TIME CONSTANT OF ISOVOLUMIC PRESSURE FALL - DETERMINANTS IN THE WORKING LEFT-VENTRICLE
TIME CONSTANT OF ISOVOLUMIC PRESSURE FALL - DETERMINANTS IN THE WORKING LEFT-VENTRICLE
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DOI：
10.1152/ajpheart.1978.235.6.h701
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发表时间：
1978-01-01
影响因子：
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通讯作者：
WEISFELDT, ML
中科院分区：
文献类型：
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作者：
FREDERIKSEN, JW;WEISS, JL;WEISFELDT, ML
在工作犬右心转流的基础上，研究了血流动力学和药物对等容压下降时程的影响。测定了最大负dp/dt后左室压下降的指数部分的时间常数(T)。在恒定峰值LVP和心率(n=8)时，心输出量在1.5~4.0 L/min之间变化，或LVP峰值在85.+-之间变化，对T无显著影响。3和192。+-。3毫米汞柱，心输入量和心率恒定(n=7)。心率从110次/分钟突然变化到180次/分钟，在每搏输出量和峰值LVP不变的情况下，T从27.+-缩短。4至23。+-。3毫秒。(P<；0.02)心得安后T显著升高，去甲肾上腺素降低T，心得安降低T，乙酰花青素降低T。为区分收缩速度增加对T的影响与肌力增强的影响，对9例心脏的平均周向纤维缩短速度(VCF)进行了估计。将峰值LVP从160。+-下调。5至83。+-。3毫米汞柱导致平均VCF值由1.19±-增加。0.27至1.54。+-0.31直径/S(P<；0.01)；T无显著变化，42.+-。4比45。+-。4毫秒(不重要)。去甲肾上腺素引起的平均VCF值也有类似的增加，从1.59+-。0.16至2.00。+-。0.22直径/S(P<；0.05)，但T缩短，36.+-。2至27。+-。2ms(P<；0.01)。在工作准备阶段，T在较宽的生理范围内与每搏输出量、LVP峰值和纤维缩短速度无关。心率的大幅增加会导致微小但明显的T缩短，T被认为是影响心脏主动松弛系统和/或变力状态的药物改变。
The influence of hemodynamics and pharmacologic agents on the time course of isovolumic pressure fall was studied in the working dog, right-heart-bypass preparation. The time constant (T) was determined for the exponential portion of the left ventricular pressure (LVP) fall following maximum negative dP/dt. No significant changes in T occurred as a result of variation in cardiac input between 1.5 and 4.0 l/min at constant peak LVP and heart rate (n = 8) or variation in peak LVP between 85 .+-. 3 and 192 .+-. 3 mmHg at constant cardiac input and heart rate (n = 7). Abrupt changes in heart rate from 110 to 180 beats/min at constant stroke volume and peak LVP shortened T from 27 .+-. 4 to 23 .+-. 3 ms. (P < 0.02). A significant increase in T occurred after administration of propranolol and norepinephrine decreased T and acetylstrophanthidin after propranolol decreased T. To dissociate possible effects of increased shortening velocity on T from effects of increased inotropy, mean velocity of circumferential fiber shortening (VCF) was estimated in 9 hearts. Lowering peak LVP from 160 .+-. 5 to 83 .+-. 3 mmHg resulted in increased mean VCF from 1.19 .+-. 0.27 to 1.54 .+-. 0.31 diameters/s (P < 0.01); T did not change significantly, 42 .+-. 4 vs. 45 .+-. 4 ms (not significant). Norepinephrine caused a similar increase in mean VCF from 1.59 .+-. 0.16 to 2.00 .+-. 0.22 diameters/s (P < 0.05), but T shortened, 36 .+-. 2 to 27 .+-. 2 ms (P < 0.01). In the working preparation, T appears independent of stroke volume, peak LVP and fiber shortening velocity within broad physiological ranges. Large increases in heart rate result in small but significant shortening of T. T is altered by pharmacologic agents thought to influence the active cardiac relaxing system and/or the inotropic state.