Quantification of incomplete left ventricular relaxation: relationship to the time constant for isovolumic pressure fall.
Quantification of incomplete left ventricular relaxation: relationship to the time constant for isovolumic pressure fall.
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不完全左心室舒张的量化：与等容压下降时间常数的关系。
DOI：
10.1093/eurheartj/1.suppl_1.119
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发表时间：
1980
影响因子：
39.3
通讯作者：
Yin,FC
中科院分区：
文献类型：
--
作者：
Weisfeldt,ML;Weiss,JL;Frederiksen,JT;Yin,FC
我们最初发现等容舒张期间左心室压力下降呈指数规律，因此以时间常数（T）为特征。就等容压下降反映舒张期间的心肌事件而言，T 指示左心室舒张的时程。在离体犬心脏中，从等容到射血的负荷突然从等容变化到射血，缩短了 T。相反，在稳定的血流动力学条件下，T 在一个广泛的、生理上显着的范围内与负荷无关。例如：（1）在舒张末压为7±0.5至22±0.5毫米汞柱、左心室峰值压（LVP）为95±11至155±12毫米汞柱的9颗等容心脏中，T没有显着变化； (2) 在每搏输出量为 10 至 20 ml、峰值 LVP 为 85 至 192 mm Hg 的 7 颗射血心脏中，T 没有改变。 T随着心率、儿茶酚胺和缺血恢复等影响主动心脏舒张系统的因素而显着变化。为了量化两次心跳之间左心室舒张不完全的程度，并确定舒张不再影响舒张心室压力-尺寸关系的时间，我们通过声测法测量了十只工作犬心脏的压力和心内膜尺寸。我们从延长舒张期后的压力维度值获得了个体心脏完全松弛的压力维度关系。根据压力和尺寸之间的线性关系，我们预测了左心室尺寸，如果完全舒张，则在任何观察到的舒张压下都会出现左心室尺寸。以 0.25 T 或更小的间隔，我们将预测的完全松弛尺寸与实际尺寸进行比较。在任何心跳的舒张末期，预测尺寸和实际尺寸没有显着差异，其中下一次心跳在最大负 dP/dt 之后开始 > 3.5 T。这表明所有此类心跳在舒张末期之前完成了松弛。预测舒张末期尺寸与实际尺寸的差异（当最大负 dP/dt 后心跳开始 < 3.5 T 时）确定不完全松弛。预测的完全松弛尺寸与实际尺寸之间的差异量化了不完全松弛的程度。在舒张期早期，这种差异量化了舒张对心室尺寸以及舒张期充盈的影响。在广泛变化的血流动力学条件下，除严重衰竭外，舒张压维度舒张效应结束的时间为最大负 dP/dt 后的 2.85 ± 0.33 (s.d.) T。在严重的血流动力学应激下，这一次发生在舒张期较早。松弛对舒张压-尺寸关系的影响的早期结束可以通过最大负 dP/dl 时的 P、T 和完全松弛的舒张压-尺寸关系来预测。因此，T 是稳定血流动力学条件下左心室压力下降的负荷无关指数。 T 的使用有助于识别松弛时间过程的变化、不完全松弛的量化以及舒张期充盈期间松弛对压力-维度关系的影响的时间过程和程度。不完全松弛的程度和/或松弛对整个舒张期舒张尺寸的影响可以通过将实际尺寸与舒张期间任何压力下的完全松弛尺寸进行比较来量化。
We initially found that the fall in left ventricular pressure during isovolumic relaxation is exponential and therefore characterized by a time constant (T). To the extent that isovolumic pressure fall reflects myocardial events during relaxation, T indexes the time course of relaxation of the left ventricle. In isolated canine hearts sudden beat to beat loading changes from isovolumic to ejection shorten T. In contrast, under stable hemodynamic conditions T is independent of load across a broad, physiologically significant range. For example:(1) in nine isovolumic hearts with end-diastolic pressure from 7±0.5 to 22±0.5 mm Hg and peak left ventricular pressure (LVP) from 95 ± 11 to 155 ± 12 mm Hg, T did not change significantly; (2) in seven ejecting hearts from a stroke volume of 10 to 20 ml and from a peak LVP of 85 to 192 mm Hg, T was not altered. T changed significantly with factors thought to affect the active cardiac relaxing system such as heart rate, catecholamines and recovery from ischaemia.To quantify the extent of incomplete left ventricular relaxation between beats and to identify the time at which relaxation no longer influences the diastolic ventricular pressure-dimension relationships, we measured pressure and endocardial dimension by sonomicrometry in ten working dog hearts. We obtained the fully relaxed pressure-dimension relationship for individual hearts from pressure-dimension values following prolonged diastoles. From the linear relationship between pressure and dimension we predicted the left ventricular dimension which would be present at any observed diastolic pressure if relaxation were complete. At intervals of 0.25 T or less we compared this predicted fully relaxed dimension with the actual dimension. The predicted and actual dimension were not significantly different at end-diastole in any beat where the next beat began > 3.5 T after maximal negative dP/dt. This indicates completion of relaxation prior to end-diastole in all such beats. An end-diastolic difference in predicted v. actual dimension (when the beat began < 3.5 T after maximal negative dP/dt) identified incomplete relaxation. This difference between the predicted fully relaxed dimension and the actual dimension quantified the extent of incomplete relaxation. Earlier in diastole this difference quantified the effect of relaxation on ventricular dimension and thus diastolic filling. Under widely varying hemodynamic conditions, except with severe failure, the time of the end of the effect of relaxation on diastolic pressure-dimension was 2.85 ± 0.33 (s.d.) T after maximal negative dP/dt. Under severe hemodynamic stress this time occurred earlier in diastole. This early end of the influence of relaxation on diastolic pressure-dimension relationships could be predicted from P at maximal negative dP/dl, T, and the fully relaxed diastolic pressure-dimension relationship.Thus, T is a load-independent index of left ventricular pressure fall under stable hemodynamic conditions. Use of T aids in the identification of changes in the relaxation time course, quantification of incomplete relaxation and the time course and extent of the effect of relaxation on pressure-dimension relationships during the diastolic filling period. The extent of incomplete relaxation and/or the effect of relaxation on diastolic dimensions throughout diastole can be quantified by comparing the actual dimension to the fully relaxed dimension at any pressure during diastole.
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狗左心室不完全舒张的证据：根据等容压下降的时间常数进行预测。
DOI：
10.1172/jci109250
发表时间：
1978
期刊：
The Journal of clinical investigation
影响因子：
--
作者：
M. Weisfeldt;J. Frederiksen;F. Yin;J. Weiss
通讯作者：
J. Weiss
DOI：
10.1113/jphysiol.1960.sp006467
发表时间：
1960
期刊：
The Journal of Physiology
影响因子：
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作者：
B. R. Jewell;D. Wilkie
通讯作者：
D. Wilkie
影响因子：
--
作者：
FREDERIKSEN, JW;WEISS, JL;WEISFELDT, ML
通讯作者：
WEISFELDT, ML
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影响因子：
20.1
作者：
A. Wiegner;O. H. Bing
通讯作者：
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影响因子：
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作者：
KARLINER, JS;LEWINTER, MM;OROURKE, RA
通讯作者：
OROURKE, RA