| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
a Sibley Heart Center Cardiology, Department of Pediatrics, Division of Pediatric Cardiology, Emory University School of Medicine, Atlanta, Georgia
b Department of Surgery, Division of Cardiothoracic Surgery, Emory University School of Medicine, Atlanta, Georgia
Accepted for publication July 10, 2009.
* Address correspondence to Dr Mahle, Children's Healthcare of Atlanta, Emory University School of Medicine, 1405 Clifton Rd, NE, Atlanta, GA 30322-1062 (Email: wmahle{at}emory.edu).
| PEDIATRIC CARDIAC SURGERY:
The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.
|
 |
Abstract |
|---|
 Top Abstract IntroductionMaterial and MethodsResultsCommentReferences |
|---|
Methods: We reviewed the clinical data for all preadolescents (
13 years) with TOF who underwent cardiac magnetic resonance imaging (cMRI) or PVR, or both. Serial cMRI data were analyzed to determine the change in indexed right ventricular end-diastolic volume (RVEDV) and biventricular ventricular ejection fractions. Available cMRI data after PVR were compared with data before PVR.
Results: During the study period, 101 preadolescents with TOF had cMRI. The median age of complete repair was 6 months (range, 6 days to 3.4 years). The mean RVEDV at the first study was 135 ± 39 mL/m2. For 32 with serial cMRI studies, the RVEDV increased at a mean yearly rate of 9 mL/m2. Ventricular systolic function was impaired in 46 (46%). Forty-two patients underwent PVR at a mean age of 8 ± 3 years. No hospital deaths occurred, and no pulmonary valve reinterventions have been required.
Conclusions: Significant right ventricular dilatation is common in preadolescents after transannular patch repair of TOF. Routine follow-up of this population should incorporate cMRI. Further studies will be needed to determine whether a strategy of early PVR might improve intermediate-term outcome.
Surgical repair for tetralogy of Fallot (TOF) often requires a transannular incision to relieve right ventricular (RV) outflow obstruction. This results in pulmonary insufficiency and may lead to progressive RV dilatation, RV dysfunction, and a propensity towards arrhythmias. Surgical pulmonary valve replacement (PVR) results in normalization of RV dimensions, improvement in both right and left ventricular contractility, decreased incidence of symptomatic arrhythmias, and reversal of clinical symptoms [1–3]. PVR in repaired tetralogy of Fallot is nearly inevitable and has proven benefits. The optimal timing of PVR, however, remains elusive.
Our institution has previously reported improvement in children, adolescents, and young adults undergoing PVR [2, 4, 5]. To date, most studies have examined the deleterious effect of chronic pulmonary insufficiency in the adult or older adolescent. In our experience, however, severe pulmonary insufficiency can result in RV dilatation early in childhood. The safety and efficacy of PVR in the very young preadolescent population remains unknown.
Given that RV function may be compromised severely or irreversibly by long-term pulmonary insufficiency, patients with TOF may benefit from early PVR. This study examines our institution's experience with PVR in preadolescent patients in an attempt to determine whether this procedure is warranted in such a young population.
|
Material and Methods |
|---|
|
TopAbstractIntroductionMaterial and MethodsResultsCommentReferences |
|---|
|
Cardiac MRI
The MRI protocol used for this study has been described elsewhere [2]. Cardiac-triggered non-breath-held MRI studies were performed with the patient supine using commercially available 1.5T MR scanners (Signa Twinspeed 12.45; General Electric Medical Systems, Milwaukee, WI). Gradient (torso, head, or cardiac phased array) coils appropriate for patient size were selected. Volumetric (RV and LV) analysis was performed offline on commercially available GE Advantage (ADW 4.3), Windows (Microsoft Corp, Bellingham, WA), or Sun (sparc 10, Sun Microsystems, Santa Clara, CA) workstations (early studies) equipped with CV Flow software (MASS Vol. 4.0 or 4.1; Medis, Leiden, the Netherlands).
In early studies, we used a 4-chambered, axial oblique, FastCard dynamic set of 7 to 10 slices, 20 phases/cycle at 7- to 9-mm thickness encompassing the ventricular volumes. In later studies, we used 8 to 12 slices, 20 phases/cycle at 7- to 10-mm thickness in the short-axis plane as a steady-state free precession data set. Both data sets were suitable for tracing endocardial borders for volume determination (end systole and end diastole). Stroke volume (SV) was determined by [end diastolic volume (EDV) – end systolic volume (ESV)], ejection fraction by [SV/EDV x 100%], and volume ratios were determined as a comparison between RVEDV and LVEDV.
Owing to the retrospective nature of this study, there are some inherent limitations to comparing cMRI data gathered at different times during the evolution of our MRI program. Measuring the same structure using different techniques (eg, axial plane vs short-axis volume measurements) will yield different values [6, 7]. In addition, the different sequences that were used (Fast Card vs Fiesta) introduced errors in the volume and function calculations [8]. There is emerging evidence that flow calculations will differ depending on the magnets being used [9]. These differences can be significant if flow calculations are not corrected for a stationary flow phantom [10]. The studies performed before 2002 did not include this correction.
Indications for PVR
There is no consensus regarding the indications for PVR in those patients with TOF who have undergone transannular repair. Initially at our institution, we compared RVEDV and LVEDV. When the RVEDV/LVEDV ratio exceeded 2:1, we generally considered that was an indication for PVR when combined with pulmonary insufficiency greater than 35%, moderate to severe tricuspid regurgitation, decreased RV or LV function, arrhythmias, or clinical decline. Recent work by Geva [11] and others led us to subsequently revise our guidelines. Currently, we would consider an indexed RVEDV exceeding 165 mL/m2, impaired RV function, or New York Heart Association functional class III symptoms, or worse, as indications for PVR.
Surgical Procedure
All operations were performed at Children's Healthcare of Atlanta, Egleston campus, Atlanta, Georgia. The initial TOF repair was performed using a transannular patch. The transannular incision was made just large enough to ensure that both the valve and infundibulum just below the valve were both widely patent. PVR was performed using cardiopulmonary bypass and bicaval cannulation through a redo sternotomy. The type of valve used for PVR was chosen at the surgeon's discretion. No mechanical valves or conduits were used. The valves used included 3 pulmonary or aortic homografts, 10 Biocor (St. Jude Medical, St. Paul, MN), 1 Carpentier-Edwards (Edwards Lifesciences, Irvine, CA), 6 Epic (St. Jude Medical), 11 Freestyle (Medtronic, Minneapolis, MN) and 11 Mosaic (Medtronic). The surgical approaches and early surgical results have been reported elsewhere [4, 5]. All valves were placed in the anatomic pulmonary position. Mean age at PVR was 8 ± 3 years.
Statistics
Results are reported as mean ± standard deviation or median and range, where appropriate. The paired t test was used to compare data before and after PVR. Significance was determined at a value of p < 0.05. Multiple regression analysis was used to determine any relationship between various risk factors and early PVR. Analysis was performed with STATA 6.0 software (StataCorp, College Station, TX).
|
Results |
|---|
|
TopAbstractIntroductionMaterial and MethodsResultsCommentReferences |
|---|
|
There were no in-hospital deaths. The mean length of stay was 4 days (range, 2 to 25 days). One patient had a residual ventricular septal defect, and 1 patient had persistent second-degree Wenckebach type atrioventricular block. Otherwise, there were no significant rhythm abnormalities in the cohort. No patients reported any heart failure symptoms at the most recent outpatient follow-up. At a mean follow-up of 26 months, none of the 42 patients have undergone repeat PVR. Calcified pulmonary valve leaflets were noted in 1 patient at 4.5 years of follow-up.
Multiple regression analysis looking at risk factors for early PVR did not find any significant correlation with age at TOF repair (p = 0.67), previous Blalock-Taussig shunt (p = 0.34), sex (p = 0.96), presence of branch pulmonary artery stenosis (p = 0.64), or presence of an identified genetic abnormality (p = 0.26).
PVR Patients with cMRI
The cMRI study was performed an average of 6 months before PVR. The mean RVEDV before PVR was 165 ± 32 mL/m2, and the mean pulmonary regurgitant fraction was 45% ± 10%. The average initial RVESV was 93 ± 23 mL/m2. The mean RVEDV/LVEDV ratio was 2.3 ± 0.4 before PVR. Preoperatively, 16 patients (38%) had signs of reduced ventricular function (RVEF < 0.45 or LVEF < 0.55, or both). Only 8 patients had follow-up cMRI after PVR, and serial cMRI demonstrated a reduction in RVEDV (181 ± 28 to 135 ± 27 mL/m2, p = 0.04). Review of the 2-dimensional echocardiograms from 39 patients with available studies before and after PVR demonstrated RV internal diastolic diameter decreased from 31.5 ± 8 mm before PVR to 21.4 ± 7 mm (p = 0.01). One patient had free pulmonary insufficiency, 2 had moderate, and the rest had no more than mild pulmonary insufficiency at the most recent follow-up.
|
Comment |
|---|
|
TopAbstractIntroductionMaterial and MethodsResultsCommentReferences |
|---|
Although we have established that RV enlargement occurs early after TOF repair, even in young children, multiple regression analysis did not identify any specific risk factors for needing early PVR in this study group. Risk factors for RV dilatation have been described previously and include pulmonary insufficiency, RV outflow tract aneurysm/akinesia, and tricuspid regurgitation [12–14]. Deleterious effects of RV dilatation include RV dysfunction, arrhythmias (ventricular and supraventricular tachycardia), and sudden death. In adults, cMRI has demonstrated indexed RVEDV and RVESV both decrease after PVR [15]. Kleinveld and colleagues [2] demonstrated similar cMRI findings in young children and adolescents.
PVR mitigates many of the aforementioned complications of RV dilatation; however, there may be a "point of no return," after which, many of the benefits of PVR are lost [16, 17]. The search is currently underway to determine which markers are most indicative of impending RV failure and potential for recovery. Our institution has recently begun analyzing RV strain as a predictor of myocardial recovery. It has become increasingly clear that PVR before severe or irreversible injury to the myocardium occurs should be the goal in each patient.
The literature is varied on the development of irreversible RV injury due to RV dilatation. Therrien and colleagues [17] looked at RV function and EDV after PVR for pulmonary insufficiency and found that if RV systolic dysfunction (EF < 0.40) was present before PVR, only 13% had normalized function at the time of follow-up. Furthermore, RV size or function did not improve when PVR was performed at the extremes of RVEDV (
227 mL/m2) [17]. Their study described a much older population, in which complete repair was performed at an older age and right ventriculotomy was commonly used to close the ventricular septal defect. More recently, this group reported no improvement in RV volumes after PVR in patients with more modest preoperative elevations of EDV ( 170 mL/m2); whereas nearly all patients with EDV of 170 mL/m2 or less had normalization of RV volumes at follow-up [18]. Studies by van Straten and colleagues [19] established that a significant decrease in RV size occurs after PVR when the mean preoperative RVEDV was 167 mL/m2 or less. Thus, there seems to be a threshold, above which the potential benefits of PVR diminish.
Early PVR, before adolescence, has some potential advantages. Studies agree that pulmonary insufficiency will worsen predictably over time after TOF repair [20, 21]. The severity of pulmonary insufficiency is related to the degree of RV enlargement as measured by cMRI [13]. As the RV enlarges, derangements in normal compensatory mechanisms lead to a failure of the normal mechanisms of hypertrophy. Ventricular hypertrophy is essential for maintaining normal wall stress and compliance in the failing heart. Exactly how these derangements occur is unknown, but evidence from LV failure models suggests it may be mediated by endomyocardial fibrosis [22, 23]. In addition, patients with repaired TOF have a high incidence of sudden death, largely due to ventricular arrhythmias [16]. Gatzoulis and colleagues [24] reported that moderate to severe pulmonary insufficiency was most common in patients with repaired TOF who had experienced ventricular tachycardia or sudden death.
The potential benefits of early PVR must be weighed against potential risks. Open heart procedures always carry the risk of operative death; and although this risk is low, a number of series have reported surgical deaths associated with the procedure. There were no deaths in our study group, and the average length of stay was 4 days. Taken together, these data seem to suggest that a strategy of early PVR has an acceptable risk profile and may attenuate future complications. Although we did not identify other serious morbidities such as cerebrovascular accidents or serious arrhythmias, these need to be considered before deciding to proceed with elective surgical intervention. In addition, currently available bioprosthetic valves are prone to calcification and impairment. Early PVR practically guarantees repeated operations. As with most issues in medical decision making, one must choose between competing risks. The decision to undertake PVR in preadolescence may mean additional open heart surgical procedures for benefits, which at this point remain speculative.
Further studies are needed to determine the markers of impending RV compromise. Therrien and others have described patients with TOF who do not recover ventricular function after PVR, and most have been adults. To our knowledge, no authors have reported adolescents with severe pulmonary insufficiency who did not demonstrate improvement in RV dimensions or contractility, or both, after PVR. In those from whom only echocardiographic data were available after PVR, all had normal LVEFs and qualitatively normal RV function at the most recent follow-up. The question arises, therefore, whether preadolescents might develop irreversible RV remodeling or myocardial impairment.
Work by Norgard and colleagues [25] would seem to suggest that the diastolic filling patterns observed in the initial postoperative repair period have implications on future outcomes. This institution did not routinely perform comprehensive diastology studies on postoperative TOF repairs in the 1990s. Therefore, any conclusions about postoperative restrictive physiology and its implications on subsequent PVR operations in this population would be purely speculative.
Our study is not randomized and our practice generally favored an aggressive approach to PVR; thus, we cannot answer that question from the data available. Because of the retrospective nature of this study, the timing of cMRI was variable, especially in the postoperative period, because of the retrospective nature of this study.
Although no data show that PVR improves survival, the data do suggest that PVR deserves strong consideration in any strategy that optimizes each patient's well-being after TOF repair. Surgical PVR has an excellent overall track record; however, newer percutaneous PVR techniques not presently available in this country may prove beneficial in select patients [26, 27]. Although young age at the time of PVR is the primary risk factor for repeat replacement [14], the studies indicate that PVR is safe, well-tolerated, and young age should not be a deterrent.
|
References |
|---|
|
TopAbstractIntroductionMaterial and MethodsResultsCommentReferences |
|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 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 |
