title: Preload-adjusted right ventricular maximal power: concept and validation.
abstract: Right ventricular (RV) maximal power (PWR(mx)) is dependent on preload. The objective of this study was to test our hypothesis that the PWR(mx) versus end-diastolic volume (EDV) relationship, analogous to the load-independent stroke work (SW) versus EDV relationship (preload-recruitable SW, PRSW), is linear, with the PWR x-axis intercept (V(0PWR)) corresponding to the PRSW intercept (V(0SW)). If our hypothesis is correct, the preload sensitivity of PWR(mx) could be eliminated by adjusting for EDV and V(0PWR). Ten dogs were instrumented with a pulmonary flow probe, micromanometers, and RV conductance catheter. Data were obtained during bicaval occlusions under various conditions and fitted to PWR(mx) = a.(EDV - V(0PWR))(beta), where a is the slope of the relationship. The PWR(mx) versus EDV relationship did not deviate from linearity (beta = 1.09, P = not significant vs. 1), and V(0PWR) correlated with V(0SW) (r = 0.93, P <0.0001). V(0PRW) was related to steady-state EDV and left ventricular end-diastolic pressure, allowing for estimation of V(0PWR) (V(0Est)) and single-beat PWR(mx) preload adjustment. Dividing PWR(mx) by the difference of EDV and V(0PWR) (PAMP(V0PWR)) eliminated preload dependency down to 50% of the baseline EDV. PWR(mx) adjustment using V(0Est) (PAMP(V0Est)) showed similar preload independency. Enhancing contractility increased PAMP(V0PWR) and PAMP(V0Est) from 176 +/- 52 to 394 +/- 205 W/ml x 10(4) and 145 +/- 51 to 404 +/- 261 W/ml x 10(4), respectively, accompanied by an increase of PRSW from 13.0 +/- 4.5 to 29.7 +/- 16.4 mmHg (all P <0.01). PAMP(V0PWR) and PAMP(V0Est) correlated with PRSW (r = 0.85; r = 0.77; both P <0.001). Numerical modeling confirmed the accuracy of our experimental data. Thus preload adjustment of PWR(mx) should consider a linear PWR(mx) versus EDV relationship with distinct V(0PWR). PAMP(V0PWR) is a preload-independent estimate of RV contractility that may eventually be determined noninvasively.
authors.affiliation: Dept. of Biomedical Engineering/ ND20, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
authors.forename: Soren
authors.initials: S
authors.lastname: Schenk
authors.forename: Zoran B
authors.initials: ZB
authors.lastname: Popović
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Ochiai
authors.forename: Fernando
authors.initials: F
authors.lastname: Casas
authors.forename: Patrick M
authors.initials: PM
authors.lastname: McCarthy
authors.forename: Randall C
authors.initials: RC
authors.lastname: Starling
authors.forename: Michael W
authors.initials: MW
authors.lastname: Kopcak
authors.forename: Raymond
authors.initials: R
authors.lastname: Dessoffy
authors.forename: Jose L
authors.initials: JL
authors.lastname: Navia
authors.forename: Neil L
authors.initials: NL
authors.lastname: Greenberg
authors.forename: James D
authors.initials: JD
authors.lastname: Thomas
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Fukamachi
mesh_terms: D000818:Animals; D003198:Computer Simulation; D004285:Dogs; D006334:Heart Function Tests / Q000379:methods* / Q000592:standards; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016278:Ventricular Function, Right / Q000502:physiology*