102 Myocardial oxygen consumption (MVO2)
Myocardial oxygen consumption (MVO₂) is the amount of oxygen used by the heart muscle. The heart works continuously and relies almost entirely on aerobic metabolism, so its oxygen use is high and closely tied to its workload. The three main determinants are heart rate, wall tension (which depends on pressure and ventricular size) and contractility. Even an arrested heart consumes about 20% of the oxygen of a beating heart for its basal needs. Because the heart already extracts most of the oxygen from coronary blood at rest, increased demand must be met mainly by increased coronary flow.
Clinical significance
Angina occurs when demand exceeds the supply that narrowed coronary arteries can provide; this is why it appears during exertion, emotion, cold or after a heavy meal, and is relieved by rest. Treatments for angina work largely by reducing MVO₂: beta-blockers and some calcium-channel blockers slow the heart and reduce contractility, and nitrates reduce wall tension by lowering preload. Tachycardia, hypertension, left ventricular hypertrophy, fever, hyperthyroidism and stimulants increase MVO₂. During exercise, oxygen demand of the left ventricle rises about sixfold, matched mainly by increased coronary flow. In this application, myocardial oxygen consumption is also related to oxygen use by the stomach, liver and smooth muscles.
for chest pain or pressure lasting more than a few minutes or occurring at rest, especially with breathlessness, sweating or nausea.
References
- Duncker DJ, Bache RJ. Regulation of coronary blood flow during exercise. Physiol Rev. 2008;88(3):1009–1086. doi:10.1152/physrev.00045.2006
This article is for general information and does not replace a consultation with a doctor. Measurements must be interpreted by a physician together with symptoms and other tests.
Published on 6 May 2024