American journal of physiology. Heart and circulatory physiology
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Am. J. Physiol. Heart Circ. Physiol. · Jun 2015
Randomized Controlled TrialExposure to medium and high ambient levels of ozone causes adverse systemic inflammatory and cardiac autonomic effects.
Epidemiological evidence suggests that exposure to ozone increases cardiovascular morbidity. However, the specific biological mechanisms mediating ozone-associated cardiovascular effects are unknown. To determine whether short-term exposure to ambient levels of ozone causes changes in biomarkers of cardiovascular disease including heart rate variability (HRV), systemic inflammation, and coagulability, 26 subjects were exposed to 0, 100, and 200 ppb ozone in random order for 4 h with intermittent exercise. ⋯ Inhalation of ozone induced dose-dependent adverse changes in the frequency domains of HRV across exposures consistent with increased sympathetic tone [increase of (parameter estimate ± SE) 0.4 ± 0.2 and 0.3 ± 0.1 in low- to high-frequency domain HRV ratio per 100 ppb increase in ozone at 4 h and 24 h, respectively (P = 0.02 and P = 0.01)] and a dose-dependent increase in serum C-reactive protein (CRP) across exposures at 24 h [increase of 0.61 ± 0.24 mg/l in CRP per 100 ppb increase in ozone (P = 0.01)]. Changes in HRV and CRP did not correlate with ozone-induced local lung inflammatory responses (BAL granulocytes, IL-6, or IL-8), but changes in HRV and CRP were associated with each other after adjustment for age and ozone level. Inhalation of ozone causes adverse systemic inflammatory and cardiac autonomic effects that may contribute to the cardiovascular mortality associated with short-term exposure.
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Am. J. Physiol. Heart Circ. Physiol. · Mar 2010
Randomized Controlled TrialCardiovascular and metabolic effects of 48-h glucagon-like peptide-1 infusion in compensated chronic patients with heart failure.
The incretin hormone glucagon-like peptide-1 (GLP-1) and its analogs are currently emerging as antidiabetic medications. GLP-1 improves left ventricular ejection fraction (LVEF) in dogs with heart failure (HF) and in patients with acute myocardial infarction. We studied metabolic and cardiovascular effects of 48-h GLP-1 infusions in patients with congestive HF. ⋯ GLP-1 infusion increased circulating insulin levels and reduced plasma glucose concentration but had no major cardiovascular effects in patients without diabetes but with compensated HF. The impact of minor increases in heart rate and diastolic blood pressure during GLP-1 infusion requires further studies. Hypoglycemia was frequent and calls for caution in patients without diabetes but with HF.
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Am. J. Physiol. Heart Circ. Physiol. · Oct 2006
Randomized Controlled TrialLeg crossing improves orthostatic tolerance in healthy subjects: a placebo-controlled crossover study.
Vasovagal syncope is the most common cause of transient loss of consciousness, and recurrent vasovagal fainting has a profound impact on quality of life. Physical countermaneuvers are applied as a means of tertiary prevention but have so far only proven useful at the onset of a faint. This placebo-controlled crossover study tested the hypothesis that leg crossing increases orthostatic tolerance. ⋯ During leg crossing, mean arterial pressure (81 vs. 81 mmHg) and cardiac output (95 vs. 94% supine) remained unchanged; heart rate increase was lower (13 vs. 18 beats/min, P < 0.05); stroke volume was higher (79 vs. 74% supine, P < 0.05); and there was a trend toward lower thoracic impedance. Leg crossing increases orthostatic tolerance in healthy human subjects. As a measure of prevention, it is a worthwhile addition to the management of vasovagal syncope.