| Autor: |
Schenk, Soren, Popovié, Zoran B., Ochiai, Yoshie, Casas, Fernando, McCarthy, Patrick M., Starling, Randall C., Kopcak Jr., Michael W., Dessoffy, Raymond, Navia, Jose L., Greenberg, Neil L., Thomas, James D., Fukamachi, Kiyotaka |
| Předmět: |
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| Zdroj: |
American Journal of Physiology: Heart & Circulatory Physiology; Oct2004, Vol. 287 Issue 4, pH1632-H1640, 9p, 5 Charts, 13 Graphs |
| Abstrakt: |
Right ventricular (RV) maximal power (PWRmx) is dependent on preload. The objective of this study was to test our hypothesis that the PWRmx 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 (VOPWR) corresponding to the PRSW intercept (VOSW). If our hypothesis is correct, the preload sensitivity of PWRmx could be eliminated by adjusting for EDV and VOPWR. 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 PWRmx = a·(EDV - VOPWR)β, where a is the slope of the relationship. The PWRmx versus EDV relationship did not deviate from linearity (β = 1.09, P = not significant vs. 1), and VOPWR correlated with VOSW (r = 0.93, P <0.0001). VOPRW was related to steady-state EDV and left ventricular end-diastolic pressure, allowing for estimation of VOPWR (VOEst) and single-beat PWRmx preload adjustment. Dividing PWRmx by the difference of EDV and VOPWR (PAMPVOPWR) eliminated preload dependency down to 50% of the baseline EDV. PWRmx adjustment using VOEst (PAMPVOEst) showed similar preload independency. Enhancing contractility increased PAMPVOPWR and PAMPVOEst from 176 ± 52 to 394 ± 205 W/ml × 104 and 145 ± 51 to 404 ± 261 W/ml × 104, respectively, accompanied by an increase of PRSW from 13.0 ± 4.5 to 29.7 ± 16.4 mmHg (all P <0.01). PAMPVOPWR and PAMPVOEst 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 PWRmx should consider a linear PWRmx versus EDV relationship with distinct VOPWR. PAMPVOPWR is a preload-independent estimate of RV contractility that may eventually be determined noninvasively. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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