Boltwood C M, Appleyard R F, Glantz S A
Cardiovascular Research Institute, University of California, San Francisco 94143.
Circulation. 1989 Nov;80(5):1360-77. doi: 10.1161/01.cir.80.5.1360.
The conductance catheter is a promising new instrument for continuously measuring left ventricular (LV) volume. Absolute LV volume (V[t]) is related to uncorrected conductance volume, B(t), according to the equation: V(t) = (1/alpha)(B(t) - alpha Vc). The alpha Vc factor represents parallel-conductance volume due to conducting material outside the LV blood pool, and may be estimated by transiently changing blood conductivity using a bolus injection of hypertonic saline. alpha is the slope in the relation between B(t) and true LV volume. We tested the assumption that alpha Vc and alpha are constant over a range of hemodynamic conditions. We performed multiple hypertonic saline alpha Vc determinations in seven intact dogs during control conditions and subsequent temporary balloon occlusions of inferior vena cava (IVCO), aorta (AO), and pulmonary artery (PAO). We also compared B(t) with simultaneous biplane angiographic LV volume during similar control and intervention conditions. The saline-derived alpha Vc was 76 +/- 2 ml during control and fell significantly by -7 +/- 2 ml during IVCO (p less than 0.001) but not during AO or PAO. According to multiple linear regression analyses, the strongest predictor of saline-derived alpha Vc was uncorrected end-systolic Bes, with a sensitivity coefficient of 0.60 +/- 0.06 ml/ml (p less than 0.001). Angiographically derived alpha Vc showed a similar dependence on Bes, with a coefficient of 0.77 +/- 0.14 ml/ml (p less than 0.001). Angiographically determined alpha also showed significant variation with hemodynamic interventions, largely reflecting an underlying dependence on alpha Vc. The variation in alpha Vc and alpha with LV size may stem from nonlinearity in the B(t)-V(t) relation. Although the conductance catheter provides a useful measure of relative LV volume, measurement of absolute LV volume over a wide hemodynamic range using constant alpha Vc and alpha factors is unrealistic. This result calls into question the current use of this technique for the measurement of the absolute end-systolic--pressure-volume relation.
电导导管是一种很有前景的新型仪器，可用于连续测量左心室（LV）容积。左心室绝对容积（V[t]）与未校正的电导容积B(t) 相关，其关系式为：V(t) = (1/α)(B(t) - αVc)。αVc因子代表左心室血池外导电物质导致的平行电导容积，可通过静脉推注高渗盐水短暂改变血液电导率来估算。α是B(t) 与左心室真实容积之间关系的斜率。我们检验了αVc和α在一系列血流动力学条件下保持恒定的假设。我们在7只完整犬的对照条件下以及随后对下腔静脉（IVCO）、主动脉（AO）和肺动脉（PAO）进行临时球囊阻塞期间，多次测定了高渗盐水αVc。我们还在相似的对照和干预条件下，将B(t) 与同步双平面血管造影左心室容积进行了比较。对照期间，盐水衍生的αVc为76±2 ml，IVCO期间显著下降至-7±2 ml（p<0.001），但AO或PAO期间未下降。根据多元线性回归分析，盐水衍生的αVc的最强预测因子是未校正的收缩末期Bes，敏感系数为0.60±0.06 ml/ml（p<0.001）。血管造影衍生的αVc对Bes表现出类似的依赖性，系数为0.77±0.14 ml/ml（p<0.001）。血管造影测定的α也随血流动力学干预表现出显著变化，这在很大程度上反映了对αVc的潜在依赖性。αVc和α随左心室大小的变化可能源于B(t)-V(t) 关系的非线性。尽管电导导管可提供左心室相对容积的有用测量值，但使用恒定的αVc和α因子在较宽的血流动力学范围内测量左心室绝对容积是不现实的。这一结果对目前使用该技术测量绝对收缩末期压力-容积关系提出了质疑。
