Left ventricular endocardial longitudinal and transverse changes during isovolumic contraction and relaxation: a challenge

Abstract

. Left ventricular endocardial longitudinal and transverse changes during isovolumic contraction and relaxation: a challenge. Am J Physiol Heart Circ Physiol 289: H196-H201, 2005. First published February 11, 2005 doi:10.1152/ajpheart.00867.2004 longitudinal and transverse geometric changes during isovolumic contraction and relaxation are still controversial. This confusion is compounded by traditional definitions of these phases of the cardiac cycle. High-resolution sonomicrometry studies might clarify these issues. Crystals were implanted in six sheep at the LV apex, fibrous trigones, lateral and posterior mitral annulus, base of the aortic right coronary sinus, anterior and septal endocardial wall, papillary muscle tips, and edge of the anterior and posterior mitral leaflets. Changes in distances were time related to LV and aortic pressures and to mitral valve opening. At the beginning of isovolumic contraction, while the mitral valve was still open, the LV endocardial transverse diameter started to shorten while the endocardial longitudinal diameter increased. During isovolumic relaxation, while the mitral valve was closed, LV transverse diameter started to increase while the longitudinal diameter continued to decrease. These findings are inconsistent with the classic definitions of the phases of the cardiac cycle. mitral valve; ventricles; hemodynamics; isovolumic contraction; isovolumic relaxation; mitral valve closure; cardiac cycle phases; left ventricle diameters THE CARDIAC CYCLE IS TRADITIONALLY divided into isovolumic contraction (IVC), ejection, isovolumic relaxation (IVR), and diastole (7). The concept of an initial isometric contraction during ventricular systole was originated by Wiggers (32), who stated that the first elevation in intraventricular pressure closes the atrioventricular valves while the ventricles contract in an isometric fashion. During the interval between the beginning of the rise in intraventricular pressure and the opening of the semilunar valves, the ventricular cavities are completely enclosed with a rising tension without change in ventricular volume. Later, Rushmer (23) showed that the initial phase of contraction was not an isometric contraction of all myocardial fibers of the left ventricle (LV). During IVC, he observed a rapid increase in LV pressure, a fast expansion of LV external circumference, and a rapid shortening of LV internal length. His conclusions were drawn from two experiments where he could successfully place internal distance gauges. In all other experiments, he failed to demonstrate the initial shortening of internal longitudinal dimension during IVC. Nevertheless, he concluded that the LV abruptly shortens during IVC and that this shortening is accompanied by an outward bulging of the LV main body (24,26). This sphericity of the external LV during IVC has also been described by several investigators (9, 27), who, in most cases, used epicardial markers. Others demonstrated the opposite, i.e., an elliptical pattern due to shortening of the LV internal mi...

Apex-to-Base Dispersion in Regional Timing of Left Ventricular Shortening and Lengthening

“…For relating the electrophysiologic sequences with the kinematics of regional LV deformation, a high-temporalresolution technique such as sonomicrometry is required because shortening and lengthening sequences originate rapidly during the isovolumic periods of the cardiac cycle (12). The utility of high-resolution (Յ4 ms) sonomicrometry in understanding transient time-related changes in cardiac geometry in vivo has been highlighted in recent investigations (12)(13)(14).…”

“…The utility of high-resolution (Յ4 ms) sonomicrometry in understanding transient time-related changes in cardiac geometry in vivo has been highlighted in recent investigations (12)(13)(14). The purpose of this study was to: 1) clarify the apex-versus-base variations in depolarization and repolarization sequences and in the onset and progression of shortening and lengthening, and 2) link these electrophysiologic and mechanical sequences by their selective analysis within the subendocardial and subepicardial regions of LV anterior wall.…”

Tomographic Left Ventricular Volumetric Emptying Analysis by Real-Time 3-Dimensional Echocardiography

“…Several studies using different noninvasive and invasive imaging techniques, such as 2-dimensional (2D) tissue Doppler imaging (TDI), [1][2][3] 2D strain by speckle tracking, 4,5 magnetic resonance imaging (MRI), 6,7 and implanted ultrasonic crystals, 8 have attempted to assess global and regional myocardial motion. In particular, some have focused on the mechanisms that control the regional timing of myocardial contraction and demonstrated that mechanical events parallel the apex-to-base direction of electrical activation.…”

Letter by Sengupta et al Regarding Article, “Mechanisms of Preejection and Postejection Velocity Spikes in Left Ventricular Myocardium: Interaction Between Wall Deformation and Valve Events”

“…5 Such deformation changes may have important roles in explaining the observed biphasic velocity spikes. In the discussion, the authors 1 present a picture of LV flow showing that apical flow displacement during preejection closes the mitral valve.…”