Impaired Muscle Oxygenation and Elevated Exercise Blood Pressure in Hypertensive Patients

Abstract

E ssential hypertension is characterized by sustained elevations of blood pressure (BP) that can lead to target organ damage and an increased risk for cardiovascular disease. 1Potential life-threatening outcomes of hypertension, such as stroke, renal insufficiency, and cardiac hypertrophy, had been initially perceived as a result of macrovascular alterations. These macrovascular events, however, do not occur independently of microvascular derangement. [2][3][4] Studies have shown that alterations in microvascular structure (rarefaction), vasomotor tonus (enhanced vasoconstriction or blunted vasodilation), and endothelial dysfunction are principal processes in the pathogenesis of hypertension and are evident in several organs/tissue types. [5][6][7][8] In the skeletal muscle, microvascularization is important for oxygen and nutrient supply and for effective metabolite clearance. Studies in hypertension have shown structural or functional impairments in the microvasculature within skeletal muscles, 8 implying a reduced capacity for oxygen delivery and exchange. Furthermore, animal studies using experimental models of hypertension suggested that mitochondrial dysfunction (ie, decreased expression of mitochondrial components and defects in respiratory complexes) and increased oxidative stress result in impaired oxidative capacity and reduced mitochondrial ATP production.9,10 Importantly, in these animals, the mitochondrial dysfunction and the reduced oxidative capacity were present before the development of hypertension, suggesting a possible role of these processes to the pathogenesis of hypertension.11 However, information on skeletal muscle microvascular alterations and oxidative Abstract-This study examined in vivo (1) skeletal muscle oxygenation and microvascular function, at rest and during handgrip exercise, and (2) their association with macrovascular function and exercise blood pressure (BP), in newly diagnosed, never-treated patients with hypertension and normotensive individuals. Ninety-one individuals (51 hypertensives and 40 normotensives) underwent office and 24-hour ambulatory BP, arterial stiffness, and central aortic BP assessment, followed by a 5-minute arterial occlusion and a 3-minute submaximal handgrip exercise. Changes in muscle oxygenated and deoxygenated hemoglobin and tissue oxygen saturation were continuously monitored by nearinfrared spectroscopy and beat-by-beat BP by Finapres. Hypertensives had higher (P<0.001) central aortic BP and pulse wave velocity versus normotensives and exhibited (1) a blunted tissue oxygen saturation response during occlusion, with slower (P=0.006) deoxygenation rate, suggesting reduced muscle oxidative capacity, and (2) a slower reoxygenation rate and blunted hyperemic response (P<0.05), showing reduced microvascular reactivity. Muscle oxygenation responses were correlated with aortic systolic and pulse pressure and augmentation index (P<0.05; age and body mass index (BMI) adjusted). When exercising at the same submaximal intensity, hypertensives required a sig...

Near-infrared spectroscopy detects age-related differences in skeletal muscle oxidative function: promising implications for geroscience

“…Moreover, given the age and medical history of our elderly group, it is entirely possible that arterial stiffness may have influenced our results. Indeed, arterial stiffness can impact tissue hemoglobin oxygenation and therefore skeletal muscle oxidative recovery kinetics (Dipla et al 2017). Because arterial stiffness was not measured in the present study, we cannot rule it out as a potential contributing factor.…”

“…Indeed, arterial stiffness can impact tissue hemoglobin oxygenation and therefore skeletal muscle oxidative recovery kinetics (Dipla et al. ). Because arterial stiffness was not measured in the present study, we cannot rule it out as a potential contributing factor.…”

The association between near‐infrared spectroscopy assessment of microvascular reactivity and flow‐mediated dilation is disrupted in individuals at high risk for cardiovascular disease

“…Additionally, Dipla et al. (2017) showed that hypertensive individuals had smaller TSI reperfusion magnitude as compared to their normotensive counterparts, showing a mismatch between O 2 delivery to O 2 demand. The authors suggested that this reduction was likely related to morphological changes in precapillary resistance vessels and capillary rarefaction, reducing the oxygen delivery to the tissue.…”

Upward-Shift and Steepening of the Blood Pressure Response to Exercise in Hypertensive Subjects at High Altitude

“…Moreover, the VO 2 /work slope was higher on active treatment than on placebo, meaning that muscle oxygen delivery and utilization was more efficient on telmisartan/ nifedipine-GITS, likely as a direct result of BP reduction. 24 This did not translate into improved exercise capacity; however, it did not result in any adverse effect nor in a reduction of physical performance. This is at variance from other antihypertensive drugs suggested to be used at altitude, such as some beta blockers, that may have a negative impact on ventilatory control and exercise capacity in hypoxic conditions.…”