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Ann Thorac Surg 2007;84:1186-1194
© 2007 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, New York, New York
b Department of Anesthesiology, Mount Sinai School of Medicine, New York, New York
Accepted for publication March 20, 2007.
* Address correspondence to Dr Etz, Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029 (Email: christian.etz{at}mountsinai.org).
Presented at the Fifty-third Annual Meeting of the Southern Thoracic Surgical Association, Tucson, AZ, Nov 8–11, 2006.
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Abstract |
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Methods: Two hundred six BAV patients (mean, 53 ± 14 years, 84% male) underwent composite aortic root replacement between September 1987 and May 2005. One hundred nine patients (53%) presented with aortic regurgitation, 24 patients (12%) presented with aortic stenosis, and 55 patients (26%) presented with combined aortic stenosis and aortic regurgitation. Median preoperative aortic diameter was 5.5 cm (range, 3 to 9 cm). Twenty-two patients (11%) underwent urgent or emergent procedures; 11 had acute type A dissection (5%). Sixty-one percent had a mechanical valve Bentall prosthesis; in 39%, a biologic valve was implanted. Thirty-two percent had concomitant procedures.
Results: Overall hospital mortality was 2.9% (n = 6), and stroke rate was 1.9% (n = 4). Risk factors for adverse outcome (death or stroke), which occurred in 4.8% (n = 10), were presence of clot or atheroma (p = 0.02) and age older than 65 years (p = 0.05). During a mean follow-up of 5.9 years (1,200 patient-years; range, 5 to 18 patient-years), no patient required ascending aortic reoperation. Long-term survival was 93% after 5 years and 89% after 10 years. Discharged patients enjoyed survival equivalent to a normal age- and sex-matched population and superior to survival reported for a series of patients with aortic valve replacement alone.
Conclusions: In patients with BAV, the Bentall procedure has an operative mortality no worse than that for aortic valve replacement, with superior long-term survival and a lower rate of aortic reoperation.
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Introduction |
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Aortic valve replacement for aortic stenosis is the second most common reason for heart surgery in developed countries, and BAV is the second most common cause of aortic valve disease requiring surgery. The recognition that patients with a BAV are at risk for aorta-related death (rupture or dissection) has favored the concept of composite aortic root replacement in BAV patients who require aortic valve replacement for valve dysfunction, as well as elective Bentall procedures in BAV patients with significant aortic root dilatation.
We report the results of Bentall operations in 206 patients with BAV during an 18-year interval.
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Patients and Methods |
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Surgical Technique
All patients included in this study had a button Bentall operation, a modification of the original technique described by Kouchoukos and coworkers in 1991 [6]. All operations were performed with an open distal anastomosis using a period of deep hypothermic circulatory arrest, often with so-called hemiarch replacement, but occasionally involving replacement of the entire arch. Our current technique and its rationale have been described in detail elsewhere [7].
Briefly, cannulation for cardiopulmonary bypass was through the femoral artery in the majority of patients through 1999. In 2000, cannulation of the right axillary artery became the standard approach. Until 1995, crystalloid cardioplegia solution was infused directly into the coronary ostia, and topical cooling was also used. Later in the series, intermittent cold antegrade cardioplegia was used, and topical cooling abandoned. The temperature was lowered to 20°C during the proximal aortic reconstruction, and then to 12° to 15°C before circulatory arrest for performance of an open distal anastomosis. A vent was placed in the left ventricle to allow decompression of the heart.
After sizing the aortic annulus, a series of pledgeted mattress sutures was placed from the ventricular to the aortic aspect of the annulus for fixation of a heterograft in an epiannular position. Annular stitches engaged both the valve-sewing ring and the vascular graft to facilitate subsequent replacement of the heterograft valve within the conduit. For a prosthetic valve, the sutures were placed from the aortic to the ventricular aspect of the annulus to effect intraannular fixation of the valve. A composite of a St. Jude valve (St. Jude Medical, St. Paul, MN) and a Hemashield graft (Boston Scientific Corp, Wayne, NJ) was used in cases for which a mechanical valve was indicated (Fig 1). In cases in which a biologic valve was chosen, a homemade composite, consisting of a pericardial (Edwards Lifesciences LLC, Irvine, CA) or porcine valve (Medtronic Inc, Minneapolis, MN) and a Hemashield graft, was used (Fig 1). After the proximal suture line was completed, the diseased aortic segment was resected, and buttons including the coronary ostia were excised. The first centimeter of the coronary arteries was mobilized, and the buttons were implanted in an end-to-side fashion with a running suture incorporating a polytetrafluoroethylene (Teflon) felt strip to reinforce the adventitial surface of the coronary arteries (Fig 1).
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Choice of Valve: Biologic Versus Mechanical
Patients older than 65 years of age and those with contraindications to anticoagulation were generally advised to opt for a biologic valve. Patients younger than 55 years of age usually received a mechanical valve unless a contraindication to anticoagulation was present, although the patient’s preference was respected, with some active younger patients preferring a biologic valve despite their understanding that this would lead eventually to a second operation. In cases in which a second operation was anticipated, the pericardium was closed primarily, or with a Gore-Tex (W. L. Gore & Assoc, Flagstaff, AZ) membrane. In recent years, there has been a tendency toward more biologic valve implantations in younger patients, and valve-sparing operations have also become an option under some circumstances.
Patients with biologic valves were advised to take 325 mg daily of aspirin for the first 3 months, and thereafter were discharged for follow-up to their referring cardiologists or internists. Although no sodium warfarin (Coumadin) was mandated by the surgeons, some of the patients were placed on chronic anticoagulation for other indications during follow-up. All patients with a prosthetic valve were treated with Coumadin, with a target international normalized ratio of 2.0 to 2.5.
Follow-Up
A retrospective review of these patients was conducted using data gathered contemporaneously in our departmental database and supplemented from patient records. Follow-up information was gathered from yearly routine computed tomographic scans (with contrast) of the aorta, direct telephone interview of the patient or a close relative, and contact with the referring physician.
Statistical Methods
Data were entered in an Excel (Microsoft Corp, Redmond, WA) spreadsheet and transferred to a SAS (SAS Institute, Cary, NC) file for data description and analysis. Characteristics are described as percentages or as means and standard deviations. Kaplan–Meier life tables were calculated for the risk of death.
Follow-up time for survival was measured from the date of the operation to the earlier of the date of death or of last contact alive. Long-term adverse events included death and morbid conditions as defined by Edmunds and coworkers [9]: stroke, hemorrhage requiring transfusion or hospitalization, peripheral embolization, and endocarditis.
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Results |
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Short-Term Outcome
Adverse outcome (AO) was defined as postoperative death or stroke within 30 days after operation; postoperative deaths occurring before discharge from the hospital were included as AO even if hospital stay extended beyond 30 days. Ten patients had an AO (4.9%). Four patients (1.9%) had permanent strokes.
Only 1 patient (0.5%) had temporary neurologic dysfunction as defined by Ergin and associates [7]. As detailed in Table 3, 17 patients had cardiac complications (8%). Nineteen patients required prolonged ventilation (9%), with an early tracheostomy in 11 patients (5%). Five patients had infectious complications (2.4%). None of the patients required chronic dialysis. The average intensive care unit stay was 2.8 ± 2 days, and the mean hospital stay was 10.5 ± 10.5 days.
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Table 2 details other possible risk factors and their lack of a statistical association with AO. Among these factors were use of a biologic rather than a mechanical valve (7.1% versus 3.7% AO); sex; emergency rather than elective surgery (10% versus 4.3% AO); need for a concomitant procedure (coronary artery bypass grafting, mitral valve replacement, other); presence of coronary artery disease (AO 7.7%, versus 4.2% without coronary artery disease), or need for complete arch replacement. There were only 3 patients with chronic obstructive pulmonary disease.
Long-Term Outcome
Median follow-up time was 5.9 years (1,200 patient-years). No patient required ascending aortic reoperation during follow-up.
Three patients had distal aortic surgery. One patient, who had emergent root and hemiarch replacement for type A dissection, was followed for a residual tear in the arch and required arch replacement for expanding intramural hematoma and progressive arch dilation 6 years later. Another patient had emergent root and arch replacement for acute type A dissection with placement of an elephant trunk; he underwent thoracoabdominal replacement using the elephant trunk 3 years after his primary surgery. A third patient underwent planned correction of his aortic coarctation in a second procedure during follow-up.
Complete follow-up was obtained in 88% of patients. The linearized stroke rate was 0.7 per 100 patient-years (n = 7). Three patients who suffered a stroke had a biologic valve graft; 4 had a mechanical composite valve graft and were receiving oral anticoagulation at the time of the event. There were 0.5 hemorrhages per 100 patient-years (n = 5) requiring transfusion or hospitalization. Four patients who experienced hemorrhage had a mechanical and 1 had a biologic composite valve graft; all were receiving oral anticoagulation at the time of the event. There were no instances of peripheral embolization.
The cause of death was known in 69% of cases (11 of 16). Two patients had severe infection, most likely endocarditis, and 2 had sudden death (1 probably because of aortic rupture). Two patients died of heart disease: 1 of ischemic cardiomyopathy, and another after coronary artery bypass graft surgery at another institution. Two patients died of renal failure, and 1 each of gastric cancer, massive stroke, complex chronic obstructive pulmonary disease, and Creutzfeldt-Jakob disease.
Long-term survival compared with the sex- and age-matched US population, and also compared with a series of aortic valve replacements in BAV patients, is shown in Figure 3.
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At the time of aortic root replacement, only the patient mentioned above had a significantly dilated diameter of the distal aorta. The median aortic arch diameter was 3.6 cm (range, 2.4 to 5.1 cm), the descending thoracic aorta had a median diameter of 3.4 cm (range, 2.4 to 5.6 cm), and the abdominal aorta median diameter was 2.8 cm (range, 1.8 to 4.8 cm). Only the 3 patients previously described—one with an arch tear, another with an elephant trunk at the time of initial surgery, and a third with coarctation—underwent distal surgery after the Bentall procedure.
One hundred forty-two patients (69%) had digitized computed tomographic scan follow-up of the aortic arch, descending thoracic aorta, and abdominal aorta with a minimum of two scans at least 6 months apart. The median follow-up time was 5.3 years (range, 0.5 to 15.3 years). There were no significant increases in the median growth rates in any portion of the distal aorta during follow-up: the median growth rate in the aortic arch during follow-up was 0.00 mm/year (range, –0.4 to +1.2 mm/year), in the descending thoracic aorta it was 0.03 mm/year (range, –0.3 to +0.7 mm/year), and in the abdominal aorta it was 0.02 mm/year (range, –0.2 to +0.7 mm/year).
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Comment |
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For decades, BAV replacement was accepted as the appropriate strategy to treat and prevent ascending aortic or root dilatation, which was thought to occur as a consequence of the hemodynamic burden of aortic valve dysfunction, particularly of aortic regurgitation. More recently, it has been recognized that a predisposition to aortic root enlargement occurs in patients with BAV irrespective of altered valve function [16]. Yasuda and associates [17] found that BAV patients—in contrast to patients with tricuspid aortic valves—showed progressive dilation of the aorta even after BAV replacement.
The aorta of a patient with a BAV contains less elastic tissue than the aorta associated with a normal (tricuspid) aortic valve [18]: specifically, the aortic media of patients with BAV is characterized by thinner elastic lamellae and a greater distance between them [19]. Currently, it is estimated that 5% of individuals with BAV will experience aortic dissection. In 1984, of 161 necropsy cases of aortic dissection, Larson and Edwards [15] reported an incidence of Stanford type A aortic dissections in patients with congenital BAV 11 times higher (5.8%, 17 of 293 patients) than in a population with a normal tricuspid aortic valve at necropsy (0.5%, 107 of 21,105 patients; p < 0.001). In contrast, the incidence for BAV patients of type B dissection (0.3%, 1 of 293 patients) was not significantly different from normal. This suggests that the intrinsic problem within the aortic wall in patients with BAV may be limited to the aortic root or ascending aorta [15], and therefore that root replacement may eliminate the risk of rupture and dissection in the majority of patients with BAV.
Several clinical studies have confirmed that the risk of aortic dissection increases progressively as the diameter of the aorta increases. But the implication of these observations—the need to address the risk of rupture or dissection of the ascending aorta in patients with BAV by early replacement of the ascending aorta or root—has not been widely accepted. In 2002, Russo and associates [20] reported on 100 consecutive patients with tricuspid and bicuspid (n = 50) aortic valves who had undergone valve replacement without repair or replacement of the ascending aorta, despite mean diameters in the ascending aorta of 4.8 cm (with some as high as 6 cm). A significantly higher rate of acute aortic dissection and sudden death occurred in the patients with BAV.
In the current series, only 2% of patients (n = 4) required concomitant arch replacement, suggesting that the aneurysm was most frequently confined to the ascending aorta. Furthermore, only three operations in the distal aorta were required during follow-up, all with disease already present at the time of the initial operation. Because the long-term survival in this series is the same as that of age-matched normal control subjects, this suggests that BAV patients do not have a predisposition to aneurysm or dissection of the downstream aorta.
To explore this possibility further, we examined our patient cohort using the digitized computed tomographic scans obtained during routine follow-up. We confirmed that the distal aorta is not affected by progressive dilatation: mean diameters at the time of aortic root replacement were normal in all parts of the distal aorta, and no significant increase in the maximum diameters in the aortic arch, the descending aorta, or the abdominal aorta were seen during a mean follow-up of 5 years after composite valve-graft replacement. Thus, within the limits of a retrospective study, there are two lines of evidence suggesting that successful composite replacement of the aortic valve and ascending aorta in patients with BAV eliminates the predisposition to aneurysm formation, and allows patients to experience longevity equivalent to that of a normal age- and sex-matched population.
Yasuda and associates [17] compared the rate of dilation after BAV replacement between patients with aortic regurgitation versus aortic stenosis, and found that the regurgitation-dominant group tended to show more progressive dilation than the stenosis-dominant group. In our series, preoperative aortic stenosis was independently associated with smaller ascending aortic diameters. Nevertheless, aortic root dimensions are higher than the upper normal range in 60% of BAV patients with aortic stenosis [21].
In children and young adults, the Ross procedure has been used for treatment of BAV dysfunction with satisfying short-term results [22], but dilation of the pulmonary autograft (as reported in a population with 81% BAV patients) occurs frequently [23]. In a study of 117 Ross patients, Favaloro and colleagues [24] report that the subset of patients with regurgitant BAV had a significantly greater tendency toward autograft dysfunction than those with stenotic BAV (65% versus 100%; p = 0.004). This finding—more than the fact that BAV stenosis was associated with less-marked ascending aorta dilatation in our study—suggests that patients with stenotic BAV may be genetically less likely to develop aortic root disease than those with regurgitant BAV. In any case, it seems plausible that both the pulmonary root and the ascending aorta suffer from similar intrinsic vessel wall abnormalities in patients with BAV, making the use of the Ross procedure problematic.
Bicuspid aortic valve is one of the major causes of aortic regurgitation [25], which appears to affect predominantly a relatively young population [5] in whom one is reluctant to use a heterograft valve, or burden with anticoagulation. It is not surprising, therefore, that it has been argued that reconstruction of a BAV is not contraindicated in the presence of pliable leaflets, or that BAV repair is, in fact, increasingly considered a reasonable option [26]. But, unfortunately, the reoperation rates reported after BAV repair (>10% at 2 years) are rather disillusioning [26], and long-term results of repair of BAVs have yet to be reported.
In contrast, Schafers and associates [27, 28] report excellent early outcomes in their initial experience with 16 BAV patients (median age, 50 years; range, 35 to 73 years) undergoing valve repair and root remodeling, and Veldtman and coworkers [29] have also had excellent early results with valve-sparing root replacement in 21 BAV patients with ascending aortic aneurysms (median diameter, 55 mm; range, 43 to 65 mm). In young patients with contraindications for mechanical valved conduits, this approach certainly is an option for experienced centers, although long-term durability has yet to be proven equal to that of biologic valved conduits.
Sundt and associates [18], in a series of 45 patients with ascending aortic aneurysm and BAV, compared those who underwent separate valve and graft operations (n = 27) with those who had a composite valve graft (n = 18). There were no significant differences in operative risk, but actuarial survival was superior among patients undergoing composite root replacement as compared with separate valve and supracoronary graft replacement.
Although no consensus on pharmacologic treatment to limit progressive dilatation of the aortic root in patients with BAV has been established, controlling arterial hypertension seems prudent in BAV patients with aortic dilatation. Borger and colleagues [30] suggest an aggressive approach toward concomitant ascending aorta replacement in patients with BAV dysfunction, beginning with diameters of 4.5 cm, but we have a somewhat higher threshold—5.5 cm—in the absence of BAV dysfunction, rapid ascending aortic expansion, or aneurysm-related symptoms. If operative treatment of BAV dysfunction is indicated, however, we agree that preventive replacement of the aortic root should be undertaken even with mild dilatation, 4 to 4.5 cm.
In summary, our intent in this study was to evaluate the effectiveness of the Bentall strategy for managing the aortic root in BAV patients. We have found that operative mortality after the Bentall procedure in BAV patients is comparable with that of aortic valve replacement or repair, but that the Bentall operation is associated with superior long-term survival and a lower rate of aortic reoperation [30, 31]. Although separate valve replacement or repair and ascending aortic replacement may appear technically less challenging than root replacement, this study demonstrates that comparable operative outcomes are achievable with the Bentall procedure, and that long-term survival may be better. Finally, this study suggests that a patient with BAV who survives a Bentall procedure has a low risk of complications, and a normal life expectancy thereafter.
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Discussion |
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With regard to the bicuspid disease, your presentation brings to mind three important issues: when should we replace the valve, when should we replace the aorta, and how much aorta do we need to replace both proximally and distally. So I have got a couple of quick clinical scenarios and two questions.
First of all, what is your approach for a 25-year-old gentleman, who obviously does not want to take Coumadin, as none of them do, who has a 6-cm ascending aorta and a normal valve? The second clinical scenario is a similarly young patient who cannot take Coumadin, who has a severely stenotic valve but a 4-cm ascending aorta?
Third, you obviously come from an institution that has an extensive experience with circulatory arrest, as your senior author essentially invented the procedure years ago; however, in my experience, most bicuspid aneurysms end before the arch and can be replaced without using circulatory arrest. So I was wondering how your group determines which patients require extension into the arch such that circulatory arrest is no mandatory?
And finally, have you performed redos in the patients who have undergone biologic valve graft conduits that you have created? I suspect the way that you have constructed your root, with the valve down at the bottom, it would require a complete root replacement in order to redo it. If you fold the graft and then sew your valve up about a centimeter or two from the end of the graft and then sew the graft to the root leaving the valve about a centimeter up, then you may be able to do a redo AVR (aortic valve replacement) without having to take out the whole root.
That was an outstanding presentation.
DR ETZ: Thank you, Dr Moon. This certainly is a very interesting question: you are right that the center I am from may be unusually experienced in root replacement. If one does not feel comfortable with a root replacement, there is no proof yet that ascending plus valve replacement is an inferior option. It is just that we feel leaving diseased tissue behind is not a perfect solution.
There is one series of Dr Sundt that directly compares root replacement and ascending valve replacement in 45 patients which has shown that root replacements are superior in long-term survival, but that is certainly something which has to be proven in the future.
As far as the two clinical scenarios: a 25-year-old patient with an isolated ascending aneurysm and a perfectly functional valve would certainly be a candidate in whom we could consider just replacing the ascending aorta and putting him on close annual surveillance. If the root is also dilated, as it is in some bicuspid valve patients, a valve sparing root replacement would also be appropriate. In the second patient, we would consider a biologic Bentall the first choice, and a Ross the second.
One of the reasons for our enthusiasm for the biologic Bentall is the ease with which the valve can be replaced. From within the conduit, the valve tissue, and inner layer of cloth are excised, the support (metal or plastic) is lifted out, and the snippets of cloth are trimmed. A biologic or prosthetic valve is then sewn in with three continuous sutures of 2-0 prolene, holding the valve up in the air and taking stitches through the base of the graft and the valve sewing skirt. The valve is then parachuted into place, and the sutures tightened and tied.
With regard to the extent of resections, we carry out an open distal anastomosis at the base of the innominate artery under HCA in all cases. Although this adds to the length of the operation, we are confident that it does not increase the risk. The advantages are: a better quality anastomosis; resection of the clamp site (cannulation is via the axillary artery); removal of distal ascending aorta which does sometimes dilate, and finally a larger graft, which is important in facilitating a subsequent replacement of the valve within it.
DR THORALF SUNDT (Rochester, MN): Since our previous study was brought up, I will tell you that I think that the reason why the survival was superior in the root group rather than the separate valve and graft was that the root replacements were done in healthier patients. So it is a matter of selection bias. I continue to be very concerned about this message that is being sent that we should be doing root replacements on people who do not have dilated roots. Now, you may be able to get away with it at Mount Sinai, but I think most of us find that it is more challenging to do a root replacement and to reimplant coronaries that are in a root that is not enlarged and are not displaced. So I think that we need to be very cautious about doing root replacements instead of just valves or just valve and grafts because of a theoretical concern about the disease in the aortic wall.
DR ETZ: We agree with that. If a patient has severe cardiac disease and a really low ejection fraction, it certainly makes sense to have a shorter cross-clamp time and do a standard replacement.
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