Ejection fraction EF is a measurement, expressed as a percentage, of how much blood the left ventricle pumps out with each contraction. An ejection fraction of 60 percent means that 60 percent of the total amount of blood in the left ventricle is pushed out with each heartbeat. This indication of how well your heart is pumping out blood can help to diagnose and track heart failure.
An ejection fraction measurement higher than 75 percent may indicate a heart condition such as hypertrophic cardiomyopathy. When examined using an echocardiogram , a significant number of patients with heart failure are revealed to have normal ventricular ejection fraction. Learn more about common tests for diagnosing heart failure. Written by American Heart Association editorial staff and reviewed by science and medicine advisers. See our editorial policies and staff. Heart Failure. What is Heart Failure?
To provide you with the most relevant and helpful information and to understand which information is beneficial, we may combine your e-mail and website usage information with other information we have about you.
If we combine this information with your PHI, we will treat all of that information as PHI, and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of e-mail communications at any time by clicking on the Unsubscribe link in the e-mail. Our Housecall e-newsletter will keep you up-to-date on the latest health information. Mayo Clinic does not endorse companies or products.
Advertising revenue supports our not-for-profit mission. Any use of this site constitutes your agreement to the Terms and Conditions and Privacy Policy linked below. Mayo Clinic is a nonprofit organization and proceeds from Web advertising help support our mission.
Mayo Clinic does not endorse any of the third party products and services advertised. A single copy of these materials may be reprinted for noncommercial personal use only. This content does not have an English version. This content does not have an Arabic version.
See more conditions. Request Appointment. Ejection fraction: What does it measure? Products and services. What does the term "ejection fraction" mean? What does it measure? Answer From Rekha Mankad, M. Multimedia Chambers and valves of the heart. Thank you for Subscribing Our Housecall e-newsletter will keep you up-to-date on the latest health information. However, the acoustic window needs to be of sufficient quality to allow the delineation of the entire LV cavity endocardial border.
Because the image data are usually acquired over several heart beats, an ectopic beat or breathing during the imaging time will lead to artefacts which can alter the endocardial border see Figure 7 and different segments of the left ventricle will appear to contract at different times. Also, LVEF is usually calculated using commercially available software that is semi-automated, requiring the user to manually assign certain points e.
If the points are improperly assigned, the LVEF may be inaccurate. The location of the endocardial border may also be incorrectly interpreted, either by the operator or the software due to poor definition, and a papillary muscle or trabecula may be interpreted as being the endocardial surface.
The area of the tracing for each image slice is multiplied by the slice interval slice thickness plus image gap to determine a volume for that slice. The volumes of the slices are summed to determine an LV volume. This method requires few assumptions of LV shape because the entire LV cavity is traced. Because of the high contrast resolution and high signal:noise ratio of MRI, the endocardial border is usually well defined.
MRI is contraindicated in patients with implantable cardioverter defibrillators, most pacemakers and several other types of implanted devices. Cardiac MRI requires multiple breath holds, and image quality may be poor in patients who cannot hold their breath.
If the level of inspiration is different during the acquisition of different levels, segments of the LV may not be imaged while other segments may be imaged twice.
This may lead to variability in calculated volumes and LVEF. Because data are acquired over several cardiac cycles with ECG gating, image quality will be degraded in patients with cardiac arrhythmias or ectopic beats leading to decreased accuracy.
In a study by Karamitsos et al. The automated methods usually rely on the differentiation of the LV cavity from the endocardium based on Hounsfield unit measurements. As long as the contrast bolus timing is appropriate, there will be high contrast and spacial resolution resulting in a well defined endocardial border. Disadvantages of CT are the exposure of the patient to ionising radiation and the need for iodinated contrast material. Iodinated contrast material should be not be used in patients with iodinated contrast allergies — unless they have been pre-medicated to avoid any allergic reaction — and should be used judiciously in patients with poor renal function.
Also, variability in the selection of the ventricular basal segment will cause variability in LVEF calculation when using the Simpson method. Breathing during image acquisition can also lead to artefacts, which can reduce accuracy.
Because of the need for intravenous IV contrast to delineate the endocardium, a problem that is unique to CT is the need for proper coordination of the timing of contrast injection and scanning.
LVEF can be calculated by several methods using different nuclear cardiac imaging techniques. Most commonly, planar images of the left ventricle are acquired for analysis, although SPECT images can also be acquired.
If planar imaging is used, a left anterior oblique projection with best separation of the left and right ventricle is acquired for LVEF calculation. MUGA scan measures changes in radioactivity in the left ventricle between end-diastole and end-systole, rather than truly measuring LV volumes. Assignment of LV ROI can be automated, semi-automated or manual, automated and semi-automated edge detection being most commonly used.
Image acquisition is gated with an ECG and radioactive counts are acquired over multiple cardiac cycles. Each cardiac cycle is divided into a predetermined number of intervals usually 16 or 32 , corresponding to the number of frames images per cardiac cycle.
The frame with the highest counts is considered end-diastole and the frame with the lowest counts is considered end-systole. LVEF equals net counts in the end-diastolic frame minus net counts in end-systolic frame divided by net counts in end-diastole. Net counts are calculated by subtracting counts from a background ROI placed next to the left ventricle from measured LV counts. It can be performed in patients whose body habitus might prevent or limit the reliable use of other techniques.
There are no absolute contraindications to this technique. This will reduce the accuracy of LVEF calculations in patients with arrhythmias. In addition, poor labelling of the RBCs can occur, which can lead to poor count rates within the blood pool and increased background counts. If background counts are overestimated e. On the other hand, if background counts are underestimated e. Differences in software edge detection algorithms have also been shown to lead to variation in the calculated LVEF.
Gated myocardial perfusion SPECT is performed by injecting a patient with a radiolabelled myocardial perfusion agent such as technetium 99m radiolabelled sestamibi or tetrofosmin.
Ammonia, rubidium or fluorodeoxyglucose can be used as imaging agents. The LV functional assessment with LVEF calculation is usually done in conjunction with a myocardial perfusion study, 16—18 allowing function and perfusion to be evaluated with one test.
After injection, the radiopharmaceutical is taken up by the myocardium.
0コメント