal patterns in HF, which, together with the temporal evolution of resistance-area product, confirmed the disturbance in dCA in HF. Patients with HF were more likely to have impaired dCA during iHG compared with age-matched control subjects. Our results also suggest an impairment of myogenic, neurogenic, and metabolic control mechanisms in HF. The relationship between impaired dCA and neurological complications in patients with HF during exercise deserves further investigation. NEW & NOTEWORTHY Our findings provide the first direct evidence that cerebral blood flow regulatory mechanisms can be affected in patients with heart failure during isometric handgrip exercise. As a consequence, eventual blood pressure modulations are buffered less efficiently and metabolic demands may not be met during common daily activities. These deficits in cerebral autoregulation are compounded by limitations of the systemic response to isometric exercise, suggesting that patients with heart failure may be at greater risk for cerebral events during exercise.
患有射血分数降低的心力衰竭（HF）的患者，其神经并发症（包括中风和认知功能障碍）的发病率较高。我们假设等长握力（iHG）对脑血管的反应在 HF 患者中发生改变。纳入了 HF 患者和健康志愿者。在仰卧位时，使用经颅多普勒（大脑中动脉）连续记录 6 分钟的脑血流速度（CBV）和动脉血压（Finometer），对应于 1 分钟的基础状态和 3 分钟的 iHG 运动，收缩压达到最大自主收缩的 30%，然后恢复 2 分钟。阻力-面积产物是从即时血压-CBV 关系中计算出来的。使用基于自回归移动平均时域模型的 CBV 阶跃响应推导出的时变自动调节指数来评估动态脑自动调节（dCA）。研究了 40 名 HF 患者和 23 名血压匹配的健康志愿者。HF 组的左心室射血分数中位数为 38.5%（四分位距：0.075%）。与对照组相比，HF 患者在 iHG 期间的时变自动调节指数较低，表明 dCA 受损（P <0.025）。在 iHG 期间，对照组的 CBV、血压和心率急剧上升，但 HF 患者的上升模式不同，这与阻力-面积产物的时间演变一起证实了 HF 中 dCA 的紊乱。与年龄匹配的对照组相比，HF 患者在 iHG 期间更有可能出现 dCA 受损。我们的结果还表明，HF 患者存在肌源性、神经源性和代谢控制机制受损。HF 患者在运动过程中 dCA 受损与神经系统并发症之间的关系值得进一步研究。新观点和重要性：我们的研究结果首次直接证明，在等长握力运动期间，心力衰竭患者的脑血流调节机制可能受到影响。因此，在进行日常活动时，血压的调节可能效率较低，代谢需求可能无法得到满足。这些脑自动调节的缺陷与系统对等长运动反应的限制相叠加，这表明心力衰竭患者在运动过程中可能面临更大的发生脑部事件的风险。
