Document Detail

Is PA-PWRmax truly a preload-independent index of myocardial contractility in anesthetized humans?
MedLine Citation:
PMID:  15103176     Owner:  NLM     Status:  MEDLINE    
This study tested the hypothesis that the preload-adjusted maximal power index (PA-PWRmax) is a load-independent index of human myocardial contractility. Based on the ventricular pressure-volume relationship and derived from stroke work, the index is the product of instantaneous ventricular pressure and volume changes, divided by a correction term of end-diastolic volume (EDV2) or end-diastolic area (EDA3/2) to adjust for preload effects. Echocardiographic measures of instantaneous ventricular area change may be used to obtain PA-PWRmax noninvasively. We prospectively evaluated 28 human subjects undergoing cardiac evacuation before cardiopulmonary bypass procedures. Continuous peripheral arterial pressure, pulmonary arterial pressure, and echocardiographic views of the left ventricle in the transgastric short-axis view were recorded. Simultaneously gated instantaneous fractional shortening (FS) and PA-PWRmax indices were calculated, with FS = (EDA - ESA)/EDA and PA-PWRmax = [MAP (EDA - ESA)]/ EDA3/2, where ESA = end-systolic area and MAP = instantaneous mean arterial pressure. FS decreased uniformly with cardiac evacuation and decreasing pulmonary artery diastolic pressure (t = -5.4; 95% confidence interval, -10 to -0.046; p < 0.001), as did PA-PWRmax (t = -5.8; 95% confidence interval, -2.25 to -1.08; p < 0.001). FS and PA-PWRmax showed a strong downward correlation (r = 0.81). Unlike previous studies of autonomically denervated animals, our study did not find PA-PWRmax to be preload independent, perhaps because of the instantaneous homeostatic mechanisms of the human autonomic nervous system linking contractility to loading conditions.
Steven J Lester; Henry Shin; A Stephane Lambert; Joseph P Miller; Michael K Cahalan; Manfred D Seeberger; Elyse Foster; Nelson B Schiller
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Publication Detail:
Type:  Journal Article     Date:  2004-04-19
Journal Detail:
Title:  Cardiology     Volume:  102     ISSN:  0008-6312     ISO Abbreviation:  Cardiology     Publication Date:  2004  
Date Detail:
Created Date:  2004-07-06     Completed Date:  2004-10-05     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  1266406     Medline TA:  Cardiology     Country:  Switzerland    
Other Details:
Languages:  eng     Pagination:  77-81     Citation Subset:  IM    
Copyright Information:
Copyright 2004 S. Karger AG, Basel
Adult Echo Laboratory, University of California, San Francisco, San Francisco, Calif, USA.
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MeSH Terms
Anesthesia, General*
Cardiac Output / physiology*
Myocardial Contraction / physiology*
Prospective Studies
Ventricular Function, Left / physiology*
Ventricular Pressure / physiology*

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