Can noncardiac muscle provide useful cardiac assistance? Preliminary studies of the properties of skeletal muscle.
The treatment of end-stage cardiac disease is the focus of extensive investigation. Both cardiac transplantation and mechanically powered assist devices are currently in use. However, transplant recipients are at constant risk of infection and rejection, and patients with mechanical assists are tethered to external driving devices. These limitations have led to the investigation of methods of cardiac support that rely on autogenous tissue. The current study tests the ability of skeletal muscle to produce cardiac-type work. The cephalic half of one rectus abdominis muscle was mobilized (taking care to preserve the attachment to the superior epigastric vessels) in 12 canines. The muscle was formed into a cylindric pouch around a bladder device. This allowed the determination of the pressure and flow produced by the muscle. The muscle was stimulated to contract at a rate of 60 contractions per minute using twin stimuli of 80 ms duration. The muscle pouch yielded a maximal isovolumetric pressure of 282 mm Hg, which equalled 245 per cent of the dog's systolic blood pressure. In addition, the pouch produced a flow of 1.88 L per minute (73% of the dog's cardiac output) and a power output of 0.22 watts (39% of the dog's left ventricular power), while pumping against an afterload of approximately 2/3 the systemic resistance. Also, the muscle demonstrated an ejection fraction of 62.7 per cent. These data indicate that a hydraulic pouch formed from rectus abdominis muscle is capable of pumping function that may be able to assist the compromised ventricle. However, total replacement of cardiac function does not seem feasible.(ABSTRACT TRUNCATED AT 250 WORDS)
D000009:Abdominal Muscles / Q000502:physiology / Q000601:surgery; D000818:Animals; D001243:Assisted Circulation / Q000379:methods*; D002302:Cardiac Output; D004285:Dogs; D004558:Electric Stimulation; D006352:Heart Ventricles / Q000503:physiopathology; D008954:Models, Biological; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology* / Q000601:surgery; D011312:Pressure