Final Feigenbaum’s Echocardiography DIGITAL

Feigenbaum’s Echocardiography

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Feigenbaum’s Echocardiography

Determination of Left Ventricular Mass Echocardiography was one of the rst imaging modalities used clinically for determination of le ventricular mass. It has seen widespread acceptance in epidemiologic studies of hypertension in which the presence of hypertrophy has been associated with wors- ened outcomes and its regression has been a goal of therapy. Le ventricular mass can be determined using a number of echocardio- graphic algorithms. e earliest methodology for determining le ventricular mass was based on M-mode measurement of septal and posterior wall thickness and the le ventricular internal dimension. M-mode cal- culations assume a prede ned ventricular geometry, and their accu- racy will diminish in instances in which the le ventricular shape is abnormal. One of the methods for determining le ventricular mass is the cubed (Teichholz) formula, which assumes that the le ventri- cle is a sphere. e diameter of this sphere is the interior dimension of the le ventricle and the sphere wall thickness is that of ventric- ular myocardium. e formula calculates the outer dimensions of the sphere and then the inner dimension, the di erence being the presumed le ventricular myocardial volume. e cubed formula is expressed as le ventricular mass = (interventricular septum + le ventricular interior dimension + posterior wall) 3 – le ventricular interior dimension 3 (Figs. 5.33 and 5.34). is then gives the vol- ume of the stylized sphere of the myocardium, which, when mul- tiplied by the speci c gravity of muscle (1.05 g/cm 3 ), provides an estimate of le ventricular mass. Several investigators subsequently modi ed this approach using regression analysis. e cubed volume approach has the obvious limitation of determining ventricle size and wall thickness only along a single line and incorrectly assum- ing spherical ventricular shape. As it is common for the M-mode dimension to exceed the true minor-axis dimension, further error is introduced. Although the regression equations allow calculation of mass that correlates with autopsy specimens, there can be substan- tial error in the actual mass determination. e cubed methodol- ogy has been widely used, especially in serial evaluations, because for any given patient, the magnitude and direction of the error is expected to remain constant. In theory a more accurate determination of le ventricular mass can be obtained with two-dimensional echocardiography. When

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FIGURE 5.31. Schematic representation of posterior dyskinesis with posterolateral trans- lation, using separate diastolic and systolic centers of mass for determining radian length. Note that because there is posterior dyskinesis, the systolic center of mass moves toward the dyskinetic wall, resulting in an apparent reduction in the degree of dyskinesis when separate systolic and diastolic radian lengths are then compared. This results in an artifactual under- estimation of the severity of the wall motion abnormality and a simultaneous underestima- tion of function in the noninvolved zones.

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FIGURE 5.32. Schematic representation of hori- zontal tethering. This diagram represents posterior dyskinesis without translational motion. Note that the true extent of the infarct is as noted in the darkly shaded area, encompassing radian five and parts of radians six and four. Note that there is a border zone ( lightly shaded area ) adjacent to the infarct area that is anatomically normal but has abnormal motion due to the tethering effect of pos- terior dyskinesis. In the schematic, the true ana- tomic defect represents 20% of the circumference of the left ventricle with the tethered border zone giving an apparent total extent of 30%.

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