Left ventricular volume measurement by conductance catheter in intact dogs. Parallel conductance volume depends on left ventricular size. Circulation 80: 1360–1377

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/a)(B(t)-aVe). The aV, 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. a is the slope in the relation between B(t) and true LV volume. We tested the assumption that aVc and av are constant over a range of hemodynamic conditions. We performed multiple hypertonic saline aV, 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 LVvolume during similar control and intervention conditions. The saline-derived cvV, was 76±2 ml during control and fell significantly by-7±2 ml during IVCO (p<0.001) but not during AO or PAO. According to multiple linear regression analyses, the strongest predictor of saline-derived aV, was uncorrected end-systolic Bes, with a sensitivity coefficient of 0.60+±0.06 ml/ml (p<0.001). Angiographically derived aVc showed a similar dependence on Bes, with a coefficient of0.77±0.14 ml/ml (p<0.001)