Ejection fraction, measurement

Type 1 question regarding diagnostic accuracy of a test In patients coming to the emergency department with shortness of breath, how well does B-type natriuretic peptide (BNP) or N-terminal pro-BNP predict (identify the presence of) heart failure as assessed by the cardiac ejection fraction measured by echocardiography ... 

Monitor patients ejection fraction (measure of cardiac function) to assess cardiac toxicity. 

During hospitalization, a measurement of left ventricular function, such as an echocardiogram, is performed to identify patients with low ejection fractions (less than 40%) who are at high risk of death following hospital discharge. 

Radionuclide angiocardiography is used to measure ejection fraction (EF), regional ventricular performance, cardiac output, ventricular volumes, valvular regurgitation, asynchrony or wall motion abnormalities, and intracardiac shunts. 

Cardiac function may be evaluated by the determination of left (or right) ventricular ejection fraction (VEF). In this procedure, regions of interest are defined at the end diastolic and end systolic phases of heart beat. The ejection fraction is defined as the ratio of tracer (blood) in the heart in the contracted (systolic) versus the relaxed (diastolic) phases of the heart cycle with appropriate corrections for decay and gamma camera dead time. The value obtained provides a measure of the ability of the heart to pump blood through the lungs (RVEF) or the body (LVEF). A criticism of Ir-191m for this application has been that the half-life (4.96s) is too short to allow effective visualization and quantitation of left ventricular function in adults, particularly those with delayed transit times. A recent... 

Ideally biomarkers of activity should be identified at various times over the course of the study to support the pharmacodynamic activity (e.g., normalization of insulin, improvement in beta cell function as measured by C-peptide level, or control of glucose following transplantation of P pancreatic islet cells) improvement of motor coordination in mice with spinal cord damage following transplant of neurons or repair of heart function (e.g., functional measures such as LV ejection fraction, pressure volume loops, ventricular pressure and heart wall thickness). Such markers may also be useful in subsequent clinical... 

Cardiotoxic effects are relatively uncommon with mianserin (2). In a placebo-controlled study in 50 patients with a variety of cardiac conditions who were taking anticoagulants, mianserin (up to 30 or 60 mg) had no effects on electrocardiography, blood pressure, or pulse rate after 3 weeks. In a second phase, mianserin (up to 60 mg/day) was compared with amitriptyline (up to 150 mg/day) and placebo in 18 healthy volunteers. Measurements included systolic time intervals, electrocardiography at rest and during exercise, echocardiography, and blood pressure. Amitriptyline had a negative inotropic effect mianserin increased ejection fraction. The results of both these experiments led the authors to conclude that mianserin is an antidepressant with very low cardiac toxicity. 

Note that each question (1) identifies the patienfs problem (shortness of breath and the clinical setting [emergency department or hospital]), (2) the test being used (BNP or N-terminal pro-BNP), (3) the reference standard for the diagnosis (ejection fraction as measured by echo) or for the clinical outcome (rate of subsequent readmission), and (4) an outcome (abifity to detect the presence of heart failure or ability to treat heart failure). 

The importance of other factors additional to amount ofnecrosis has also been studied. In patients with first acute MI treated with PCI, LAD-related MI show for a similar amount of myocardial necrosis as determined by enzymatic infarct size, lower left-ventricular ejection fraction (LVEF) when compared to non-LAD-related MI. LVEF-measured 6-month post-MI showed a decrease, for every 1000 cumulative lactate dehydrogenase release, of 4.8% for LAD and 2.4% for non-LAD-related infarcts (p < 0.0001), and these results remain in the multivariate analysis (Elsman et al., 2006). 

A new system for the metabolic investigation of the isolated perfused rat heart has been developed. The novel two surface-coil probe was combined with a dual perfusion system which allows spectra to be collected independently from the two coronary beds of the heart. The technique has been demonstrated in an experiment where P NMR spectra were collected from a perfused rat heart in which the septum and right ventricle were made ischaemic whilst the left ventricle wall was fully perfused.Spatially localised in vivo P NMR and MRI have been used to measure mean murine myocardial PCr/ ATP ratios of 2.0 0.2 and left ventricular ejection fractions of 65 7% at a physiological heart rate of approximately 600 beats min . ... 

Cardiac performance is also best assessed during catheterization procedures as direct visuahzation of performance along with calculated parameters that can he obtained simultaneously and represent real-time values. Measured and observed parameters obtained during catheterization are used to determine cardiac performance. Contractility, as judged by wall motion and ejection fraction, can be used to assess global cardiac performance and to plan and evaluate or assess therapy. 

Left ventricular ejection fraction—Also known simply as the ejection fraction, it is the fraction or percentage of the end diastolic blood volume ejected by the left ventricle during systole. It is a measurement of cardiac systolic function with a normal ejection being >60%. It can be determined noninvasively by an echocardiogram. 

Thus, echocardiography is recommended as a screening tool, but not as the definitive diagnostic tool in patients suspected of having pulmonary hypertension. For a particular patient, following the initial correlation of the echo estimate of PA pressure with direct catheterization measurement will allow subsequent patient specific correlations. Tricuspid annular plane systolic excursion (TAPSE) has been shown to correlate strongly with RV ejection fraction as assessed by radionuclide angiography (34). It has been used in both two- and three-dimensional evaluations, and as a means of serial follow-up studies of... 

Strauss HW, Zaret BL, Hurley PJ, Natarajan TK, Pitt P (1971) A scintiphotographic method for measuring left ventricular ejection fraction in man without cardiac catheterization. Am J Cardiol 28 575-580... 

Figure 13-2. Ventricular function (Frank-Starling) curves. The abscissa can be any measure of preload—fiber length, filling pressure, pulmonary capillary wedge pressure, etc. The ordinate is a measure of useful external cardiac work—stroke volume, cardiac output, etc. In congestive heart failure, output is reduced at all fiber lengths and the heart expands because ejection fraction is decreased. As a result, the heart moves from point A to point B. Compensatory sympathetic discharge or effective treatment allows the heart to eject more blood, and the heart moves to point C on the middle curve.

The same ventricle may be coupled to a pathological arterial system, for example, one with doubled peripheral resistance R. As expected, increased peripheral resistance raises arterial pulse pressure (to 140/95 mmHg) and impedes the ventricle s ability to eject blood (Figure 8.6). The ejection fraction decreases to 50% in this experiment. Other experiments, such as altered arterial stiffness, may be performed. The model s flexibility allows description of heart pathology as well as changes in blood vessels. This one equation (Equation 8.8) with one set of measured parameters is able to describe the wide range of hemodynamics observed experimentally [11],... 

In mammals, there are characteristic variations in cardiac function with heart size. In the power law relation for heart rate as a function of body mass (analogous to Equation 54.3), the coefficient k is 241 beats.min and the power a is —0.25 [5]. In the smallest mammals, hke soricine shrews that weigh only a few grams, maximum heart rates exceeding 1000 beats.min have been measured [ 57]. Ventricular cavity volume scales linearly with heart weight, and ejection fraction and blood pressure are reasonably invariant from rats to horses. Hence, stroke work also scales directly with heart size [58], and thus work rate and energy consumption would be expected to increase with decreased body size in the same manner as heart rate. However, careful studies have demonstrated only a twofold increase in myocardial heat production as body mass decreases in mammals ranging from humans to rats, despite a 4.6-fold increase in heart... 

There are many direct and indirect (noninvasive) methods of measuring cardiac output. Of equal importance to the number that represents cardiac output is the left-ventricular ejection fraction (stroke volume divided by diastolic volume), which indicates the abUity of the left ventricle to pump blood. 

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