title: Pressure-volume-based single-beat estimations cannot predict left ventricular contractility in vivo.
abstract: 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.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, University Hospital of Tromsø, N-9038 Tromsø, Norway. knutek@fagmed.uit.no
authors.forename: Knut E
authors.initials: KE
authors.lastname: Kjørstad
authors.forename: Christian
authors.initials: C
authors.lastname: Korvald
authors.forename: Truls
authors.initials: T
authors.lastname: Myrmel
mesh_terms: D000818:Animals; D001794:Blood Pressure; D002302:Cardiac Output; D002316:Cardiotonic Agents / Q000008:administration & dosage; D004298:Dopamine / Q000008:administration & dosage; D004548:Elasticity; D006321:Heart / Q000033:anatomy & histology*; D006339:Heart Rate; D006352:Heart Ventricles / Q000033:anatomy & histology; D009200:Myocardial Contraction; D012680:Sensitivity and Specificity; D013552:Swine; D013599:Systole; D016277:Ventricular Function, Left; D017725:Ventricular Pressure
chemical_list: D002316:Cardiotonic Agents; D004298:Dopamine