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Ann Thorac Surg 2006;82:1292-1300
© 2006 The Society of Thoracic Surgeons
a Division of Cardiovascular Surgery, Department of Pediatrics, University of Toronto, Hospital for Sick Children, Toronto, Canada
b Division of Cardiology, Department of Pediatrics, University of Toronto, Hospital for Sick Children, Toronto, Canada
c Department of Cardiology, Stollery Children's Hospital, Alberta, Canada
d King Faisal Heart Institute at King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia
Accepted for publication April 7, 2006.
* Address correspondence to Dr Alsoufi, King Faisal Heart Institute (MBC 16), King Faisal Specialist Hospital and Research Centre, PO Box 3354, Riyadh 11211, Saudi Arabia (Email: balsoufi{at}hotmail.com).
Presented at the Forty-second Annual Meeting of The Society of Thoracic Surgeons, Chicago, IL, Jan 30–Feb 1, 2006.
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Abstract |
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METHODS: Twenty-two children (ages 5–18 years) underwent aortic cusp extension with autologous pericardium between 1999 and 2005. Sixteen children had previous surgical or percutaneous intervention. Ten children had bicuspid aortic valves. Cusp extensions were performed on 1 cusp in 3 patients, 2 cusps in 3, and 3 cusps in 16. Serial echocardiographic measures (n = 81) were obtained during a 5-year period and underwent blinded review. Longitudinal trajectories of ventricular and aortic valve function were modeled using mixed linear regression analysis.
RESULTS: There was no hospital or late mortality. Five-year freedom from valve replacement was 75%. Comparison of preoperative and post-repair echocardiograms demonstrated reductions in aortic insufficiency (decreased in jet-width/aortic valve diameter ratio from 0.39 ± 0.12 to 0.22 ± 0.11; p < 0.0001), aortic stenosis (decreased in peak aortic valve gradient from 41 ± 25 mm Hg to 29 ± 15 mm Hg; p = 0.04), and left ventricular end-diastolic dimensions Z-score (decreased from 1.39 ± 0.38 to 1.16 ± 0.34; p < 0.001). During the follow-up period, post-repair jet-width and aortic valve diameter increased nonlinearly (p < 0.001). Patients with postoperative peak aortic gradients greater than 30 mm Hg had progression of aortic stenosis, whereas those with lesser postoperative peak gradients tended to regress during follow-up (p < 0.001). The decrement in Z-score of the left ventricular end-diastolic dimensions remained stable during the follow-up period.
CONCLUSIONS: Aortic valve cusp extension can result in acceptable hemodynamic results with stabilization of left ventricular geometry. However, residual lesions are common and progression and regression of these lesions can be predicted based on echocardiographic data.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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Improved understanding of aortic valve anatomy and the mechanism of AI and the refinement of surgical repair techniques have prompted surgeons to consider repair of incompetent aortic valves in children as an attractive alternative to valve replacement. Several groups have reported encouraging early and mid-term results for cusp extension in the treatment of adult patients with rheumatic aortic valve disease [10–13]. However, few of these studies have attempted to identify intraoperative predictors of early successful repair or evaluated predictors of the long-term durability of the repair. Consequently, we evaluated the short-term and mid-term results of aortic cusp extension at our institution with the objective of assessing the relationships between operative techniques and intraoperative results, as well as attempting to identify predictors of the durability of this repair strategy.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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Intraoperative transesophageal echocardiography was also recorded in all patients (n = 22) at the time of aortic valve repair. All echocardiographic studies included the aortic jet width that was measured using color Doppler and was indexed to the size of the aortic valve diameter and to the body surface area. Left ventricular end-diastolic dimensions (LVEDD) were converted into Z-scores of the left ventricular end-diastolic dimensions (Z-LVEDD) using regression equations based on previously published nomograms [14, 15].
Operative Technique
All procedures were performed though a midline sternotomy and are similar to previously published techniques [12]. Autologous pericardium was harvested and treated with buffered glutaraldehyde solution (0.625%) for 5 minutes. Cardiopulmonary bypass was established through a standard aortic and dual-stage venous cannulation. The left ventricle was decompressed by venting through the right superior pulmonary vein. Mild hypothermia (32°C to 34°C) was used with a combination of antegrade and retrograde cold blood cardioplegia. Antegrade cardioplegia was initially administered through the root and then by direct coronary artery cannulation. The aorta was opened through a transverse incision that was extended downward toward the noncoronary sinus. The aortic valve was then inspected and the pathology was analyzed. In patients in whom a cusp was found detached from the aortic wall (n = 3), the cusp was reattached with a running monofilament nonabsorbable suture (polypropylene). Cusp perforation was repaired with fresh autologous pericardial patch (n = 1). Extended commissurotomy was done in patients with fused commissures. The subvalvular area was evaluated and myectomy or subaortic fibrous membrane excision was performed if indicated. Thickened and fibrotic areas of the cusps were thinned out by sharp dissection. Each leaflet was inspected with respect to the height of the cusps and the commissures, and the length of the free edge. Glutaraldehyde-treated pericardial patches were trimmed and fashioned into the proper shape to fill the defective length and depth of each cusp. The length of the patch was determined by the diameter of the aorta supplemented with an additional 15% length to account for a reduction in the pericardial cusp free edge width associated with pericardial shrinkage. The height of the pericardial cusp was tailored based on the height of the most normal cusp so as to extend the line of coaptation of the repaired cusps 5 mm longer than the highest cusp, and to bring the extended aortic cusps into a coaptation point in the center of the aorta. The cusp extensions were sutured to the free edges of the native cusps with a running suture of 5-0 polypropylene. The extensions were also attached to the aortic wall creating neo-commissures at the level of the sinotubular junction. With all the patch extensions in place, the newly constructed cusp edges were trimmed to provide a uniform cusp height.
In patients with bicuspid aortic valve, the raphe was excised and an attempt was made to convert the bicuspid into a tricuspid valve by opening the rudimentary commissure all the way to the aortic wall followed by fashioning and suturing the cusp extensions as previously described. Finally, if the annulus was dilated, subcommissural plication was performed to increase coaptation area of the cusps. The aortic wall was closed with a single layer of running polypropylene, and the heart was vented to evacuate any residual air.
Intraoperative transesophageal echocardiography was performed in all patients. Aortic insufficiency was estimated as none [grade 0], trace [1+], mild [2+], moderate [3+], or severe [4+] on the basis of information from color flow mapping and continuous-wave Doppler echocardiography. Complete operative data are summarized in Table 2.
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Statistical Analysis
All data analyses were performed using SAS statistical software (version 9 [SAS Institute, Inc, Cary, NC]). Data are presented as frequency, median with range, or mean ± standard deviation as appropriate, with the number of non-missing values indicated. Unrelated two-group comparisons were performed with unpaired, 2-tailed t tests for means of normally distributed variables, or the Mann-Whitney U test for non-normal data. Paired data were examined using paired two-tailed t tests. Time-related freedom from reoperation was analyzed by the Kaplan-Meier method. Serial echocardiographic assessments of peak instantaneous aortic valve gradient, aortic jet width and aortic valve diameter ratio, and left ventricular end-diastolic dimension Z-scores were modeled and risk factors sought by using general linear mixed regression models. These models consider every measurement within each patient as opposed to every patient as an observation, increasing our available sample size from 22 observations to 59 observations. General mixed linear models, treating each factor as a fixed effect, account for within-subject correlation inherent in repeated measures outcomes. Mixed linear regression models are well-characterized in the literature and have been shown to be superior to standard analysis of variance techniques that require data be gathered at fixed intervals on all patients (generally not possible outside of the scope of a prospective randomized trial), and ignore both within-subject correlation and within-time changes in covariance, thus producing erroneous standard errors and confidence limits [16–18]. Univariable exploratory plots were initially generated to determine the longitudinal relationship (ie, linear, quadratic, cubic, and so forth) between each potential predictor and outcome. Factors were then entered using a stepwise selection algorithm, with interaction terms added in a hierarchical manner. Candidate covariance structures were tested explicitly with the final matrix selected based on variograms and minimization of the information criteria (Akaike's information criterion and Bayesian information) generated from the mixed procedure. For the mixed models, time zero was taken to be the date of aortic valve surgery so that only postoperative values (n = 59) were used. However, preoperative values (as time independent covariables) were used as potential predictors in all models.
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Results |
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There was no operative mortality, and there was no major hospital morbidity with no bleeding, wound, or arrhythmia complications.
Comparison of Preoperative to Pre-Discharge Transthoracic Echocardiogram
There was reduction in the mean AI jet width/aortic valve diameter ratio (0.39 ± 0.12 preoperatively versus 0.22 ± 0.11 postoperatively; p < 0.0001). The Z-score of the left ventricular end-diastolic diameter decreased from 1.39 ± 0.38 to 1.16 ± 0.34 (p < 0.001). The mean aortic valve peak gradient decreased from 41 ± 25 to 29 ± 15 mm Hg (p = 0.04). Transthoracic echocardiographic data are summarized in Table 3.
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Change in Echocardiographic Measurements During Follow-up Period
The trajectory of jet width/aortic valve diameter ratio were determined. Post-repair AI quantified by the jet width/aortic valve diameter ratio increased nonlinearly in all patients over time (p < 0.001) (Fig 1). Factors associated with a higher jet width/aortic valve diameter ratio over time were sought and are shown in Table 4. These included creation of a tricuspid valve at the time of aortic valve repair (p = 0.03) and an interaction term between creation of a tricuspid valve and time (p = 0.007).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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Various series using this technique have reported encouraging mid-term outcomes in heterogeneous groups of patients. Grinda and colleagues [10] reported 89 patients (mean age, 16 ± 5 years) with rheumatic aortic valve disease who underwent triple pericardial aortic cusp extension. Five-year survival and freedom from aortic reoperation were 96% and 92%, respectively [10]. Similarly, Bozbuga and colleagues [11] reported 46 patients with rheumatic valve disease (mean age, 35 ± 12 years) with survival of 98% at 8.6 years and freedom from aortic reoperation of 76.1% at 7.5 years. Kalangos and colleagues [12] reported 42 children (mean age, 11.5 ± 2.7 years) with rheumatic aortic valve insufficiency and actuarial survival at 3 years was 97% with no reoperations. The longest available results for as many as 16 years were recently reported by Al Halees and colleagues [13] for 92 patients (mean age, 30 years) with mainly rheumatic valve disease. The survival rate was 85%. There were no episodes of thromboembolism and freedom from reoperation was 68% at 10 years and 47% at 16 years. Several groups have recently explored the results of pericardial cusp extensions in patients with congenital aortic valve disease. Odim and colleagues [19] reported 62 patients with congenital heart disease treated with pericardial cusp extensions (mean age, 25 ± 20 years). Two-year freedom from reoperation was 92%. Smith and colleagues [20] reported echocardiographic follow-up for 22 patients (mean age, 7 ± 5 years) after pericardial cusp augmentation for congenital aortic insufficiency. Similar to our results, they noted decreased regurgitation jet area, decreased left ventricular end-diastolic dimensions, and decreased Z-score of the left ventricular end-diastolic volume.
Different techniques have been applied in the aforementioned studies with variations in the total number of cusp extensions, complete excision of the cusps versus augmentation only, tricuspidization of the bicuspid aortic valves, the type of material used, pericardial treatment with buffered glutaraldehyde, and the use of multiple pericardial patches versus a single strip of pericardium to augment all 3 cusps.
Residual regurgitation is a well-established risk factor for repair failure and reoperation in adults undergoing mitral [21] or aortic valve repair [22], and we believe that residual regurgitation may confer a similar disadvantage after a cusp augmentation technique in children with congenital AI. Optimal immediate surgical outcome would be a competent valve with no AI or trace AI and mild or less aortic stenosis. However, in the operating room, the surgeon is often faced with a combination of residual lesions and has to decide whether to revise the repair, abandon the repair and replace the valve, or accept residual aortic stenosis or AI, or both. Eight patients in our series had residual peak aortic valve gradients greater than 30 mm Hg on intraoperative transesophageal echocardiography. The progression of these peak gradients during the brief follow-up period suggests that intraoperative revision of the repair should be strongly considered. In contrast, the data suggest that aggressive attempts to reduce AI should be pursued even at the expense of creating a mild peak gradient (< 30 mm Hg) as these gradients tend to regress. Further follow-up will be important to determine the consistency of this pattern.
However, it is important to note that there was a significant and sustained nonlinear decrease in the Z-LVEDD over time that continued to the end of our follow-up interval among all the patients. Because protection of ventricular geometry is frequently the indication for the valve procedure in this patient population, in this regard, the cusp augmentation technique can be considered a successful therapy despite the presence of residual hemodynamic lesions. Clearly the degree to which a hemodynamically imperfect result can be tolerated in the long term will be an important component of the assessment of the cusp augmentation technique.
Without question, the development of techniques, whereby a hemodynamically perfect repair is routinely achieved, is the best solution. We have begun to evaluate the utility of the 3-dimensional echocardiography as an important tool in the perioperative evaluation of diseased aortic valves. Because this technique can cut the valve in any plane, thorough inspection of leaflet motion and regurgitant volumes is possible. Identification of the 3-dimensional origin of residual turbulence or abnormal cusp coaptation can be expected to shed insight on methods to improve repair techniques. To this end we have introduced the concepts of systolic and diastolic mobility to begin building a vocabulary, whereby aortic valve pathology can be better defined to identify valves amenable to repair, assist in intraoperative planning and intraoperative repair, and clarify the cause and likelihood of progression of residual lesions.
Conclusion
Aortic valve repair with autologous pericardial extensions is a safe procedure resulting in acceptable intraoperative results with reduction and stabilization of left ventricular dimensions. However, residual lesions are common, and attempts to reduce residual insufficiency should be considered even at the expense of creating mild stenosis. However, more than moderate stenosis is likely to progress. Longer echocardiographic and clinical follow-up is needed to assess the long-term utility of this technique, the durability of repair, and the progression of residual lesions. Increased experience with 3-dimensional echocardiography and better understanding of the effects of both diastolic and systolic mobility after repair are likely to play a promising role in the surgical treatment of these complex patients in the future.
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Discussion |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionReferences |
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DR ALSOUFI: I don't believe that we can say this is a permanent treatment based on our current report and on others' experience as well. We believe that aortic valve cusp extension technique is a good temporizing solution as it offers reduction of regurgitation and stenosis and stabilization of the ventricular dimensions until the patients grow older at which time we can offer them the full range of possible treatment options including [a] mechanical valve or the Ross procedure. Hopefully, increased experience with aortic valve repair techniques and better understanding of the mode of failure or recurrence, and the influence of residual lesions on long-term outcome will help us improve our repair techniques and, maybe at some point, we can offer cusp extension as a permanent treatment for children with congenital aortic valve disease.
DR MICHAEL D. BLACK (San Francisco, CA): My question deals with further sub-segmenting your patient population into those that had 1-, 2- and 3-cusp repairs. We saw this morning, from Dr. Brown's group, excellent longevity in aortic valve replacement with the Ross procedure with 96% freedom from reintervention over 12 years of follow-up. I was wondering, if you broke down your group a little bit further, would the longevity and the success of your repair be better if you refrained from repairing all 3 leaflets and maybe stuck to 1 or 2. Would that have given you a better long-term, not just short-term result?
DR ALSOUFI: It is our current practice to perform 3-cusp extension. In this series, 16 patients had 3 cusp extensions and only 6 patients had either 1 or 2 cusp extensions. The small numbers in this series did not permit analysis of the effect of the number of pericardial extensions on early or late failure. One patient who had 2 cusp extensions had persistent insufficiency on postoperative transesophageal echocardiography (TEE) and required reinstitution on cardiopulmonary bypass and placement of an additional pericardial extension which resolved the insufficiency. Obviously, the current results are inferior to those of the Ross procedure. We do explain all surgical options to the family, and obviously aortic valve repair using cusp extensions doesn't preclude the use of Ross operation as a fallback option in case of immediate failure or late recurrence.
DR BRADLEY S. ALLEN (Houston, TX): I'm confused on some of the numbers and how you deal with bicuspid valves. Sixteen patients had extensions of 3 cusps. This means you had to change a bicuspid valve to a trileaflet valve in at least in 4 patients.
DR ALSOUFI: Eight patients had tricuspidization.
DR ALLEN: Nevertheless, you did commissural re-suspension in only 3 patients. So I'm confused how you made a bicuspid valve into a trileaflet valve without cusp re-suspension. I therefore have two questions. First, what's the technique you used to convert the bicuspid valve into a trileaflet valve? How are you doing this without cusp re-suspension? Second, when do you convert a bicuspid valve into 3 leaflet valve, as compared to leaving it as bicuspid?
DR ALSOUFI: The 3 patients you mentioned are those who had torn cusps, usually as a result of previous aortic balloon valvuloplasty, and in those patients, the cusps were reattached to the wall with running polypropylene sutures. Obviously, commissural suspension is part of the tricuspidization and all the patients who required tricuspidization had commissural suspension. As to when to do the tricuspidization, it depends on the degree of development of the raphe, which can be heterogeneous in patients with bicuspid aortic valve. In those patients who have a well-developed raphe, we tend to cut down into it and tricuspidize the valve.
DR JOHN E. MAYER, JR (Boston, MA): In your abstract you said you replaced one aortic valve, and so I have two questions. What did the explanted valve look like grossly? And microscopically was there any evidence of cellular ingrowth into the pericardial extensions?
DR ALSOUFI: I do not know the specific operative and pathologic details of this patient who required reoperation and aortic valve replacement.
DR CHAWKI EL ZEIN (Chicago, IL): How do you prepare the autologous pericardial patch?
DR ALSOUFI: The pericardial patch is harvested following sternotomy and treated at the back table by the scrub nurse with 0.625% buffered glutaraldehyde for 5 minutes. Then it's rinsed and cut to the proper shape based on the defect of the length and the height of the aortic cusps.
DR EL ZEIN: We have started using the autologous pericardium around 12 years ago, and now we moved back to the bovine pericardium, the CardioFix, and we found that the degeneration and calcification of the augmented leaflet is less so far compared to the autologous pericardium.
DR ALSOUFI: Well, that's interesting, because immunological factors may contribute to calcification of xenograft pericardial patches, and therefore autologous pericardium may manifest the advantage of greater resistance to degeneration than xenografts, which may explain the improved durability of repair in some series. We did not use bovine pericardium, but I do know that several series compared the outcome between bovine and autologous pericardium. While some groups demonstrated equivalent results with the use of either bovine or autologous pericardium, other groups demonstrated improved performance with autologous rather than bovine pericardial material for cusp extension. The largest series with the longest follow-up of 16 years is by Dr. Al-Halees, and he found no difference in the outcomes using bovine or autologous pericardium.
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