title: Characterization of systolic intervals in healthy, conscious sheep.
abstract: OBJECTIVE
  To characterize systolic intervals of the left ventricle and their relationship with heart rate in conscious sheep. Animals-11 healthy Romanov sheep (age range, 3 months to 10 years).
  
  
  METHODS
  Systolic intervals and indices of myocardial contractility of the left ventricle were measured in conscious sheep by use of polycardiography.
  
  
  RESULTS
  The mean +/- SD pre-ejection period was 59 +/- 12 milliseconds, and the mean left ventricular ejection time was 194 +/- 34 milliseconds. The mean myocardial tension index was 0.22 +/- 0.05, and the mean ratio of the pre-ejection period to ejection time was 0.30 +/- 0.09. Total electromechanical systole, mechanical systole, and ejection time varied inversely with heart rate. The electromechanical delay and pre-ejection period were not correlated with heart rate, nor were the myocardial tension index and the ratio of the pre-ejection period to ejection time. The isovolumetric contraction index and isovolumetric contraction time were not significantly correlated with heart rate, although the values for the correlation coefficient were moderate (r = -0.561 and r = -0.482, respectively).
  
  
  CONCLUSIONS
  Although a larger study would be needed to provide reference intervals for healthy sheep, the results of the study reported here provided useful information for the cardiac evaluation of sheep.
authors.affiliation: Institute of Physiology of the Komi Science Centre, Ural Branch of the Russian Academy of Sciences, 167000, Komi Republic, Russia.
authors.forename: Sergey N
authors.initials: SN
authors.lastname: Kharin
authors.forename: Dmitry N
authors.initials: DN
authors.lastname: Shmakov
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Vityazev
mesh_terms: D000818:Animals; D005260:Female; D006334:Heart Function Tests; D008297:Male; D012756:Sheep / Q000502:physiology*; D013599:Systole / Q000502:physiology*; D016277:Ventricular Function, Left / Q000502:physiology