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New Aspects of Septal Function by Using 1-Dimensional Strain and Strain Rate Imaging
New Aspects of Septal Function by Using 1-Dimensional Strain and Strain Rate Imaging Per Lindqvist, PhD, Stellan Mörner, MD, PhD, Kjell Karp, MD, PhD, and Anders Waldenström, MD, PhD, FESC, Umeå, Sweden
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 (⑀) and ⑀ rate (SR) imaging can improve the measurement of the septal function. Methods: Thirty healthy participants (18 women; age 60 ⴞ 11 years, range 42-72) were randomly selected from the population. Systolic ⑀ 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 ⑀ (myocardial shortening), ⴚ20.1 ⴞ 11.5% for RE and ⴚ25.0 ⴞ 14.1% for LE during systole. However, in the middle layer we found a positive radial ⑀ (myocardial lengthening), ⴙ11.5 ⴞ 13.2%, significantly different from the two endocardial layers (P < .001 for both).
Anatomic studies have shown that the septum con-
sists of longitudinal subendocardial fibers of the right ventricle (RV) and left ventricle (LV), together with a middle layer (ML) composed of circumferential fibers.1 Functionally, the septum contributes to both LV and RV function.2 Septal motion is routinely studied by traditional M-mode echocardiography, and the relation between septal long- and shortaxis motions in health and disease has been extensively studied.3 Longitudinal septal motion has been shown to alter with age,4 coronary artery disease,5 hypertension, and hypertrophy,6,7 with a reduction in systolic amplitude or velocity and From the Departments of Cardiology and Clinical Physiology (P.L., K.K.), Heart Centre, Umeå University. Reprint requests: Per Lindqvist, PhD, Department of Public Health and Clinical Medicine, Umeå University, S-90185 Umeå, Sweden (E-mail: [email protected]). 0894-7317/$32.00 Copyright 2006 by the American Society of Echocardiography. doi:10.1016/j.echo.2006.05.002
SR was negative in the two endocardial layers and significantly higher for LE, (ⴚ2.9 ⴞ 1.8 1/s) than for RE (ⴚ1.2 ⴞ 1.8 1/s, P < .001) and positive for the middle layer (ⴙ1.1 ⴞ 1.0 1/s), significantly different in comparison with the two endocardial layers (P < .001). Finally, there was a higher longitudinal ⑀ compared with radial endocardial ⑀ for right ventricle (ⴚ26.5 ⴞ 11.5 vs ⴚ20.1 ⴞ 11.5, P < .05) whereas there was significantly higher left ventricular radial ⑀ and SR compared with the longitudinal ⑀ and SR (ⴚ25.0 ⴞ 14.1 vs ⴚ16.8 ⴞ 9.5, P < .05; and ⴚ2.9 ⴞ 1.8 vs ⴚ1.1 ⴞ 0.4, P < .001). Conclusion: Systolic ⑀ 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. (J Am Soc Echocardiogr 2006;19:1345-1349.)
changes in early and late diastolic contribution to ventricular filling. It is difficult to measure circumferential and radial septal wall motion using Doppler tissue imaging (DTI) echocardiography, because of the presence of different myocardial fiber layers, with different directions in motion.8 This might cause the ultrasound beam not to be parallel to the combination of longitudinal, radial, and circumferential fibers, which are present in the septum.1 Because of these difficulties, DTI has not been much used in the assessment of radial septal function.7,9 Myocardial strain (⑀) is dimensionless and represents the fractional or percentage change in dimension.10 Recently ultrasound-determined ⑀ has been developed with excellent correlation to sonomicrometry data.11 Furthermore, clinical approaches have been proposed, eg, quantifying regional myocardial function.12 In this study, we wanted to investigate whether ⑀ or ⑀ rate (SR) echocardiography could improve the understanding of septal function in healthy individuals.
1345
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Table 1 General characteristics of the healthy participants Mean (SD)
Age, years Female/male Systolic blood pressure, mm Hg Diastolic blood pressure, mm Hg Height, m Weight, kg Heart rate, beats/min
60 ⫾ 11 18/12 135 ⫾ 16 76 ⫾ 10 1.69 ⫾ 8.7 71 ⫾ 11 62 ⫾ 9
METHODS Study Population A total of 30 healthy participants (18 women; 60 ⫾ 11 years, range 42-72) were randomly selected and constituted the study population. Some general characteristics of the participants are shown in Table 1. All gave their informed consent to participate in the study, which was approved by our local ethics committee. Standard Echocardiography A digital ultrasound system (Vivid 7, GE Vingmed, Horten, Norway) with a phased-array transducer (1.5-4 MHz) was used. Standard 2-dimensional and Doppler echocardiography was used, as was pulsed and color myocardial DTI. The echocardiographic examination was performed with the participant in the left lateral decubitus position and recordings were made during expiration. Parasternal and apical projections were obtained according to the recommendations of the American Society of Echocardiography.13 All recordings were performed with a simultaneous superimposed electrocardiogram. A phonocardiogram was applied to display the S2 as definition of end systole.14 Recordings were taken at a sweep speed of 100 mm/s. ⑀ Echocardiography By convention, myocardial lengthening is given a positive ⑀ value and shortening is given a negative value. Onedimensional ⑀ is defined by ⑀ ⫽ ⌬L/L0 where ⌬L is the change in length and L0 is the original length of a myocardial segment. The longitudinal ⑀ was assessed from the apical 4-chamber view and radial ⑀ and SR from parasternal long-axis view. SR and ⑀ data from tissue velocity imaging were analyzed offline using archiving application software (EchoPac 6.3, GE Vingmed, Horten, Norway). Measurements of the 3 septal layers–left endocardial layer (LE), right endocardial layer (RE), and ML– were all performed with a sampling volume of 2 mm in width and 2 mm in length for radial ⑀ and SR (Figure 1). Longitudinal ⑀ and SR were both measured in a central position at the basal level of the septum and RV free wall, with a sample volume of 12 mm in length and 6 mm in width. The frame rate was 96 ⫾ 11 frames/s (range 71-137) for both longitudinal and radial measurements.
Echocardiographic Measurements M-mode echocardiographic measurements were made. LV diameter, interventricular septal thickness, and posterior wall thickness were all measured at end diastole (onset of the Q wave of the electrocardiogram). LV and left atrial diameters were also measured at end systole and LV fractional shortening was calculated.15 LV ejection fraction was derived from Simpson’s modified biplane method.13 The LV lateral, septal, anterior, and posterior systolic atrioventricular plane displacements were measured and the mean value was calculated.16 Peak early (E) and late atrial (A) diastolic velocities were measured from pulsed wave Doppler recordings of the mitral flow velocities, and E/A ratio was calculated.17 LV E-wave deceleration time was measured from the peak to the zero velocity of the E wave. LV isovolumic relaxation time was measured as the time interval between aortic valve closure (S2) and the onset of the E wave.17 Systolic ⑀ and SR were obtained by measuring the total extent of myocardial deformation during systole. The S2 from the phonocardiogram was used as reference point of end systole.18 Statistics A commercially available statistics program (SPSS 11.1, SPSS Inc., Chicago, Ill.) was used. All data are presented as mean ⫾ SD. A paired t test was used to compare values between segments. A P value less than .05 was considered significant.
RESULTS Standard Echocardiography Basic echocardiographic indices of LV function are summarized in Table 2. Radial ⑀ and SR In both the endocardial septal layers, LE and RE, we found mean negative ⑀ values, ⫺20.1 ⫾ 11.5% for RE and ⫺25.0 ⫾ 14.1% for LE. However, in the ML we found a positive ⑀ value, 11.5 ⫾ 13.2%, significantly different from the two endocardial layers (P ⬍ .001 for both) (Figure 2). The same relationship was found for SR with negative values for the two endocardial layers, ⫺1.2 ⫾ 1.8 1/s for RE and ⫺2.9 ⫾ 1.8 1/s for LE and positive values for the ML, 1.1 ⫾ 1.0 1/s (P ⬍ .001 for both). SR was significantly higher for LE compared with RE (P ⬍ .001) (Figure 3). Longitudinal and Radial ⑀ and SR There was a significantly higher longitudinal free wall ⑀ compared with radial (RE) ⑀ in the RV (⫺26.5 ⫾ 11.5% vs ⫺20.1 ⫾ 11.4%, P ⬍ .05), whereas there was a significantly higher radial (LE) ⑀ and SR in the LV compared with the longitudinal ⑀ and SR (⫺25.0 ⫾ 14.1% vs ⫺16.8 ⫾ 9.5%, P ⬍ .05; and ⫺2.9 ⫾ 1.8 vs ⫺1.1 ⫾ 0.4 1/s, P ⬍ .001).
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Figure 1 Radial septal strain in 3 different layers: left (red ) and right (yellow) ventricular endocardial and middle (green).
Figure 2 Strain in different fiber layers. LV, Left ventricle; RV, right ventricle.
DISCUSSION Recently, DTI and ⑀ echocardiography techniques have been developed and are reported to be more objective for assessing regional myocardial function.10 However, radial septal tissue velocities are difficult to measure, most likely because of the fact
Figure 3 Strain rate in different fiber layers. LV, Left ventricle; RV, right ventricle.
that there are different functional layers in the interventricular septum with different velocity gradients.8 Therefore, there is a need for further studies to better understand the complex septal function. In this study, we detected 3 functional septal layers with different radial ⑀ signals, corresponding to myocardial shortening of the two endocardial septal LE and RE and lengthening of the septal ML.
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Table 2 Echocardiographic indices of left ventricular function 2D/M-mode
LA diameter, mm LV end-diastolic dimension, mm LV end-systolic dimension, mm LV septal end-diastolic thickness, mm LV PW end-diastolic thickness, mm LV EF, % AV plane displacement, mean, mm
Mean (SD)
38 49 29 9.2 8.1 59 12.6
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
6 5 5 1.8 1.7 8 2.0
Doppler
Mitral E/A ratio Mitral E deceleration, ms Mitral IVRt, ms
1.0 ⫾ 0.3 202 ⫾ 61 84 ⫾ 21
A, Peak late atrial diastolic velocity; AV, atrioventricular; E, peak early diastolic velocity; EF, ejection fraction; IVRt, isovolumic relaxation time; LA, left atrium; LV, left ventricular; PW, posterior wall; 2D, 2-dimensional.
During systole, the endocardial layers are compressed, suggested by the negative ⑀ values found in this study. The circumferential septal ML, however, lengthens during the same part of the cardiac cycle. This phenomenon might correspond to the anatomic fiber layers with different fiber orientations in the septum.1 In a recent study, Boettler et al19 investigated the septum as a bilayered structure using tissue Doppler. They placed one small sample volume to the right and one sample volume to the left of a bright echo in the septal midline observed in 2-dimensional and M-mode echocardiography. In that study, both septal parts showed lengthening with positive radial ⑀, with higher values in the left part. This is in agreement with the positive radial ⑀ seen in the septal ML in our study. We were interested in subendocardial deformation and our data suggest a subendocardial compression on both the LV and RV side of the septum. We also found that radial septal ⑀ in the LV endocardial surface was larger than the longitudinal septal ⑀, whereas the opposite relation was found in the RV. This likely reflects to some extent that the intraventricular pressure is considerably higher in the LV. Knowing that radial motion is more prominent in the LV and longitudinal motion more prominent in the RV, the general functional properties of the respective chambers may contribute to the findings.20,21 The clinical use of ⑀ and SR in assessment of regional myocardial function is potentially of considerable importance. The differences found between the right and left heart measurements correspond to known differences in dP/dt. Limitations The method used is relatively new and probably very sensitive to technical limitations, including
settings of sample volumes, filters, and frame rates. We used a small sample volume to be able to select the subendocardial layers.22 The SD was relatively large, especially in the radial measurements. This could reflect a decreased signal-to-noise ratio in small sample volumes. Different sample volumes were used in the radial and longitudinal motions, which could influence the results. Because the angle between the ultrasound beam and myofiber spatial orientation can affect the results, further investigations are needed. Conclusion Systolic ⑀ and SR imaging indicate 3 functional layers in the septum, with systolic compression at the endocardial borders and systolic lengthening in the middle part of the septum. These functional layers correspond to the anatomy of fiber directions in the septum. The results underscore the complexity of radial septal function and may explain why the DTI technique has been limited in assessing radial myocardial septal velocities. Finally, we have shown that the LE generates higher SR compared with the RE, which might correspond to the higher dP/dt in LV compared with RV. REFERENCES 1. Greenbaum RA, Ho SY, Gibson DG, Becker AE, Anderson RH. Left ventricular fiber architecture in man. Br Heart J 1981;45:248-63. 2. Kaul S. The interventricular septum in health and disease. Am Heart J 1986;112:568-81. 3. Jones CJ, Raposo L, Gibson DG. Functional importance of the long axis dynamics of the human left ventricle. Br Heart J 1990;63:215-20. 4. Henein M, Lindqvist P, Francis D, Morner S, Waldenstrom A, Kazzam E. Tissue Doppler analysis of age-dependency in diastolic ventricular behavior and filling: a cross-sectional study of healthy hearts (the Umea general population heart study). Eur Heart J 2002;23:162-71. 5. Kukulski T, Jamal F, D’Hooge J, Bijnens B, De Scheerder I, Sutherland GR. Acute changes in systolic and diastolic events during clinical coronary angioplasty: a comparison of regional velocity, strain rate, and strain measurement. J Am Soc Echocardiogr 2002;15:1-12. 6. Nunez J, Zamorano JL, Perez De Isla L, Palomeque C, Almeria C, Rodrigo JL, et al. Differences in regional systolic and diastolic function by Doppler tissue imaging in patients with hypertrophic cardiomyopathy and hypertrophy caused by hypertension. J Am Soc Echocardiogr 2004;17:717-22. 7. Cardim N, Oliveira AG, Longo S, Ferreira T, Pereira A, Reis RP, et al. Doppler tissue imaging: regional myocardial function in hypertrophic cardiomyopathy and in athlete’s heart. J Am Soc Echocardiogr 2003;16:223-32. 8. Sutherland GR, Di Salvo G, Claus P, D’Hooge J, Bijnens B. Strain and strain rate imaging: a new clinical approach to quantifying regional myocardial function. J Am Soc Echocardiogr 2004;17:788-802. 9. Vinereanu D, Khokhar A, Fraser AG. Reproducibility of pulsed wave tissue Doppler echocardiography. J Am Soc Echocardiogr 1999;12:492-9.
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10. Smiseth OA, Ihlen H. Strain rate imaging: why do we need it? J Am Coll Cardiol 2003;42:1584-6. 11. Jamal F, Bergerot C, Argaud L, Loufouat J, Ovize M. Longitudinal strain quantitates regional right ventricular contractile function. Am J Physiol Heart Circ Physiol 2003; 285:H2842-7. 12. Sutherland GR, Hatle L. Pulsed Doppler myocardial imaging. A new approach to regional longitudinal function? Eur J Echocardiogr 2000;1:81-3. 13. Schiller NB, Shah PM, Crawford M, DeMaria A, Devereux R, Feigenbaum H, et al. Recommendations for quantitation of the left ventricle by two-dimensional echocardiography: American Society of Echocardiography committee on standards, subcommittee on quantitation of two-dimensional echocardiograms. J Am Soc Echocardiogr 1989;2:358-67. 14. Garcia-Fernandez MA, Azevedo J, Moreno M, Bermejo J, Perez-Castellano N, Puerta P, et al. Regional diastolic function in ischemic heart disease using pulsed wave Doppler tissue imaging. Eur Heart J 1999;20:496-505. 15. Sahn DJ, DeMaria A, Kisslo J, Weyman A. Recommendations regarding quantitation in M-mode echocardiography: results of a survey of echocardiographic measurements. Circulation 1978;58:1072-83. 16. Henein MY, O’Sullivan CA, Coats AJ, Gibson DG. Angiotensin-converting enzyme (ACE) inhibitors revert abnormal right ventricular filling in patients with restrictive left ventricular disease. J Am Coll Cardiol 1998;32:1187-93.
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17. Quinones MA, Otto CM, Stoddard M, Waggoner A, Zoghbi WA. Recommendations for quantification of Doppler echocardiography: a report from the Doppler quantification task force of the nomenclature and standards committee of the American Society of Echocardiography. J Am Soc Echocardiogr 2002;15:167-84. 18. Kukulski T, Jamal F, Herbots L, D’Hooge J, Bijnens B, Hatle L, et al. Identification of acutely ischemic myocardium using ultrasonic strain measurements: a clinical study in patients undergoing coronary angioplasty. J Am Coll Cardiol 2003;41:810-9. 19. Boettler P, Claus P, Herbots L, McLaughlin M, D’Hooge J, Bijnens B, et al. New aspects of the ventricular septum and its function: an echocardiographic study. Heart 2005;91: 1343-8. 20. Kowalski M, Kukulski T, Jamal F, D’Hooge J, Weidemann F, Rademakers F, et al. Can natural strain and strain rate quantify regional myocardial deformation? A study in healthy subjects. Ultrasound Med Biol 2001;27:1087-97. 21. Kukulski T, Hubbert L, Arnold M, Wranne B, Hatle L, Sutherland GR. Normal regional right ventricular function and its change with age: a Doppler myocardial imaging study. J Am Soc Echocardiogr 2000;13:194-204. 22. Sengupta PP, Khandheria BK, Korinek J, Wang J, Belohlavek M. Biphasic tissue Doppler waveforms during isovolumic phases are associated with asynchronous deformation of subendocardial and subepicardial layers. J Appl Physiol 2005;99: 1104-11.
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 (⑀) and ⑀ rate (SR) imaging can improve the measurement of the septal function. Methods: Thirty healthy participants (18 women; age 60 ⴞ 11 years, range 42-72) were randomly selected from the population. Systolic ⑀ 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 ⑀ (myocardial shortening), ⴚ20.1 ⴞ 11.5% for RE and ⴚ25.0 ⴞ 14.1% for LE during systole. However, in the middle layer we found a positive radial ⑀ (myocardial lengthening), ⴙ11.5 ⴞ 13.2%, significantly different from the two endocardial layers (P < .001 for both).
Anatomic studies have shown that the septum con-
sists of longitudinal subendocardial fibers of the right ventricle (RV) and left ventricle (LV), together with a middle layer (ML) composed of circumferential fibers.1 Functionally, the septum contributes to both LV and RV function.2 Septal motion is routinely studied by traditional M-mode echocardiography, and the relation between septal long- and shortaxis motions in health and disease has been extensively studied.3 Longitudinal septal motion has been shown to alter with age,4 coronary artery disease,5 hypertension, and hypertrophy,6,7 with a reduction in systolic amplitude or velocity and From the Departments of Cardiology and Clinical Physiology (P.L., K.K.), Heart Centre, Umeå University. Reprint requests: Per Lindqvist, PhD, Department of Public Health and Clinical Medicine, Umeå University, S-90185 Umeå, Sweden (E-mail: [email protected]). 0894-7317/$32.00 Copyright 2006 by the American Society of Echocardiography. doi:10.1016/j.echo.2006.05.002
SR was negative in the two endocardial layers and significantly higher for LE, (ⴚ2.9 ⴞ 1.8 1/s) than for RE (ⴚ1.2 ⴞ 1.8 1/s, P < .001) and positive for the middle layer (ⴙ1.1 ⴞ 1.0 1/s), significantly different in comparison with the two endocardial layers (P < .001). Finally, there was a higher longitudinal ⑀ compared with radial endocardial ⑀ for right ventricle (ⴚ26.5 ⴞ 11.5 vs ⴚ20.1 ⴞ 11.5, P < .05) whereas there was significantly higher left ventricular radial ⑀ and SR compared with the longitudinal ⑀ and SR (ⴚ25.0 ⴞ 14.1 vs ⴚ16.8 ⴞ 9.5, P < .05; and ⴚ2.9 ⴞ 1.8 vs ⴚ1.1 ⴞ 0.4, P < .001). Conclusion: Systolic ⑀ 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. (J Am Soc Echocardiogr 2006;19:1345-1349.)
changes in early and late diastolic contribution to ventricular filling. It is difficult to measure circumferential and radial septal wall motion using Doppler tissue imaging (DTI) echocardiography, because of the presence of different myocardial fiber layers, with different directions in motion.8 This might cause the ultrasound beam not to be parallel to the combination of longitudinal, radial, and circumferential fibers, which are present in the septum.1 Because of these difficulties, DTI has not been much used in the assessment of radial septal function.7,9 Myocardial strain (⑀) is dimensionless and represents the fractional or percentage change in dimension.10 Recently ultrasound-determined ⑀ has been developed with excellent correlation to sonomicrometry data.11 Furthermore, clinical approaches have been proposed, eg, quantifying regional myocardial function.12 In this study, we wanted to investigate whether ⑀ or ⑀ rate (SR) echocardiography could improve the understanding of septal function in healthy individuals.
1345
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Table 1 General characteristics of the healthy participants Mean (SD)
Age, years Female/male Systolic blood pressure, mm Hg Diastolic blood pressure, mm Hg Height, m Weight, kg Heart rate, beats/min
60 ⫾ 11 18/12 135 ⫾ 16 76 ⫾ 10 1.69 ⫾ 8.7 71 ⫾ 11 62 ⫾ 9
METHODS Study Population A total of 30 healthy participants (18 women; 60 ⫾ 11 years, range 42-72) were randomly selected and constituted the study population. Some general characteristics of the participants are shown in Table 1. All gave their informed consent to participate in the study, which was approved by our local ethics committee. Standard Echocardiography A digital ultrasound system (Vivid 7, GE Vingmed, Horten, Norway) with a phased-array transducer (1.5-4 MHz) was used. Standard 2-dimensional and Doppler echocardiography was used, as was pulsed and color myocardial DTI. The echocardiographic examination was performed with the participant in the left lateral decubitus position and recordings were made during expiration. Parasternal and apical projections were obtained according to the recommendations of the American Society of Echocardiography.13 All recordings were performed with a simultaneous superimposed electrocardiogram. A phonocardiogram was applied to display the S2 as definition of end systole.14 Recordings were taken at a sweep speed of 100 mm/s. ⑀ Echocardiography By convention, myocardial lengthening is given a positive ⑀ value and shortening is given a negative value. Onedimensional ⑀ is defined by ⑀ ⫽ ⌬L/L0 where ⌬L is the change in length and L0 is the original length of a myocardial segment. The longitudinal ⑀ was assessed from the apical 4-chamber view and radial ⑀ and SR from parasternal long-axis view. SR and ⑀ data from tissue velocity imaging were analyzed offline using archiving application software (EchoPac 6.3, GE Vingmed, Horten, Norway). Measurements of the 3 septal layers–left endocardial layer (LE), right endocardial layer (RE), and ML– were all performed with a sampling volume of 2 mm in width and 2 mm in length for radial ⑀ and SR (Figure 1). Longitudinal ⑀ and SR were both measured in a central position at the basal level of the septum and RV free wall, with a sample volume of 12 mm in length and 6 mm in width. The frame rate was 96 ⫾ 11 frames/s (range 71-137) for both longitudinal and radial measurements.
Echocardiographic Measurements M-mode echocardiographic measurements were made. LV diameter, interventricular septal thickness, and posterior wall thickness were all measured at end diastole (onset of the Q wave of the electrocardiogram). LV and left atrial diameters were also measured at end systole and LV fractional shortening was calculated.15 LV ejection fraction was derived from Simpson’s modified biplane method.13 The LV lateral, septal, anterior, and posterior systolic atrioventricular plane displacements were measured and the mean value was calculated.16 Peak early (E) and late atrial (A) diastolic velocities were measured from pulsed wave Doppler recordings of the mitral flow velocities, and E/A ratio was calculated.17 LV E-wave deceleration time was measured from the peak to the zero velocity of the E wave. LV isovolumic relaxation time was measured as the time interval between aortic valve closure (S2) and the onset of the E wave.17 Systolic ⑀ and SR were obtained by measuring the total extent of myocardial deformation during systole. The S2 from the phonocardiogram was used as reference point of end systole.18 Statistics A commercially available statistics program (SPSS 11.1, SPSS Inc., Chicago, Ill.) was used. All data are presented as mean ⫾ SD. A paired t test was used to compare values between segments. A P value less than .05 was considered significant.
RESULTS Standard Echocardiography Basic echocardiographic indices of LV function are summarized in Table 2. Radial ⑀ and SR In both the endocardial septal layers, LE and RE, we found mean negative ⑀ values, ⫺20.1 ⫾ 11.5% for RE and ⫺25.0 ⫾ 14.1% for LE. However, in the ML we found a positive ⑀ value, 11.5 ⫾ 13.2%, significantly different from the two endocardial layers (P ⬍ .001 for both) (Figure 2). The same relationship was found for SR with negative values for the two endocardial layers, ⫺1.2 ⫾ 1.8 1/s for RE and ⫺2.9 ⫾ 1.8 1/s for LE and positive values for the ML, 1.1 ⫾ 1.0 1/s (P ⬍ .001 for both). SR was significantly higher for LE compared with RE (P ⬍ .001) (Figure 3). Longitudinal and Radial ⑀ and SR There was a significantly higher longitudinal free wall ⑀ compared with radial (RE) ⑀ in the RV (⫺26.5 ⫾ 11.5% vs ⫺20.1 ⫾ 11.4%, P ⬍ .05), whereas there was a significantly higher radial (LE) ⑀ and SR in the LV compared with the longitudinal ⑀ and SR (⫺25.0 ⫾ 14.1% vs ⫺16.8 ⫾ 9.5%, P ⬍ .05; and ⫺2.9 ⫾ 1.8 vs ⫺1.1 ⫾ 0.4 1/s, P ⬍ .001).
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Figure 1 Radial septal strain in 3 different layers: left (red ) and right (yellow) ventricular endocardial and middle (green).
Figure 2 Strain in different fiber layers. LV, Left ventricle; RV, right ventricle.
DISCUSSION Recently, DTI and ⑀ echocardiography techniques have been developed and are reported to be more objective for assessing regional myocardial function.10 However, radial septal tissue velocities are difficult to measure, most likely because of the fact
Figure 3 Strain rate in different fiber layers. LV, Left ventricle; RV, right ventricle.
that there are different functional layers in the interventricular septum with different velocity gradients.8 Therefore, there is a need for further studies to better understand the complex septal function. In this study, we detected 3 functional septal layers with different radial ⑀ signals, corresponding to myocardial shortening of the two endocardial septal LE and RE and lengthening of the septal ML.
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Table 2 Echocardiographic indices of left ventricular function 2D/M-mode
LA diameter, mm LV end-diastolic dimension, mm LV end-systolic dimension, mm LV septal end-diastolic thickness, mm LV PW end-diastolic thickness, mm LV EF, % AV plane displacement, mean, mm
Mean (SD)
38 49 29 9.2 8.1 59 12.6
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
6 5 5 1.8 1.7 8 2.0
Doppler
Mitral E/A ratio Mitral E deceleration, ms Mitral IVRt, ms
1.0 ⫾ 0.3 202 ⫾ 61 84 ⫾ 21
A, Peak late atrial diastolic velocity; AV, atrioventricular; E, peak early diastolic velocity; EF, ejection fraction; IVRt, isovolumic relaxation time; LA, left atrium; LV, left ventricular; PW, posterior wall; 2D, 2-dimensional.
During systole, the endocardial layers are compressed, suggested by the negative ⑀ values found in this study. The circumferential septal ML, however, lengthens during the same part of the cardiac cycle. This phenomenon might correspond to the anatomic fiber layers with different fiber orientations in the septum.1 In a recent study, Boettler et al19 investigated the septum as a bilayered structure using tissue Doppler. They placed one small sample volume to the right and one sample volume to the left of a bright echo in the septal midline observed in 2-dimensional and M-mode echocardiography. In that study, both septal parts showed lengthening with positive radial ⑀, with higher values in the left part. This is in agreement with the positive radial ⑀ seen in the septal ML in our study. We were interested in subendocardial deformation and our data suggest a subendocardial compression on both the LV and RV side of the septum. We also found that radial septal ⑀ in the LV endocardial surface was larger than the longitudinal septal ⑀, whereas the opposite relation was found in the RV. This likely reflects to some extent that the intraventricular pressure is considerably higher in the LV. Knowing that radial motion is more prominent in the LV and longitudinal motion more prominent in the RV, the general functional properties of the respective chambers may contribute to the findings.20,21 The clinical use of ⑀ and SR in assessment of regional myocardial function is potentially of considerable importance. The differences found between the right and left heart measurements correspond to known differences in dP/dt. Limitations The method used is relatively new and probably very sensitive to technical limitations, including
settings of sample volumes, filters, and frame rates. We used a small sample volume to be able to select the subendocardial layers.22 The SD was relatively large, especially in the radial measurements. This could reflect a decreased signal-to-noise ratio in small sample volumes. Different sample volumes were used in the radial and longitudinal motions, which could influence the results. Because the angle between the ultrasound beam and myofiber spatial orientation can affect the results, further investigations are needed. Conclusion Systolic ⑀ and SR imaging indicate 3 functional layers in the septum, with systolic compression at the endocardial borders and systolic lengthening in the middle part of the septum. These functional layers correspond to the anatomy of fiber directions in the septum. The results underscore the complexity of radial septal function and may explain why the DTI technique has been limited in assessing radial myocardial septal velocities. Finally, we have shown that the LE generates higher SR compared with the RE, which might correspond to the higher dP/dt in LV compared with RV. REFERENCES 1. Greenbaum RA, Ho SY, Gibson DG, Becker AE, Anderson RH. Left ventricular fiber architecture in man. Br Heart J 1981;45:248-63. 2. Kaul S. The interventricular septum in health and disease. Am Heart J 1986;112:568-81. 3. Jones CJ, Raposo L, Gibson DG. Functional importance of the long axis dynamics of the human left ventricle. Br Heart J 1990;63:215-20. 4. Henein M, Lindqvist P, Francis D, Morner S, Waldenstrom A, Kazzam E. Tissue Doppler analysis of age-dependency in diastolic ventricular behavior and filling: a cross-sectional study of healthy hearts (the Umea general population heart study). Eur Heart J 2002;23:162-71. 5. Kukulski T, Jamal F, D’Hooge J, Bijnens B, De Scheerder I, Sutherland GR. Acute changes in systolic and diastolic events during clinical coronary angioplasty: a comparison of regional velocity, strain rate, and strain measurement. J Am Soc Echocardiogr 2002;15:1-12. 6. Nunez J, Zamorano JL, Perez De Isla L, Palomeque C, Almeria C, Rodrigo JL, et al. Differences in regional systolic and diastolic function by Doppler tissue imaging in patients with hypertrophic cardiomyopathy and hypertrophy caused by hypertension. J Am Soc Echocardiogr 2004;17:717-22. 7. Cardim N, Oliveira AG, Longo S, Ferreira T, Pereira A, Reis RP, et al. Doppler tissue imaging: regional myocardial function in hypertrophic cardiomyopathy and in athlete’s heart. J Am Soc Echocardiogr 2003;16:223-32. 8. Sutherland GR, Di Salvo G, Claus P, D’Hooge J, Bijnens B. Strain and strain rate imaging: a new clinical approach to quantifying regional myocardial function. J Am Soc Echocardiogr 2004;17:788-802. 9. Vinereanu D, Khokhar A, Fraser AG. Reproducibility of pulsed wave tissue Doppler echocardiography. J Am Soc Echocardiogr 1999;12:492-9.
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10. Smiseth OA, Ihlen H. Strain rate imaging: why do we need it? J Am Coll Cardiol 2003;42:1584-6. 11. Jamal F, Bergerot C, Argaud L, Loufouat J, Ovize M. Longitudinal strain quantitates regional right ventricular contractile function. Am J Physiol Heart Circ Physiol 2003; 285:H2842-7. 12. Sutherland GR, Hatle L. Pulsed Doppler myocardial imaging. A new approach to regional longitudinal function? Eur J Echocardiogr 2000;1:81-3. 13. Schiller NB, Shah PM, Crawford M, DeMaria A, Devereux R, Feigenbaum H, et al. Recommendations for quantitation of the left ventricle by two-dimensional echocardiography: American Society of Echocardiography committee on standards, subcommittee on quantitation of two-dimensional echocardiograms. J Am Soc Echocardiogr 1989;2:358-67. 14. Garcia-Fernandez MA, Azevedo J, Moreno M, Bermejo J, Perez-Castellano N, Puerta P, et al. Regional diastolic function in ischemic heart disease using pulsed wave Doppler tissue imaging. Eur Heart J 1999;20:496-505. 15. Sahn DJ, DeMaria A, Kisslo J, Weyman A. Recommendations regarding quantitation in M-mode echocardiography: results of a survey of echocardiographic measurements. Circulation 1978;58:1072-83. 16. Henein MY, O’Sullivan CA, Coats AJ, Gibson DG. Angiotensin-converting enzyme (ACE) inhibitors revert abnormal right ventricular filling in patients with restrictive left ventricular disease. J Am Coll Cardiol 1998;32:1187-93.
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17. Quinones MA, Otto CM, Stoddard M, Waggoner A, Zoghbi WA. Recommendations for quantification of Doppler echocardiography: a report from the Doppler quantification task force of the nomenclature and standards committee of the American Society of Echocardiography. J Am Soc Echocardiogr 2002;15:167-84. 18. Kukulski T, Jamal F, Herbots L, D’Hooge J, Bijnens B, Hatle L, et al. Identification of acutely ischemic myocardium using ultrasonic strain measurements: a clinical study in patients undergoing coronary angioplasty. J Am Coll Cardiol 2003;41:810-9. 19. Boettler P, Claus P, Herbots L, McLaughlin M, D’Hooge J, Bijnens B, et al. New aspects of the ventricular septum and its function: an echocardiographic study. Heart 2005;91: 1343-8. 20. Kowalski M, Kukulski T, Jamal F, D’Hooge J, Weidemann F, Rademakers F, et al. Can natural strain and strain rate quantify regional myocardial deformation? A study in healthy subjects. Ultrasound Med Biol 2001;27:1087-97. 21. Kukulski T, Hubbert L, Arnold M, Wranne B, Hatle L, Sutherland GR. Normal regional right ventricular function and its change with age: a Doppler myocardial imaging study. J Am Soc Echocardiogr 2000;13:194-204. 22. Sengupta PP, Khandheria BK, Korinek J, Wang J, Belohlavek M. Biphasic tissue Doppler waveforms during isovolumic phases are associated with asynchronous deformation of subendocardial and subepicardial layers. J Appl Physiol 2005;99: 1104-11.