Breathing manoeuvre-dependent changes in myocardial oxygenation in healthy humans

Eur Heart J Cardiovasc Imaging. 2014 Apr;15(4):409-14. doi: 10.1093/ehjci/jet171. Epub 2013 Sep 27.

Abstract

Aims: CO₂ is an intrinsic vasodilator for cerebral and myocardial blood vessels. Myocardial vasodilation without a parallel increase of the oxygen demand leads to changes in myocardial oxygenation. Because apnoea and hyperventilation modify blood CO₂, we hypothesized that voluntary breathing manoeuvres induce changes in myocardial oxygenation that can be measured by oxygenation-sensitive cardiovascular magnetic resonance (CMR).

Methods and results: Fourteen healthy volunteers were studied. Eight performed free long breath-hold as well as a 1- and 2-min hyperventilation, whereas six aquatic athletes were studied during a 60-s breath-hold and a free long breath-hold. Signal intensity (SI) changes in T₂*-weighted, steady-state free precession, gradient echo images at 1.5 T were monitored during breathing manoeuvres and compared with changes in capillary blood gases. Breath-holds lasted for 35, 58 and 117 s, and hyperventilation for 60 and 120 s. As expected, capillary pCO₂ decreased significantly during hyperventilation. Capillary pO₂ decreased significantly during the 117-s breath-hold. The breath-holds led to a SI decrease (deoxygenation) in the left ventricular blood pool, while the SI of the myocardium increased by 8.2% (P = 0.04), consistent with an increase in myocardial oxygenation. In contrast, hyperventilation for 120 s, however, resulted in a significant 7.5% decrease in myocardial SI/oxygenation (P = 0.02). Change in capillary pCO₂ was the only independently correlated variable predicting myocardial oxygenation changes during breathing manoeuvres (r = 0.58, P < 0.01).

Conclusion: In healthy individuals, breathing manoeuvres lead to changes in myocardial oxygenation, which appear to be mediated by CO₂. These changes can be monitored in vivo by oxygenation-sensitive CMR and thus, may have value as a diagnostic tool.

Keywords: BOLD-sensitive MRI; T2*-weighted imaging; apnoea; carbon dioxide; hyperventilation; vasodilation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Blood Gas Analysis
  • Carbon Dioxide / metabolism*
  • Coronary Circulation
  • Female
  • Healthy Volunteers*
  • Humans
  • Hyperventilation*
  • Magnetic Resonance Imaging, Cine* / methods
  • Male
  • Myocardium / metabolism*
  • Myocardium / pathology
  • Oxygen Consumption
  • Respiration*
  • Sports*
  • Swimming

Substances

  • Carbon Dioxide