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 5.1. Schematic of a parasternal long-axis view of the left ventricle depicting linear measurements. By convention, linear measurements of the left ventricle are made at the level of the mitral chordae. From the linear internal dimension of the left ventricle in diastole and systole, fractional shortening can be calculated as noted. When measur- ing ventricular septal thickness, caution is advised to avoid measuring the most prox- imal portion of septum, which is frequently an area of isolated hypertrophy and angula- tion that does not truly represent ventricular wall thickness. FS, fractional shortening; LVID d , left ventricular internal dimension in diastole; LVID S , left ventricular internal dimension in systole; PW, posterior wall.

Evaluation of Systolic Function of the Left Ventricle

dimension. is phenomenon is illustrated in Figure 5.2 and is very common in elderly patients in whom there is angulation of the ven- tricular septum. In this instance, an M-mode beam traverses the ventricle in a tangential manner and overestimates the true inter- nal dimension. As a two-dimensionally guided M-mode cursor must still adhere to beam direction from the transducer, it is oen not possible to align the beam truly perpendicular to the long axis of the ventricle so that it reects the true minor-axis dimension. Some platforms may allow an “anatomical M-mode” beam to be derived from a two-dimensional dataset and thereby remove this limitation. When comparisons are made between M-mode and two-dimensional minor-axis dimensions, the M-mode dimension typically overestimates the true minor axis of the le ventricle by 6 to 12 mm. is systematic discrepancy becomes greater with age and the attendant angulation of the heart. For any given patient, one can generally assume that the degree of oƒ-axis interrogation will remain stable over time and this overestimation will remain con- stant. As such, in the absence of new regional abnormalities, diƒer- ences in serial measurements retain their clinical validity, although the actual dimension may be incorrect. M-mode echocardiography provides a slight advantage for timing of events but confers no real advantage over direct two-dimensional measurements for chamber dimensions. ere are several additional parameters of ventricular performance that can be derived from M-mode measurements. ese include rates of systolic wall thicken- ing of the posterior wall and calculation of velocity of circumferen- tial shortening. For the latter calculation, the minor-axis is assumed to represent a circle of known diameter from which the circumfer- ence can be calculated and the rate of change of circumference deter- mined. is measurement, typically standardized by normalizing to heart rate, is rarely used in contemporary practice. An additional M-mode measurement that has been employed in the past is the descent of the base. During ventricular contraction, the base (annulus) of the heart moves toward the apex. In the pres- ence of global le ventricular dysfunction, the magnitude of this motion is directly proportional to systolic function. M-mode inter- rogation is undertaken of the lateral mitral annulus, and annular excursion toward the transducer is then calculated (Fig. 5.3). ere is a relatively linear correlation between the magnitude of systolic

FIGURE 5.2. Parasternal long-axis echocardiogram and two-dimensional–derived M-mode echocardiogram in a patient with normal ventricular function. On the M-mode echocardio- gram, note the internal dimension of the left ventricle of 5.5 cm and the derived values. On the two-dimensional echocardiogram, the longer white line represents the M-mode interro- gation beam. Note that it traverses the left ventricle in a tangential manner and results in an internal dimension of 5.5 cm. The yellow line is the true short-axis dimension of the left ventricle which is substantially smaller at 4.5 cm. PW, posterior wall.

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