These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Caffeine decreases exercise-induced myocardial flow reserve.
    Author: Namdar M, Koepfli P, Grathwohl R, Siegrist PT, Klainguti M, Schepis T, Delaloye R, Wyss CA, Fleischmann SP, Gaemperli O, Kaufmann PA.
    Journal: J Am Coll Cardiol; 2006 Jan 17; 47(2):405-10. PubMed ID: 16412869.
    Abstract:
    OBJECTIVES: We studied the acute effect of caffeine on myocardial blood flow (MBF) at rest and exercise in healthy volunteers at normoxia and during acute exposure to simulated altitude. BACKGROUND: Caffeine is a widely consumed stimulant, although its cardiovascular safety remains controversial and its effect on MBF is unknown. METHODS: 15O-labeled H2O and positron emission tomography (PET) were used to measure regional MBF at rest and immediately after supine bicycle exercise in healthy volunteers at normoxia (n = 10; mean workload, 175 W; 98% predicted; mean age, 27 +/- 6 years) as well as during hypoxia, simulating an altitude of 4,500 m by inhalation of a mixture of 12.5% oxygen (n = 8; 148 W; 78% predicted; mean age, 29 +/- 4 years). Measurements were repeated 50 min after oral ingestion of caffeine (200 mg). Myocardial flow reserve (MFR) was calculated as the ratio of hyperemic to resting MBF. RESULTS: Resting MBF was not affected by caffeine at normoxia (1.05 +/- 0.36 ml/min/g vs. 1.17 +/- 0.27 ml/min/g; p = NS), although it was significantly increased at hypoxia (1.71 +/- 0.41 ml/min/g vs. 2.22 +/- 0.49 ml/min/g; p < 0.001). By contrast, exercise-induced hyperemic MBF decreased significantly at normoxia (2.51 +/- 0.58 ml/min/g vs. 2.15 +/- 0.47 ml/min/g; p < 0.05) and hypoxia (5.15 +/- 0.79 ml/min/g vs. 3.98 +/- 0.83 ml/min/g; p < 0.005 vs. baseline; p < 0.005 vs. normoxia). The MFR decreased by 22% at normoxia (2.53 +/- 0.69 to 1.90 +/- 0.49; p < 0.01) and by 39% at hypoxia (3.13 +/- 0.60 to 1.87 +/- 0.45, p < 0.005; p < 0.05 vs. normoxia). CONCLUSIONS: In healthy volunteers, a caffeine dose corresponding to two cups of coffee (200 mg) significantly decreased exercise-induced MFR at normoxia and was even more pronounced during exposure to altitude.
    [Abstract] [Full Text] [Related] [New Search]