On the basis of both short- and long-term improved contractility, as well as diminished necrosis in the area at risk, these results indicate that transmyocardial laser revascularization may be an alternative method of treating ischemic heart disease.

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 LV volume 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 of 0.77±0.14 ml/ml (p<0.001).Angiographically determined a also showed significant variation with hemodynamic interventions, largely reflecting an underlying dependence on aV,. The variation in aV, and av 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 aVc and a factors is unrealistic. This result calls into question the current use of this technique for the measurement of the absolute end-systolicpressure-volume relation. (Circulation 1989;80:1360-1377

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