title: Effects of changes in loading conditions and heart rate on the myocardial performance index in cats.
abstract: OBJECTIVE
  To evaluate the effect of changes in hemodynamics on the myocardial performance index (MPI) in cats.
  
  
  METHODS
  6 mixed-breed cats.
  
  
  METHODS
  Cats were anesthetized by administration of thiopental sodium; anesthesia was maintained by administration of isoflurane. Systolic arterial pressure and central venous pressure were measured by use of catheters, and heart rate was controlled by right atrial pacing. Afterload was increased by balloon occlusion of the descending aorta, and preload was increased by IV infusion of lactated Ringer's solution at a rate of 40 mL/kg/h. Echocardiography was performed for each condition.
  
  
  RESULTS
  Atrial pacing significantly increased heart rate. The MPI did not change with heart rate. Arterial pressure and MPI increased significantly during aortic occlusion. The IV infusion increased fractional shortening but did not change the MPI. Multiple regression analysis revealed that the MPI was not affected by heart rate, systolic arterial pressure, central venous pressure, fractional shortening, or velocity of the E wave.
  
  
  CONCLUSIONS
  The MPI can be used to assess cardiac function in healthy cats. The MPI is independent of heart rate and systolic arterial pressure but is sensitive to changes in afterload.
authors.affiliation: Department of Small Animal Internal Medicine, School of Veterinary Medicine, Kitasato University, 23-35-1 Higashi, Towada, Aomori 034-8628, Japan.
authors.forename: Yasutomo
authors.initials: Y
authors.lastname: Hori
authors.forename: Masami
authors.initials: M
authors.lastname: Uechi
authors.forename: Atsuko
authors.initials: A
authors.lastname: Indou
mesh_terms: D000818:Animals; D016280:Atrial Function, Right / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002415:Cats / Q000502:physiology*; D004452:Echocardiography / Q000662:veterinary; D005260:Female; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D012044:Regression Analysis