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Original Articles: Adult Cardiac

Early Results of Valve-Sparing Aortic Root Replacement in High-Risk Clinical Scenarios

^a Cardiothoracic and Vascular Surgeons, Austin, Texas
^b Division of Cardiothoracic Surgery, Emory University School of Medicine, Atlanta, Georgia

Accepted for publication October 13, 2009.

^_* Address correspondence to Dr Chen, 1365 Clifton Rd, Suite A2236, Atlanta, GA 30322 (Email: edward.p.chen{at}emory.edu).

Presented at the Fifty-fifth Annual Meeting of the Southern Thoracic Surgical Association, Austin, TX, Nov 5–8, 2008.

	Abstract

Top Abstract Introduction Patients and Methods Results Comment Discussion References

 
Background: The feasibility of valve-sparing aortic root procedures (David) in certain high-risk situations has been questioned. We sought to determine the safety of the David procedure in the following high-risk subgroups: acute type A dissection, severe aortic insufficiency (AI), and reoperations.

Methods: From 2005 through 2007, 110 root replacements were performed for the above criteria: 73 root replacements with a composite valve-conduit (Bentall) and 37 David procedures. The reimplantation technique was used in all 37 David patients, with 7 requiring aortic cusp repair.

Results: There were no significant differences in preoperative or intraoperative variables between the groups, with the exception of cross-clamp time, which was longer for David patients. There was a slight, but nonsignificant increase in mortality among Bentall patients (8.2% [6 of 73]) compared with David patients (5.4% [2 of 37], p = 0.59]. There were no differences with respect to postoperative stroke, renal failure, or respiratory failure. Predischarge echocardiogram in the surviving 35 David patients demonstrated no AI in 25 patients and trace/mild AI in 10. Freedom from AVR at a mean follow-up of 8.8 months (range, 1 to 40) was 94.3% (33 of 35). One patient required AVR because of endocarditis at 9 months, and 1 had severe AI 13 months postoperatively.

Conclusions: Valve-sparing aortic root replacement can be performed safely in the setting of acute dissection, severe AI, and reoperations with acceptable early results. Long-term follow-up is needed to determine the durability of repair in these high-risk groups.

	Introduction

Top Abstract Introduction Patients and Methods Results Comment Discussion References

 
Valve-sparing aortic root replacement (VSRR) has been popularized as an alternative to aortic valve replacement in patients with aneurysmal disease or dissection involving the aortic root [1, 2]. Unlike aortic root replacement with a composite valve-conduit (Bentall), VSRR carries the theoretical benefits of avoiding anticoagulation therapy required for mechanical valves as well as possible reoperation related to prosthetic valve degeneration.

In spite of its advantages, however, widespread application of VSRR has been somewhat limited because of the technical complexity of the procedure. Furthermore, some have questioned the benefit of VSRR for certain high-risk patients. This study aims to determine the safety of VSRR, specifically the David reimplantation technique [2], in the following high-risk subgroups: patients with acute type A dissection, patients with severe aortic insufficiency (AI), and patients undergoing reoperations. Furthermore, perioperative outcomes for these high-risk David patients are compared with those undergoing Bentall operations.

	Patients and Methods

Top Abstract Introduction Patients and Methods Results Comment Discussion References

 
Patients
This study was conducted with approval of the Emory University Institutional Review Board with a waiver for individual patient consent. From January 2005 through April 2008, 110 aortic root replacements were performed at the Emory University affiliated hospitals for the above-listed high-risk criteria: 73 underwent replacement with a composite valve-conduit (Bentall) and 37 underwent valve-sparing aortic root replacement utilizing the Tirone David reimplantation technique (David). Fifty-eight of these procedures were performed in patients with severe aortic insufficiency, 40 were performed in patients with acute type A dissections, and 19 were done in patients undergoing reoperations. Patients having undergone previous aortic valve replacement were excluded from this analysis as they were not candidates for valve-sparing procedures. Likewise, patients with dilation of the sinotubular junction leading to aortic insufficiency that could be repaired with ascending aortic replacement alone and narrowing of the sinotubular junction were not included in this study. In patients who had severe aortic insufficiency, the cause was either dilation of the aortic annulus or significant cusp prolapse or perforation requiring repair. The decision to attempt a valve-sparing procedure versus root replacement with a valve-conduit was made at the discretion of the attending surgeon. During the study period, two surgeons at this institution performed valve-sparing procedures, whereas the remainder did not. Consequently, although some patients required valve replacement due to the nature of their aortic valve pathology, most patients were eligible for either procedure.

Surgical Technique
All procedures were performed through standard median sternotomy utilizing cardiopulmonary bypass and moderate systemic hypothermia at 32°C. In selected cases for which aortic arch replacement under circulatory arrest was necessary, right axillary cannulation and selective cerebral perfusion were utilized, and patients were cooled to 24°C. Myocardial protection consisted of topical hypothermia with intermittent antegrade and continuous retrograde cold blood cardioplegia. The left ventricle was routinely vented through a cannula inserted in the right superior pulmonary vein.

For valve-sparing procedures, the sinus of Valsalva tissue was excised down to the left ventricular outflow tract (LVOT), leaving a 3 to 4 mm rim of aortic tissue around the commissures and subcommissural triangles. The coronary buttons were dissected free and mobilized. The aortic prosthesis was sized using David and Feindel's formula [2]:

(1)

where H_leaflet = average height of the three leaflets. This size would correspond to a woven polyester Gelweave Valsalva graft (Vascutek, Renfrewshire, Scotland) approximately 5 to 6 mm larger than the measured annular diameter. The base of the graft was then plicated down using interrupted 3-0 polypropylene sutures placed to match the annulus and tied down over a Medtronic Freestyle valve sizer (Medtronic, Minneapolis, MN). The graft was anchored to the LVOT using 6 to 12 interrupted 2-0 braided polyester horizontal mattress sutures. The valve was then reimplanted within the graft using three separate running 4-0 polypropylene sutures starting at the nadir of each cusp. Techniques for cusp repair involved both free margin shortening to eliminate prolapse and closure of fenestrations. The coronary buttons were reimplanted using 5-0 polypropylene. Valve competency was primarily assessed by visual inspection for proper cusp coaptation and absence of prolapse, and occasionally by instilling saline into the aortic root. The distal aortic anastomosis was completed with 4-0 polypropylene, and the cross-clamp was removed after appropriate deairing maneuvers.

For the modified Bentall procedure, all aortic valve tissue and sinus tissue was excised, and the coronary arteries were dissected and mobilized. Valve conduits consisted of either commercially available mechanical valve conduits or bioprosthetic valves that were sutured to a Dacron (C.R. Bard, Haverhill, PA) graft at the time of surgery, based on the patients' age and clinical situation. The valve conduit was anchored to the LVOT using a series of pledgeted 2-0 braided polyester horizontal mattress sutures. The coronary arteries were then reimplanted, and the distal anastomosis was completed using 4-0 polypropylene.

Follow-Up Echocardiograms
Echocardiograms were obtained on all patients before hospital discharge. During the follow-up period, echocardiograms were performed based on clinical symptoms or at the discretion of the primary cardiologist. All studies were performed and interpreted at one center. The grade of aortic insufficiency was interpreted based on a semiquantitative scale and reported as none (0), trivial (1), mild (2), moderate (3), or severe (4). More quantitative measures of valve incompetence (such as regurgitant volume and regurgitant orifice area) were not available for all patients and are not reported here.

Statistical Analysis
Missing data were scarce in this study. Endpoint data and outcomes were 100% complete. However, some of the potential confounding variables had small amounts of missing data, including degree of aortic insufficiency (n = 9, 6.7%) and ejection fraction (n = 22, 16.3%). To reduce the potential for bias due to missing values, a multiple imputation algorithm originally described by Rubin and more recently by Molenberghs was instituted [3]. This approach does not seek to replace the missing values but rather is designed to reflect the uncertainty surrounding the missing values so that data that are present can be analyzed. Five imputed datasets were used to model this uncertainty.

The retrospective nature of this study and the associated risk of selection bias indicated the use of propensity scoring methodology. This method "balances" patients with respect to the effect of their preoperative risk factors on their probability of group assignment (Bentall versus David). The propensity score in this study was the probability of assignment to David based on 37 preoperative risk factors and six indicators of missing data. Surgery type (David versus Bentall) was not included in the propensity score calculation because its direct effect was of primary interest. Once formulated, the propensity score was used as a single covariate in a multiple logistic regression model that also included surgery type so that the adjusted effect of surgery type could be evaluated.

Adjusted odds ratios (AOR) with associated 95% confidence intervals (CI) for outcomes of interest were computed. These represent the increased (AOR >1) or decreased (AOR <1) risk associated with the David procedure. For continuous outcomes (length of stay, intensive care unit hours, and ventilator hours), general linear models were fit that regressed the outcome as a function of surgery type and the propensity score. The adjusted effect of the David procedure is expressed as a positive number when the David surgery results in longer stays and a negative number when the David surgery results in a shorter stay.

Kaplan-Meier survival estimates and associated survival curves were calculated for each surgery type. A log-rank test was used to determine whether the long-term survival of the groups was statistically different. The data were analyzed with SAS version 9.1 (SAS Institute, Cary, NC). All statistical tests were evaluated at the 0.05 alpha level. All comparisons and model terms were preplanned. No adjustment for multiple comparisons was made.

	Results

Top Abstract Introduction Patients and Methods Results Comment Discussion References

 
Perioperative Risk Factors
Preoperative risk factors are listed in Table 1. Patients undergoing the Bentall procedure had a greater incidence of peripheral vascular disease among patients undergoing reoperations and among patients with acute type A dissections. Bentall patients were also older than David patients, particularly in the acute dissection group. The remaining preoperative risk factors were similar between groups, including left ventricular ejection fraction (50% in Bentall versus 53% in David, p = 0.35).

View larger version (11K): [in this window] [in a new window]   Fig 1. Survival curves for David group (dotted line) and Bentall group (solid line). No significant difference is seen at 3.5-year follow-up.

	Comment

Top Abstract Introduction Patients and Methods Results Comment Discussion References

Although these short-term results are encouraging, it will be important to ensure that valve-sparing in these complex patients will be beneficial in the long term. The results of aortic root replacement with a composite valve conduit have proven to be excellent, despite the inherent risk of bleeding and thrombotic complications with a prosthetic valve [4, 5]. Consequently, valve-sparing procedures must compare favorably to the long-term results of conventional root replacement. David and colleagues [6] have demonstrated the durability of valve-sparing operations with a 10 year survival of 88% and freedom from moderate/severe AI of 85%. It remains to be seen, however, whether these results can be duplicated at other centers, particularly as the indications for valve-sparing procedures are expanded.

Valve-sparing aortic replacement has already gained popularity for other complex patient subgroups, including those with Marfan syndrome [6–10]. Although long-term survival after valve-sparing in Marfan patients has shown to be excellent [9], the durability of valve repair has not been as successful [7, 9]. Other complex situations in which valve sparing has been attempted with mixed results include patients with bicuspid valves [11–14], patients requiring leaflet repair [6, 12, 15, 16], and patients with previous Ross procedures [17, 18] In this report, 10.8% of David patients had bicuspid valves and 18.9% underwent cusp repair. In our experience, these variables add differing levels of complexity when performing valve-sparing procedures. The majority of patients requiring cusp repair had an outstanding result. One patient, however, continued to have cusp prolapse and moderate aortic insufficiency on postoperative echocardiograms that progressed and ultimately required AVR 13 months postoperatively. Consequently, our strategy has been modified to not accept any degree of cusp prolapse, even when there is only trace aortic insufficiency present. Likewise, bicuspid valves have also prompted some changes in our practice. For these valves, the graft size is chosen based on the length of free margin of the aortic valve cusps rather than the cusp height. Because this value often exceeds the diameter of the largest commercially available Valsalva grafts, our tendency has been to use straight grafts for these patients. As a result, we have migrated toward utilizing straight grafts for all patients, and using plication sutures at the level of the annulus and sinotubular junction to create neosinuses.

The feasibility of correcting severe aortic insufficiency with valve-sparing procedures has been addressed by a number of previous studies. Because of the difficulty in achieving the appropriate three-dimensional geometry, these patients present an added challenge in preventing early and late development of AI [6]. Among our 18 patients with severe AI preoperatively, 15 had no AI on postoperative transthoracic echocardiography, and 3 patients had trace/mild AI. Likewise, David and colleagues [6] have shown that valve sparing is feasible for patients with moderate to severe AI, although those patients were not examined independently in the long-term analysis. Kallenbach and associates [19] demonstrated equivalent mortality and grade of aortic insufficiency at 3 years after valve-sparing procedures for patients with moderate to severe AI when compared with patients who had mild or no AI [19].

Acute type A dissections present an added dimension of complexity because of the historically poor operative mortality in these patients. In the current series, both deaths in the valve-sparing group were of patients undergoing emergent operations for type A dissections (2 of 16, 12.5%). This mortality is still below the typical expected mortality of 25% for this patient group. Other studies [20–23] have shown similar results with acceptable perioperative risks and good short-term outcomes [23], although there may appear to be a propensity for late failure with the Yacoub root remodeling technique [22]. Most would agree that although type A dissection should not preclude valve-sparing aortic surgery, it should likely only be attempted at centers with a large experience in these procedures [24].

The current study has several limitations that should be addressed. First, this is a retrospective review of a heterogeneous group of patients, who were not randomized and carries the inherent errors of a nonrandomized comparison. Furthermore, the majority of valve-sparing procedures were performed by one surgeon, which may introduce some bias in our statistical analyses. We have attempted to account for these shortcomings by utilizing propensity-matched comparisons. Also, the number of patients in the David group is relatively small compared with the Bentall group. Nevertheless, our goal was to review our outcomes with valve-sparing aortic surgery in these high-risk situations, particularly as these cases are relatively early in our experience. Finally, while we have demonstrated acceptable outcomes in the short-term, our results lack long-term follow-up with objective echocardiographic evidence of valve function.

In summary, valve-sparing aortic root surgery is technically demanding and carries a steep learning curve. However, as we and others have shown, acceptable outcomes with reasonable perioperative risk can be achieved if patients are chosen appropriately. That includes evaluating the overall hemodynamic status of the patient as well as cusp anatomy both by echocardiography and by direct inspection. Finally, the indications for valve-sparing aortic surgery are likely to expand with increasing surgeon experience. However, it is imperative that long-term results are acceptable and compare favorably with those of conventional aortic root replacement.

	Discussion

Top Abstract Introduction Patients and Methods Results Comment Discussion References

 
DR JOHN S. IKONOMIDIS (Charleston, SC): I would like to congratulate Dr Kerendi and the Emory group for a very nicely presented and very timely paper, because it really illustrates a change in practice pattern, in that most surgeons now who have performed a reasonable number of valve-sparing roots and have become facile with the procedure are beginning to extend this operation into higher-risk scenarios such as those presented here. I have several questions for you.

First, what was the mechanism of severe aortic insufficiency in the one VSR patient requiring reoperation and what did you learn from it?

DR KERENDI: That patient was one of several in the group who actually had cusp repair at the time of the initial operation, and when going back, it was apparent that the repair sutures had torn out.

DR IKONOMIDIS: Has it modified your approach toward concomitant aortic valve repair in these patients?

DR KERENDI: I don't think it has, but since Dr Chen was the surgeon in the majority of these cases, I would ask him to elaborate further on the details of that.

DR EDWARD P. CHEN (Atlanta, GA): John, that patient was very early in our experience within the first 10, and I think at that time I relied more heavily on the saline test and probably not as much on what I think now is more important, visual inspection of cusps, the lack of prolapse, the adequacy of a good coaptation zone. So as time has gone on, I think in retrospect we probably did not correct the prolapse as much, and over time there was probably more stress on that leaflet leading to tear. But we have not decreased our tendency to do cusp repair in isolated cusps. In multiple cusps, we tend not to do that.

DR IKONOMIDIS: Second question. How many bicuspid aortic valve patients were in the valve-sparing group?

DR KERENDI: There were 4 patients that were included in this series. There were additional patients with isolated bicuspid valves who underwent valve-sparing that we did not include.

DR IKONOMIDIS: In your manuscript you mention that you used the prefabricated Valsalva graft in this series. Have you encountered any problems with that graft in terms of the fact that it is a single size and not all aortic roots are created equal?

DR KERENDI: I realize that that is a concern, but so far we have not experienced that problem.

DR IKONOMIDIS: The last question I have for you is a statistical question, and that is, I was intrigued by the difference in mortality between the two groups, and I suspect part of the reason for that is because there is a disproportionate percentage of reoperations versus dissections between the groups. I know you tried to correct for this with propensity analysis, but a problem arises, because in the Bentall group, 25 of those patients already had previous aortic valve replacement. This would exclude these patients from a propensity scoring analysis because there is no selection bias in those patients; that is, one cannot choose between whether to do a valve-sparing root or a formal root replacement in a patient whose aortic valve was already removed with a previous operation. Hence, if the propensity analysis is performed in the whole series, the correct answer may not be obtained. I wonder if you have considered a subanalysis eliminating those 25?

DR KERENDI: That is an excellent point, and that is exactly right, that those patients are not eligible for valve-sparing. Nevertheless, we felt since redo operations was one of the inclusion criteria, we did include those patients. As you have suggested, we did do a subanalysis of the patients without the redos, and the results were similar in that analysis.

DR HAROLD G. ROBERTS (Lauderdale Lakes, FL): I noticed in your presentation that the average clamp time with the valve-sparing procedure were around 208 minutes versus about 180 minutes for Bentalls. Have you looked at any of these valve-sparing patients echocardiographically to see if there is any difference in long-term LV function and if perhaps there might be some price to pay for that extra clamp time?

DR KERENDI: We have looked at that. As I stated, all the patients did have postoperative echocardiograms, and there was no difference in LV function from preoperative values. Our follow-up is somewhat limited in that we don't have long-term echocardiographic follow-up of all the patients. So I can't tell you what happens to the ventricle in the long term.

DR JOSEPH E. BAVARIA (Philadelphia, PA): Two quick questions, most of them statistically and methods oriented. Were there any valve-sparing operation failures in the operating room that then went to composite grafts, and if so, which group did you put them in?

DR KERENDI: I don't believe we had any in this series, and so there was no question as to where to put them.

DR BAVARIA: Because sometimes you will get those when you start doing complicated leaflet pathology, especially some leaflet repair issues.

The second question is, and it gets to the question that John asked, which was, how many of the severe AI cases were not dissection cases?

DR KERENDI: I don't know that offhand. That is something that I have to go back and look at.

DR BAVARIA: Because the data regarding complex David V operations with cusp repair techniques, which is really the issue you are getting at when you talk about severe AI David V cases, and this is a whole different kind of group than any other AI David V case—severe AI is a whole different animal—so it would be interesting to find out how many of your severe AI cases were dissections (many of the dissections will have severe AI). Severe AI dissection cases are a different issue, compared with the nondissection severe AI cases.

DR KERENDI: That is a good point. We would have to go back and look those up.

DR CHEN: Joe, I could probably enlighten you a little bit on that. There was just a handful of those patients, but we were very conservative in electing to perform that procedure in those patients. If the AI jet was eccentric because of single or multiple cusp prolapse, we tended not to perform that. If it was simply a result of annular or STJ dilation, we were more inclined to do that. We could certainly test the valve by creating a vacuum effect on the LV before we proceeded, and if we saw good coaptation of a cusp without prolapse, knowing that it was primarily annular or sinotubular dilations, then we proceeded.

DR G. CHAD HUGHES (Durham, NC): Ed, excellent results. I have one question. The thing that we struggle with a lot with this is a lot of these patients, especially the AI patients, have stress fenestrations, the leaflets are excessively thinned at the commissures, and I always struggle with how much is too much. What are your guidelines there? What do you accept in terms of stress fenestrations, leaflet thinning, that kind of thing?

DR CHEN: I think, again, because this is a high-risk group, we tend to be very conservative, and I think if you have an isolated fenestration in one cusp, we will close that, but if you have a cusp with two fenestrations higher or two separate cusps with a single fenestration, we tend to just use a conventional root replacement.

	References

Top Abstract Introduction Patients and Methods Results Comment Discussion References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Faraz Kerendi Robert A. Guyton Edward P. Chen Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kerendi, F. Articles by Chen, E. P. Search for Related Content PubMed PubMed Citation Articles by Kerendi, F. Articles by Chen, E. P. Related Collections Great vessels Valve disease