Submitted on August 29, 2006
Accepted on January 30, 2007
Wave Intensity Analysis of Left Ventricular Filling: Application of Windkessel Theory
Jacqueline Flewitt1, Tracy Hobson1, Jiun-Jr Wang2, Clifton Johnston3, Nigel G Shrive4, Israel Belenkie5, Kim H Parker6, and John V. Tyberg7*
1 Cardiac Sciences, Physiology and Biophysics, University of Calgary, Calgary, Canada
2 Cardiac Science, Physiology and Biophysics, University of Calgary, Calgary, Canada
3 Department of Mechanical & Manufacturing Engineering, University of Calgary, Calgary, Canada
4 Civil Engineering, University of Calgary, Calgary, Canada
5 Medicine, University of Calgary, Calgary, Canada
6 Bioengineering, Imperial College, London, United Kingdom
7 Medical Physiology, University of Calgary, Calgary, Canada
* To whom correspondence should be addressed. E-mail: jtyberg{at}ucalgary.ca.
In this paper, we extend our recently published Windkessel-wave interpretation of vascular function to the wave intensity analysis (WIA) of left ventricular (LV) filling dynamics by separating the pressure changes due to the Windkessel from those due to traveling waves. Using LV compliance (CLV), the change in pressure due solely to LV volume changes (Windkessel pressure - PWk) can be isolated. As the pressure measured in the cardiovascular system is the sum of its Windkessel and wave components (excess pressure - PEx), PEx can be substituted into WIA, yielding the isolated wave effects on LV filling. Our study of 6 open-chest dogs demonstrated that once the Windkessel effects are removed from WIA, the energy of diastolic suction is 2.6 times greater than we previously calculated. Volume-related changes in pressure (i.e., the Windkessel or reservoir effect) must be considered first when analyzing wave motion.
