title: Relationships between myocardial bioenergetic and left ventricular function in hearts with volume-overload hypertrophy.
abstract: BACKGROUND
  Left ventricular (LV) hypertrophy secondary to volume overload can result in alterations in myocardial bioenergetics and LV dysfunction. This study examined whether bioenergetic abnormalities contribute to the pump dysfunction.
  
  
  RESULTS
  Severe mitral regurgitation (MR) was produced in 10 dogs by disruption of the chordal apparatus. Hemodynamics and ventricular function were examined 11.7 months later under baseline conditions and during treadmill exercise. Myocardial high-energy phosphates were measured by using magnetic resonance spectroscopy at rest, during coronary vasodilation with adenosine, and during oxidative stress induced by rapid pacing and dobutamine. Chronic MR caused a 30% increase in LV mass and a 65% increase in LV volume. In MR animals, the hemodynamic and LV function were normal at rest, but abnormalities developed during beta-blockade and exercise. Myocardial creatine phosphate-to-ATP ratios were significantly lower in each layer across the LV wall in MR hearts than normal hearts. Myocardial blood flow and coronary reserve were normal in MR hearts. Moreover, hyperperfusion did not correct the abnormal bioenergetics. Despite altered bioenergetics at rest, the MR hearts tolerated rapid pacing and dobutamine infusion well.
  
  
  CONCLUSIONS
  In volume-overloaded LV hypertrophied hearts, alterations in myocardial high-energy phosphate levels do not induce abnormal mechanical performance at rest but may be related to a decreased contractile reserve during exercise.
authors.affiliation: Department of Medicine, University of Minnesota Medical School, Minneapolis 55455, USA. zhang047@maroon.tc.umn.edu
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: C
authors.initials: C
authors.lastname: Toher
authors.forename: M
authors.initials: M
authors.lastname: Erhard
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: K
authors.initials: K
authors.lastname: Ugurbil
authors.forename: R J
authors.initials: RJ
authors.lastname: Bache
authors.forename: T
authors.initials: T
authors.lastname: Lange
authors.forename: D C
authors.initials: DC
authors.lastname: Homans
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis; D000818:Animals; D001706:Biopsy; D006332:Cardiomegaly / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D004285:Dogs; D004734:Energy Metabolism / Q000502:physiology*; D008944:Mitral Valve Insufficiency / Q000150:complications; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D009929:Organ Size; D016277:Ventricular Function, Left / Q000502:physiology*
chemical_list: D000255:Adenosine Triphosphate