engleski

Regional differences in radial function in a closed chest, closed pericardium model of acute left ventricular afterload increase.

Purpose: Chronic pressure overload as in hypertension leads to regional LV remodelling, primarily affecting the basal iv. septum (IVS) which hypertrophies and shows reduced longitudinal function. This can be compensated by increased radial function, particularly in early disease. Measurement of systolic upstroke and diastolic downstroke of LV wall motion by M-mode might provide similar radial data. We have tested these easily obtainable measurements on our closed chest/closed pericardium pig model, pertaining as close to physiology as possible. In this model, we aimed to study LV wall systolic thickening and diastolic thinning velocities in acute pressure overload. Methods: 7 anesthetised, closed chest/closed pericardium pigs were instrumented with a descending aorta balloon, partially inflated during 5-10 heartbeats creating an 30% LV pressure increase. Echocardiographic LV LAX B-mode cine-loops were acquired (5 pre-, 5-10 inflation, 10 postinflation beats). The velocity of systolic thickening upstroke and diastolic thinning downstroke of the IVS and the LV posterior wall (LVPW) were measured from anatomic M-mode images of the LV base, mid and apex. Results: During balloon inflation, a reduction in the upstroke and downstroke velocities occurred in the basal LVPW, mid and apical IVS and LVPW, recovering after balloon deflation. However, the basal IVS showed the opposite-increased thickening and thinning velocities in response to afterload (Table 1). Conclusions: The basal LV septum differs from the remaining LV as the segment with the highest wall stress. In this model, we have demonstrated the increase in radial thickening and relaxation of the basal IVS with acute afterload, as opposed to the other LV segments where these parameters acutely decrease. These findings provide better insight into LV functional remodelling in acute afterload and, due to the selected animal model, might provide better translational data for the clinical setting.

Animal model; afterload; pressure; basal septum; radial function.

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