Eur J Cardiothorac Surg 2003;23:609-613
© 2003 Elsevier Science NL
MRI evaluation of left ventricular function in anterior LV aneurysms before and after surgical resection
Michel I.M. Versteegha*,
Hildo J. Lambb,
Jeroen J. Baxc,
Franklin B. Curielb,
Ernst E. van der Wallc,
Albert de Roosb,
Robert A.E. Diona
a Department of Cardio-thoracic Surgery, Leiden University Medical Center, Leiden, The Netherlands
b Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
c Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands
Received 5 November 2002;
received in revised form 23 December 2002;
accepted 29 December 2002.
* Corresponding author. Tel.: +31-71-5262355; fax: +31-71-5266965
e-mail: m.i.m.versteegh{at}lumc.nl
 |
Abstract
|
|---|
Objectives: Whether resection of a left ventricular (LV) aneurysm leads to improved global LV function remains controversial. Echo-planar magnetic resonance imaging (MRI) is a sensitive tool to detect changes in LV function. Therefore, the purpose of the present study was to monitor changes in global LV function and anatomy following LV aneurysm resection using MRI. Methods: The present study includes 12 patients with an anterior LV aneurysm. Echo-planar MRI evaluation of LV function was performed before surgery and 6 weeks and 3 months after LV remodeling surgery, in most patients combined with coronary artery by-pass grafting (CABG). Results: Following LV aneurysm resection, a decrease was found in end-diastolic volume from 238±63 to 180±54 ml at 6 weeks to 198±51 ml (P<0.05) at 3 months and in end-systolic volume from 156±62 to 105±44 to 111±43 ml (P<0.01), whereas the ejection fraction increased from 37±11 to 43±9 to 45±10% (P<0.01). Conclusions: LV remodeling surgery leads to a cardiac anatomy more closely resembling normal anatomy. As a consequence, LV contractile function improved significantly. In addition, it was shown that echo-planar cardiac MRI is a sensitive tool to study subtle changes in heart anatomy and function. In this preliminary experience, pre- and postoperative MRI has demonstrated that LV remodeling surgery may restore cardiac anatomy and improve LV contractile function.
Key Words: Magnetic resonance imaging • Left ventricular aneurysm
|
1. Introduction
|
|---|
About 85% of left ventricular (LV) aneurysms are located anteriorly and involve the apex and septum. Different techniques have been proposed to resect the aneurysm [1–4]. We have used a LV remodeling technique modified from that previously described by Stoney and colleagues [3]. Most of the earlier studies showed clinical improvement [3] but were generally unable to express these improvements in functional parameters including LV dimensions, ejection fraction or stroke volume. Echo-planar magnetic resonance imaging (MRI) is a highly reliable, well-validated technique for measuring heart function and analyzing the structural anatomy of the heart [5,6]. MRI is superior to other frequently used imaging modalities [7,8], such as 2D echocardiography and SPECT imaging in evaluating anatomical defects, e.g. LV aneurysms [7]. Also MRI is a non-invasive technique without the use of radiation or radioactivity. Moreover, reproducibility of the technique is high allowing accurate detection of changes in different parameters [8].
The purpose of the present study was to evaluate LV dimensions and global heart function before and after LV remodeling surgery, and to demonstrate that cardiac MRI may provide an accurate and objective technique to evaluate the surgical results.
|
2. Methods
|
|---|
2.1. Patients
Twelve (11 males and one female) patients with a well-defined apico-anterior LV aneurysm underwent LV remodeling and could be subjected to the full pre- and postoperative MRI protocol. The age of the patients averaged 65 years (range, 49–78 years). MRI scans were performed 5±4 days before surgery (pre-surgery), 44±8 days after the surgery (6 weeks) and 89±13 days after surgery (3 months). LV remodeling was achieved by a modified Stoney technique [3] as described in Fig. 1
. CABG was performed in nine patients with an average of 2.0 distal anastomoses per patient (range, 1–3). In three patients, resection of the endocardium along the edge of the infarction scar was performed because of pre-operative ventricular arrhythmias.
2.2. Magnetic resonance imaging
MRI studies were performed using a standard Philips 1.5T ACS/NT15 MR system (Philips Medical Systems International, Best, The Netherlands). All scans were obtained using a whole body coil and prospective electrocardiographic (ECG) triggering. Scout images were obtained using the multishot echo-planar imaging (EPI) sequence as described below. Based on images in the transverse plane (Fig. 2
), right anterior oblique equivalent (two-chamber view) images were centered through the apex of the LV to intersect the mitral valve plane. To acquire a four-chamber view, a slice was positioned to transect the apex of the LV on the diastolic and systolic two-chamber images and was centered low on the mitral valve plane. Planned on the diastolic and systolic two- and four-chamber images, the heart was imaged from apex to base with ten imaging levels in the short-axis orientation. All ten sections were imaged with multishot EPI during 90 min MRI examination, including patient positioning and instruction time.
2.3. Multishot echo-planar gradient-echo
Maximum gradient amplitude was 15 mT/m, which could be reached in 0.9 ms. Consequently, the slew rate was 16.7 mT/m/ms for the x, y and z gradient axes. TE was 11 ms with a resulting echo spacing of (11/4=) 2.75 ms, the time to measure a single k-space line. The currently applied EPI sequence was not a partial echo technique; no data averaging and no fat suppression were applied. Images were obtained as a 112x128 matrix and were reconstructed to 256x256 pixel images. With the use of the currently applied multishot EPI technique, seven lines in k-space (total, 112 lines) were obtained after a single excitation by 30° radio frequency pulse, whereas single shot EPI techniques acquire all k-space lines following a single 
-pulse. The number of heart phases during one cardiac cycle was between 18 and 25, yielding a TR and a temporal resolution of 35–39 ms per cardiac phase, depending on the actual heart rate. Each section level was scanned separately during a single breath-hold in expiration with a maximal duration of 15 s, dependent on the actual heart rate. This was repeated ten times to image all short-axis slices. Total acquisition time did not exceed 2.5 min. With nine breathing intervals of 
30 s, actual examination time was 7 min.
2.4. Analysis of images
For analysis, images were displayed on a computer monitor in a cine-loop mode. The epi- and endocardial borders were outlined manually with a trackball cursor. The computer measured the enclosed surface areas. The cardiac phases in which the LV had the largest (end-diastolic) and smallest (end-systolic [ESV]) cavity volumes were determined. These were used to establish end-diastolic volume, ESV, stroke volume, ejection fraction and LV mass.
2.5. Statistical analysis
All data are expressed as mean±standard deviation. Paired Student t-tests were applied when appropriate to determine the significance of the difference of means of continuous variables. A P value of less than 0.05 was considered significant.
|
3. Results
|
|---|
Table 1 shows LV dimensions and global heart function of the patients with LV aneurysm before and on two occasions after aneurysm resection. Individual data are shown in the Figs. 3–6
.
3.1. End-diastolic volume
Six weeks (44±8 days) after LV aneurysm resection a decrease of about 25% was found in end-diastolic volume from 238±63 to 180±54 ml (P<0.01). At 3 months (88±13 days), the reduction in end-diastolic volume was sustained (198±51 ml, P<0.05 vs. baseline and not significant vs. the first post-operative measurement, see Fig. 3).
3.2. End-systolic volume
At 6 weeks after surgery, there was also a decrease in ESV from 156±62 to 105±44 ml (P<0.01), which remained unchanged at 3 months follow-up (111±43 ml, Fig. 4). As expected, the ESV index (ESV per square meter body surface area) followed these figures and decreased from 79±33 ml/m2 before the operation to 53±24 ml/m2 (P<0.0005) at the first postoperative follow-up and was found to remain stable at 3 months (56±21 ml/m2).
3.3. Ejection fraction
In the observed postoperative period, the ejection fraction improved gradually. At 6 weeks after aneurysm resection, the ejection fraction increased from 37±11 to 43±9% (P<0.01) and at 3 months, it was increased to 45±10% (P<0.01, as compared to pre-surgery values, Fig. 5).
3.4. Stroke volume
Stroke volume showed an initial decline after surgery, followed by a subsequent improvement. On the 6 weeks follow-up MRI, stroke volume tended to decrease (although not significant) from 82±14 to 75±15 ml (P=ns), but at the 3 months follow-up, a significant improvement was observed to 87±17 ml (P<0.01 vs. 6 weeks follow-up). Although improved, these values were not significantly different from baseline values (Fig. 6).
3.5. Left ventricular mass
No statistically significant difference was observed in LV mass during the period of follow-up. The LV mass index (LV mass per square meter body surface area) did not change significantly.
|
4. Discussion
|
|---|
Although clinical improvement after resection of an LV aneurysm is described frequently, it proved to be difficult to assess the improvement by objective measurements. In this study, we have focused on the use of MRI as a non-invasive imaging technique to evaluate different parameters before surgery, and 6 weeks and 3 months after surgery. With this technique, we assessed functional parameters of the global LV function. MRI is a non-invasive imaging technique with an excellent resolution, without the use of radiation [8]. Serial measurements have shown excellent reproducibility [8], making the technique ideal to assess changes over time, as was done in the current study.
4.1. End-diastolic volume
Postmortem studies indicate that most patients with LV aneurysm have increased cardiac volume and weight [10]. The increase in volume is in part the result of simple thinning and bulging of the aneurysmal portion of the LV wall. However, the non-aneurysmal portions of the LV also increased in volume and thickness secondary to the hemodynamic stress posed on them by the dyskinesia of the aneurysm and by LaPlace's law. As the ventricular size increases, it may ultimately lose its systolic reserve and contribute to LV enlargement and failure [11]. This process is aggravated by any myocardial ischemia that develops in the non-aneurysmal portion of the LV wall. Remodeling surgery results in a sudden decrease of the end-diastolic volume. Afterwards the heart adapts to the new shape and the end-diastolic volume slightly increases, although not significant in the current study. This phenomenon is also described by Dor [9]. The main result is an acute reduction in LV end-diastolic volume, which remained reduced at 3 months follow-up, as evidenced by the serial MRI measurements.
4.2. End-systolic volume and stroke volume
The paradoxical movement in the aneurysmal portion of the wall compromises the efficiency of the ventricle because systolic work is wasted on expansion of the aneurysm. In dilated hearts, the residual volume can become greater than the stroke volume. The ESV significantly decreases after surgery, inferring an overall decrease in the residual volume and an improved LV function. The stroke volume first decreases then increases significantly, suggesting that the heart needs time to recover from surgical intervention, perhaps related to post-operative stunning.
4.3. Ejection fraction
In the present study, the post-operative MRI shows a continuous increase of the ejection fraction during 3 months after the operation. This suggests that the contractility of the heart is improved. Resection of the aneurysm and the resulting decrease in LV volume diminishes wall stress (LaPlace's law), thereby facilitating myocardial fiber shortening, and improving stroke volume and ejection fraction.
4.4. Left ventricular mass
No significant differences were seen between the scans: the mass of the dyskinetic area removed at surgery is minimal resulting in a slight decrease of LV mass, which seems to be below the sensitivity threshold of MRI. Also the LV mass index does not change significantly. The very fact that the ESV index significantly decreases in the absence of reduction of LV mass seems to infer a more efficient recruitment of the muscular mass.
|
5. Conclusion
|
|---|
LV remodeling surgery yields a significant improvement of the function and anatomy of the LV. Parameters such as end-diastolic volume and ESV tend to normalize resulting in a significant improvement in ejection fraction. Cardiac MRI is a sensitive tool to study subtle changes in anatomy and function of the heart and is thus expected to play a growing role in the evaluation of surgical results. Further investigations are needed to prove that the improvement of the LV function persists during longer follow-up.
|
References
|
|---|
- Dor V., Saab M., Coste P., Kornaszewska M., Montiglio F. Left ventricular aneurysm: a new surgical approach. Thorac Cardiovasc Surg 1989;37:11-19.[Medline]
- Cooley D.A., Frasier O.H., Duncan J.M. Intracavitary repair of ventricular aneurysm and regional dyskinesia. Ann Surg 1992;215:417-421.[Medline]
- Stoney W.S., Alford W.C., Jr, Burrus G.R., Thomas C.S., Jr Repair of anteroseptal ventricular aneurysm. Ann Thorac Surg 1973;15:394-404.[Medline]
- Kirklin J.W., Barrat-Boyes B.G. Left ventricular aneurysm. In: Kirklin J.W., Barrat-Boyes B.G., eds. Cardiac surgery, 2nd ed. New York, NY: Wiley, 1993:383-402.
- Pattynama P.M.T., de Roos A., van der Wall E.E., van Voorthuisen A.E. Evaluation of cardiac function with MR imaging: an overview. Am Heart J 1994;128(3):595-607.[CrossRef][Medline]
- Lamb H.J., Doornbos J., van der Velde E.A., Kruit M.C., Reiber J.H.C., de Roos A. Echo-planar MRI of the heart on a standard system: validation of measurements of left ventricular function and mass. J Comput Assist Tomogr 1996;20:942-949.[CrossRef][Medline]
- Ahmad M., Johnson R.J., Fawcett H.D., Schreiber M.H. Left ventricular aneurysm in short axis: a comparison of magnetic resonance, ultrasound and thallium-201 SPECT images. Magn Reson Imaging 1987;5:293-300.[CrossRef][Medline]
- Bellenger N.G., Burgess M.I., Ray S.G., Lahiri A., Coats A.J., Cleland J.G., Pennel D.J. Comparison of left ventricular ejection fraction and volumes in heart failure by echocardiography, radionuclide ventriculography and cardiovascular magnetic resonance; are they interchangeable?. Eur Heart J 2000;21:1387-1396.[Abstract/Free Full Text]
- Dor V., Sabatier M., Donato M., Maioli M., Toso A., Montiglio F. Late hemodynamic results after left ventricular patch repair associated with coronary grafting in patients with postinfarction akinetic or dyskinetic aneurysm of the left ventricle. J Thorac Cardiovasc Surg 1995;110:1291-1301.[Abstract/Free Full Text]
- Phares W.S., Edwards J.E., Burchell H.B. Cardiac aneurysms: clinicopathologic studies. Mayo Clin Proc 1953;28:264.
- Gaudron P., Eilles C., Kugler I., Ertl G. Progressive left ventricular dysfunction and remodeling after myocardial infarction. Potential mechanisms and early predictors. Circulation 1993;87:755-763.[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
M. Cotrufo, L. S. De Santo, A. D. Corte, G. Romano, C. Amarelli, M. De Feo, G. Santarpino, M. Scardone, and G. Nappi
Acute hemodynamic and functional effects of surgical ventricular restoration and heart transplantation in patients with ischemic dilated cardiomyopathy.
J. Thorac. Cardiovasc. Surg.,
May 1, 2008;
135(5):
1054 - 1060.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. C. Walker, M. B. Ratcliffe, P. Zhang, A. W. Wallace, E. W. Hsu, D. A. Saloner, and J. M. Guccione
Magnetic resonance imaging-based finite element stress analysis after linear repair of left ventricular aneurysm.
J. Thorac. Cardiovasc. Surg.,
May 1, 2008;
135(5):
1094 - 1102.e2.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
E. Konen, N. Merchant, C. Gutierrez, Y. Provost, L. Mickleborough, N. S. Paul, and J. Butany
True versus False Left Ventricular Aneurysm: Differentiation with MR Imaging--Initial Experience
Radiology,
July 1, 2005;
236(1):
65 - 75.
[Abstract]
[Full Text]
[PDF]
|
|
|
Top
Abstract
1. Introduction
