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School of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
Submitted 5 November 2003 ; accepted in final form 18 March 2004
Mechanical activation of the normal left ventricle (LV) is not simultaneous; however, the potential consequences of the ejection function of the ventricle are not entirely known. We studied contraction of the LV free wall to determine whether it reveals a contraction wave in the axial direction during ejection. Seven guinea pig hearts in situ were studied via thoracotomy. In each heart, the ventricular and aortic pressures were measured by two microtipped manometers (2-Fr, Millar). Contraction of the LV free wall was assessed with a video system (Dalsa D6-0256 camera and EPIX PIXCI D32 frame grabber; acquisition rate, 500 frames/s), and 1518 epicardial markers were used to divide the region into 2025 triangular areas. The area sizes were studied during contraction to locate the position of the contraction wave. For each triangular area, two variables were determined as follows: the time (tc) from the end of diastole until the size of the area reached 80% of maximum size reduction (normalized with the duration of systole) and the normalized latitude (Lax) of the area (determined at the end of diastole). A relationship between these two variables was determined by regression analysis. We found that the tc at which the contraction wave reached a triangular area was in positive correlation with the Lax value for that triangular area with a slope of 0.25 ± 0.09 and a linear correlation coefficient of 0.41 ± 0.08. Thus contraction in the guinea pig LV free wall occurs progressively from apex to base with successive areas reaching 80% contraction.
latitude; triangular area; epicardial marker; apex; base
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