Increased myocardial blood flow during acute exposure to simulated altitudes

Kaufmann, Philipp A.; Schirlo, Christian; Pavlíček, V.; Berthold, Thomas; Burger, Cyrill; Schulthess, Gustav K. von; Koller, E. A.; Buck, Alfred

doi:10.1067/mnc.2001.112537

Cited by 23 publications

(13 citation statements)

References 31 publications

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“…Our finding that marked hypoxemia caused vasodilation in angiographically normal (presumably nondiseased) coronary arterial segments expands the findings of Kaufmann et al [3], who reported that myocardial perfusion (assessed scintigraphically) increased markedly with moderate to severe hypoxemia (corresponding to an altitude of approximately 4,500 m) in healthy volunteers. Our results also provide direct evidence that diseased coronary artery segments fail to dilate adequately in response to hypoxemia as speculated by Wyss et al [4], who showed that coronary flow reserve declined in diseased coronary arteries during a combination of mild hypoxemia and exercise.…”

Section: Discussionsupporting

confidence: 77%

“…during airline travel, residing at or venturing to high altitude for recreational activities or due to various pulmonary diseases); however, little is known about the acute effect of hypoxemia on coronary arterial dimensions and coronary blood flow in humans. Previous assessments of myocardial perfusion with scintigraphic techniques suggested that myocardial blood flow increased in response to hypoxemia in healthy volunteers [3] but to a lesser extent in patients with coronary artery disease (CAD) [4]. In contrast, humans who adapted to high altitude and hypoxia showed no difference in coronary blood flow compared to controls [5].…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Acute Hypoxemia on Coronary Arterial Dimensions in Patients with Coronary Artery Disease

et al. 2008

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Objectives: To assess the influence of acute hypoxemia on the dimensions of diseased and nondiseased coronary arterial segments in humans. Methods: In 18 subjects (age 53 ± 8 years) with known or suspected coronary artery disease, quantitative coronary angiography was performed before and after being randomly assigned to breathing (1) an inspired oxygen concentration (fraction of inspired oxygen, FIO₂) of 21% (room air, RA) for 20 min (n = 4, controls) or (2) an FIO₂ of 15 and 10% for 10 min each (corresponding to altitudes of 2,500 and 5,500 m, respectively; n = 14). Results: In the control subjects, no hemodynamic, oximetric or angiographic variable changed. In the 14 study subjects, the arterial partial pressure of oxygen averaged 85 ± 13 mm Hg on RA, 65 ± 15 mm Hg on 15% FIO₂ and 44 ± 13 mm Hg on 10% FIO₂. Average arterial segment diameter was 2.52 ± 0.63 mm on RA, 2.55 ± 0.62 mm on 15% FIO₂ (not significant vs. RA) and 2.66 ± 0.66 mm on 10% FIO₂ (p < 0.001 vs. RA). The increase in coronary arterial diameter with 10% FIO₂ occurred only in normal segments (2.74 ± 0.64 vs. 2.97 ± 0.64 mm; p < 0.001), but not in diseased segments (2.34 ± 0.57 vs. 2.38 ± 0.55 mm; not significant). Conclusions: In humans, severe hypoxemia induces vasodilation of angiographically normal coronary arterial segments, whereas it causes no change in diseased segments.

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Section: Discussionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

The Effect of Acute Hypoxemia on Coronary Arterial Dimensions in Patients with Coronary Artery Disease

et al. 2008

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“…After a cardiorespiratory steady state was achieved, as assessed by a steady PetCO 2 , SaO 2 , and heart rate, positron emission tomography (PET) measurements were performed. 9 For safety reasons, CAD patients were only exposed to a simulated altitude of 2500 m, whereas volunteers were exposed to a simulated altitude of 4500 m. Cardiorespiratory reactions during normobaric hypoxia and altitude have been shown to be identical for at least the first hours of exposure. 13 …”

Section: Altitude Simulationmentioning

confidence: 99%

“…We have recently reported that high-altitude exposure increases resting MBF in healthy controls. 9 It remains unclear, however, how this affects coronary flow reserve (CFR). Thus, the aim of the present study was to assess the influence of altitude exposure on adenosine-and physical exercise-induced, hyperemic MBF and CFR in nonacclimated healthy controls and in CAD patients.…”

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confidence: 99%

Influence of Altitude Exposure on Coronary Flow Reserve

et al. 2003

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Background-Although no data exist on the effect of altitude exposure on coronary flow reserve (CFR), patients with coronary artery disease (CAD) are advised not to exceed moderate altitudes of Ϸ2500 m above sea level. We studied the influence of altitude on myocardial blood flow (MBF) in controls and CAD patients. Methods and Results-In 10 healthy controls and 8 patients with CAD, MBF was measured by positron emission tomography and 15 O-labeled water at rest, during adenosine stress, and after supine bicycle exercise. This protocol was repeated during inhalation of a hypoxic gas mixture corresponding to an altitude of 4500 m (controls) and 2500 m (CAD). Workload was targeted to comparable heart rate-blood pressure products at normoxia and hypoxia. Resting MBF increased significantly in controls at 4500 m (ϩ24%, PϽ0.01) and in CAD patients at 2500 m (ϩ24%, PϽ0.05). Altitude had no influence on adenosine-induced hyperemia and CFR. Exercise-induced hyperemia increased significantly in controls (ϩ38%, PϽ0.01) at 4500 m (despite a reduction in workload, Ϫ28%, PϽ0.0001) but not in CAD patients at 2500 m (moderate decrease in workload, Ϫ11%, PϽ0.05). Exercise-induced reserve was preserved in controls (ϩ10%, PϭNS) but decreased in CAD patients (Ϫ18%, PϽ0.005). Conclusions-At 2500 m altitude, there is a significant decrease in exercise-induced reserve in CAD patients, indicating that compensatory mechanisms might be exhausted even at moderate altitudes, whereas healthy controls have preserved reserve up to 4500 m. Thus, patients with CAD and impaired CFR should be cautious when performing physical exercise even at moderate altitude.

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“…It should be noted, however, that despite the vasoconstrictor effects of the sympathetic nervous system, the selective dilatation of the coronary [15] and cerebral blood vessels [16] occurs. Moreover, the reduction of coronary artery constriction happens in response to angiotensin and norepinephrine [17].…”

Section: Introductionmentioning

confidence: 97%

Hypertension at High Altitude

Sarybaev

Mulajkar

Sikri

et al. 2014

Translational Research in Environmental and Occupational Stress

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Systemic hypoxia is associated with conditions like anemia, lung diseases, sleep disorders, breathing, and exposure to high altitude. The physiological responses including blood pressure regulation to acute, chronic, intermittent normobaric, and hypobaric hypoxia have been under intense investigation for the past many years; however, the regulatory mechanisms are incompletely understood. The available literature indicates a differential response to hypoxia in pulmonary versus systemic circulation. Multiple physiological and metabolic changes contribute towards high-altitude acclimatization; yet, in some individuals, exposure to high altitude could be life threatening due to maladaptation. There are a few studies on the prevalence of hypertension in high-altitude natives and sea-level dwellers exposed to high altitude (acute and chronic). Elevated blood pressure is an established risk factor for different cardiovascular disease and the evidence suggests that the blood pressure rises to a modest extent in patients with mild to moderate hypertension upon acute ascent to high altitude (Luks et al., Congenit Heart Dis 5:220-232, 2010), but there is no clear evidence on increased risk of complications due to increased systemic blood pressures. This book chapter reviews available literature on systemic blood pressure responses to high altitude. A. Sarybaev (*)

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Increased myocardial blood flow during acute exposure to simulated altitudes

Cited by 23 publications

References 31 publications

The Effect of Acute Hypoxemia on Coronary Arterial Dimensions in Patients with Coronary Artery Disease

The Effect of Acute Hypoxemia on Coronary Arterial Dimensions in Patients with Coronary Artery Disease

Influence of Altitude Exposure on Coronary Flow Reserve

Hypertension at High Altitude

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