Szwarc R S, Mickleborough L L, Mizuno S, Wilson G J, Liu P, Mohamed S
University of Toronto, Canada.
Cardiovasc Res. 1994 Feb;28(2):252-8. doi: 10.1093/cvr/28.2.252.
It has recently been suggested that conductance catheter parallel conductance (alpha Vc) is a function of left ventricular volume. To confirm this, alpha Vc was measured in this study over a wide range of steady state volumes. In addition, conductance derived volumes were compared to those obtained by radionuclide angiography to determine if the conductance catheter can be used to measure absolute left ventricular volume accurately in the intact dog heart.
Seven dogs were anaesthetised and instrumented with left ventricular conductance and pressure tip catheters, a flow through rho cuvette to continually measure blood resistance, a thermodilution catheter, and a venous catheter for volume infusion/withdrawal. Conductance and angiographic data were acquired at 8(SD 1) variably loaded states. Parallel conductance was measured twice at each state using a saline dilution technique and a new non-linear algorithm that allows variability in the observations of both maximum and minimum conductance volumes.
The mean value of alpha Vc was 89.1(18.0) ml (71.8 to 111.3 ml) with a mean within-animal coefficient of variation of 7.3(3.4)%. Multiple linear regression using dummy variables to account for the large interanimal variability did not reveal any relationship between alpha Vc and either maximum or minimum left ventricular volume. Furthermore, no difference was found when alpha Vc values measured at the lowest and highest loading levels in each dog were compared. Linear regression showed good agreement between conductance and radionuclide derived end diastolic volumes (slope = 0.94, R = 0.9, p < 0.001).
While alpha Vc varies between animals, it remains constant within any given animal over a broad range of left ventricular volumes. Thus the conductance catheter can provide reliable absolute left ventricular volume measurements under steady state conditions.
最近有人提出，电导导管的并联电导（αVc）是左心室容积的函数。为证实这一点，本研究在很宽的稳态容积范围内测量了αVc。此外，将电导法得出的容积与通过放射性核素血管造影获得的容积进行比较，以确定电导导管能否用于准确测量完整犬心脏的绝对左心室容积。
对7只犬进行麻醉，并植入左心室电导和压力尖端导管、用于持续测量血流阻力的流通式ρ比色皿、热稀释导管以及用于容积输注/抽取的静脉导管。在8个（标准差为1）不同负荷状态下采集电导和血管造影数据。使用盐水稀释技术和一种新的非线性算法在每个状态下测量两次并联电导，该算法允许最大和最小电导容积的观测值存在变化。
αVc的平均值为89.1（18.0）ml（71.8至111.3 ml），动物内平均变异系数为7.3（3.4）%。使用虚拟变量进行多元线性回归以解释动物间的巨大变异性，未发现αVc与最大或最小左心室容积之间存在任何关系。此外，比较每只犬在最低和最高负荷水平下测量的αVc值时，未发现差异。线性回归显示电导法和放射性核素法得出的舒张末期容积之间具有良好的一致性（斜率 = 0.94，R = 0.9，p < 0.001）。
虽然αVc在不同动物之间有所变化，但在任何给定动物的广泛左心室容积范围内它保持恒定。因此，电导导管在稳态条件下可提供可靠的绝对左心室容积测量值。
