Final Feigenbaum’s Echocardiography DIGITAL

Feigenbaum’s Echocardiography

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Feigenbaum’s Echocardiography

DISEASE FOR WHICH MYOCARDIAL STRAIN IS ABNORMAL PRIOR TO DETECTION OF TRADITIONAL FINDINGS

Table 5.4

Systemic disease Hypertension

Diabetes mellitus Glycogen storage disease Cardiac amyloid Primary myocardial disease Hypertrophic cardiomyopathy Dilated cardiomyopathy Adriamycin toxicity Cardiac rejection posttransplant Coronary artery disease

Low-grade ischemic Hibernation/stunning Stress-induced ischemia

e highly quantitative and detailed techniques of strain and strain rate analysis clearly detect abnormalities in myocardial con- traction or deformation that are not apparent by visual analysis of wall motion characteristics. ey remain limited by the technical and biologic factors discussed above but have shown promise as markers of preclinical disease in a number of conditions (Table 5.4). While reduced strain or strain rate may be noted in many diseases, early in their course, and before abnormalities are otherwise detectable, a reduction in strain or strain rate remains nonspecic for any given disease, and in many instances the dierential diagnosis includes two or more entities with similar early presentations. While tech- nically feasible, calculation of radial and circumfractional strain has seen little clinical acceptance. Multiple studies have suggested that longitudinal strain and GLS are the more stable, reproducible, and clinically feasible calculations. For this reason, they have seen increasing clinical acceptance for evaluation of leƒ ventricular func- tion, determination of prognosis, and serial follow-up in a variety of clinical scenarios. Ventricular Torsion Normal contraction is a complex process involving contraction of circumferentially located myocardial bers. In early systole, the leƒ ventricle rotates clockwise (as viewed from the apex). Subsequently, the base of the heart continues with clockwise rotation and the apex develops counterclockwise rotation. is results in a “wringing” motion of the ventricle in systole. e degree of twisting of the heart varies with age and is altered in a variety of disease states. Loss of this normal wringing motion may be an early marker of preclinical cardiomyopathy. While recognition of this twisting motion of the heart allows more detailed recognition of myocardial mechanics in both diastole and systole, clinical application of this phenomenon has not yet been established. e twisting motion of the heart can be analyzed using either Doppler tissue imaging or speckle track- ing and has likewise been conrmed with tagged, magnetic reso- nance imaging. Figure 5.26 was recorded in a patient with normal leƒ ventricular contractility using a hybrid speckle tracking system in which the clockwise rotation at the base of the heart and coun- terclockwise rotation at the apex are clearly demonstrated. is phenomenon can also be demonstrated using Doppler tissue tech- niques in which dierential timing to peak velocity of subepicardial and subendocardial regions can be displayed as well as direction of motion in opposing walls from which the torsion can likewise be surmised. Rotation of the heart is described in degrees and when viewed as noted above, the normal myocardium has a positive rota- tion at the base and a negative rotation at the apex. e dierence between the two represents the total rotation which, when divided by the distance between the two analyzed segments, results in cal- culation of torsion dened as the twist in degrees divided by the distance (Fig. 5.27).

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FIGURE 5.26. Parasternal short-axis view recorded at the base and apical levels in a patient with normal ventricular function. A modified speckle tracking algorithm has been used to track endocardial targets and displayed as a vector velocity map in which the length of an arrow represents magnitude of motion. The vector also demonstrates the direction of motion. Note in this normal example, the clockwise orientation of the velocity vectors at the base of the heart and the counterclockwise direction of the velocity vectors at the apex, consistent with normal “wringing” motion of the left ventricle.

ASSESSMENT OF REGIONAL LEFT VENTRICULAR FUNCTION

Coronary artery disease, with its sequelae of myocardial ischemia, infarction, and chronic remodeling is the most common form of acquired heart disease encountered in adults. Coronary artery dis- ease typically results in regional rather than global abnormalities, which requires a dierent approach to analysis from that used for assessment of global function (Table 5.5). Normal ventricular contraction involves several simultaneous events. Myocardial bers are oriented in a spiral fashion around

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