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Left Ventricular Structure and Function

Basic Science for Cardiac Imaging

Partho P. Sengupta, MBBS, MD, DM^_*, Josef Korinek, MD^_*, Marek Belohlavek, MD, PhD, FACC, FESC^_*, Jagat Narula, MBBS, MD, DM, PhD, FACC, FAHA, Mani A. Vannan, MBBS, FACC, Arshad Jahangir, MD, FACC^_* and Bijoy K. Khandheria, MD, FESC, FASE, FACC^,_*

^_* Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota
Division of Cardiology, University of California at Irvine, Irvine, California
Division of Cardiovascular Diseases, Mayo Clinic, Scottsdale, Arizona

View larger version (89K): [in this window] [in a new window] [Download PPT slide]   Figure 1 Embryonic development of the left ventricular wall in a chick. (A) The tubular myocardium (My) (2 to 3 cell layers thick) is separated from the endocardium (En) by acellular cardiac jelly (CJ). (B) The inner layers proliferate to form trabeculations (Tr), which are nourished by the blood circulating through the intertrabecular spaces (ITS). The outer layers proliferate and undergo compaction (Co) and are covered by epicardium (arrowhead). (C) By the sixth embryonic day, the compact layer has thickened and is invaded by developing coronaries from the epicardial surface. (D) In the neonatal (day 10) heart, the multilayered compact architecture of the left ventricular wall is clearly appreciated with the innermost layer merging with the papillary muscle (mp). On the right side of each picture is a schematic drawing illustrating the major steps in development of ventricular myoarchitecture. Scale bars = A, B, C, 100 µm; D, 500 µm. Reproduced from Sedmera et al. (20) with permission.

View larger version (78K): [in this window] [in a new window] [Download PPT slide]   Figure 2 Helical arrangement of muscle fibers in the left ventricle of an explanted adult porcine heart. The arrangement of muscle fibers as seen in the circumferential-longitudinal plane changes from a left-handed helix in the subepicardium (A) to a right-handed helix in the subendocardium (B). The helical arrangement of the endocardial region is also reflected in the arrangement of trabeculae near the apex (C). A = anterior; P = posterior.

View larger version (54K): [in this window] [in a new window] [Download PPT slide]   Figure 3 Arrangement of left ventricular fiber sheets and cleavage planes in long-axis slices. (A) Longitudinal cross section of the left ventricle fixed in diastole (hematoxylin and eosin stain). (B) Radial orientation of the cleavage planes and the quantification of diastolic and systolic angles of the sheets and the cleavage planes from the boxed area in A. Reproduced from Chen et al. (33) with permission.

View larger version (105K): [in this window] [in a new window] [Download PPT slide]   Figure 4 Cross-sectional view of a rat's left ventricle (LV) when viewed along the short axis. The cross section obtained from the midsegment of the interventricular septum has been viewed from the basal end of the LV. The fiber sheets (dashed arrows) are seen to diverge away from midwall (hematoxylin and eosin stain) (A). The cleavage planes (arrow) separating the myofiber sheets are distinctly appreciated using high-resolution confocal laser scanning micrograph (B) magnification. Scale bar in B = 200 µm. RV = right ventricle.

View larger version (84K): [in this window] [in a new window] [Download PPT slide]   Figure 5 Assessment of cardiac muscle fiber orientation by diffusion tensor magnetic resonance imaging. In these examples (A and B), scalar and tensor glyph visualization methods have been used to investigate the helical structure of the heart muscle in an explanted fixed canine heart. Right-handed helical orientation (subendocardium) is shown in shades of purple, and left-handed helical muscle fiber orientation (subepicardium) is shown in shades of blue. The cross-sectional view (B) has been viewed from the basal end of the left ventricle. Reproduced from Zhukov and Barr (46) with permission. LV = left ventricle; RV = right ventricle.

View larger version (39K): [in this window] [in a new window] [Download PPT slide]   Figure 6 Longitudinal deformation of the anterior wall of the left ventricle by 2-dimensional speckle tracking of B-mode ultrasound images (2-dimensional strain). Longitudinal shortening starts during isovolumic contraction period and occurs earlier in the apex as compared with the base. Shortening-lengthening crossover of the basal anteroseptal segment is delayed until the end of isovolumic relaxation. Phase 1, isovolumic contraction; 2, ejection; 3, isovolumic relaxation; 4, early diastole; 5, late diastole. ECG = electrocardiogram.

View larger version (40K): [in this window] [in a new window] [Download PPT slide]   Figure 7 Circumferential deformation of the subendocardial and subepicardial regions of left ventricular apex by 2-dimensional speckle tracking of B-mode ultrasound images (2-dimensional strain). Note the presence of positive strains (lengthening) during the phase of isovolumic contraction. Note the higher circumferential strains of the subendocardial regions as compared with the subepicardial region. Peak shortening in some segments of the subepicardial region extends beyond the timing of aortic valve closure (postsystolic shortening, arrow). Phases 1 to 5 are described in the legend to Figure 6. ECG = electrocardiogram.

View larger version (52K): [in this window] [in a new window] [Download PPT slide]   Figure 8 Time sequence of circumferential shortening in a healthy subject by tagged magnetic resonance imaging. Several segments contract beyond aortic valve closure. + = measured data points; – = fitted line model to data for estimating T onset; circled + = end point of data used in the fit; upside-down triangles = estimated T onset; triangles = T peak. The vertical lines denote, from left to right, the moment of aortic valve opening (dashed), aortic valve closure (solid), and mitral valve opening (dashed). AL = anterolateral; AN = anterior; AS = antero-septal; IL = inferolateral; IN = inferior; IS = inferoseptal. Reproduced from Zwanenburg et al. (77) with permission.

View larger version (106K): [in this window] [in a new window] [Download PPT slide]   Figure 9 Direct in vivo imaging of anterior wall of a beating porcine left ventricle using high-resolution linear array transducer (10 MHz). (A) Anatomic M-mode imaging of the different layers of anterior segment of left ventricular apex at high temporal resolution (250 frames/s). During isovolumic contraction, the endocardium moves toward the cavity (blue arrows) and is accompanied with a reciprocal outward movement of the subepicardium (white arrows). A reverse pattern of movement is seen during isovolumic relaxation. These reciprocal movements of the subendocardial and subepicardial regions also are seen in tissue Doppler imaging, in the form of simultaneous red and blue colors within the inner and outer layers of the same segment of the myocardial wall during isovolumic contraction and vice versa during isovolumic relaxation (B). Phases 1 to 5 are described in the legend to Figure 6.

View larger version (133K): [in this window] [in a new window] [Download PPT slide]   Figure 10 Digital particle image velocimetry profiles of left ventricular flow during each phase of the cardiac cycle. Under specific conditions of dilution and administration to blood circulation, the echo contrast particles (microbubbles) can be tracked for calculating vectors and trajectories of flow within a 2-dimensional ultrasound scan plane. The ensemble-averaged velocity magnitudes are superimposed on the vector fields during isovolumic contraction (a), ejection (b), isovolumic relaxation (c), early diastole (d), diastasis (e), and late diastole (f). Note the apex-to-base redirection of blood flow during isovolumic contraction with formation of a dynamic vortex across the inflow-outflow region and the base-to-apex reversal of blood flow during isovolumic relaxation. LA = left atrium; LV = left ventricle. Reproduced from Sengupta et al. (61).