During
systole, the ventricles contract, pumping blood through the body. During
diastole, the ventricles relax and fill with blue blood again. The left ventricle receives oxygenated blood from the
left atrium via the
mitral valve and pumps it through the
aorta via the
aortic valve, into the systemic circulation. The left ventricular muscle must relax and contract quickly and be able to increase or lower its pumping capacity under the control of the nervous system. In the diastolic phase, it has to relax very quickly after each contraction so as to quickly fill with the oxygenated blood flowing from the
pulmonary veins. Likewise in the systolic phase, the left ventricle must contract rapidly and forcibly to pump this blood into the aorta, overcoming the much higher aortic pressure. The extra pressure exerted is also needed to stretch the aorta and other arteries to accommodate the increase in blood volume. The right ventricle receives deoxygenated blood from the right atrium via the
tricuspid valve and pumps it into the pulmonary artery via the
pulmonary valve, into the pulmonary circulation.
Pumping volume The typical healthy adult heart pumping volume is ~5 liters/min, resting. Maximum capacity pumping volume extends from ~25 liters/min for non-athletes to as high as ~45 liters/min for Olympic level athletes.
Volumes In
cardiology, the performance of the ventricles are measured with several volumetric parameters, including
end-diastolic volume (EDV),
end-systolic volume (ESV),
stroke volume (SV) and
ejection fraction (Ef). of various events of a
cardiac cycle, showing left ventricular volume as a red trace.
Pressures .Red = aortic pressureBlue = left ventricular pressureYellow = left atrial pressure.
Ventricular pressure is a measure of
blood pressure within the ventricles of the
heart.
Left During most of the
cardiac cycle, ventricular pressure is less than the pressure in the
aorta, but during
systole, the ventricular pressure rapidly increases, and the two pressures become equal to each other (represented by the junction of the blue and red lines on the diagram on this page), the
aortic valve opens, and blood is pumped to the body. Elevated left ventricular end-diastolic pressure has been described as a risk factor in cardiac surgery. Noninvasive approximations have been described. An elevated pressure difference between the
aortic pressure and the left ventricular pressure may be indicative of
aortic stenosis.
Right Right ventricular pressure demonstrates a different pressure-volume loop than left ventricular pressure.
Dimensions The heart and its performance are also commonly measured in terms of
dimensions, which in this case means
one-dimensional distances, usually measured in millimeters. This is not as informative as volumes but may be much easier to estimate with (e.g.,
M-Mode echocardiography or with
sonomicrometry, which is mostly used for animal model research). Optimally, it is specified with which plane the distance is measured in, e.g. the dimension of the
longitudinal plane.
Fractional shortening (
FS) is the
fraction of any diastolic dimension that is lost in systole. When referring to endocardial
luminal distances, it is EDD minus ESD divided by EDD (times 100 when measured in percentage). Normal values may differ somewhat dependent on which
anatomical plane is used to measure the distances. Normal range is 25–45%, Mild is 20–25%, Moderate is 15–20%, and Severe is <15%. Cardiology Diagnostic Tests Midwall fractional shortening may also be used to measure diastolic/systolic changes for inter-ventricular septal dimensions and posterior wall dimensions. However, both endocardial and midwall fractional shortening are dependent on myocardial wall thickness, and thereby dependent on long-axis function. By comparison, a measure of short-axis function termed epicardial volume change (EVC) is independent of myocardial wall thickness and represents isolated short-axis function. ==Clinical significance==