Copyright © 2004, The European Society of Cardiology
Ultrasonic strain/strain rate imaging—a new clinical tool to evaluate the transplanted heart
Department of Cardiology, University Hospital Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium
Received 6 July 2004; .
* Corresponding author. Tel.: +32 16 34 75 69; fax: +32 16 34 34 67. bart.bijnens{at}uz.kuleuven.ac.be (B. Bijnens).
 |
Abstract |
|---|
 Top Abstract IntroductionMethodsResultsDiscussionLimitationsConclusionsReferences |
|---|
Objective The aim of this study was to investigate the clinical applicability of strain and strain rate imaging (
/SRI) in heart transplantation (Htx) patients and to establish "normal" post-Htx regional systolic deformation values.
Background /SR indices have been shown to be a more sensitive measure of regional systolic function than standard echo measurements. Thus, they might provide a new tool to better define both normal cardiac graft function and detect changes due to post-Htx complications. However, prior to investigating the role of /SRI in detecting abnormalities, "normal" post-Htx regional deformation values must be established as graft regional function can be altered by a number of factors such as ischemic time, surgical technique or accelerated graft ageing.
Methods A total of 57 Htx patients (age 36±12 years; post-Htx 5.5±3 years) without any documented complication were studied. /SRI data were acquired from the septum, left ventricular (LV) free walls and right ventricular free wall (RVFW). A total of 29 age-matched healthy subjects served as controls.
Results Htx longitudinal peak systolic velocities (V sys) were lower in inferior, septal and RVFW segments compared to controls. Peak systolic /SR ( sys/SRsys) did not differ from controls except in septum and RVFW in which the values were significantly reduced. Radial V sys in the Htx group were higher than controls while sys/SRsys were reduced. There was a significant decrease in SRsys in apical LV segments with increasing time post-Htx, whereas those measured in RVFW showed an increase by that time.
Conclusion /SRI demonstrated that "healthy" Htx hearts have normal global systolic function but altered regional systolic deformation indices compared to normal hearts. Post-Htx time has a diminishing effect on the regional systolic deformation indices in LV segments but an improving effect in RVFW. These "normal" Htx values should provide the basis for subsequent studies into the role of /SRI in the non-invasive detection of post-Htx complications.
Keywords: Echocardiography; Strain rate imaging; Heart transplantation
|
Introduction |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionsReferences |
|---|
Ultrasonic strain (
) and strain rate (SR) indices have been shown to be a more sensitive measure than standard echo parameters in assessing alterations in regional systolic function.1,2 Recent clinical studies in patients with systemic diseases such as amyloidosis, Fabry, Friedreich's Ataxia and Type II Diabetes have demonstrated that /SR imaging can detect reduced regional myocardial function before any measurable changes in conventional grey-scale or Doppler echo parameters.3–6
Thus, /SR imaging (/SRI) might provide a new tool to detect early changes in regional cardiac graft function due either to rejection, vasculopathy or immunosuppressive therapy. However, prior to any prospective study to investigate the potential role of /SRI in detecting such abnormalities, "normal" Htx /SR values must be established as cardiac graft regional function could be altered by a number of reasons.
Donor brain death, ischemic time, use of cardioplegia and/or increased pulmonary vascular resistance in the recipient may all impair donor ventricular function. Age mismatch and/or subsequent degeneration of the donor heart are also factors which may alter cardiac graft function after Htx. As a result, both structural and functional changes in the cardiac graft can occur which are directly related to the Htx procedure itself.
Therefore, the purpose of this study was to assess the robustness of ultrasound-based systolic /SRI indices in quantifying regional systolic myocardial function after Htx and to establish normal values of regional longitudinal and radial velocity (V) and SR/ for left (LV) and right ventricular (RV) segments in a representative cross-section of "healthy" Htx patients who were in a stable clinical state. These values could then serve as the reference baseline dataset for further studies which would determine the sensitivity and specificity of these new functional indices in detecting post-Htx complications.
|
Methods |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionsReferences |
|---|
Study population
A prospective study enrolled orthotopic heart Htx patients who were being admitted to the Cardiology Department of University Hospital Gasthuisberg for routine annual post-Htx follow up. Standard investigations included physical examination, a 12 lead ECG, 24h ambulatory blood pressure measurement, standard echocardiography, right heart catheterization, and coronary angiography (with a correlative intracoronary ultrasound study if clinically indicated). According to the protocol, an endomyocardial biopsy is also routinely performed in the first year post-Htx. After the first year, a biopsy is only performed on the basis of the clinical and/or abnormal laboratory findings.
Left ventricular ejection fraction (LVEF) was measured from standard grey-scale M-mode echocardiography. Tricuspid regurgitation (TR) was graded as either none/trivial, mild, moderate or severe. The diagnosis of rejection was made in accordance with the International Society of Heart and Lung Transplantation (ISHLT) standardized cardiac biopsy grading. Coronary vasculopathy was defined as epicardial coronary narrowing of > 50% or moderate to severe distal attenuation.
All patients to be included in the study were to have a normal ECG with a QRS duration of less than 120ms, a normal LVEF, TR of less than moderate severity, a cardiac biopsy
ISHLT Grade 1A, a normal invasive measurement of right heart pressures as well as normal coronary angiography which is defined as to have less than 50% of focal stenosis and/or more than mild distal vessel attenuation.
The Institutional Review Board on Human Research approved this study, and all participants gave informed consent.
A total of 57 heart Htx recipients (17 female, 40 male) with a mean post-Htx time of 5.5±3 years fulfilled these criteria and were included in the study. Six of the patients had correlative negative intracoronary ultrasound studies. The descriptive data and the hemodynamic measurements of the Htx patients are given in Table 1. The cardiac age for each patient was calculated by adding the time after Htx to the donor's age. Twenty-nine age-matched healthy normal subjects (12 female, 17 male) served as the control group. All had normal 12 lead ECGs and blood pressure measurements. None had clinical or echocardiographic evidence of cardiac disease.
|
The impact of the post-Htx time on regional systolic myocardial deformation indices was evaluated by dividing the Htx patients into two subgroups: early (< 5 years, 25 patients) and late (> 5 years, 32 patients) Htx.
The standard ultrasound examination
Standard TTE, blood pool Doppler and 2-D Colour Doppler Myocardial Imaging (CDMI) examinations were performed using commercially available equipment (Vivid 7, GE Vingmed Ultrasound, Horten, Norway) and a 1.7/3.4MHz transducer. The thickness of the interventricular septum, LV posterior wall and the LV end-diastolic (LVEDD) and end-systolic diameters (LVESD) were determined by M-mode recordings taken at the level of the tips of the mitral leaflets, and LV ejection fraction was calculated. LV mass (LVM) was calculated from the formula7: LVM=0.8[1.04 (septal WT+LVEDD+posterior WT)3–(LVEDD)3]+0.6g and was corrected for the body surface area. Right ventricular (RV) major long axis dimension was measured from the apical endocardium to the plane of tricuspid valve using an apical four-chamber end-diastolic frame. Pulsed Doppler recording of transmitral flow velocities was performed by positioning the sample volume at the tips of the mitral leaflets. The peak velocities of early and late filling waves and deceleration time of early filling were measured from transmitral flow velocities.
Colour Doppler myocardial data acquisition
In each patient, datasets from the parasternal long axis (radial data), apical two- and four-chamber views (longitudinal data) were acquired. Real time two-dimensional CDMI data were recorded from the interventricular septum, lateral, anterior, inferior LV and RV free walls. Data were acquired wall by wall with the wall to be interrogated imaged in the center of the sector angle. Three consecutive cardiac cycles were collected and stored in a cineloop format at a frame rate of 200–300 frames per second for off-line analysis. The narrowest image sector angle possible (usually 30°) and the optimal depth of imaging were used to increase temporal resolution. Special attention was paid to the colour Doppler velocity range setting in order to avoid any aliasing within the image. Velocity aliasing was eliminated by setting appropriate PRF values.
Echocardiographic data analysis
All digital data were transferred for post-processing on a stand-alone workstation. The CDMI data sets were analyzed off-line using standardized software Speqle4 (Catholic University, Leuven, Belgium). Standard regions of interest were selected in the basal, mid and apical segments of the interventricular septum, lateral, inferior and anterior LV walls for apical four- and two-chamber views. In contrast, a two segmental RV free wall analysis model was chosen, in which data were acquired from the basal and apical segments.
SR measures the rate of segmental deformation and corresponds to the local spatial velocity gradient, expressed in s–1. defines the amount of local deformation in terms of percentage and is derived by integrating the SR over time. By convention, SR values are expressed as being positive when a myocardial segment thickens/lengthens and negative when a segment thins/shortens. A computation area of 10 and 5mm were used for the longitudinal and radial SR estimation, respectively. A semi-automatic M-mode based tracking algorithm was applied to maintain the sample volume within the region of interest throughout the cardiac cycle. V and SR data were averaged over three consecutive cycles and then smoothed with a mask of 5x1 pixels (axialxlateral) to reduce the noise. The regional SR profiles were integrated over time to obtain the natural profiles.
To determine the duration of ejection, the aortic valve (AV) opening and closure clicks were introduced from blood pool pulsed wave Doppler tracings recorded from cycles with the same R–R interval. For each segment analyzed, regional peak systolic values were derived (Vsys/SRsys/sys). For the regional , end-systolic and maximal values were also measured to calculate the post-systolic strain index (PSI). PSI is an index of the relative amount of segmental thickening/shortening, which occurs after aortic valve closure. The formula used to calculate PSI (previously defined by Kukulski et al.) is PSI=[maximum overall (max)–end-systolic (endsys)]/max.8 The intra- and inter-observer variability of the technique (given in percent of mean values) has previously been reported by our group and is 10% for radial and 14% for longitudinal systolic /SR parameters.9
Cardiac catheterization
Right-side cardiac catheterization, endomyocardial biopsy and coronary angiography were performed using standard procedures. The assignment of the myocardial segments to coronary artery territories was made according to the AHA scientific statement on standardized myocardial segmentation and nomenclature for tomographic imaging of the heart.10
Statistical analysis
Statistical analysis was performed using SAS v8.02 (SAS Institute, Cary, North Carolina) and Stat Soft, Inc. [2001] STATISTICA (data analysis software system), version 6.0. Continuous values are reported as mean value±SD (standard deviation). ANOVA (analysis of variance) techniques were used to assess differences between groups (Htx vs control group; and early vs late Htx group), adjusted for age and heart rate. Significance testing of the differences between groups was done by means of an F-test. Correlations between parameters were evaluated using the Spearman correlation coefficient. A p value <0.05 was considered statistically significant.
|
Results |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionsReferences |
|---|
Clinical characteristics and standard echocardiographic data
The clinical characteristics and the standard echocardiographic measurements obtained from both the Htx and control groups are given in Table 2. The body surface area (BSA), systolic and diastolic blood pressure, LV and RV diastolic diameters and LVEF were similar in the two groups. However, the heart rate (HR), LV mass index (LVMI) and posterior WT in the Htx group were higher compared to controls.
|
Strain and strain rate imaging data
Of the 1290 segments interrogated (Htx and controls), good velocity profiles were obtained from all. When processed for regional deformation indices, data from 1167 were defined to be of good quality and included in the study. A total of 123 (9.5%) segments were excluded because the estimation of the Vsys/SRsys/
sys was not reliable due either to the failure of aligning region of interest with the ultrasound beam or reverberation artifacts. The percentage of the segments excluded in the Htx group (10%) did not differ from that excluded in controls (9%). The majority of the excluded segments were from the LV lateral (27%) and anterior (30%) walls, which are difficult to align longitudinally to the ultrasound beam due the curvature of these walls. In terms of the findings set out below, it is important to note that only 10% of the dataset were excluded from the posterior (5%) and septal walls (5%).
Regional LV radial function
The parasternal long axis view was used to quantify the regional radial systolic function of the posterior wall. Although Vsys was significantly higher in the Htx group (5.2±1.6cm/s vs 4±1.2cm/s, p<0.05), both SRsys (3.6±1.4s–1 vs 4±1.1s–1, p=NS) and sys (41±14% vs 51±13%, p<0.01) were lower compared to controls. There was a significant correlation between the SRsys and the posterior WT (r=0.40, p<0.005). The PSI in the Htx group (10%) was similar to that in the control group (9%).
Regional LV longitudinal function
The mean Vsys/SRsys/sys values for each of the four walls for basal, mid and apical segments are given in Table 3. Note that the peak systolic velocities for all walls are highest at the base and decrease as the sample volume is moved apically. This longitudinal velocity gradient has been previously described as a normal finding11 and was present in all walls. Unlike Vsys, SRsys/sys was homogenous throughout all the walls in both groups. Regional Vsys was found to be lower in inferior and septal segments in the Htx group compared to controls. However, there was no difference in SRsys/sys values between the two groups except for septal segments. Both SRsys/sys values in the septum (base, mid and apex) were significantly reduced in the Htx group compared to controls. The comparison of the mean Vsys/SRsys/sys values for the two groups is given in Fig. 1.
|
p<0.05.
|
The PSI in the Htx group was similar to that in controls for all segments. The values for the Htx group were 10% for basal, 7.5% for mid and 6% for apical segments. These values were also comparable to the findings of Voigt et al., who had defined the normal range of PSI in a cross-section of healthy normals.12
Because of the homogeneity in deformation parameters throughout a wall, peak longitudinal systolic and SR values from basal, mid and apical levels of each LV wall were averaged for subsequent correlative analysis. Only LVMI and septal WT showed a significant correlation with sys in the interventricular septum (r=0.40, p<0.0001 and r=0.35, p<0.002, respectively). There was no correlation between recipient age, donor age, heart rate, BSA, total IT, SBP, DBP and SRsys/sys.
Regional RV longitudinal function
The mean values for Vsys/SRsys/sys derived from the RV free wall are set out in Table 3. The RV free wall showed changes similar to those found in the interventricular septum. Both Vsys/SRsys/sys values were significantly reduced in all segments in the Htx group compared to controls (Fig. 2). As in all LV walls, a systolic base to apex velocity gradient was present within the RV free wall, while SRsys/sys were homogeneous. There was no correlation between the RV free wall deformation indices and peak systolic right heart pressure.
|
LV/RV deformation vs post-Htx time
The subgroup analysis showed no difference in clinical characteristics, standard echocardiographic measurements and right heart pressures between the early and late Htx groups except for a slight increase in LVMI, SBP and DBP in the late Htx group (p=NS for all). There was no difference in regional
sys values between the two groups. SRsys values were also similar for basal and midwall segments. However, apical segments in the late Htx group had significantly reduced SR values compared to the early Htx group (–1.7±0.6 vs –1.4±0.4s–1, p<0.05). The comparison of regional SRsys values for basal, mid and apical segments between the early and late Htx groups is given in Fig. 3.
|
Interestingly, the regional SRsys values in the RV free wall segments showed an increase as the time post-Htx increased (base, –2.1±0.9 vs –2.6±1.3s–1; apex, –1.5±0.5 vs –1.8±0.7s–1p<0.05 for both). However, there was no similar increase in regional
sys values.
Timing analysis
The mean time to maximal segmental thickening (radial deformation) vs shortening (longitudinal deformation) did not differ in the Htx group. There was also no significant difference between any of the three segments within a wall. Although the time to peak systolic deformation was shorter for all segments in the Htx group compared to controls, the difference did not reach significance. However, there was a significant correlation between the time to peak shortening/thickening and HR for every segment. The strongest correlation was found for the basal posterior segment (r=–0.60, p<0.0001).
The potential role of /SRI in monitoring post-Htx complications
Although it was never the aim of the study to identify the changes in regional myocardial deformation induced by post-Htx complications, during the study period six clinical patients (not entered into the "normal" post-Htx study) were found to have post-Htx complications during routine follow up. As little is known how regional deformation is altered by such complications, we have included here a description of the changes in regional myocardial deformation induced by either acute rejection or vasculopathy. Two patients had endomyocardial biopsies showing ISHLT grade 1B rejection and four patients had coronary angiograms showing severe diffuse Htx vasculopathy. All patients with complications were asymptomatic and had normal global systolic function on their standard echocardiographic examination.
In the two patients with Grade 1B biopsy results, there was no significant difference in longitudinal Vsys/SRsys/sys and radial Vsys compared to those measured in "normal" Htx group. However, radial SRsys/sys values were significantly reduced in the posterior wall when compared to both normal Htx values and control values (V=4.5cm/s, 4.7cm/s, =25%, 29% and SR=2.1s–1, 2.5s–1, respectively, for the two patients). In both the cases the normal shape of the curve was preserved with only peak systolic values markedly reduced.
Despite the fact that they had normal global systolic function, all four patients with severe Htx vasculopathy had decreased SRsys/sys in the "at risk" segments supplied by the angiographically abnormal artery (p<0.005 vs normal Htx group and controls for both). In each case, the decrease in sys was associated with a PSI of nearly 50%. This pattern of regional deformation, the decreased sys combined with increased post-systolic occurs in ischemic (or post-ischemic) myocardium.8,13 The regional radial patterns associated with each of the two complications are shown in Fig. 4.
|
Although the number of the patients with each complication was too small to make any conclusions about the clinical role of ultrasonic deformation imaging in detecting such complications in clinical practice, these preliminary findings are promising and are in accordance to the previous findings in deformation changes reported for other conditions where ischemia is present14 or myocardial tissue is altered.3–5
|
Discussion |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionsReferences |
|---|
This study was set out to investigate the robustness and clinical potential of one-dimensional ultrasonic SRI technique in quantifying regional systolic function of the left and right ventricles in Htx patients.
The Htx procedure itself could potentially limit the use of ultrasonic deformation imaging in these patients. The size mismatch between the donor heart and the recipient pericardial sac results in lateral malposition of the post-Htx heart thus potentially giving rise both to difficulty in imaging the standard echo views and to aligning the ultrasound beam at less than 15° to deformation in the region of interest. Size mismatch may also cause increased overall cardiac motion due to the loss of pericardial restraint. An exaggerated swinging motion of the entire heart in an antero-medial direction during systole has already been reported as a normal echo finding after Htx.15 The precise mechanism for this translational motion of the heart is unknown. Previous theories have proposed that this is a result of the attachment of the donor atria to a cuff of the remaining recipient atria.
All of the above could have given rise to problems in the application of /SRI technique in Htx patients. However, we found that with increasing operator expertise (during a preliminary pilot study), full data sets could be obtained in most patients. Indeed, during the study itself, the data yield for the post-Htx patients was the same as in the control group (peak systolic velocities 100% for both, /SR 90%, 91% Htx vs controls).
The abnormal exaggerated antero-medial motion of the post-Htx heart could also account for the increase in radial systolic velocities found in posterior segments and the decreased longitudinal velocities found in inferior segments.
In the septum, there was a decrease in both Vsys/SRsys/sys. Such a decrease in long axis motion and deformation is a well-documented sequel of cardiac bypass surgery and also occurs in the transplanted heart.16,17
Deformation indices have been shown to change with myocardial ageing. Barrios et al. have already shown radial SRsys to decline with age.18 Thus accelerated ageing of the transplanted heart might be associated with a premature decline in regional SRsys values. Although there was a trend to a decrease in regional SRsys/sys values in all LV segments with increasing time post-Htx, this was only statistically significant for SRsys in the apical segments. This fall in SRsys in the apical segments could equally well have been due to undetected distal transplant vasculopathy.
Right ventricular dysfunction in heart transplant recipients is multifactorial in etiology. Donor brain death and the ischemia associated with organ preservation cause an initial significant reduction in RV contractile function.19 Right ventricular function is often further reduced by coupling the non-adapted donor heart to the increased pulmonary resistance in the recipient.20,21
The majorities of RV myocardial fibres originate at the apex of the heart and insert into the right atrioventricular junction. The main bulk of the RV myocardium is composed of longitudinally arranged fibres.22 Thus the analysis of longitudinal myocardial deformation may be especially relevant when attempting to quantify regional RV function. In this study there was a significant early decrease in RV longitudinal peak systolic deformation in the Htx group. This was more pronounced in apical segments. However, in contrast to LV segments, there was a subsequent significant increase in regional SRsys SR values in the RV free wall with time post-Htx. This finding in Htx patients would be in keeping with the data of Wranne et al. who showed an initial decrease in right ventricular long axis function following routine cardiopulmonary bypass with a later improvement as the right ventricle recovered.23 In Htx patients the degree of recovery will vary and will depend to a large extent on the recipient's pulmonary vascular resistance.
There was an increase in posterior wall thickness in the Htx group, which correlated with the decrease in SRsys in this segment. This hypertrophy (and the related changes in segmental deformation) is most likely due to the increased afterload induced by immunosuppressive therapy and is a common finding in Htx patients.
This finding would be in agreement with the prior results of Shimizu et al., who studied hypertensive patients with left ventricular hypertrophy and showed decreased midwall fibre shortening.24 This was best expressed as a reduction in radial systolic thickening (=peak systolic ).
The time to peak systolic deformation in the Htx group was shorter for both radial and longitudinal directions in all segments compared to controls. This could be explained by a significantly increased mean HR in the Htx group compared to controls. However, there was no correlation between HR and regional Vsys/SRsys/sys values in any segment, which indicates that resting HR did not influence either velocity or any of the deformation indices.
Prior studies on transplant complications have suggested that regional peak systolic velocity data may be of value in detecting acquired abnormalities in regional function.25,26 Surprisingly, we could detect no significant abnormality in systolic motion parameters (either radial or longitudinal), in the segments with abnormal deformation either due to rejection or vasculopathy. This relative insensitivity in peak systolic velocities in detecting functional changes has already been well documented in many clinical studies. In addition we found a consistent decrease in regional Vsys in all segments of the inferior wall in which deformation was normal again illustrating the point that velocity and deformation indices are not interchangeable.
|
Limitations |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionsReferences |
|---|
One-dimensional ultrasonic measurement of segmental deformation is angle dependent. To minimize this problem we only acquired data when the insonation angle was less than 15°. Signal noise was another potential problem in these post-operative patients as this is amplified during the strain rate calculation. Other image artifacts such as reverberations can degrade the calculation of regional deformation. These artifacts are most prominent in the lateral aspects of the sector image. To minimize this problem all data were acquired at narrow sector angle with the wall to be interrogated placed in the center of the sector angle. Despite these potential limitations, only 10% of all segments in the Htx group had to be excluded from the final data analysis. The proportion of segments excluded was similar to controls.
In this study, the conventional coronary angiography has been used for the exclusion of significant coronary vasculopathy. Although it is the most widely used technique in the follow up of these patients, the use of intravascular ultrasound has been shown to be more reliable in the diagnosis of post-Htx coronary artery disease. Hence, it might be useful to study such patients with intravascular ultrasound.
Although, it was one of the inclusion criteria for the study not to have an acute rejection episode more than Grade 1A, the rejection has been excluded with a correlative endomyocardial biopsy in 26 of the patients. For the rest of the patients the acute rejection has been excluded with the clinical examination and using the other diagnostic tools including the ECG, standard echocardiography, right heart catheterization and 24h of ambulatory blood pressure monitorization. It is of note to mention that none of the patients included to the study had severe acute rejection episode in the past.
|
Conclusions |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionsReferences |
|---|
/SR imaging is a robust technique for the quantification of the regional myocardial function in Htx patients. In this study, we defined the normal values for both radial and longitudinal regional peak systolic V/SR/ for "healthy" Htx hearts, which could later serve as the reference value for the early detection of myocardial abnormalities due to the post-Htx complications. In a small group of post-transplant patients, /SR imaging was also able to detect the changes in regional systolic deformation associated with either acute rejection or Htx vasculopathy. If the sensitivity and specificity for identifying post-Htx complications are shown to be high in future larger prospective series, /SR imaging could offer an alternative non-invasive approach to the investigation of these complex patients by selecting the appropriate patients for subsequent invasive studies. |
References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionLimitationsConclusionsReferences |
|---|
- Heimdal A., Stoylen A., Torp H., Skjaerpe T. Real-time strain rate imaging of the left ventricle by ultrasound. J Am Soc Echocardiogr (1998) 11:1013–1019.[CrossRef][ISI][Medline]
- D'hooge J., Bijnens B., Thoen J., Van de Werf F., Sutherland G.R., Suetens P. Echocardiographic strain and strain-rate imaging: a new tool to study regional myocardial function. IEEE Trans Med Imaging (2002) 21(9):1022–1030.[CrossRef][ISI][Medline]
- Koyama J., Ray-Sequin P., Falk R.H. Longitudinal myocardial function assessed by tissue velocity, strain, and strain rate tissue Doppler echocardiography in patients with AL (primary) cardiac amyloidosis. Circulation (2003) 107:2446–2452.
[Abstract/Free Full Text] - Weidemann F., Breunig F., Beer M., Sandstede J., Turschner O., Voelker W., et al. Improvement of cardiac function during enzyme replacement therapy in patients with Fabry disease: a prospective strain rate imaging study. Circulation (2003 Sep 16) 108(11):1299–1301.[CrossRef]
- Weidemann F., Eyskens B., Mertens L., Di Salvo G., Strotmann J., Buyse G., et al. Quantification of regional right and left ventricular function by ultrasonic strain rate and strain indexes in Friedreich's ataxia. Am J Cardiol (2003 Mar 1) 91(5):622–626.[CrossRef]
- Andersen N.H., Poulsen S.H., Eiskjaer H., Poulsen P.L., Mogensen C.E. Decreased left ventricular longitudinal contraction in normotensive and normoalbuminuric patients with Type II diabetes mellitus: a Doppler tissue tracking and strain rate echocardiography study. Clin Sci (Lond) (2003 Jul) 105(1):59–66.[Medline]
- Devereux R.B., Alonso D.R., Lutas E.M., Gottlieb G.J., Campo E., Sachs I., et al. Echocardiographic assessment of left ventricular hypertrophy: comparison to necropsy findings. Am J Cardiol (1986 Feb 15) 57(6):450–458.[CrossRef]
- 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 Mar 5) 41(5):810–819.[CrossRef]
- 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 Aug) 27(8):1087–1097.[CrossRef][ISI][Medline]
- Cerqueira M.D., Weissman N.J., Dilsizian V., Jacobs A.K., Kaul S., Laskey W.K., et al. Standardized myocardial segmentation and nomenclature for tomographic imaging of the heart: a statement for healthcare professionals from the Cardiac Imaging Committee of the Council on Clinical Cardiology of the American Heart Association. Circulation (2002 Jan 29) 105(4):539–542.[CrossRef]
- Edvardsen T., Gerber B.L., Garot J., Bluemke D.A., Lima J.A., Smiseth O.A. Quantitative assessment of intrinsic regional myocardial deformation by Doppler strain rate echocardiography in humans: validation against three-dimensional tagged magnetic resonance imaging. Circulation (2002) 106:50–56.
[Abstract/Free Full Text] - Voigt J.U., Lindenmeier G., Exner B., Regenfus M., Werner D., Reulbach U., et al. Incidence and characteristics of segmental postsystolic longitudinal shortening in normal, acutely ischemic, and scarred myocardium. J Am Soc Echocardiogr (2003 May) 16(5):415–423.[CrossRef][ISI][Medline]
- Jamal F., Kukulski T., D'hooge J., De Scheerder I., Sutherland G. Abnormal postsystolic thickening in acutely ischemic myocardium during coronary angioplasty: a velocity, strain, and strain rate doppler myocardial imaging study. J Am Soc Echocardiogr (1999 Nov) 12(11):994–996.[CrossRef][ISI][Medline]
- Weidemann F., Dommke C., Bijnens B., Claus P., D'hooge J., Mertens P., et al. Defining the transmurality of a chronic myocardial infarction by ultrasonic strain rate imaging. The implications for identifying intramural viability - an experimental study. Circulation (2003 Feb 18) 107(6):883–888.[CrossRef]
- Gorcsan J. 3rd, Snow F.R., Paulsen W., Arrowood J.A., Thompson J.A., Nixon J.V. Echocardiographic profile of the transplanted human heart in clinically well recipients. J Heart Lung Transplant (1992 Jan–Feb) 11(1 Pt 1):80–89.[ISI][Medline]
- Chaturvedi R.R., Lincoln C., Gothard J.W., Scallan M.H., White P.A., Redington A.N., et al. Left ventricular dysfunction after open repair of simple congenital heart defects in infants and children: quantitation with the use of a conductance catheter immediately after bypass. J Thorac Cardiovasc Surg (1998 Jan) 115(1):77–83.
[Abstract/Free Full Text] - Jacobson A.F., Tow D.E., Lapsley D., Khuri S. Changes in septal regional ejection fraction early and late following coronary artery bypass grafting in patients without postoperative myocardial infarction. Nucl Med Commun (1992 Oct) 13(10):749–756.[ISI][Medline]
- Barrios L., D'Hooge J., Aubert A., et al. Age dependency of regional systolic and early diastolic radial strain rates. Eur Heart J (2001 Sep) 22:582. (abstr).
- Bittner H.B., Chen E.P., Biswas S.S., Van Trigt P. 3rd, Davis R.D. Right ventricular dysfunction after cardiac transplantation: Primarly related to status of donor heart. Ann Thorac Surg (1999) 68:1605–1611.
[Abstract/Free Full Text] - Page R.D., Harringer W., Hodakowski G.T., Guerrero J.L., LaRaia P.J., Austen W.G. Determinants of maximal right ventricular function. J Heart Lung Transplant (1992 Jan–Feb) 11(1):90–98.[ISI][Medline]
- Leeman M., Van Cutsem M., Vachiery J.L., Antoine M., Leclerc J.L. Determinants of right ventricular failure after heart transplantation. Acta Cardiol (1996) 51(5):441–449.[ISI][Medline]
- Rushmer R., Crystal D., Wagner C. The functional anatomy of ventricular contraction. Circ Res (1952) 1:162–170.[ISI]
- Wranne B., Pinto F.J., Hammarström E., St Goar F.G., Puryear J., Popp R.L. Abnormal right heart filling after cardiac surgery:time course and mechanisms. Br Heart J (1991 Dec) 66(6):435–442.
[Abstract/Free Full Text] - Shimizu G., Hirota Y., Kita Y., Kawamura K., Saito T., Gaasch W.H. Left ventricular midwall mechanics in systemic arterial hypertension. Myocardial function is depressed in pressure-overload hypertrophy. Circulation (1991 May) 83(5):1676–1684.
[Abstract/Free Full Text] - Dandel M., Hummel M., Muller J., Wellnhofer E., Meyer R., Solowjowa N., et al. Reliability of tissue Doppler wall motion monitoring after heart transplantation for replacement of invasive routine screenings by optimally timed cardiac biopsies and catheterizations. Circulation (2001 Sep 18) 104(12 Suppl 1):I184–I191.
- Mankad S., Murali S., Kormos R.L., Mandarino W.A., Gorcsan J. 3rd. Evaluation of the potential role of color-coded tissue Doppler echocardiography in the detection of allograft rejection in heart transplant recipients. Am Heart J (1999 Oct) 138(4):721–730.[CrossRef][ISI][Medline]
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  A. Marciniak, E. Eroglu, M. Marciniak, C. Sirbu, L. Herbots, W. Droogne, P. Claus, J. D'hooge, B. Bijnens, J. Vanhaecke, et al. The potential clinical role of ultrasonic strain and strain rate imaging in diagnosing acute rejection after heart transplantation Eur J Echocardiogr, June 1, 2007; 8(3): 213 - 221. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||