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

FIGURE 5.33. Schematic representation of the cubed formula for determining left ventricular mass. All measurements can be taken from either a two-dimensional or an M-mode echocardiogram of the minor axis of the left ventricle. The formula for calculation of left ventricular mass is as noted. Based on comparison with anatomic specimens, several regression equations have been developed that are variations on the basic cubed formula. LVID d , left ventricular internal dimension in diastole; PW, posterior wall.

Evaluation of Systolic Function of the Left Ventricle

resonance imaging as standards. Determination of le ventricular mass by these techniques is problematic in less than ideal studies and is rarely used in clinical practice. Physiologic Versus Pathologic Hypertrophy Le ventricular hypertrophy can be characterized as concentric, eccentric, or physiologic (Fig. 5.36). It should be emphasized that calculation of le ventricular mass is a determination of the mass of the le ventricular muscle and may not relate to overall cardiac enlargement. Increases in le ventricular mass can occur with chamber enlargement and relatively normal wall thickness (eccen- tric hypertrophy), as is seen in regurgitant valvular lesions, or sec- ondary to a predominant increase in wall thickness with normal chamber sizes, as is seen in the pressure overload of systemic hyper- tension. When evaluating patients for le ventricular hypertrophy, it is important to characterize the hypertrophy as being due to either chamber enlargement or increased wall thickness. One additional index of hypertrophy is relative wall thickness which is de†ned as (posterior wall thickness + interventricular septal thickness)/le ventricular internal dimension. Relative wall thickness of ≥ 0.42 has been used as a threshold of pathologic le ventricular hypertrophy.

using two-dimensional echocardiography, geometric assumptions of the ventricular shape are typically still employed but the assump- tion is that of a bullet-shaped ventricle rather than a sphere. In addi- tion, mean le ventricular wall thickness is determined rather than wall thickness at only one point on the septum and posterior wall. Mean wall thickness can be calculated by determining the epicardial and endocardial areas of the short axis of the le ventricle at the midcavity level. e dierence between these two areas then rep- resents myocardial area. Le ventricular mass can then be calculated either by an area length method or by assuming a truncated ellipse geometry (Fig. 5.35). More recently, three-dimensional echocardi- ography has been used to extract epicardial and endocardial borders from multiple orthogonal planes, from which le ventricular mass can also be determined. Limited studies have suggested excellent correlation of three-dimensional mass with anatomic and magnetic

FIGURE 5.34. Two-dimensionally guided M-mode echocardiogram recorded in a patient with mild hypertension. Note in the small inset, the tangential M-mode interrogation beam which is a result of beam orientation and slight angulation of the heart. The M-mode is as displayed from which a left ventricular internal dimension of 5.77 cm is measured. The true minor-axis dimension of the left ventricle is 4.7 cm. The bottom panel represents the calculated M-mode report from the measured values. The numbers in parentheses are the corresponding values from a true minor-axis dimension (4.7 cm) used rather than the off-axis 5.77 cm. Note the substantial overstatement of left ventricular mass using the dedicated M-mode measure- ment versus a true minor-axis dimension from the two-dimensional echocardiogram.

FIGURE 5.35. Illustration of methodology for calculating left ventricular mass using two-di- mensional imaging. In the central figure note that the epicardium and endocardium have been outlined in the short-axis view of the left ventricle from which mean wall thicknesses are calculated. At the lower right is an apical four-chamber view in which the length of the left ventricle has been measured. At the upper left of the calculations of left ventricular mass using an area length (A/L) method.

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