HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 294/3/H1216    most recent 00983.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Wang, J.-J. Articles by Tyberg, J. V. PubMed PubMed Citation Articles by Wang, J.-J. Articles by Tyberg, J. V.

Effects of vasoconstriction and vasodilatation on LV and segmental circulatory energetics

¹Libin Cardiovascular Institute of Alberta, Departments of Cardiac Sciences, Physiology and Biophysics, and Civil Engineering, University of Calgary, Calgary, Canada; and ²Department of Bioengineering, Imperial College of Science, Technology and Medicine, London, England

Submitted 24 August 2007 ; accepted in final form 12 December 2007

Although the hydraulic work generated by the left ventricle (LV) is not disputed, how the work was dissipated through the systemic circulation is still subject to interpretation. Recently, we proposed that the systemic circulation should be considered as waves and a reservoir system (Wk). By combining the arterial and venous reservoirs, the systemic vascular resistance can be viewed as a series of resistors, which in sequence are the large-artery resistance, arterial reservoir resistance, the microcirculatory resistance, venous reservoir resistance, and large-vein resistance, and propelling blood through these resistance elements represents resistive losses. We then studied the changes in the fraction of the work consumed by each element when infusing methoxamine (MTX), a vasoconstrictor, and sodium nitroprusside (NP), a vasodilator. Results show that, under control condition, 50% of the LV stroke work was dissipated through arterial reservoir resistance (NP, 36%; MTX, 27%), another 25% was dissipated by the microcirculation (NP, 20%; MTX, 66%), and 20% of work by the large-artery resistances (NP, 37%; MTX, 6%). The energy dissipated by the venous resistances was small and had limited variation with NP and MTX, where the large-vein and venous reservoir resistances shared 1 and 3% of LV stroke work, respectively. Approximately 60% of LV stroke work is stored as the potential energy during systole under control, and the ratio decreases to 45% with NP and 80% with MTX.

left ventricle circulatory coupling; systemic vascular resistance; arterial and venous reservoirs