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New aspects of septal function by using 1-dimensional strain and strain rate imaging.

Lindqvist P, Mörner S, Karp K, Waldenström A

Department of Clinical Physiology, Heart Centre, Umeå University, Umeå, Sweden. per.lindqvist@medicin.umu.se <per.lindqvist@medicin.umu.se>

BACKGROUND: The interventricular septum is a complex structure, both anatomically and functionally, which limits the use of Doppler tissue imaging in the assessment of radial septal function. In this study we investigated whether strain (epsilon) and epsilon rate (SR) imaging can improve the measurement of the septal function. METHODS: Thirty healthy participants (18 women; age 60 +/- 11 years, range 42-72) were randomly selected from the population. Systolic epsilon and SR measurements were made of the radial motion from right endocardial layer (RE), left endocardial layer (LE), and middle layer of septum. Furthermore, we also compared RE and longitudinal right ventricular free wall and left ventricular longitudinal and LE septal motion. RESULTS: In both the endocardial sampling sites, LE and RE, we found negative radial epsilon (myocardial shortening), -20.1 +/- 11.5% for RE and -25.0 +/- 14.1% for LE during systole. However, in the middle layer we found a positive radial epsilon (myocardial lengthening), +11.5 +/- 13.2%, significantly different from the two endocardial layers (P < .001 for both). SR was negative in the two endocardial layers and significantly higher for LE, (-2.9 +/- 1.8 1/s) than for RE (-1.2 +/- 1.8 1/s, P < .001) and positive for the middle layer (+1.1 +/- 1.0 1/s), significantly different in comparison with the two endocardial layers (P < .001). Finally, there was a higher longitudinal epsilon compared with radial endocardial epsilon for right ventricle (-26.5 +/- 11.5 vs -20.1 +/- 11.5, P < .05) whereas there was significantly higher left ventricular radial epsilon and SR compared with the longitudinal epsilon and SR (-25.0 +/- 14.1 vs -16.8 +/- 9.5, P < .05; and -2.9 +/- 1.8 vs -1.1 +/- 0.4, P < .001). CONCLUSION: Systolic epsilon and SR imaging indicate differences in the radial deformation in different layers of the interventricular septum, which might be explained by the complexity of the septal fiber arrays and function. It might also explain why using Doppler tissue imaging technique is limited in assessing radial myocardial septal velocities. Furthermore, these results suggest that longitudinal shortening dominates in the right ventricle whereas the radial shortening dominates in the left ventricle.

Published 13 November 2006 in J Am Soc Echocardiogr, 19(11): 1345-9.
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