|
|
||||||||||
|
J Am Coll Cardiol, 2002; 40:2182-2188 © 2002 by the American College of Cardiology Foundation |






* Radiology, Leiden, The Netherlands
Cardiology, Leiden University Medical Center, Leiden, The Netherlands
Manuscript received March 6, 2002; revised manuscript received August 16, 2002, accepted September 6, 2002.
* Reprint requests: Dr. Ernst E. van der Wall, Department of Cardiology, C5-P28, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands.
E.E.van_der_Wall{at}lumc.nl
| Abstract |
|---|
|
|
|---|
BACKGROUND: Aortic valve disease is associated with eccentric or concentric LV hypertrophy and changes in LV function. The relationship between LV geometry and LV function and the effect of LV remodeling after AVR on diastolic filling, in patients with aortic valve stenosis compared with aortic regurgitation, are largely unknown.
METHODS: Nineteen patients with aortic valve disease (12 aortic valve stenosis, 7 aortic regurgitation) were studied using magnetic resonance imaging to assess LV geometry and LV function before and 9 ± 3 months after AVR. Ten age-matched healthy males served as control subjects.
RESULTS: Before AVR, the ratio between left ventricular mass index (LVMI) and left ventricular end-diastolic volume index (LVEDVI) was only increased in patients with aortic valve stenosis (1.37 ± 0.16 g/ml) compared with control subjects (0.93 ± 0.08 g/ml, p < 0.05). After AVR, LVMI/LVEDVI decreased significantly in aortic valve stenosis (to 1.15 ± 0.14 g/ml, p < 0.0001), but increased significantly in aortic regurgitation (1.02 ± 0.20 g/ml to 1.44 ± 0.27 g/ml, p < 0.0001). Before AVR, diastolic filling was impaired in both aortic valve stenosis and aortic regurgitation. Early after AVR, diastolic filling improved in patients with aortic valve stenosis, whereas patients with aortic regurgitation showed a deterioration in diastolic filling.
CONCLUSIONS: Early after AVR, patients with aortic valve stenosis show a decrease in both LVMI and LVMI/LVEDVI and an improvement in diastolic filling, whereas in patients with aortic regurgitation, LVMI decreases less rapidly than LVEDVI, causing concentric remodeling of the LV, most likely explaining the observed deterioration of diastolic filling in these patients.
| ||||||||||||||||||||
The LV geometrical shape also influences the outcome of AVR (3,1418). Previous studies have focused on the postoperative regression of LV mass or LV volume (1,3,19,20). The relationship between LV remodeling and changes in LV diastolic filling properties after AVR and the differences between these changes in patients with aortic valve stenosis compared with patients with aortic regurgitation have not been studied previously.
Magnetic resonance (MR) imaging is a noninvasive, highly reproducible method for accurate measurement of LV mass and LV volume without the use of geometric assumptions (2124). Magnetic resonance phase contrast flow velocity mapping allows measurement of flow-velocity as well as flow-volumes across the mitral valve orifice, providing a new means of diastolic function assessment which may even be a more sensitive method than Doppler echocardiography (2527). The superior image quality and accuracy of MR imaging compared with echocardiography (2124) has never been used to assess LV remodeling after AVR and to correlate the observed geometric changes to LV diastolic function. Therefore, the purpose of the present study was to assess the relationship between LV geometry and LV diastolic function in patients with either severe aortic valve stenosis or severe aortic regurgitation, before and early after AVR, using MR imaging.
| Methods |
|---|
|
|
|---|
|
Phase contrast flow velocity measurements across the mitral valve orifice were acquired using a gradient echo acquisition sequence with retrospective gating. Velocity maps were acquired across the mitral orifice using a flip angle of 20° and an echo time of 10 to 12 ms. The image section had a thickness of 8 mm, a field of view of 350 mm, and consisted of two measurements of a 128 x 128 acquisition matrix which was interpolated to a display matrix of 256 x 256 pixels. Depending on the actual heart rate, between 30 and 45 time frames were evenly distributed over the cardiac cycle, resulting in a temporal resolution of 25 to 30 ms. Total acquisition time was about 3 min. The maximum phase shift of 180° was set to occur at a velocity of 100 cm/s.
MR image analysis
The MR images and velocity maps were analyzed on a remote workstation (Sun Microsystems Computer Corp., Mountain View, California). The LV short-axis acquisitions were used to assess LV dimensions, wall mass, ejection fraction, and cardiac output (CO). The endocardial, epicardial, and papillary muscle borders of the end-diastolic and end-systolic images from each short-axis slice were manually traced using the MR analytical software system developed at this institution (22). Measurements were performed on separate occasions by two independent experienced observers. Reported data represent the average value from both observers. Myocardial borders were detected in the same way as previously reported, with an intraobserver and interobserver variability of 4 ± 2% and 9 ± 3%, respectively (27). The left ventricular mass index (LVMI), left ventricular end-diastolic volume index (LVEDVI), CO, and left ventricular ejection fraction (LVEF) were calculated as described before (23). The ratio of LVMI and LVEDVI (LVMI/LVEDVI) was used as an indicator of LVMI normalized to chamber size. The classification in concentric or eccentric hypertrophy was based on comparison of patients with the control group: a statistically significant increase in LVMI, LVEDVI, and LVMI/LVEDVI is concentric hypertrophy, but a nonstatistically significant difference in LVMI/LVEDVI is eccentric hypertrophy.
Volumetric flow across the mitral valve was calculated by manually tracing the borders of the mitral valve in all time frames of the velocity map series, using the FLOW analytical software package (MEDIS Medical Imaging Systems, Leiden, The Netherlands) (28). Contour tracings were performed on two occasions by a different observer. Flow curves were automatically analyzed following a manual indication of the start of early (E) filling, peak E filling, peak atrial (A) contribution to filling, and the end of filling as described previously (26). To correct for differences in stroke volume and/or heart rate, the E-wave acceleration and deceleration slopes were also normalized for CO.
Statistical analysis
Reported data are expressed as mean values ± 1 SD. When applicable, paired two-tailed Student t tests were used, otherwise two-sample two-tailed Student t tests were used. A p value of <0.05 was considered statistically significant. Correlations were determined using linear regression analysis.
| Results |
|---|
|
|
|---|
|
|
Before AVR, diastolic function was impaired in both groups of patients. For example, the E-wave acceleration peak normalized for CO was lower in patients with aortic valve stenosis and aortic regurgitation (0.046 ± 0.017 s1 x 103 and 0.048 ± 0.008 s1 x 103, respectively) than in control subjects (0.081 ± 0.033 s1 x 103). In patients with aortic valve stenosis, E-wave acceleration peak and deceleration peak slopes normalized for CO improved after AVR, whereas these parameters deteriorated postoperatively in patients with aortic regurgitation (Fig. 2, Table 2).
|
| Discussion |
|---|
|
|
|---|
Our findings are in agreement with Carroll et al. (17) who found that in most patients with aortic regurgitation LV end-diastolic dimensions and volumes became near normal within two weeks after AVR, whereas a significant regression of LVH took at least six months. However, other studies have shown that several patients with aortic regurgitation who had a severely depressed LVEF and a strongly dilated LV before surgery, failed to achieve regression of LVH after AVR (29,30). These studies also recognized relative wall thickness as an important prognostic parameter in patients with aortic regurgitation (3,29,30).
An increase in LV wall thickness proportional to the increase in LV radius preserves LV systolic wall stress and can prevent irreversible cardiac dilation and failure (3). In patients with aortic valve stenosis, the presence of a supernormal ejection fraction and "disproportionally high" relative wall thickness before AVR is associated with an excessive perioperative risk of morbidity and mortality (2,15,16). Alternatively, aortic valve stenosis patients with a low relative wall thickness and eccentric hypertrophy showed decreased systolic function as well as symptoms of heart failure (18). The clinical implications associated with the contrasting changes in LVMI/LVEDVI after AVR in patients with aortic valve stenosis compared with patients with aortic regurgitation, as observed in the present study, merit future investigation. In the present study, follow-up was relatively short (9 ± 3 months) and only associated with partial regression of LVMI. Complete regression of LVH may take many years (1,3,13,19,20), but it is important because incomplete regression of LVH after AVR is also associated with decreased survival (29).
Diastolic function
Before AVR, all patients with aortic valve disease demonstrated abnormal diastolic filling, resulting from impaired LV relaxation, increased chamber stiffness, and/or chamber dilation (11,31,32). After AVR, in patients with aortic valve stenosis, LV geometry and diastolic properties both showed a trend towards normalization, illustrated by a decrease in both LVMI and LVMI/LVEDVI and an increase of the E-wave acceleration peak and deceleration peak normalized for CO (Table 2, Figs. 1 and 2). However, in patients with aortic regurgitation, the decline of LVEDVI after AVR occurs faster than normalization of LVMI, resulting in concentric remodeling. Concentric LVH is associated with impaired LV relaxation and increased chamber stiffness (510,31) and, therefore, may have contributed to the observed worsening of diastolic filling parameters illustrated by a decrease of the E-wave acceleration peak and deceleration peak normalized for CO in patients with aortic regurgitation after AVR. The decrease of the E-wave deceleration peak normalized for CO in patients with aortic regurgitation after AVR is probably largely due to a reduction in left atrial pressure.
The importance of assessment of diastolic function before aortic valve surgery was underlined by two studies of Lund et al. (12,33) who found that impaired diastolic function in patients with aortic valve stenosis is associated with increased mortality in the period before AVR, and is an independent risk factor for early and late postoperative mortality. Other studies have addressed the early and late changes in diastolic function after AVR, both in patients with aortic valve stenosis and in patients with aortic regurgitation (5,8,10,13,14). Patients with aortic valve stenosis had increased diastolic stiffness early after AVR, parallel to the relative increase in interstitial fibrosis (13). Moreover, diastolic stiffness and relaxation normalized late (81 ± 24 months) after AVR owing to regression of both muscular and nonmuscular tissue. Relaxation was correlated to the extent of hypertrophy, whereas passive elastic properties were correlated to changes in nonmuscular tissue (13).
In the present study, MR phase contrast flow velocity mapping was used to assess diastolic function. The studied groups represented a wide range of LV sizes and corresponding stroke volumes. Usually, the shape of the LV filling curve is influenced by LV relaxation, left atrial pressure, elastic properties of the LV, but also by stroke volume, ventricular size, and heart rate (11,31,32). Mirsky (34) suggested inclusion of LV volume in the chamber stiffness-pressure relationship and introduced the term "volume elasticity." To follow the concept of volume elasticity, we normalized the E acceleration peak and E deceleration peak for CO. As demonstrated in Table 2, the differences in diastolic properties of the LV between patients and control subjects, but also between aortic valve stenosis and aortic regurgitation patients, only became fully apparent after normalization of early diastolic filling (E) for CO.
Ejection fraction
Ejection fraction was largely unaffected in the present group of patients with severe aortic valve disease. Before and after AVR, LVEF was slightly lower in patients with aortic regurgitation compared with both control subjects and patients with aortic valve stenosis, although LVEF differed significantly only between postoperative patients with aortic valve stenosis and postoperative patients with aortic regurgitation. These findings confirm that diastolic function in aortic valve disease is affected at an earlier stage of the disease process than the ejection fraction. Therefore, deterioration of the ejection fraction should be considered as a sign of severe and advanced aortic valve disease (12,14).
Correlation between LV geometry and LV diastolic function
Increased LVMI and increased LVMI/LVEDVI were negatively correlated to the E acceleration peak normalized for CO. The acceleration peak of E is influenced by several determinants such as left atrial pressure, the LV relaxation constant, LV end-systolic volume, LV systolic function, and intrinsic myocardial stiffness (11,31,32). In patients with aortic valve stenosis before AVR, the depressed E acceleration peak is due to prolonged LV relaxation and increased myocardial stiffness (31). After surgery, LVMI and LVMI/LVEDVI both decreased, whereas the E acceleration peak increased, the latter largely due to improved myocardial relaxation and reduced myocardial stiffness (31). In patients with aortic regurgitation before AVR, the depressed E acceleration peak slope results from prolonged LV relaxation and increased myocardial stiffness (11,31,32). After surgery, LVMI decreased but LVMI/LVEDVI increased, leading to concentric remodeling. The further decrease of the E acceleration peak slope is most likely caused by a reduced left atrial pressure combined with a prolongation of myocardial relaxation and increment of myocardial stiffness (31).
The LVMI and LVMI/LVEDVI were positively correlated to the E deceleration peak normalized for CO. Concentric LVH increases intrinsic myocardial stiffness and is known to shorten the deceleration time and to increase the deceleration peak of E (11,31,32). In patients with aortic valve stenosis before AVR, the depressed E deceleration peak slope, therefore, is due to prolonged LV relaxation (11,31). After surgery, LVMI and LVMI/LVEDVI both decreased, whereas the E deceleration peak slope increased, most likely as a result of improved myocardial relaxation (31).
In patients with aortic regurgitation before AVR, the depressed E deceleration peak also results from prolonged LV relaxation (31). After surgery, LVMI decreased but LVMI/LVEDVI increased, leading to concentric remodeling. The further decrease of the E deceleration peak slope after AVR, therefore, is mainly caused by a reduction of left atrial filling pressure and a prolongation of myocardial relaxation (11,31,32).
Study limitations
Patient follow-up after surgery was performed at 9 ± 3 months, so early and late effects of surgery are mixed. Thus, changes in morphology and function are not completely uniform, which is reflected by the reported standard deviations.
The clinical definition for concentric and eccentric hypertrophy or remodeling, as described in the present study, may be different from the pathophysiologic definition. The main difference is that with the currently applied imaging technique it is not possible to evaluate sarcomere orientation. Therefore, the parallel sarcomere deposition in concentric hypertrophy cannot be discriminated from the serial deposition in eccentric hypertrophy.
In the present study, it was not clinically feasible to measure invasive left atrial pressures. Therefore, on the basis of previous reports, we only speculate on the effects of changes in left atrial pressures on diastolic filling characteristics.
| Conclusions |
|---|
|
|
|---|
| Footnotes |
|---|
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
A. Della Corte, G. Salerno, E. Chiosi, D. Iarussi, G. Santarpino, M. Miraglia, S. Naviglio, and M. De Feo Preoperative, postoperative and 1-year follow-up N-terminal pro-B-type natriuretic peptide levels in severe chronic aortic regurgitation: correlations with echocardiographic findings Interactive CardioVascular and Thoracic Surgery, June 1, 2008; 7(3): 419 - 424. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Iyem, C. Sekuri, M. Tavli, and S. Buket Left Ventricular Hypertrophy and Remodeling after Aortic Valve Replacement Asian Cardiovasc Thorac Ann, December 1, 2007; 15(6): 459 - 462. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. van Straten, H. W. Vliegen, H. J. Lamb, S. D. Roes, E. E. van der Wall, M. G. Hazekamp, and A. de Roos Time Course of Diastolic and Systolic Function Improvement After Pulmonary Valve Replacement in Adult Patients With Tetralogy of Fallot J. Am. Coll. Cardiol., October 18, 2005; 46(8): 1559 - 1564. [Abstract] [Full Text] [PDF] |
||||
![]() |
U. C. Sharma, P. Barenbrug, S. Pokharel, W. R. M. Dassen, Y. M. Pinto, and J. G. Maessen Systematic review of the outcome of aortic valve replacement in patients with aortic stenosis Ann. Thorac. Surg., July 1, 2004; 78(1): 90 - 95. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | SUBSCRIPTIONS | CURRENT ISSUE | PAST ISSUES | CARDIOSOURCE | SEARCH | HELP | FEEDBACK |