Skeletal muscle ventricles: improved performance at physiologic preloads.
We attempted to construct skeletal muscle ventricles (SMVs) so that they would develop optimal stroke work at physiologic preloads of 5 to 15 mm Hg. Thirty-one SMVs were constructed in mongrel dogs. The effects of electrical preconditioning with 2 Hz continuous and 25 Hz burst patterns were evaluated, as well as the application of passive stretch to the muscle fibers during preconditioning. We evaluated the stroke work developed by these SMVs at afterloads of 30 mm Hg and 80 mm Hg in vivo, using a mock circulation device. During mock circulation studies, the SMVs were stimulated via the thoracodorsal nerve with either a 25 Hz or 85 Hz burst pattern. SMVs with 2 Hz preconditioning developed significantly higher stroke work than SMVs with 25 Hz preconditioning under all conditions of afterload, preload, and stimulation frequency (p less than or equal to 0.001). Under these conditions, for the 2 Hz preconditioned SMVs, passive stretch during preconditioning resulted in a further significant increase in developed stroke work (p less than 0.05). For these SMVs, with an 85 Hz stimulation frequency, stroke work averaged 410% of canine RV stroke work, and 59% of canine LV stroke work at physiologic preloads and afterloads.
Bridges
C R
CR
University of Pennsylvania, Harrison Department of Surgical Research, Philadelphia 19104.
Brown
W E
WE
Hammond
R L
RL
Anderson
D R
DR
Anderson
W A
WA
Dimeo
F
F
Stephenson
L W
LW
D000818:Animals; D001243:Assisted Circulation; D004285:Dogs; D004558:Electric Stimulation; D004867:Equipment Design; D006352:Heart Ventricles; D006353:Heart-Assist Devices; D009119:Muscle Contraction; D009132:Muscles / Q000201:enzymology / Q000473:pathology / Q000502:physiology*; D009218:Myosins / Q000378:metabolism
D009218:Myosins