Mandarino W A, Pinsky M R, Gorcsan J
Division of Cardiology, University of Pittsburgh Medical Center, Pennsylvania 15213, USA.
J Am Coll Cardiol. 1998 Mar 15;31(4):861-8. doi: 10.1016/s0735-1097(98)00005-9.
We sought to assess the ability of preload-adjusted maximal power measured by echocardiographic automated border detection (ABD) to quantify left ventricular (LV) contractility by determining the effects of alterations in preload, afterload and contractile state.
Preload-adjusted maximal power can reflect LV contractile state relatively independent of changes in loading conditions.
Eight anesthetized dogs had placement of aortic electromagnetic flow probes, LV and arterial pressure catheters and inferior vena caval (IVC) occluders; four had placement of thoracic aortic balloon occluders. Echocardiographic ABD measures of cross-sectional area were used as a surrogate for LV volume, and flow was estimated as the first derivative of area with respect to time. Power was calculated as the product of flow and pressure.
Preload independence during vena caval occlusions was achieved by preload adjustment (1/[end-diastolic area]3/2). Afterload independence was demonstrated by preload-adjusted maximal power being unaffected by acute increases in LV systolic pressure induced by aortic occlusion. ABD preload-adjusted maximal power reflected changes in contractile state: increasing with dobutamine infusion from 36+/-14 to 70+/-15 mW/cm4 (p < 0.05 vs. control) and decreasing with propranolol infusion from 35+/-13 to 17+/-7 mW/cm4 (p < 0.05 vs. control). These changes were significantly correlated with calculations of preload-adjusted maximal power using aortic flow (r = 0.90, SEE 10.5 mW/cm4) and load-independent measures of end-systolic elastance from pressure-area loops (r = 0.90, SEE 10.6 mW/cm4). Calculations of normalized preload-adjusted maximal power using arterial pressure were also closely correlated with similar calculations using LV pressure (r = 0.99, SEE 3%).
Preload-adjusted maximal power using echocardiographic ABD can predict LV contractile state relatively independent of loading conditions and has potential for clinical application.
我们试图通过确定前负荷、后负荷和收缩状态改变的影响，评估经超声心动图自动边界检测（ABD）测量的前负荷调整后最大功率量化左心室（LV）收缩力的能力。
前负荷调整后最大功率可相对独立于负荷条件变化反映LV收缩状态。
8只麻醉犬植入主动脉电磁血流探头、LV和动脉压导管以及下腔静脉（IVC）阻断器；4只植入胸主动脉球囊阻断器。超声心动图ABD测量的横截面积用作LV容积的替代指标，血流估计为面积相对于时间的一阶导数。功率计算为血流与压力的乘积。
通过前负荷调整（1/[舒张末期面积]3/2）实现了腔静脉阻断期间的前负荷独立性。前负荷调整后最大功率不受主动脉阻断引起的LV收缩压急性升高的影响，证明了后负荷独立性。ABD前负荷调整后最大功率反映了收缩状态的变化：多巴酚丁胺输注时从36±14增加至70±15 mW/cm4（与对照组相比，p<0.05），普萘洛尔输注时从35±13降低至17±7 mW/cm4（与对照组相比，p<0.05）。这些变化与使用主动脉血流计算的前负荷调整后最大功率（r = 0.90，标准误10.5 mW/cm4）以及压力-面积环的负荷独立收缩末期弹性测量值（r = 0.90，标准误10.6 mW/cm4）显著相关。使用动脉压计算的标准化前负荷调整后最大功率与使用LV压力的类似计算也密切相关（r = 0.99，标准误3%）。
使用超声心动图ABD的前负荷调整后最大功率可相对独立于负荷条件预测LV收缩状态，具有临床应用潜力。
