title: Cardiomyocyte stiffness in diastolic heart failure.
abstract: BACKGROUND
  Heart failure with preserved left ventricular (LV) ejection fraction (EF) is increasingly recognized and usually referred to as diastolic heart failure (DHF). Its pathogenetic mechanism remains unclear, partly because of a lack of myocardial biopsy material. Endomyocardial biopsy samples obtained from DHF patients were therefore analyzed for collagen volume fraction (CVF) and sarcomeric protein composition and compared with control samples. Single cardiomyocytes were isolated from these biopsy samples to assess cellular contractile performance.
  
  
  RESULTS
  DHF patients (n=12) had an LVEF of 71+/-11%, an LV end-diastolic pressure (LVEDP) of 28+/-4 mm Hg, and no significant coronary artery stenoses. DHF patients had higher CVFs (7.5+/-4.0%, P<0.05) than did controls (n=8, 3.8+/-2.0%), and no conspicuous changes in sarcomeric protein composition were detected. Cardiomyocytes, mechanically isolated and treated with Triton X-100 to remove all membranes, were stretched to a sarcomere length of 2.2 microm and activated with solutions containing varying [Ca2+]. Compared with cardiomyocytes of controls, cardiomyocytes of DHF patients developed a similar total isometric force at maximal [Ca2+], but their resting tension (F(passive)) in the absence of Ca2+ was almost twice as high (6.6+/-3.0 versus 3.5+/-1.7 kN/m2, P<0.001). F(passive) and CVF combined yielded stronger correlations with LVEDP than did either alone. Administration of protein kinase A (PKA) to DHF cardiomyocytes lowered F(passive) to control values.
  
  
  CONCLUSIONS
  DHF patients had stiffer cardiomyocytes, as evident from a higher F(passive) at the same sarcomere length. Together with CVF, F(passive) determined in vivo diastolic LV dysfunction. Correction of this high F(passive) by PKA suggests that reduced phosphorylation of sarcomeric proteins is involved in DHF.
authors.affiliation: Laboratory for Physiology, Institute for Cardiovascular Research, VUMC, Amsterdam, The Netherlands.
authors.forename: Attila
authors.initials: A
authors.lastname: Borbély
authors.forename: Jolanda
authors.initials: J
authors.lastname: van der Velden
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Papp
authors.forename: Jean G F
authors.initials: JG
authors.lastname: Bronzwaer
authors.forename: Istvan
authors.initials: I
authors.lastname: Edes
authors.forename: Ger J M
authors.initials: GJ
authors.lastname: Stienen
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Paulus
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002118:Calcium / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003971:Diastole / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000473:pathology*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000473:pathology; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000473:pathology*; D013318:Stroke Volume / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology; D017725:Ventricular Pressure / Q000502:physiology
chemical_list: D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium