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

more distal distributions of these arteries as well as in the posterior circulation in general. Following coronary artery bypass surgery, the location of wall motion abnormalities may be atypical, depending on the location of the myocardium perfused by the residual native arteries and by bypass gra s. In clinical practice, the most common wall motion analysis is a segment-by-segment description of wall motion as either being normal, hypokinetic, akinetic, or dyskinetic. A numeric score (1, 2, 3, 4) is then ascribed to each segment, and a score index is calculated by summing the scores and dividing by the number of visualized segments. e techniques for calculating a wall motion score are discussed in Chapter 15. Quantitative Techniques ere are a number of quantitative techniques for analyzing le ventricular regional function which have been used for investiga- tional purposes but are rarely used in routine clinical practice. ey are discussed here for historical purposes and because they o en provide insight into the limitations of more advanced quantitative techniques. ese include measurement of radian or area shrink- age in the short axis of the le ventricle. is is accomplished by describing a series of radians from the center of mass of the ven- tricle. e number of radians can range from 8 to 100, with each radian de†ned as the length from the center of mass to the endo- cardial border in diastole and subsequently in systole. Normal ven- tricular motion is represented by a reduction in the length of each of the constructed radians from diastole to systole (Fig. 5.29). In

Evaluation of Systolic Function of the Left Ventricle

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the presence of a regional wall motion abnormality, radians in the involved wall segment will lengthen rather than shorten (Fig. 5.30). In addition to radian length, sector area and myocardial thickness can be calculated using similar methods. Because of rotation of the heart in systole, there may not be exact correspondence of each radian position in diastole and systole, but rather the systolic length of a radian may be compared with the diastolic length of another. A more troublesome issue results from cardiac translation. Because there is motion of the center of the heart from diastole to systole, this results in motion and displacement of the systolic contour com- pared with the location of the diastolic contour. is has the eŠect of arti†cially shortening the radians that lie in the direction of transla- tional motion and lengthening the radians in the opposite direction if the diastolic center of mass is used as a reference (Fig. 5.31). is can be corrected by realigning the center of mass of the contour before radian comparisons are made. When dealing with a normal, symmetrically contracting ventricle, this will correct for the errors attributable to cardiac translation. However, if a wall motion abnor- mality is present, the center of mass in diastole and systole will not be equivalent with respect to the distance from either the normal or abnormal walls. If one then corrects by using a separate center of mass, there will be predictable underestimation of the extent of wall motion abnormality. Complicating any of the quantitative analyses of regional wall motion in ischemic disease is the phenomenon of tethering. is can occur on either a horizontal or vertical basis and occurs because the motion of a segment with intrinsically normal function may be altered by its proximity to an abnormal segment which “teth- ers” the adjacent normal segment and reduces its apparent function (Fig. 5.32). Regional wall motion abnormalities and the impact of coronary artery disease are discussed in more detail in Chapter 15. FIGURE 5.30. Schematic demonstration of posterior dyskinesis with no translational or rota- tional motion using the diastolic center of mass for both systole and diastole. Top: The dark outer ring represents the contour of the ventricle in diastole and the inner circle represents the endocardial contour in systole. Note the maximal area of dyskinesis at segment five with less dyskinesis at segment four and akinesis at segment six. Bottom: The change in radian length from diastole to systole is graphed. Note the apparent hyperkinesis of the noninvolved segments with increased radian shortening compared with normal contraction in Figure 5.19.

FIGURE 5.29. Schematic diagram of normal endocardial wall motion without translational motion. Top: The outer dark circle represents the diastolic thickness of the left ventricle and the inner lighter shaded circles represents the extent of systolic contraction. Eight radians from the center of mass have been drawn for both the diastolic ( dotted line ) and systolic ( solid line ) endocardial boundaries. Bottom: The percentage of change in length from dias- tole to systole is schematized. The dotted line represents zero change in length and the solid line represents the actual percentage of change in length for the normally contracting ven- tricle, which in this example is a 20% reduction in length. This diagram is subsequently repeated for demonstration of wall motion abnormalities and algorithms for correction of translation motion. In each subsequent similar figure, the darker outer ring represents the normal diastolic contour and the solid line represents the systolic endocardial contour.

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