title: Influence of heart rate on myocardial function using two-dimensional speckle-tracking echocardiography in healthy dogs.
abstract: OBJECTIVE
  The objective of this study was to evaluate the influence of heart rate (HR) on myocardial function assessed by two-dimensional speckle-tracking echocardiography (2D-STE) in healthy dogs.
  
  
  METHODS
  Thirteen healthy beagle dogs.
  
  
  METHODS
  Animals were anesthetized and HR was controlled with right atrial pacing. Myocardial function of each dog was assessed using 2D-STE at pacing rates of 120, 140, 160, and 180 bpm.
  
  
  RESULTS
  All strain and strain rate variables in the longitudinal, circumferential, and radial directions were not significantly different between pacing rates. Peak early diastolic torsion rate at 180 bpm was significantly increased compared with that at 120 bpm (P = 0.003).
  
  
  CONCLUSIONS
  Torsion rate in early diastole was elevated at 180 bpm, which may reflect improved myocardial relaxation with higher HR. Changes in left ventricular torsion during tachycardia may play an important role in preserving stroke volume in the presence of shortened ejection and filling times.
authors: Division of Veterinary Internal Medicine, Department of Veterinary Science, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo 180-8602, Japan. d01005@nvlu.ac.jp
authors: Ryohei
authors: R
authors: Suzuki
authors: Hirotaka
authors: H
authors: Matsumoto
authors: Takahiro
authors: T
authors: Teshima
authors: Hidekazu
authors: H
authors: Koyama
mesh_terms: D000818:Animals; D004285:Dogs / Q000502:physiology*; D004452:Echocardiography / Q000379:methods / Q000662:veterinary*; D006339:Heart Rate / Q000502:physiology*