Lv

Short Ribs Definition

Fig. 7. (A) Tissue harmonic imaging. Even with suboptimal imaging (left panel, parasternal short axis view of the left ventricle) tissue harmonic imaging markedly improves endocardial definition. Note reverberation artefacts (arrows) arising from ribs. (B) Left ventricular opacification/endocardial border definition. Contrasts methods assist in delineating the endocardial border. Left ventricular opacification using microspheres (e.g., Optison® or Definity®) are popular (compare left and middle panels). Another myocardial contrast imaging technique is shown in right panel. (Please see companion DVD for corresponding video.)

Fig. 7. (A) Tissue harmonic imaging. Even with suboptimal imaging (left panel, parasternal short axis view of the left ventricle) tissue harmonic imaging markedly improves endocardial definition. Note reverberation artefacts (arrows) arising from ribs. (B) Left ventricular opacification/endocardial border definition. Contrasts methods assist in delineating the endocardial border. Left ventricular opacification using microspheres (e.g., Optison® or Definity®) are popular (compare left and middle panels). Another myocardial contrast imaging technique is shown in right panel. (Please see companion DVD for corresponding video.)

In an effort to standardize nomenclature of myocardial segments across other cardiac imaging specialties, the American Heart Association (2002) issued a unifying 17-segment model (Fig. 10B). Using this model, LV segments 1-6 are at the base (mitral valve level), segments 7-12 are in the middle (papillary muscle level), segments 13-16 occupy the apical region, and segment 17 represents the very tip of the apex. The latter does not encroach into the ventricular cavity. The segmental numerical model can be matched to the more practical anatomical descriptive terminology as shown in Fig.10B.

The segmental numerical model nomenclature also corresponds well with coronary artery distribution (see Chapter 3, Fig. 58; Chapter 7, Figs. 3-6). From this, various indices of coronary artery territory involvement, e.g., left anterior descending artery, may be derived.

limitations of regional wall motion assessment

Regional wall motion assessment is heavily influenced by image quality. Endocardial border definition deteriorates when still frames are acquired from digital video files. The audio/video interleaved (AVI) and the digital imaging and communications in medicine (DICOM) video format are the two most popular. Digital videos consist of multiple still frames in rapid succession, usually in the order of 30-60 frames per second. When the video is stopped, and a single still frame is selected, image quality characteristically degrades, including endocardial border definition.

Angulation of the transducer during acquisition of short-axis views may misrepresent true segmental

Dicom Format Definition

APi< AP2 BiPione Other

Fig. 8. Dynamic endocardial border analysis. Dynamic left ventricular endocardial border analysis is shown in this patient with mitral stenosis (and a severely dilated left atrium). (Please see companion DVD for corresponding video.)

APi< AP2 BiPione Other

Fig. 8. Dynamic endocardial border analysis. Dynamic left ventricular endocardial border analysis is shown in this patient with mitral stenosis (and a severely dilated left atrium). (Please see companion DVD for corresponding video.)

anatomy and is avoided by using the recommended technique (Fig. 11). Translational and rotational movements of the heart during the cardiac cycle cannot be avoided, but can be minimized by acquiring images during end-expiration. Care should be taken to avoid triggering the Valsalva maneuver.

Restricted septal movement can be mistaken for septal hypokinesis or akinesis. Apparent hypokinesis of the septum can be seen following any surgery that breaches the pericardium. Closer observation of the septum will often show normal systolic thickening in the absence of true ischemic injury.

Paradoxical septal motion in the presence of otherwise normal septal myocardium is seen in right ventricle (RV) pressure and volume overload states (Chapters 18 and 21), pericardial effusion and constrictive pericarditis (Chapter 10), or with certain arrhythmias, e.g., left bundle branch block.

quantitative measures of lv systolic function

Comparisons of LV end-diastolic and end-systolic dimensions form the basis of quantitative estimates of LV function, e.g., fractional shortening and EF (Fig. 12, Table 6). Fractional shortening—the percentage change in the LV minor axis in a symmetrically contracting ventricle—can be derived using the formula:

Fractional Shortening (FS)(%)

= (LVIDd - LVIDs)/LVIDd x 100% FS = 25% - 45% (normal range)

Volumetric estimates of LV volumes by 2D echocar-diography are based on three geometric methods that combine measurements of LV dimensions and area to calculate volume (Table 6; Fig. 13A). These are:

1. Prolate ellipsoid method.

2. Hemi-ellipsoid (bullet) method.

3. Biplane method of discs (modified Simpson's rule).

The prolate ellipsoid method assumes a prolate ellipsoid systolic and diastolic LV geometry). Area-length or length-diameter methods can be used. The singleplane and biplane area-length methods are shown in Fig. 13B,C.

The combined geometric model—of a hemisphere and an ellipsoid (hemi-ellipsoid)—provides a better estimate of LV volume (Fig. 13D), but the biplane method of discs (modified Simpson's rule) is recommended by the ASE and the European Association of Echocardiography. This method does not assume a predetermined geometry of the LV, but instead defines the LV geometry following manual tracing of the acquired LV cavity borders. The LV volume is then quantified by assuming the LV cavity is a stack of elliptical discs whose volumes are quantified and summated (Fig. 14).

Two orthogonal views—apical four-chamber and apical two-chamber—and manual tracing of endocardial borders manually traced at end systole and end-diastole are needed. Automated software divides the LV into a stack of discs oriented perpendicular to the long axis of the ventricle, and summates their individual volumes (Fig. 14).

Systole

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