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Ann Thorac Surg 2001;71:601-608
© 2001 The Society of Thoracic Surgeons
a Department of Thoracic Surgery, Leiden University Medical Center, Leiden, The Netherlands
b Department of Cardiac Surgery, Center Hospitalier Regional, Lille, France
c Department of Cardiology, Catharina Hospital, Eindhoven, The Netherlands
d Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands
Address reprint requests to Dr Kappetein, Department of Cardio-Thoracic Surgery, Thoraxcenter, University Hospital Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands
e-mail: kappetein{at}thch.azr.nl
Presented at the Thirty-sixth Annual Meeting of The Society of Thoracic Surgeons, Fort Lauderdale, FL, Jan 31–Feb 2, 2000.
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Abstract |
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 TopFootnotes Abstract IntroductionMaterial and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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Methods. A total of 280 patients were operated on from June 1993 to July 1999 as part of a multicenter investigation. Factors influencing hospital mortality and long-term survival were assessed by logistic regression and Cox proportional hazards analysis. Patients were evaluated postoperatively at discharge, at 3 to 6 months, and yearly by clinical examination and color flow Doppler echocardiography.
Results. Hospital mortality in this group was relatively high (9.6%). Logistic regression analysis showed that cross-clamp time, age, myocardial infarction, diabetes, left ventricular hypertrophy, coronary artery disease, New York Heart Association class III or IV and female gender were the independent predictive factors. According to the Kaplan-Meier method, the 4-year survival for hospital survivors was 94%. In the multivariate Cox proportional hazard analysis, only coronary artery disease proved to be prognostic. During follow-up, 11 patients developed paravalvular leakage due to prosthetic dehiscence at the side of the noncoronary cusp. Performance of the prosthesis as assessed by echocardiography was excellent. Mean gradient decreased significantly between discharge and follow-up at 3 to 6 months. At 1-year follow-up trivial regurgitation was found in 6 patients (3%) and mild regurgitation in 4 (2%). Regurgitation did not increase with time. The effective orifice area increased significantly from discharge to follow-up at 3 to 6 months.
Conclusions. Hospital mortality after implantation of a stentless bioprosthesis was higher compared to conventional prosthesis. A high incidence of prosthesis dehiscence at the proximal suture line was found, which was probably due to technique. Hemodynamic performance up to 3 years showed low transvalvular gradients. There is echocardiographic evidence for reduction of left ventricular hypertrophy and improvement of left ventricular function.
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Introduction |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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The Freestyle stentless bioprosthesis is a nonstented bioprosthesis with a new antimineralization process and a new tissue fixation technique. The prosthesis can be inserted by the subcoronary, root inclusion, and total root techniques. In the present study we prospectively evaluated the hemodynamic performance of the Freestyle valve and the clinical outcome of implantation in 280 patients.
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Material and methods |
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All patients were followed up prospectively with serial echocardiography, which was performed preoperatively, at discharge, at 3 to 6 months, at 1 year, and annually thereafter. Details of echocardiographic measurements have been previously described [6]. In summary, echocardiography was performed according to the guidelines of by the American Society of Echocardiography. All echocardiography was performed by the same physicians on the same echocardiographic equipment at the respective centers. The highest peak aortic flow velocity across the Freestyle prosthesis was measured with the continuous wave Doppler technique. Doppler measurements of at least three cardiac cycles were averaged. Aortic valve mean gradient was calculated according to the equation p = 4(Vao2– Vlvot2) (p = pressure gradient [in mm Hg], Vao = aortic valve velocity, and Vlvot = velocity over the LVOT). Aortic valve peak gradient was calculated as p = 4 Vao2. The effective orifice area of the Freestyle prosthesis was calculated with the continuity equation. Assessment of aortic regurgitation was done with color flow imaging and continuous flow Doppler imaging. Grading of aortic insufficiency was done according to the criteria used by Perry and colleages [7]. Left ventricular mass was calculated with M-mode measurements of wall thickness and left ventricular end-diastolic diameter. The effective orifice area (EOA) of the aortic valve was calculated by the continuity equation, and the mean transvalvular gradient at rest was derived from the simplified Bernoulli equation accounting for the flow velocity across the left ventricular outflow tract. Preoperative patient characteristics are summarized in Table 1.
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In the root-inclusion technique the aorta was also opened with a transverse incision. A quadrangular portion of the porcine aortic sinus was excised to remove the porcine coronary artery for both the left and right coronary arteries. Inflow sutures were applied to the aortic annulus so as to maintain the porcine inflow in a single plane. Three running sutures of Prolene were used (one per cusp). Sutures were used to attach the porcine graft to the native aortic wall at the level of the commissures to guarantee the spatial orientation of the valve commissures. A double-arm polypropylene suture was used to attach the edges of the coronary ostia to the native aortic wall. A 4-0 polypropylene suture was used to suture the outflow portion of the graft to the crest of the native aorta. In the total root replacement the aorta was also transected above the sinotubular ridge. Both coronary ostia were mobilized with buttons of aortic wall. The remaining tissue of the sinus of Valsalva was excised. The inflow anastomosis was accomplished using running sutures of 4-0 polypropylene in a single plane. The coronary buttons were sewn to the corresponding sinus of Valsalva with a continuous suture of 5-0 polypropylene. The distal end of the bioprosthesis was sewn end-to-end to the aorta with a continuous suture of 4-0 polypropylene to complete the root replacement. Intraoperative variables are listed in Table 2.
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Morbid and fatal valve-related events were categorized as structural valve deterioration, nonstructural valve dysfunction, tromboembolism, anticoagulant-related hemorrhage, prosthetic valve endocarditis, reoperation, and valve-related mortality. After stentless valve implantation, permanent anticoagulation with warfarin was prescribed only if additional atrial fibrillation was present. Patients in the conventional group received a 3-month course of warfarin. Because there have been no problems regarding thromboembolic events, this protocol was recently changed. Currently no patient receives systemic anticoagulation therapy.
Statistical analysis
Continuous variables are expressed as means ± standard deviations. Repeated-measures analysis of variance was used to detect any significant changes in mean transvalvular gradient across the aortic valve prosthesis, EOA, and left ventricular mass index over time.
Logistic regression analysis was used to analyze predictive factors for hospital mortality. Survival was estimated by the Kaplan-Meier method, the variability is indicated by the standard error of the mean. The Cox proportional hazards model was used to examine the impact of covariates on observed late mortality.
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Results |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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A total of 5 patients developed a clinically important, anticoagulant-related bleeding event. One patient had an upper gastrointestinal hemorrhage on postoperative day 12, which resolved with conservative treatment. Another patient required laparotomy for a bleeding ulcer 3 days after surgery. One patient had severe hemoptysis 1 day after surgery, which resolved with conservative treatment. One patient had an upper gastrointestinal hemorrhage 3 months postoperatively and required readmission and medical management. The fifth patient (in whom warfarin therapy erroneously was continued after 3 months) developed a subdural hematoma 10 months postoperatively, which required neurosurgical intervention. Estimated freedom from anticoagulant-related hemorrhage at 1 and 5 years was 98% ± 1%.
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Reoperation was necessary in 12 patients. Eleven patients had a dehiscence of the proximal suture line at the site of the noncoronary cusp. Running sutures of 4-0 Prolene (Ethicon, Inc, Somerville, NJ) were used in 2 of these patients, and 3 separate running sutures of 3-0 or 4-0 Prolene were used in 9 patients. When dehiscence was diagnosed most patients were symptomatic, presenting with dyspnea (n = 8), or collapse (n = 2). Estimated freedom from reoperation for dehiscence was 100% at 1 year, 97% ± 1.4% at 3 years, and 92% ± 3.8% at 5 years. Broken sutures were found in 2 patients at reoperation. Adherence of the prosthetic free wall to the native aortic wall was not found in any patient. In 3 patients the valve was replaced with a Freestyle bioprosthesis, in 4 with another device (stented bioprosthesis or mechanical valve), and in 3 patients refixation of the Freestyle valve took place at the site of dehiscence. In 1 patient who died of myocardial infarction, suture dehiscence was found at autopsy. In this patient signs of endocarditis were found and confirmed by cultures.
During follow-up another 2 patients had positive blood cultures with Staphylococcus epidermidis. Although no vegetations were seen on echocardiography, these patients were empirically treated on the assumption of prosthetic endocarditis. One patient underwent reoperation for a subvalvular fistula to the right atrium.
New-onset AV block was seen in 11 patients postoperatively. In 6 patients, regular conduction was completely restored after a maximum of 10 days. The remaining 5 patients required permanent pacemaker implantation before discharge. Four of these 5 patients had heavily calcified aortic annuli requiring extensive decalcification. At discharge 79% were in stable sinus rhythm. At follow-up all patients were clinically improved, and tolerated more physical activities with little or no dyspnea.
The mean aortic transvalvular gradient and EOA according to valve size and for all patients at discharge, at 6 months, and at yearly intervals up to 3 and 4 years are summarized in Tables 6 and 7, respectively. As shown, mean transvalvular gradient decreased significantly after AVR and was reduced further at 3 to 6 months; thereafter the gradient remained relatively stable. There was also a difference in transvalvular gradient among the three implantation techniques for subcoronary, root-inclusion, and full root technique. The mean gradients were 11.2 ± 6.2, 9.5 ± 6.2, and 6.2 ± 4.4 at 4 weeks (p = 0.007) and were 7.2 ± 4.8, 6.2 ± 5.1, and 4.8 ± 4.1 (p = 0.02) at 3 to 6 months, remaining relatively stable thereafter. Correspondingly there was a significant increase in EOA in the immediate postoperative period and again at 3 to 6 months. At last follow-up, 91% of patients were in NYHA class I or II, with a mean of 1.3 (vs 3.23 ± 0.9 preoperatively, p = 0.001).
Left ventricular mass, indexed to body surface area was 161 ± g/m2 1 month after aortic valve replacement and decreased within 3 to 6 months to 141 ± 59 g/m2 and remained constant thereafter.
At 1 year of follow-up, trivial regurgitation was found in 6 patients (3%) and mild regurgitation in 4 (2%). Regurgitation did not increase with time during follow-up.
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Comment |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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The stentless valve was designed to mimic the hemodynamic performance of the homograft. The firmness of the tissue and the Dacron (C.R. Bard, Haverhill, PA) reinforcement of the suture lines makes the implantation technique for the Freestyle easier compared with the pliable homograft. Postoperative regurgitation seems to be even less than in other reported series of stentless valves and homografts, and is usually less than the normal closing volume observed in mechanical valves [13–15]. The physiologic concept of stentless valves and the excellent midterm performance might lead to performance of these valves equaling that of aortic homografts in long-term follow-up [16].
The 9.6% operative mortality in this series was relatively high compared to that in other series [1, 15, 17]. Logistic regression analysis showed that crossclamp time, age, history of myocardial infarction, diabetes, and female gender were independent predictive factors for hospital mortality. Patients with a concomitant cardiac procedure had a higher crossclamp time, which was also a significant risk factor in the univariate analysis but was lost in the multivariate analysis. Although implantation of the valve is somewhat easier than that of a homograft, implantation of a stentless valve is technically more demanding and needs longer ischemic times compared with traditional stented valves. Especially in patients who have additional risk factors and need additional procedures such as coronary artery bypass grafting or mitral valve repair, ischemic time may become crucial. Other investigators [15, 17, 18] also reported a longer aortic crossclamp time for stentless prostheses, but could not demonstrate an increased mortality compared to that of stented prostheses. However none of these reports performed a logistic regression analysis to analyze risk factors.
The 1- and 5-year actuarial survival rates of 94% and 84% are comparable to the 96% and 80% rates reported by Yun and colleagues [15] for the Freestyle and to the 94% and 87% rates of David and colleagues [18] for the Toronto SPV valve (93% at 5 years). Coronary artery disease was the independent prognostic factor. Age also was not a significant prognostic factor in the univariate analysis. This shows that older patients also benefit from replacement of a diseased aortic valve and restoration of left ventricular function.
The Freestyle bioprosthesis is versatile and can be used for the subcoronary implantation, root inclusion, and full root techniques. Transvalvular gradients were somewhat lower with the root inclusion and full root techniques than with the subcoronary technique.
More consistent maintenance of the sinotubular junction and commissural geometry of the Freestyle valve may be achieved with the root replacement or the inclusion cylinder techniques and might lead to a longer durability [19–21]. The full root and root-inclusion technique are technically more demanding and need longer cross-clamp time. When extensive concomitant procedures must be performed, a subcoronary or even a stented bioprosthesis should be used. In the case of a very small calcified aortic root it seems difficult to apply the root inclusion technique, which therefore should probably be avoided [19]. The high hospital mortality rate of 19.4% for the root technique found by Cartier and colleagues [22] could not be confirmed. Logistic regression analysis failed to demonstrate implantation technique as an independent risk factor.
The incidence of valvular dehiscence shows reoperation rates for dehiscence and periprosthetic leakage similar to those for homograft implants [14, 23]. Endocarditis is one of the most important risk factors for valvular dehiscence but was only suspected to be the cause in 1 patient. Dehiscence was not related to the implantation mode or the surgeon. Most dehiscence’s were seen at the site of the noncoronary sinus. We hypothesized that excessive suture traction took place at this site because blood invaded the space between the native aortic wall and the wall of the prosthesis. Together with the use of running sutures, this could have led to the dehiscence at this site. We abandoned the running technique and now use interrupted nonabsorbable sutures for the inflow suture line [24] No dehiscences have been noted since this change in technique.
There were 3 early and 2 late neurologic events. Severe stroke occurred in 2 patients with known carotid atherosclerotic disease. One patient who had extensive atherosclerotic disease died postoperatively due to occlusion of the mesenteric artery. The number of anticoagulant-related hemorrhages was low (n = 5). Four of these patients were on warfarin. A definitive diagnosis of valve endocarditis could not be documented by echocardiography. In 2 patients positive blood cultures were found, and in 1 patient with valvular dehiscence a positive culture was obtained at autopsy.
In summary, implantation of the Freestyle valve is technically more demanding, but the hemodynamics are comparable to those of homografts or autografts. The incidence of thromboembolic events and endocarditis is low. The high incidence of dehiscence at the proximal suture line is probably due to technique. The question of durability compared with conventional stented bioprostheses remains unanswered. Longer follow-up is mandatory to determine the durability of the Freestyle valve and its potential hemodynamic benefits.
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Acknowledgments |
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Footnotes |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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Discussion |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentAcknowledgmentsDiscussionReferences |
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I would like to congratulate Dr Kappetein on an excellent presentation and thank him for forwarding to me the manuscript well in advance.
He has presented a very nicely analyzed series of Freestyle stentless valves implanted at three Western European centers. Postoperative gradients were admirably low, and decreased even further over time. The majority of patients returned to functional class 1 or 2, and left ventricular mass regressed toward normal.
However, as happens so frequently in cardiac surgery, all these benefits were not achieved without some significant costs. Ischemic times were prolonged over that required for a stented valve, and operative mortality was a rather high 9%. Actuarial 5-year survival was 84%, which is not dissimilar from that achieved by third generation stented valves as reported by Tirone David and others. Whether this purported improved long-term survival with regression of left ventricular mass will indeed prove to be true is still conjectural.
I have three somewhat general questions.
Given the increased complexity of this procedure, with prolonged ischemic times and some additional measures of technical finesse, for which patients are these additional risks warranted? It seems in fact that the patient in whom we would most like to implant this valve, the elderly female patient with the small root, is perhaps the last person that you would like to implant it in because of the necessity of increased ischemic and bypass times.
Along this same line, what has been your experience with these very young patients? Are the curves for freedom from structural deterioration similar to those in older patients?
And finally, you mentioned that two thirds of your late deaths were cardiac related. Was there any evidence that suture lines, especially beneath the right and left coronary ostia, were these suture lines perhaps responsible for any of these late deaths secondary to coronary occlusive disease?
I would like to thank the Society for the privilege of discussing this very elegant manuscript.
DR JOSEPH E. BAVARIA (Philadelphia, PA): I, too, applaud your wonderful paper; 250 cases is a nice series.
Regarding this valve, I am becoming more of a "full root" surgeon as I agree with Francis Robicsek whose motion picture, "AVR, Is It a Half-Operation?" the other night was quite good.
I wanted to ask the author a couple of questions. First, was the morbidity and mortality different when comparing the full root subgroup versus the subcoronary subgroup? And second, were there any proximal suture line dehiscences in the full root group? It seems to me that the full root procedure may be a better procedure with this valve. And in my particular experience, I’ve come to the point where I can do a full root just as fast as I can do the subcoronary implant; the cross-clamp times are similar.
Thank you very much. The information in this paper was very important.
DR KAPPETEIN: I thank Dr Mitchell and Dr Bavaria for their questions.
The complexity of the procedure is really an issue. What we have shown is that cross-clamp time is longer than in a stented bioprosthesis, and that there are several risk factors that make it more likely that people could die from this operation.
In our institution we perform about 90 valve replacements per year, and about 25 of these are stentless valves. The stentless valves are implanted by only three surgeons who also have a large experience in implanting homografts. So thereby we try to combine these patients under three specific surgeons who go through the learning curve one time.
The implantation technique used was the root inclusion, the full root, and the subcoronary technique. We did not see any difference. We saw a difference in cross-clamp time for the root inclusion technique: it was much longer, and for the subcoronary technique and the root technique it was shorter. So if you have to choose a technique in a patient who has additional risk factors, you should prefer the subcoronary technique. Especially in the female patient with a small aortic size, one should weigh the risks of implanting the freestyle valve versus a stented bioprosthesis. In an elderly patient, from about 80 years, you can debate if she will benefit from implanting a stentless valve, because a stentless valve will perform better in the long-term survival and not in the short-term.
What about suture lines? We did not see any dehiscence of the suture line in the full root technique. We only saw it in the root inclusion technique and in the subcoronary implantation technique.
There was a difference in gradients among the three techniques. The subcoronary technique showed a little bit higher mean transfer of the gradient compared to the root inclusion and the root technique, but there was no difference in morbidity or mortality among these three techniques.
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References |
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