|
|
||||||||
Ann Thorac Surg 2002;73:1759-1764
© 2002 The Society of Thoracic Surgeons
a Division of Cardiothoracic Surgery Amsterdam, The Netherlands
b Division of Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
c Division of Cardiothoracic Surgery, Wilhelmina Childrens Hospital, University of Utrecht, The Utrecht, Netherlands
d Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands
* Reprint requests to Dr Dodge-Khatami, Division of Cardiothoracic Surgery, Academic Medical Center, University of Amsterdam, Postbus 22660, 1100 DD Amsterdam, The Netherlands
e-mail: a.dodgekhatami{at}amc.uva.nl
Presented at the Poster Session of the Thirty-eighth Annual Meeting of The Society of Thoracic Surgeons, Fort Lauderdale, FL, Jan 2830, 2002.
| Abstract |
|---|
|
|
|---|
Methods. Baseline and stress magnetic resonance imaging (maximum dobutamine dose, 15 µg/kg/min) assessed systemic RV function in 13 minimally or asymptomatic adult patients with CCTGA (unoperated, n = 7; physiologically repaired, n = 6). The left ventricles of 11 healthy age-matched adults served as controls.
Results. Baseline and stress end-diastolic volumes were similar between the systemic RV of unoperated patients and the left ventricle of controls, as well as base line end-systolic volumes. Stress ejection fraction was lower in unoperated and physiologically repaired patients (70 ± 6% and 60 ± 5%, respectively, vs healthy controls (84 ± 8%). However, comparable with healthy controls, both subsets of CCTGA patients responded appropriately to dobutamine stress, as illustrated by similar RV stroke volume, heart rate, mean blood pressure, and cardiac index.
Conclusions. Compared with the left ventricles of healthy controls, both patient groups had larger systemic RV volumes, diminished ejection fraction, but an appropriate response to dobutamine stress. Values of unoperated patients are closer to normal than physiologically repaired patients. Magnetic resonance imaging dobutamine may help to define the subgroups of CCTGA patients with favorable anatomy, whereby asymptomatic adult survival could be anticipated without the need for an operation.
| Introduction |
|---|
|
|
|---|
Magnetic resonance imaging (MRI) coupled with dobutamine stress testing can accurately assess cardiac reserve and represent an ideal noninvasive follow-up modality in all patient groups with right ventricular overload [1315]. It allows for early detection of ventricular dilation and impending failure, and may guide medical or surgical management before symptoms appear [13]. Our study uses dobutamine stress MRI in an attempt to define and predict the eventual subsets of patients who will never need an operation rather than an anatomic repair.
| Patients and methods |
|---|
|
|
|---|
Equally studied were 7 asymptomatic adult patients with unoperated CCTGA, with a mean age of 26.7 years (range, 22 to 35 years). One patient was in spontaneous complete heart block without a pacemaker, and the other 6 were in sinus rhythm. Five of these patients had a combination of 9 associated intracardiac anomalies, namely an atrial septal defect in 2, a ventricular septal defect in 3, pulmonary valve stenosis in 2, and Ebsteins anomaly of the tricuspid valve in 2. Tricuspid valve regurgitation (2+ to 3+), as assessed by echocardiography, was present in 4 patients.
Eleven age-matched healthy adults underwent the same study protocol and served as controls (mean age, 31 ± 11 years).
Magnetic resonance imaging
Study subjects were placed supine in a 1.5 Tesla MRI scanner (Vision, Siemens, Erlangen, Germany) with high power gradients. Electrocardiogram triggered T1-weighted turbo spin echo axial images were acquired, followed by four-chamber views of the heart. An electrocardiogram-triggered, ultrafast, breath-hold gradient-echo cine sequence with the following measurements: repetition time = R-R interval; time of echo = 4.8 ms; slice thickness, 10 mm; imaging matrix = 256 x 256; field of view = 350 mm; lip angle = 20° was then used to acquire images in the short axis plane in contiguous 10 mm slices. End-systolic volumes and end-diastolic volumes were calculated from this multi-slice, multiphase image set. Velocity maps were acquired with a flip angle of 30°, Time to Echo = 5.0 ms, slice thickness = 6 mm, field of view = 320 mm, and imaging matrix = 256 x 256, velocity encoding = 250 cm per second. The MRI protocol was repeated during dobutamine infusion with an initial dose of 5 µg per kg per minute. The infusion rate was increased by 5 µg per kg per minute every 3 minutes to a maximum of 15 µg per kg per minute. The MRI protocol during the dobutamine study started 3 minutes after the maximum dose. During each MRI measurement, the electrocardiogram, heart rate, and systolic and diastolic blood pressures were monitored.
Image analysis
A Unix workstation (Sun Microsystems, Palo Alto, CA) was used for analysis of the MR images. The MASS image analysis software (Medis, Leiden, The Netherlands) was used to display multi-slice, multiphase images, both individually and in a movie loop mode. Frames for end-diastolic and end-systolic volumes were determined by manual outlining of a midventricular slice. Papillary muscles and the moderator band were not included in the ventricular volume. The enclosed RV and left ventricle cross-sectional areas were measured by computer, multiplied by section thickness, and summed up according to Simpsons rule to provide RV and left ventricle volumes.
Calculations
Stroke volume was defined as end-diastolic volume minus end-systolic volume. The RV ejection fraction was calculated as stroke volume divided by end-diastolic volume. The dobutamine stress values were calculated as a percentage increase from values at rest. All volumetric measurements were corrected for body surface area.
Statistical analysis
Differences between groups were compared with the unpaired t test. The effects of dobutamine within groups were compared with the paired t test. A p value less than 0.05 was considered statistically significant.
| Results |
|---|
|
|
|---|
|
|
|
|
| Comment |
|---|
|
|
|---|
Assuming that the perfect result after anatomic repair entails normalization of systemic left ventricular function and reserve, the left ventricle of healthy controls was used to compare with the systemic RV of CCTGA patients. In our study, the systemic right ventricle of asymptomatic adults with unoperated CCTGA showed similar ejection fraction at rest, and lesser values at stress, compared with the systemic left ventricle of age-matched healthy controls. Suboptimal results were noted in patients after physiologic repair. In these patients, both at baseline and at stress testing, we found larger systemic ventricular end-systolic volumes. Also, baseline systemic ventricular end-diastolic volumes were larger after physiologic repair, compared with controls. As a snapshot value, the significance of this is unknown and difficult to interpret. Is this the result of surgical insult to the right ventricle, the result of long-standing volume overload of the RV, or the normal response of a morphologic right ventricle when chronically faced with systemic pressures? Furthermore, what are the true implications of these morphometric deviations in light of an apparent proper response to effort? Indeed, with stress testing, we found cardiac index to increase appropriately in both subsets of patients with CCTGA, without undue increase in heart rate or mean blood pressure, as compared with controls.
Symptomatic patients with CCTGA were originally treated with a combination of surgical procedures, either palliative or corrective, known as the "classic" or physiologic repair of CCTGA, leaving the right ventricle and tricuspid valve in the systemic circulation. In general, the results of physiologic repair have been disappointing, despite an acceptable operative mortality rate of 2% to 15% [1, 810, 16, 17]. In a 40-year review from the Toronto Hospital for Sick Children, including 118 patients having undergone a physiologic repair for CCTGA, Yeh and colleagues [8] reported a 6% operative mortality. However, 10 years after repair, survival was only 74%, and at 20 years it was an unsatisfactory 48% [8]. Termignon and colleagues [16] reported an even more concerning 55% survival rate at 10 years, when obstruction to the pulmonary ventricle was associated. Major concerns with physiologic repair include the nonnegligible incidence of complete heart block (14% to 38%) [8, 10, 16, 18] and the frequent need for reoperation on the tricuspid valve (Fig 4), but more importantly, the long-term failure of the right ventricle, which must chronically sustain systemic pressures.
|
The driving impetus towards the development of the anatomic repair of CCTGA stems from the preformed concept that a left ventricle, with or without retraining, will ultimately perform better in the systemic circulation than the right ventricle. However, there is no long-term data to support this [6, 12, 23]. In a series of 27 patients undergoing anatomic repair without early or late mortality, Imamura and colleagues [20] reported normal postoperative ejection fractions of both left and right ventricles, as assessed by echocardiography at the time of hospital discharge without further follow-up. Imai and colleagues [6] reported an operative mortality of 7.9% in a series of 76 patients with CCTGA who underwent anatomic repair at less than 16 years of age. At a mean postoperative follow-up of 4.9 years, they actually observed a slight decrease in left ventricular ejection fraction, no increase in RV ejection fraction, and unchanged left ventricular end-diastolic volumes [6]. Yagihara and colleagues [22] found subnormal postoperative left ventricular ejection fractions as assessed by cardiac catheterization, at a mean follow-up of 11 months after anatomic repair in their series of 10 patients.
Frequent failure of the right ventricle to chronically function as a systemic ventricle is another driving force to promote anatomic repair. However, findings across the literature differ, and multiple reports of normal adult survival without limitation to effort or arrhythmia exist, in unoperated CCTGA without associated intracardiac anomalies (Fig 5) [2, 7, 24, 25]. Peterson and colleagues [4] compared 17 children after atrial baffle procedures for complete transposition of the great arteries, with 8 unoperated patients with uncomplicated CCTGA, and 10 normal controls. Using radionuclide angiocardiography, stress testing revealed a normal increase in pulmonary ventricular ejection fraction in patients with CCTGA, as compared with controls. However, the systemic ventricles of patients with CCTGA did not significantly increase their ejection fractions with exercise, and both end-diastolic and end-systolic volumes were larger than controls. Cardiac index augmented appropriately in all groups, mainly because of an increase in heart rate in the CCTGA group [4]. In accordance with these findings, Parrish and colleagues [5] found subnormal increases in right and left ventricular ejection fractions in response to an effort in 5 children with CCTGA, although their exercise capacity, heart rate, and blood pressure responded appropriately. Supporting our findings, Benson and colleagues [3] found normal systemic right ventricular ejection fractions at exercise in 8 patients with uncomplicated and unoperated CCTGA, whereas the function of the pulmonary ventricle was subnormal. In their study using radionuclide angiocardiography, end-diastolic and systolic volumes of the systemic right ventricle decreased appropriately from rest to exercise [3].
|
In conclusion, defining the eventual subsets of patients with CCTGA who may never require an operation is of paramount clinical importance. With current diagnostic modalities, no such definition exists, and the therapeutic dilemma persists. Even respectable centers with a larger experience of the anatomic repair provide no long-term follow-up data to demonstrate improved systemic left ventricular function postoperatively [6, 11]. Accordingly, the open-ended question remains as to the true benefit and age cutoff to perform an anatomic repair in asymptomatic patients with CCTGA. Robust evidence is needed before more CCTGA patients with normally functioning right ventricles are enrolled in anatomic repair protocols. In those asymptomatic or minimally symptomatic patients, the use of a noninvasive follow-up modality, such as MRI dobutamine stress, could help to define morphologic and hemodynamic criteria justifying nonoperative management. As a corollary, deviations from these criteria, especially in asymptomatic patients, could serve as an early indicator of impending cardiac failure, and indicate timely surgical intervention, preferably in the form of anatomic repair.
Study limitations
Our ongoing MRI dobutamine stress protocol strives to define noninvasive criteria, whereby asymptomatic patients with CCTGA may be judged as not requiring operations, or on the contrary, as impending failures and candidates for timely anatomic repair. The small number of patients diminishes statistical power, which limits the significance of our results, and does not allow yet for a clear-cut management protocol according to the sought after criteria. To date, perhaps by unfortunate serendipity, we have had no patients enrolled who either presented initially with normal values, which then degraded over time, or presented in failure with highly abnormal MRI dobutamine stress values. These findings would strengthen the definitions of "normality" and deviations therefrom.
Using the left ventricle of healthy controls as a measuring stick to compare with the RV of patients with CCTGA is a potential weakness of the study. Although the two respective ventricles perform the same function in each group, their intrinsic morphology and geometry are clearly different.
As a group, patients with CCTGA present with a wide variety of morphology and resulting physiology, making generalizations and recommendations across such a heterogenous group hazardous. Owing to unfavorable anatomy and physiology in many instances, we fully recognize that anatomic repair is often inevitable and indicated. Our data only illustrates and quantifies the potential for a morphologic right ventricle to sustain the systemic circulation, even in the presence of associated intracardiac lesions. This view is supported by other reports, which show normal exercise tolerance and quality of life, in asymptomatic and unoperated adults with CCTGA [2, 3, 7, 24].
| Acknowledgments |
|---|
|
|
|---|
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
J. E. Deanfield, R. Yates, F. J. Meijboom, and B. J.M. Mulder CHAPTER 10 Congenital Heart Disease in Children and Adults ESC Textbook of Cardiovascular Medicine, January 1, 2009; 2(1): med-9780199566990-chapter - med-9780199566990-chapter. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. A. Warnes Transposition of the Great Arteries Circulation, December 12, 2006; 114(24): 2699 - 2709. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. M. Paridon, B. S. Alpert, S. R. Boas, M. E. Cabrera, L. L. Caldarera, S. R. Daniels, T. R. Kimball, T. K. Knilans, P. A. Nixon, J. Rhodes, et al. Clinical Stress Testing in the Pediatric Age Group: A Statement From the American Heart Association Council on Cardiovascular Disease in the Young, Committee on Atherosclerosis, Hypertension, and Obesity in Youth Circulation, April 18, 2006; 113(15): 1905 - 1920. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Dodge-Khatami, A. Kadner, F. Berger, H. Dave, M. I. Turina, and R. Pretre In the Footsteps of Senning: Lessons Learned From Atrial Repair of Transposition of the Great Arteries Ann. Thorac. Surg., April 1, 2005; 79(4): 1433 - 1444. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |