Heart function including ejection fraction (EF) is important in clinical practice because it is related to prognosis. Whether the patient suffers from valvular heart disease or ischemic heart disease, a measure of heart function including ejection fraction (EF) can predict future clinical outcome and assist in risk stratification. Several approaches to detect patients at risk for cardiac events have proven to be of value. These include exercise testing, assessment of exercise capacity, and determination of left ventricular function.
Heart function including ejection fraction (EF):
Ejection fraction (EF) is a percent measurement of how much blood the left ventricle (LV) pumps with each contraction. The left ventricle (LV) does not empty out with each contraction. Normally the left ventricle (LV) ejects between 50% and 70% of the blood it contains. Below is an echocardiogram of a patient with a normal ejection fraction (EF= 55-60%).
The stroke volume (SV) is calculated by taking the amount of blood estimated when the left ventricle is completely filled (end diastole= LVEDV = 131 ml) and subtracting the amount of blood remaining within the left ventricle when it is finished contracting (end-systole = LVESV = 55 ml). The derived stroke volume (SV = 76 ml) is then divided by the amount of blood contained when the left ventricle is completely filled (LVEDV = 131 ml) to obtain the ejection fraction (EF = 58%) (diagram below).
Patients with normal heart function and ejection fraction (EF) usually feel comfortable with exercise activity unless the patient is deconditioned and suffers from being sedentary. Another condition where patients can be suffering from shortness of breath but have a normal ejection fraction is called diastolic heart failure. The patients with this condition usually have a left ventricle with thicker and stiffer walls. The heart holds a smaller amount of blood and cannot meet the body’s needs. This is also called “heart failure with preserved ejection fraction” (HFPEF). Several elderly patients with hypertension and diabetes can be affected by this condition. Below is an MRI study followed by an echocardiogram of a patient with severe left ventricular hypertrophy and normal heart function and ejection fraction. You can see how such a thickened myocardial wall can lead to increased in stiffness and reduced compliance and elevated pressure within the left ventricle during diastole or when it is trying to fill.
A borderline heart function and ejection fraction (EF) (41-49%) can result from a cardiomyopathy, valvular heart disease or ischemic heart disease (pts with coronary artery blockages). This usually leads to shortness of breath during activity. Below is a patient with coronary disease and critical stenosis of the proximal LAD. There is hypokinesis or reduced contraction in the distal anterior wall and apex. This also contributes to a mildly reduced heart function and ejection fraction at 49%. This patient experienced shortness of breath running up a hill.
The MRI below was performed at Brookwood Baptist Medical Center at Princeton. The patient suffered an anterior myocardial infarction few months prior. Dr Bracer obtained the images using a 1.5T GE MRI system. We can see some hypokinesis of the anterior wall and overall mildly reduced heart function and ejection fraction.
A reduced heart function and ejection fraction (EF) (<40%) usually manifests as fatigue and shortness of breath, sometimes even at rest. It is usually a manifestation of a cardiomyopathy and it can be ischemic or non-ischemic. Below is an example of a patient with severe non-ischemic cardiomyopathy and ejection fraction of less than 20%. The echocardiogram depicts an enlarged and weakened left ventricle.
Below is an MRI of a patient who suffered an extensive myocardial infarction. The patient presented as an anterior STEMI with total occlusion of the LAD. Despite early intervention and PCI with coronary stenting of the LAD, the patient suffered extensive damage with a large scar involving the distal antero-septum, apex and distal antero-lateral walls (yellow arrow). Notice the thinning and absence of contraction of these walls. The global function is severely reduced and there is evidence of clinical heart failure with bilateral pleural effusions (blue arrow). In addition, there is a small pericardial effusion surrounding the right ventricle and in part the right atrium (red arrow).
Heart function assessed by measuring left ventricular volumes.
In patients with valvular insufficiency or ischemic heart disease, the enlargement of the left ventricular volume (particularly end-systolic LVESV) can be related to a poor prognosis. For this reason, serial measurements of left ventricular size and function are used to follow these patients so that surgical intervention can be performed prior to irreversible damage to the heart is done. Similarly, patients recovering from a large myocardial infarction can develop adverse left ventricular remodeling leading to irreversible damage and the development of clinical heart failure. Below is an MRI study of a patient who sustained a large anterior myocardial infarction. At baseline (upper image), the left ventricular end-diastolic volume (LVEDV) measured 250 ml, the end systolic volume (LVESV) 173 ml with reduced heart function and ejection fraction (EF) 30%. One year later, another MRI study (lower image) was performed on the same patient and revealed an enlargement of left ventricular size with LVEDV of 314 ml, LVESV of 241 ml and a weakening of the heart function and ejection fraction EF of 23%. This is called adverse remodeling and has a poorer prognosis in patients after a myocardial infarction.
Heart function assessed by analyzing regional left ventricular function.
Assessing regional function or wall motion of the left ventricle allows for the detection of ischemic heart disease (patients with coronary artery blockages). It can also detect areas of myocardial fibrosis or scarring. Regional wall motion abnormality has been linked to prognosis. In the Strong Heart study for example, men older than 60 years of age with segmental wall motion were found to have a 2.5 fold increase in coronary vascular events.
The normal wall motion of the heart is represented by a normal wall thickening during the contraction of the left ventricle. Regional heart function abnormality can be described as a weakening of the contraction of some parts of the heart muscle. This does not always lead to weakening of the global heart function. It usually depends on the degree and the extent of the heart walls involved. Below are two MRI studies depicting extensive antero-apical scars (yellow arrows). These patients suffered anterior STEMIs caused by occlusion of the proximal LAD or widow maker. This results in a large area of myocardial damage with thinning and absence of contraction (akinesis) of the walls. The area of damage is large and affects the global function of the heart. The left ventricle is enlarged and the heart function and ejection fraction EF is severely reduced (<20%).
Experimental studies have shown that a reduction of coronary blood flow resulting from transient occlusion or progressive constriction of a coronary artery results in the segmental wall motion abnormality. Studies by Gould have shown that such a reduction of coronary blood flow at rest is not present until the severity of the stenosis or narrowing exceeds 85%. Restoration of normal flow is associated with an eventual return to normal wall motion. In patients with coronary artery disease and without a previous myocardial infarction, segmental wall motion abnormality increases with decreased coronary blood flow. Myocardial perfusion using nuclear imaging technique correlates well with segmental wall motion analysis. In patients without a prior myocardial infarction, resting or stress-induced wall motion abnormalities, occur almost exclusively in regions with jeopardized perfusion. These regional abnormalities are potentially reversible when treated with myocardial revascularization (PCI or CABG). Recovery of segmental wall motion is seen also in patients treated after a myocardial infarction. Below is a patient treated with a non STEMI myocardial infarction. The wall motion abnormality (akinesis or absence of thickening) (yellow arrow, upper image) was restored toward normal (hypokinesis, yellow arrow, lower image) by reopening his artery using percutaneous coronary intervention and potentially by the stem-cell therapy that he may have received as part of the Athersys trial.
If you like the information in this article, make sure you read: Can heart attack damage be reversed? Stem cells in the treatment of a heart attack: a non-STEMI. Surviving a heart attack; the Big one and Stem cells in the treatment of Heart Failure.
We would like to acknowledge the expertise of Jay Roberson at VitalEngine and Dr Ricardo Bracer for the MRI imaging.