Final Feigenbaum’s Echocardiography DIGITAL

Chapter 5 Evaluation of Systolic Function of the Left Ventricle

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Chapter 5 Evaluation of Systolic Function of the Left Ventricle

Its role in obtaining linear measurements has already been dis- cussed. A number of two-dimensional echocardiographic views have been used to provide information regarding ventricular systolic function, some of which rely exclusively on area measurements and others of which rely on calculation of ventricular volume. Table 5.2 outlines commonly used two-dimensional measurements and their derived calculations. Table 5.3 provides the American Society of Echocardiography–recommended normal ranges for commonly obtained measurements. Most oen, apical images are used to determine ventricular vol- umes in diastole and systole, from which stroke volume and ejection fraction are calculated. €ere are several geometric assumptions and formulas that have been used in the past for calculating ventricular volume. €e advantage of the geometric assumption techniques, such as an area-length or truncated ellipse formula, is that they require only limited visualization for calculation of ventricular volume. €ese formulas work only in a symmetrically contracting ventricle and have been supplanted by more direct calculation of ventricular volumes. €e advent of high-resolution 90-degree digital two-dimensional scanners, as well as the computational capacity of quantitation pack- ages incorporated in modern platforms and o†-line analysis systems, has largely made these earlier methods for volume determination obsolete. Currently, the most common method for determining ven- tricular volumes is the Simpson rule, or the “rule of disks.” €is tech- nique requires recording an apical, four- and/or two-chamber view from which the endocardial border is outlined in end-diastole and end-systole. €e ventricle is mathematically divided along its long axis into a series of disks of equal height. Individual disk volume is calculated as the product of height and disk area, where disc height is assumed to be the total length of the le ventricular long axis divided by the number of segments or disks. €e surface area of each disk is determined from the diameter of the ventricle at that point (area = π r 2 ). €e ventricular volume is calculated as the sum of the volume of the disks. €is methodology is illustrated in Figure 5.7. If the ventricle is symmetrically contracting, either the four- or two-chamber view will re’ect the ventricular volume. For accurate volume determination, the transducer must be at the true apex and the ultrasonic beam must be through the center of the le ventricle. €ese conditions are frequently not met, resulting in underestima- tion of true ventricular volumes. €ere are several clues that help determine whether the transducer is at the true apex. Normally, the true apex is the thinnest area of the le ventricle. If the visu- alized apex has the same or greater thickness as the surrounding walls, and appreciable motion in systole, it is likely to be a tangen- tial cut through the le ventricle rather than a true on-axis view. In addition, a properly recorded apical view is de”ned as the one with the greatest long-axis (apex to base) dimension. In any view, foreshortening of the ventricular apex will result in underestimation

Evaluation of Systolic Function of the Left Ventricle

FIGURE 5.6. M-mode echocardiogram recorded through the aortic valve in a patient with reduced cardiac function and decreased forward stroke volume. Note the rounded closure of the aortic valve, indicating decreasing forward flow at the end of systole. Normal and abnor- mal aortic valve opening patterns are noted in the schematic superimposed on the figure.

E-point to septal separation and gradual closure of the aortic valve during systole. €e magnitude of opening of the mitral valve, as re’ected by E-wave height, correlates with the volume of transmitral ’ow and, in the absence of signi”cant mitral regurgitation, with le ventricular stroke volume. €e internal dimension of the le ven- tricle correlates with diastolic volume. As such, the ratio of mitral excursion to le ventricular size parallels ejection fraction. Nor- mally, the mitral valve E-point (maximal early opening) is within 6 mm of the le side of the ventricular septum. In the presence of a decreased ejection fraction, this distance is increased (Fig. 5.5). Inspection of the aortic valve opening pattern also provides indirect evidence regarding systolic function of the le ventricle. If le ventricular forward stroke volume is decreased, there may be a gradual reduction in forward ’ow in late systole. €is results in a rounded appearance of aortic valve closure in late systole (Fig. 5.6). Reliance on these earlier observations and calculations has been supplanted by direct measures of ventricular size and performance available from modern ultrasound platforms. MEASUREMENTS FROM STANDARD TWO-DIMENSIONAL IMAGING Two-dimensional echocardiography provides inherently superior spatial resolution for determining le ventricular size and function.

Table 5.2

AREA/VOLUME-BASED MEASUREMENTS FOR VENTRICULAR SIZE AND FUNCTION a

Parameter

Abbreviations

Formula

Units

cm 2

Short-axis diastolic area (at mid LV)

ASx d ASx s

cm 2

Short-axis systole area (at mid LV)

Fractional area change

FAC

(ASx d

– ASx s

)/ASx d

% or 0.XX

cm 2

Four-chamber LV area in diastole

ALV 4c–d ALV 4c–s

cm 2

Four-chamber LV area in systole

LV volume in diastole a

LVV d LVV S

mL

LV volume in systole a

mL

= LVV S

mL

Stroke volume

SV

LW d

Ejection fraction

EF

SV/LW d

% or 0.XX

a Determined by the Simpson rule, area length method, etc.

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