Four single-beat methods for calculating contractility showed unacceptably high limits of agreement (+/-2.6 to +/-3.8 mmHg/ml) compared with multiple-beat elastance and failed to predict increases.
Effect estimate: Average bias -0.3 to 0.5 mmHg/ml (95% CI +/-2.6 to +/-3.8 mmHg/ml)
The end-systolic pressure-volume relationship is regarded as a useful index for assessing the contractile state of the heart. However, the need for preload alterations has been a serious limitation to its clinical applications, and there have been numerous attempts to develop a method for calculating contractility based on one single pressure-volume loop. We have evaluated four of these methods. Pressure-volume data were obtained by combined pressure and conductance catheters in 37 pigs. All four methods were applied to 88 steady-state pressure-volume files, including eight files sampled during dopamine infusions. Estimates of single-beat contractility (elastance) were compared with preload-varied multiple-beat elastance E(es(MB)). All methods had a low average bias (-0.3 to 0.5 mmHg/ml) but limits of agreement (+/-2 SD) were unacceptably high (+/-2.6 to +/-3.8 mmHg/ml). In the dopamine group, E(es(MB)) showed an increase of 1.7 +/- 0.8 mmHg/ml (mean +/- SD) compared with baseline (P < 0.001). None of the single-beat methods predicted this increase in contractility. It is therefore doubtful whether any of the methods allow for single-beat assessment of contractility.
Kjørstad et al. (Wed,) conducted a other in Left ventricular contractility assessment (n=37). Four single-beat methods for calculating contractility vs. Preload-varied multiple-beat elastance was evaluated on Agreement of single-beat contractility estimates with preload-varied multiple-beat elastance (Average bias -0.3 to 0.5 mmHg/ml, 95% CI +/-2.6 to +/-3.8 mmHg/ml). Four single-beat methods for calculating contractility showed unacceptably high limits of agreement (+/-2.6 to +/-3.8 mmHg/ml) compared with multiple-beat elastance and failed to predict increases.
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