title: Force/shortening-frequency relationship in multicellular muscle strips and single cardiomyocytes of human failing and nonfailing hearts.
abstract: BACKGROUND
  Force of contraction (FOC) frequency-dependently increases in multicellular muscle strip preparations of human nonfailing myocardium, whereas FOC declines in human failing myocardium with increasing stimulation frequency. We investigated whether these characteristics can be observed in single isolated myocytes.
  
  
  RESULTS
  Isolated multicellular muscle strip preparations and single isolated cardiomyocytes of failing (heart transplants, dilative cardiomyopathy; n = 11) and nonfailing (donor hearts; n = 11) human hearts were studied. The changes in contraction amplitude (cell shortening in micrometers) at increasing frequency of stimulation (0.5-2 Hz) were continuously recorded with a 1-dimensional high-speed camera that detected the cell edges and measured their distance during contraction. The increase in stimulation frequency was associated with a significant decrease in FOC (2 v 0.5 Hz; 68% basal) and a decrease in cell shortening of human left ventricular cardiomyocytes from failing hearts (2 v 0.5 Hz; 65% basal). In contrast, in human nonfailing myocardium, contraction increased at increasing stimulation frequencies (2 v 0.5 Hz; FOC, 180% basal; cell shortening, 129% basal).
  
  
  CONCLUSIONS
  The negative force-frequency relationship measured in multicellular preparations of failing human myocardium results from alterations at the single cell level.
authors.affiliation: Laboratory of Muscle Research and Molecular Cardiology, Clinic III for Internal Medicine, University of Cologne, Cologne, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Brixius
authors.forename: S
authors.initials: S
authors.lastname: Hoischen
authors.forename: H
authors.initials: H
authors.lastname: Reuter
authors.forename: K
authors.initials: K
authors.lastname: Lasek
authors.forename: R H
authors.initials: RH
authors.lastname: Schwinger
mesh_terms: D002311:Cardiomyopathy, Dilated / Q000503:physiopathology*; D004558:Electric Stimulation; D005260:Female; D006352:Heart Ventricles / Q000166:cytology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000166:cytology*; D010210:Papillary Muscles / Q000166:cytology* / Q000502:physiology