title: Determinants of left ventricular preload-adjusted maximal power.
abstract: Maximal left ventricular (LV) hydraulic power output (PWR(max)), corrected for preload as PWR(max)/(V(ed))(beta) (where V(ed) is the end-diastolic volume and beta is a constant coefficient), is an index of LV contractility. Whereas preload-adjusted maximal power (PAMP) is usually calculated with beta = 2, there is uncertainty about the optimal value of beta (beta = 1 for the normal LV and 2 for the dilated LV). The aim of this work is to study the determining factors of beta. The data set consisted of 245 recordings (steady state and vena cava occlusion) in 10 animals in an ischemic heart pig model. The occlusion data yielded the slope (E(es); 2.01 +/- 0.77 mmHg/ml, range 0.71-4.16 mmHg/ml) and intercept (V(0); -11.9 +/- 22.6 ml; range -76 to 39 ml) of the end-systolic pressure-volume relation, and the optimal beta-factor (assessed by fitting an exponential curve through the V(ed)-PWR(max) relation) was 1.94 +/- 0.88 (range 0.29-4.73). The relation of beta with V(ed) was weak [beta = 0.60 + 0.02(V(ed)); r(2) = 0.20]. In contrast, we found an excellent exponential relation between V(0) and beta [beta = 2.16e(0.0189(V(0))), r(2) = 0.70]. PAMP, calculated from the steady-state data, was 0.64 +/- 0.40 mW/ml(2) (range 0.14-2.83 mW/ml(2)) with a poor correlation with E(es) (r = 0.30, P < 0.001). An alternative formulation of PAMP as PWR(max)/(V(ed) - V(0))(2), incorporating V(0), yielded 0.47 +/- 0.26 mW/ml(2) (range 0.09-1.42 mW/ml(2)) and was highly correlated with E(es) (r = 0.89, P < 0.001). In conclusion, correct preload adjustment of maximal LV power requires incorporation of V(0) and thus of data measured under altered loading conditions.
authors.affiliation: Hydraulics Laboratory, Institute Biomedical Technology, Ghent University, Belgium. patrick.segers@rug.ac.be
authors.forename: Patrick
authors.initials: P
authors.lastname: Segers
authors.forename: Vincent
authors.initials: V
authors.lastname: Tchana-Sato
authors.forename: H Alex
authors.initials: HA
authors.lastname: Leather
authors.forename: Bernard
authors.initials: B
authors.lastname: Lambermont
authors.forename: Alexandre
authors.initials: A
authors.lastname: Ghuysen
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Dogne
authors.forename: Patricia
authors.initials: P
authors.lastname: Benoit
authors.forename: Philippe
authors.initials: P
authors.lastname: Morimont
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Wouters
authors.forename: Pascal
authors.initials: P
authors.lastname: Verdonck
authors.forename: Philippe
authors.initials: P
authors.lastname: Kolh
mesh_terms: D000818:Animals; D001158:Arteries / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D004548:Elasticity; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology; D017379:Hypertrophy, Left Ventricular / Q000503:physiopathology; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology; D013552:Swine; D014655:Vascular Resistance / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology*