title: Left ventricular size determines tissue Doppler-derived longitudinal strain and strain rate.
abstract: OBJECTIVE
  Tissue Doppler-derived indices of strain (epsilon) and strain rate (SR) have been developed to assess regional cardiac function. However, the effect of left ventricular (LV) size on epsilon and SR has not been studied in depth. The aim of this study was to assess to what extent heart size influence epsilon or SR.
  
  
  RESULTS
  In 21 anaesthetized pigs ranging from 12.5 to 70.0 kg, tissue Doppler-derived epsilon and SR, and haemodynamic parameters, were assessed during controlled heart rates and different loading conditions. dP/dt did not correlate to pig weight, suggesting constant contractility during growth. Longitudinal epsilon and SR were significantly higher in smaller compared with larger hearts. The hyperbolic correlation between pigs weight and epsilon and SR was r(2)=0.621 and 0.372, respectively, both P<0.0001. Afterload elevation induced a reduction in longitudinal epsilon (from -24.2+/-3.2 to -12.1+/-5.5%, P=0.001) and SR (from -2.3+/-0.8 to -1.3+/-2.4 s(-1), P=0.034), whereas increasing preload increased epsilon (from -26.4+/-10.3 to -38.1+/-14.3%, P=0.006) and SR (from -2.3+/-0.9 to -4.22+/-1.8 s(-1), P=0.002).
  
  
  CONCLUSIONS
  Longitudinal epsilon and SR decrease with increasing LV dimensions in spite of an unaltered contractility. These results show and confirm that heart size influences epsilon and SR, which are highly load-dependent parameters.
authors.affiliation: Institute of Clinical Medicine, University of Tromsø, 9037 Tromsø, Norway. assami.rosner@unn.no
authors.forename: Assami
authors.initials: A
authors.lastname: Rösner
authors.forename: Bart
authors.initials: B
authors.lastname: Bijnens
authors.forename: Magna
authors.initials: M
authors.lastname: Hansen
authors.forename: Ole Jakob
authors.initials: OJ
authors.lastname: How
authors.forename: Erling
authors.initials: E
authors.lastname: Aarsaether
authors.forename: Stig
authors.initials: S
authors.lastname: Müller
authors.forename: George R
authors.initials: GR
authors.lastname: Sutherland
authors.forename: Truls
authors.initials: T
authors.lastname: Myrmel
mesh_terms: D000818:Animals; D015150:Echocardiography, Doppler; D053805:Fractional Flow Reserve, Myocardial; D006352:Heart Ventricles / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000473:pathology; D006439:Hemodynamics; D013318:Stroke Volume; D013552:Swine; D016277:Ventricular Function, Left