Left ventricular size determines tissue Doppler-derived longitudinal strain and strain rate.
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.
Rösner
Assami
A
Institute of Clinical Medicine, University of Tromsø, 9037 Tromsø, Norway. assami.rosner@unn.no
Bijnens
Bart
B
Hansen
Magna
M
How
Ole Jakob
OJ
Aarsaether
Erling
E
Müller
Stig
S
Sutherland
George R
GR
Myrmel
Truls
T
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