LEFT-VENTRICULAR MIDWALL MECHANICS IN SYSTEMIC ARTERIAL-HYPERTENSION - MYOCARDIAL-FUNCTION IS DEPRESSED IN PRESSURE-OVERLOAD HYPERTROPHY
LEFT-VENTRICULAR MIDWALL MECHANICS IN SYSTEMIC ARTERIAL-HYPERTENSION - MYOCARDIAL-FUNCTION IS DEPRESSED IN PRESSURE-OVERLOAD HYPERTROPHY
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DOI：
10.1161/01.cir.83.5.1676
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发表时间：
1991-05-01
期刊：
影响因子：
37.8
通讯作者：
GAASCH, WH
中科院分区：
文献类型：
--
作者：
SHIMIZU, G;HIROTA, Y;GAASCH, WH
背景左心室（LV）中壁几何形状通常被描述为腔室半径和壁厚的一半之和;该惯例基于收缩期均匀透壁增厚的假设。然而，理论考虑和实验数据表明，左心室壁的内半部分（内壳）比外半部分（外壳）更厚。因此，舒张末期周向中壁纤维在收缩期表现出向心外膜的相对迁移。因此，传统的方法提供了一个高估的程度，中壁纤维缩短。我们开发了一个椭圆形模型，同心双壳几何形状（非均匀增厚），以评估整个心动周期的中壁纤维长度瞬变。本文应用改进的室壁中段法分析了15例高血压患者和14例正常人的左室造影。根据左室质量指数（LVMI）将研究组分为：14名正常受试者（I组），8名LVMI正常的高血压患者（II组）和7名LVMI增加的高血压患者（III组）。三组间左心室舒张末期压或容积无显著差异;组II（70 +/- 5%）的射血分数略高于组I（65 +/- 8%）和组III（66 +/- 4%），但该趋势未达到统计学显著性。三组的内支架和传统壁中短轴缩短率（FS）值也相似。相比之下，第III组同心双壳几何（改良中壁法）的FS（16 +/- 2%）显著低于第I组和第II组（分别为21 +/- 4%和21 +/-5%;均p < 0.05）。当认识到组III的平均收缩周向应力（151 +/- 22 g/cm 2）低于组I和组II（分别为244 +/- 37 g/cm 2和213 +/- 38 g/cm 2;均p < 0.01）时，这种差异变得更加重要。7例III组患者中有6例的中壁应力缩短坐标超出正常（I组）受试者的95%置信限。因此，尽管射血分数正常，但高血压伴左室肥厚患者的收缩功能低于正常。腔室动力学高估了心肌功能，特别是当左室壁厚度增加时。这是由于在压力超负荷肥大中内壳增厚的贡献相对较大。
Background. Left ventricular (LV) midwall geometry has been described conventionally as the sum of the chamber radius and half of the wall thickness; this convention is based on the assumption of uniform transmural thickening during systole. However, theoretical considerations and experimental data indicate that the inner half (inner shell) of the LV wall thickens more than the outer half (outer shell). Thus, an end-diastolic circumferential midwall fiber exhibits a relative migration toward the epicardium during systole. As a result, the conventional method provides an overestimate of the extent of the midwall fiber shortening.Methods and Results. We developed an ellipsoidal model with a concentric two-shell geometry (nonuniform thickening) to assess midwall fiber length transients throughout the cardiac cycle. This modified midwall method was used in the analysis of LV cineangiograms from 15 patients with systemic arterial hypertension and 14 normal subjects. Study groups were classified according to LV mass index (LVMI): 14 normal subjects (group I), eight hypertensive patients with a normal LVMI (group II), and seven hypertensive patients with an increased LVMI (group III). There were no significant differences in LV end-diastolic pressure or volume among the three groups; the ejection fraction was slightly greater in group II (70 +/- 5%) than in groups I (65 +/- 8%) and III (66 +/- 4%), but this trend did not achieve statistical significance. Values for endocardial and conventional midwall fractional shortening (FS) were also similar in the three groups. By contrast, FS by the concentric two-shell geometry (modified midwall method) in group III (16 +/- 2%) was significantly less than that seen in groups I and II (21 +/- 4% and 21 +/- 5%, respectively; both p < 0.05). This difference achieves greater importance when it is recognized that mean systolic circumferential stress was lower in group III (151 +/- 22 g/cm2) than in groups I and II (244 +/- 37 g/cm2 and 213 +/- 38 g/cm2, respectively; both p < 0.01). The midwall stress-shortening coordinates in six of the seven group III patients were outside the 95% confidence limits for the normal (group I) subjects. Thus, despite a normal ejection fraction, systolic function is subnormal in hypertensive patients with LV hypertrophy.Conclusions. Chamber dynamics provide an overestimate of myocardial function, especially when LV wall thickness is increased. This is due to a relatively greater contribution of inner shell thickening in pressure-overload hypertrophy.