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Cardiac chemical power: 2 Application of chemical power, work and efficiency equations to characterise left ventricular energetics in man

  • Chandler A. Phillips
  • William J. Scott
  • Edward S. Grood
  • Jerrold S. Petrofsky
Article

Abstract

Thirty patients have been evaluated using single-plane left ventricular cineangiography and the contractile filament stress history, contractile element velocity history, and extrapolated Vmax were obtained. Peak chemical power (\(\widehat{CP}_\theta ,\widehat{CP}_\phi \)), endcycle chemical work (\(\widehat{CW}_\theta ,\widehat{CW}_\phi \)) and average efficiency (\(\bar \eta _\theta ,\bar \eta _\phi \)) for the circumferential (θ) and longitudinal (ϕ) directions were computed. For 11 normal patients\(\widehat{CP}_\theta \) was 84·9±25·8 mJ (cycle)−1 cm−3 and\(\bar \eta _\theta \) was 0·48±0·03, There was no significant difference between these values and five compensated volume overload patients. For six decompensated volume overload patients,\(\widehat{CP_\theta }\) and\(\widehat{CW_\theta }\) were significantly elevated (p<0·025, p<0·05, respectively) and\(\bar \eta _\theta \) significantly reduced (p<0·025). Peak mechanical stress-velocity power was maintained near normal limits, indicating that the basic defect was a poor coupling of chemical power generated to mechanical power output. For two compensated pressure overload patients,\(\widehat{CW_\theta }\) was significantly elevated (p<0·025), but\(\bar \eta _\theta \) was individually reduced below normal values, indicating that essentially no additional safety margin remained for compensation. Finally, the six congestive cardiomyopathy patients exhibited a reciprocal relationship between chemical power/work and efficiency.

Keywords

Left Ventricle Biological Engineer Average Efficiency Contractile Element Chemical Work 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

CP

instantaneous chemical power [mJ(cycle)−1 cm−3]

CW

instantaneous chemical work (mJ/cm3)

η

instantaneous efficiency

\(\widehat{CP}\)

peak chemical power [mJ(cycle)−1 cm−3]

\(\widehat{CW}\)

end-cycle chemical work (mJ/cm3)

\(\bar \eta \)

average efficiency

k, K

chemical power equation constants

Vmax,VR

maximum contractile element velocity at zero stress (end-diastolic lengths/cycle)

p

intraventricular pressure (kPa)

L

major left ventricular axis (cm)

M

minor left ventricular axis (cm)

W

left ventricular wall thickness (cm)

f

magnification correction factor

P

muscle stress (kPa)

V

velocity of muscular contraction (end-diastolic lengths/s)

σCF

contractile filament stress (kPa)

VCE

contractile element velocity (end-diastolic lengths/cycle)

dt

time increment

p.s.p.

peak systolic pressure (kPa)

e.d.v.

end-diastolic volume (ml3)

e.d.p.

end-diastolic pressure (kPa)

e.f.

ejection fraction

c.v.o.

compensated volume overload

d.v.o

decompensated volume overload

c.p.o.

compensated pressure overload

c.c.

congestive cardiomyopathy

b.s.a.

body surface area (m2)

θ

circumferential axis of the left ventricle

ϕ

longitudinal axis of the left ventricle

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Copyright information

© IFMBE 1979

Authors and Affiliations

  • Chandler A. Phillips
    • 1
  • William J. Scott
    • 2
  • Edward S. Grood
    • 3
  • Jerrold S. Petrofsky
    • 4
  1. 1.Department of EngineeringWright State UniversityDaytonUSA
  2. 2.Department of ChemistryUniv. of CaliforniaSanta CruzUSA
  3. 3.Department of Orthopedic SurgeryUniv. of CincinnatiCincinnatiUSA
  4. 4.Department of PhysiologySt. Louis Univ.St. LouisUSA

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