DOI: 10.1016/j.athoracsur.2007.02.017 2007;84:467-472 Ann Thorac Surg

Volkmar Falk and Friedrich W. Mohr Sven Lehmann, Thomas Walther, Jörg Kempfert, Sergey Leontjev, Ardawan Rastan,

Results of a Prospectively Randomized TrialStentless Versus Conventional Xenograft Aortic Valve Replacement: Midterm

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tentless Versus Conventional Xenograft Aorticalve Replacement: Midterm Results of arospectively Randomized Trial

ven Lehmann, MD, Thomas Walther, MD, PhD, Jörg Kempfert, MD,ergey Leontjev, MD, Ardawan Rastan, MD, Volkmar Falk, MD, PhD,nd Friedrich W. Mohr, MD, PhD

epartment of Cardiac Surgery, Heartcenter, University of Leipzig, Leipzig, Germany

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Background. The purpose of this study was to analyzehe 5- to 8-year clinical results after prospectively random-zed stentless versus conventional aortic valve replacement.

Methods. Two hundred twenty-three patients receivedtentless (Freestyle or Toronto, n � 127) or conventionaltented (CE porcine, n � 96) xenograft aortic valveeplacement between March 1996 and March 1999 using arospectively randomized protocol and were dischargedrom the hospital. Patient age at operation was 71.8 � 6.7ears stentless and 74.9 � 4 years stented (p < 0.05). Thereere no significant differences regarding preoperativeorphologic and hemodynamic variables. Aortic annu-

us diameter indices were comparable at 13.5 mm stent-ess and 13.6 mm stented. Follow-up after 6.9 � 0.8 yearss complete for 95.6% of the patients at a total of 1,533atient-years. Analysis of variance, unpaired t test, univar-

ate (�2), and survival analysis (log rank) were performed.Results. Eight-year survival was 78.1% � 3.8% stentless

ersus 66% � 4.9% stented (p � 0.04); mean survival was

7 months stentless versus 88 months stented. At most

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ecent follow-up, New York Heart Association functionallass was 1.6 � 0.6 stentless versus 1.5 � 0.7 stented (p �ot significant); ejection fraction was 61% � 11% versus1% � 8% (p � not significant); transvalvular maximumow velocity was 23 � 9 mm Hg versus 37 � 15 mm Hg

p < 0.01). Thrombembolic events occurred in 2 of 7atients, including 2 of 6 patients suffering major stroke

p � not significant). Most (93%) of the patients wereatisfied with the postoperative course, having a signifi-antly improved quality of life.

Conclusions. Midterm results after xenograft aorticalve replacement are satisfactory. Overall survival isignificantly better after stentless aortic valve replace-ent in this series. However, there was no cause and

ffect relationship between lower transvalvular pressureradient. Fewer thrombembolic events and better sur-ival rates were proven.

(Ann Thorac Surg 2007;84:467–72)

© 2007 by The Society of Thoracic Surgeons

ortic stenosis is the most common acquired heartvalve lesion in Western societies. It is usually

aused by degenerative changes with complex calcifica-ion of the native leaflets and the aortic annulus. Leftentricular hypertrophy (LVH) develops as an adaptationo the increased pressure load. Being an independentardiac risk factor, LVH is associated with a higherncidence of cardiovascular clinical events and death [1].n symptomatic patients or in the presence of severetenosis with significant additional LVH, aortic valveeplacement is indicated [2].

During the past decades, aortic valve replacementAVR) using mechanical valves or conventional stented

ccepted for publication Feb 6, 2007.

ddress correspondence to Dr Walther, Universität Leipzig, Herzzen-

ioprotheses (CSB) has become a routine procedure withow perioperative risk [3–8]. Stentless aortic valves (SAV)ave been used increasingly, with good functional andemodynamic results [8, 9, 14]. In longitudinal studies,arly LVH regression after stentless valve implantationas been demonstrated [8, 10, 11]. Our aim was to analyze

he midterm clinical results of a prospectively random-zed study after stentless versus conventional AVR.

aterial and Methods

rom March 1996 through March 1999, 223 patients withortic valve disease were prospectively evaluated. Thetudy was approved by the local Ethics Committee, andll patients gave informed consent after the study proto-ol was outlined in detail (Table 1).

Patients amenable for bioprosthetic AV implantation

ere randomly assigned to receive an SAV (either Free-

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tyle [Medtronic Corp, Santa Rosa, CA] or Toronto SPVSt. Jude Medical, Minneapolis, MN]), or a CSB (Carpen-ier-Edwards porcine xenograft; Edwards Lifesciences,rvine, CA). Demographic data for the two groups areiven in Figure 1. Differences in group sizes resultedrom cross over due to calcifications of the aortic root,typical coronary artery origin, or other reasons not tonsert a stentless valve. Further evaluation revealed thathe results in the cross-over patients did not differ fromhe total stented xenograft group.

All operations were performed with the use of completer partial median sternotomy and standard extracorporealirculation with hypothermic cardioplegic arrest (Custo-iol HTK solution; Köhler Chemie, Alsbach-Hähnlein,ermany). For further comparison, aortic annulus diam-

ter was measured intraoperatively by use of a standardet of sizers before the new valve was implanted [13].his was performed after excision of the diseased aorticalve and after complete decalcification. Annulus diam-ter was divided by body surface area to obtain thennulus index as baseline measure.Aortic valve implantation was performed according to

tandard techniques, as described previously [14]. All

able 1. Inclusion and Exclusion Criteria

nclusion criteria. Indication for isolated aortic valve replacement. Ability to return to the implant center for follow-up visits. Informed consent. No pregnancyxclusion criteria. Patient aged � 20 and � 80 years. Presence of noncardiac major or progressive disease, with

a life expectancy of less than 12 months. Intravenous drug or alcohol abuser, or both. Active endocarditis. Previous cardiac surgery. Participation in another study. Presence of anuloaortic ectasia, Marfan syndrome,

aneurysmal dilatation of the ascending aorta, Ehlers-Danlos syndrome, cystic media degeneration, or othercondition causing the ascending aorta or aortic annulus tobe irregular in geometry or physiology as seen onpreoperative imaging

. Presence of chronic renal failure

ig 1. Flow chart of all patients suffering aortic valve disease during

ghe period of study inclusion.

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AV were implanted in subcoronary position. For SAVmplantation, single 4-0 Tevdek stitches at the annulusithout pledgets and a continuous 4-0 polypropyline

uture line at the commissures were used. Conventionaltented bioprostheses were implanted in a supra-annularosition with 2-0 Tevdek Teflon (Impra, subsidiary of. R. Bard, Tempe, AZ) armed U stitches (horizontalattress suture).Follow-up consists of annual examinations at our out-

atient clinic and is complete in 95.6%. Mean follow-up is4.2 � 9.6 months (range, 73.8 to 114.2). Total follow-uponsists of 1,533 patient-years. Patients living more than50 km from the hospital (n � 9) were followed byelephone interview; in addition, physical and echocar-iographic examinations were performed by their familyhysicians and transferred to the hospital. All patientsere instructed to contact the hospital immediately in

he event of any unexpected deterioration of healthonditions.

Transthoracic echocardiographic examinations wereerformed preoperatively, before discharge, and at every

ollow-up visit. Multiplane transesophageal echocardiog-aphy was used intraoperatively or whenever additionalnformation besides transthoracic echocardiographic

easurements was required. Cardiac morphology andunction as well as valve hemodynamics were assessedsing standard measurements.Quality of life (QOL) was assessed using a modifica-

ion of the Nottingham Health Questionnaire and theedical Outcomes Study Short-Form 36-Item Ques-

ionnaire (SF-36) [15]. These questionnaires were trans-ated into German; further modification consisted of thenclusion of one possible positive answer in each cate-

able 2. Demographics and Operative Data

SAV CSB p Value

umber 127 96ge (year) 71.8 � 6.7 74.9 � 4 � 0.05emale (%) 50 50 nsody surface area (m2) 1.8 � 0.2 1.8 � 0.2 nsjection fraction (%) 58 � 17 58.6 � 16 nsYHA 2.6 � 0.6 2.6 � 0.6 nsreoperative aorticstenosis (%)

95 95 ns

max (mm Hg) 74.6 � 27.4 77.3 � 24.8 nsiabetes mellitus (%) 32.6 29.0 nsypertension 55.9% 53.0% nsinus rhythm (%) 84.4 84.2 nsbsolute arrhthymia (%) 13.7 14.7 nsacemaker (%) 1.9 1.1 nsortic cross-clamp time(min)

73.8 � 19 53.6 � 13 � 0.05

CC time (min) 110.7 � 31 89.0 � 26.2 � 0.01

SB � conventional stented bioprosthesis; ECC � extracorporealirculation; ns � not significant; NYHA � preoperative New Yorkeart Association; P max � preoperative transvalvulare pressure

radient; SAV � stentless aortic valve.

ory. Different aspects of QOL were analyzed, namely

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obilization, social status, level of activities, emotionaltate, pain, and sleeping disorders. Changes in QOL werevaluated between preoperative and postoperative inter-iews as well as in comparison with the follow-up. Datare given as being dimensionless by intention, with thereoperative data serving as baseline. All patients were

nterviewed preoperatively, before discharge, and at ev-ry follow-up.Valve-related morbidity and mortality were evaluated

ccording to standard guidelines [12]. Absolute and rel-tive frequencies were calculated. Results are given asean � SD. After assessing for normal distribution, the

tudent t test for matched pairs was applied. For mea-urements within groups over time one-way analysis ofariance with Bonferroni correction was used. In addi-ion, univariate (�2) and survival analysis (log rank) wereerformed. A p value less than 0.05 was consideredignificant.

esults

fter decalcification, the annulus diameter was 24.4 � 2.2m SAV and 23.5 � 2 mm CSB. Consequently, the aortic

nnulus index was 13.5 � 1.3 mm SAV and 13.6 � 1.6 mmSB (p � not significant). The mean implanted valveiameter was 25.1 � 2 mm SAV versus 23.3 � 2 mm CSB

p � 0.01). Aortic cross-clamp duration was 73.8 � 19

ig 2. Actuarial overall survival after stentless aortic valve replace-ent (dotted line), stented aortic valve replacement (broken line),

able 3. Survival Rate After Aortic Valve Replacement

5 Years 8 Years

AV 84.0% 78.1%SB 73.1% 66.7%

SB � conventional stented bioprosthesis; SAV � stentless aorticalve.

and the age-matched German normal population (solid line).

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inutes SAV versus 53.6 � 13 minutes CSB (p � 0.01;able 2).Rethoracotomy for bleeding had to be performed in a

otal of 5 patients, 3 after SAV and 2 after CSB implan-ation (p � not significant). One of these patients re-uired prolonged mechanical ventilation. All others hadn uneventful recovery. New-onset AV block was seen in1 SAV and 7 CSB patients postoperatively (p � notignificant). In 7 and 4 patients, regular conduction com-letely restored after a maximum of 5 days as docu-ented by 24-hour electrocardiography. The remaining 4

AV and 3 CSB patients required permanent pacemakermplantation before discharge. These patients hadeavily calcified aortic annuli requiring extensive decal-ification. All in-hospital mortality (n � 4) was nonvalveelated. Patients were discharged from the hospital ac-ording to the German standards. Their demographicata are summarized in Table 2.After stentless valve implantation, permanent antico-

gulation with warfarin sodium was prescribed only ifdditional atrial fibrillation was present. Patients in theonventional group received a 3-month course of warfa-in. At discharge 84% SAV and 79% CSB patients were intable sinus rhythm.

At 8-year follow-up, overall survival was 78.1% � 3.8%AV and 66.7% � 4.9% CSB (p � 0.03). During follow-up,1.9% � 0.04% SAV and 32.3% � 0.05% CSB patientsied. Death occurred after 1 year in 2.5% � 0.01% SAVatients versus 5.4% � 0.02% CSB patients, after 2 to 5ears in 10.9% � 0.03% SAV versus 20.4% � 0.05% CSB,nd after 6 to 8 years in 8.5% � 0.04% SAV versus 6.5% �.05% CSB patients (Table 3 and Fig 2). Causes of deathere heart failure in 5 SAV and 4 CSB patients, andalignancies in 2 SAV and 3 CSB patients. Four SAV

atients and 1 CSB patient died of infections. One CSBatient died of fulminant pulmonary embolism second-

ig 3. Intention-to-treat analysis after stentless aortic valve replace-ent (dotted line) versus stented aortic valve replacement (broken

ine).

ry to bone fracture. Neurologic events were the cause of

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eath in 2 SAV and 7 CSB patients (p � 0.01). This has toe judged in relation to 9 SAV patients and 7 CSBatients having atrial fibrillation at follow-up. All of theseatients as well as another 4 CSB and 4 SAV patients witho cardiac indication had received systemic anticoagula-

ion therapy using warfarin.Overall, causes of death during follow-up were non-

ardiac in 21 SAV patients and in 27 CSB patients. Whenomparing the SAV patients with an age-matched Ger-an control population, there was no significant differ-

nce in mortality after hospital discharge, as indicated inigure 2 [20].Owing to the nonstratified initial randomization pro-

ocol, significant differences in the age of the two groupsccurred. To eliminate age as a potential factor for poorerutcome, additional further analysis was performed bysing an age-matched control group. To reach a similarge at inclusion in the study, younger patients of the SAVroup were omitted from this analysis. Sample size forhis analysis was 111 SAV and 96 CSB, and patient ageas comparable at 74.6 � 3.1 years SAV (p � ns).ortality was significantly different between these

roups. SAV and CSB, at 8 years (p � 0.04, log rank).After randomization, there were 21 cross-over patients

rom SAV to CSB. Further analysis was performed on anntention-to-treat basis. That resulted in 148 SAV and 74SB patients with a similarly significant difference inortality at 8 years of follow-up (p � 0.03, log rank; Fig 3).

ig 4. Actuarial freedom from neurologic event after stentless aorticalve replacement (dotted line) and stented aortic valve replacementbroken line).

able 4. Quality of Life After Aortic Valve Replacement

SAV CSB p Value

etter 85.7% 86.7% nsame 5.4% 5.6% nsorse 8.9% 7.7% ns

SB � conventional stented bioprosthesis; ns � not significant;AV � stentless aortic valve.

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Nine thromboembolic events occurred in both groups.wo of them occurred after SAV and 7 after CSB (p �.01); these events resulted in death of the patients in allases (Fig 4). This adds up to a rate of 0.0059 events peratient year. One patient presented with endocarditis 41onths after SAV implantation; he was successfully

reated using antibiotic therapy. Repeat operation wasequired in 3 patients, 1 after SAV and 2 after CSB. Oneatient in each group presented with new-onset moder-te to severe paravalvular incompetence after 0.5 years; 1ther patient was admitted for prosthetic valve stenosis 8ears after CSB implantation.At follow-up, all patients were clinically improved and

olerated more physical activities at no or only littleyspnea. New York Heart Association functional classas 1.6 � 0.4 SAV and 1.5 � 0.6 CSB (p � not significant).ccording to the specific activity questionnaire, all pa-

ients had improved, to 5.7 � 1 for SAV and to 5.4 � 1 forSB. In all, 86.7% SAV patients and 85.7% CSB patientsoted an improved quality of life as compared with theirreoperative condition (Table 4).Good hemodynamic function was documented on fol-

ow-up echocardiographic measurements. One patientSAV) presented with significant transvalvular incompe-ence. Trivial transvalvular refluxes as caused by thelosing volume and seen with most conventional heartalve prostheses were accepted.Postoperative maximum transvalvular pressure gradi-

nts were lower after stentless valve implantation with-ut reaching significance at that time (22.8 � 9 and 26.7 �2 mm Hg). At 6 months, maximum transvalvular pres-

able 5. Maximum Transvalvular Pressure Gradient atollow-Up After SAV and CSB

maxmm Hg) SAV CSB p Value

aseline 22.8 � 9 (n � 127) 26.7 � 12 (n � 96) nsix months 16.7 � 7 (n � 126)a 20.1 � 7 (n � 96)a 0.01ne year 20.5 � 11 (n � 120) 22.1 � 11 (n � 92) 0.02ight years 23.4 � 9 (n � 92) 36.5 � 15 (n � 61) � 0.01

p � 0.05 at 6 months versus baseline in the same group.

SB � conventional stented bioprosthesis; ns � not significant;max � maximum transvalvular pressure gradient; SAV � stentless

ortic valve.

able 6. Left Ventricular Posterior Wall Diameter atollow-Up After SAV and CSB

LVPWD (mm) SAV CSB p Value

aseline 15.6 � 2 (n � 127) 14.8 � 2 (n � 96) nsix months 11.8 � 3 (n � 126)a 13.2 � 2 (n � 96)a 0.03ne year 12.9 � 3 (n � 120) 15.1 � 5 (n � 92)a 0.02ight years 12.6 � 2 (n � 92) 12.6 � 2 (n � 61)a ns

p � 0.05 versus the time before in the same group.

SB � conventional stented bioprosthesis; LVPWD � left ventricular

osterior wall diameter; ns � not significant; SAV � stentlessortic valve.

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ure gradients were 16.7 � 7.7 mm Hg SAV and 20.1 � 7.3m Hg CSB (p � 0.01). At late follow-up, maximum

ransvalvular pressure gradient was 23.4 � 9.1 mm HgAV and 36.5 � 14.7 mm Hg CSB (p � 0.01). In bothroups, there were significant differences after 6 monthsersus the baseline measurements (Table 5).Calculated cardiac indices were 2.6 � 1 SAV versus 2.8 �L · min�1 · m�2 CSB postoperatively and 3.2 � 1 SAV

ersus 3.0 � 1 L · min�1 · m�2 CSB at follow-up.ostoperative end-diastolic left ventricular posterior walliameter was 15.6 � 2.4 mm SAV versus 14.8 � 2.4 mmSB and postoperative left ventricular mass 207 � 72 gAV and 199 � 72 g CSB. After 6 months, there was aignificant decrease in wall diameter and in left ventric-lar mass between both groups. However, at late follow-p, no significant differences regarding left ventricularall thickness (12.6 � 1.6 SAV and 12.6 � 2 CSB) and left

entricular mass (156 � 47 SAV versus 158 � 47 CSB)ere documented (Tables 6 and 7).

omment

he ideal aortic valve substitute would be simple tomplant, provide a hemodynamic profile identical to aormal native valve with unlimited durability, and havelow thrombogenic potential so that anticoagulants wereot necessary. No such device is available at present.atients requiring aortic valve surgery are being oper-ted on at continuously increasing ages. That is in paral-el with more frequent use of xenografts. With conven-ional xenografts, despite good clinical results, thebstructive nature of a stent is imminent and may have aegative impact on long-term valve performance.Several randomized trails have compared SAV with

SB with different results. Cohen and coworkers [16]ound no significant differences in the effective orificerea, transvalvular gradient, or LVH regression after 12onths in 99 patients. Ali and associates [17] randomly

ssigned 161 patients to implant a stented Carpentier-dwards Perimount or a stentless Prima plus valve

Edwards Life Sciences) and found no difference inransvalvular pressure gradient and LVH regression.oss and associates [18] randomly assigned 40 patients

ged more than 75 years to stented Perimount or atentless Prima plus valves and found a difference inffective orifice area, transvalvular gradients, and LVH

able 7. Left Ventricular Mass From Parasternal M-Modechocardiography Indexed for Body Surface Area

VM (g) SAV CSB p Value

aseline 207 � 72 (n � 127) 199 � 72 (n � 96) nsix months 139 � 41 (n � 126)a 171 � 43 (n � 96)a 0.03ne year 145 � 43 (n � 120) 167 � 41 (n � 92) 0.02ight years 156 � 47 (n � 92) 158 � 47 (n � 61) ns

p � 0.05 versus the time before in the same group.

SB � conventional stented bioprosthesis; LVM � left ventricularass; ns � not significant; SAV � stentless aortic valve.

egression 1 year after implantation. Santini and cowork- d

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rs [19] compared stented (Hancock) to stentless valvesToronto SPV or Biocor; Biocor Industria Brasil), with noignificant differences in maximum transvalvular pres-ure gradients or LVH at 1 year postoperatively. Each ofhese studies were randomized; all were limited byelatively small patients sizes that may have resulted innsufficient power to detect clinically meaningful differ-nces. By comparison, the present study includes a largerumber of patients with longer term follow-up.Left ventricular hypertrophy as present in aortic ste-

osis correlates with overall cardiovascular morbiditynd mortality, especially that caused by congestive heartailure, sudden death, myocardial infarction, and stroke8]. Regression of LVH has been reported after conven-ional stented AVR and after stentless AVR [20]. Never-heless, incomplete regression of LVH was shown to bessociated with decreased survival [8]. Regression ofVH was seen in all patients after AVR. To delineate theotential benefits of stentless in comparison with con-entional xenografts for AVR, we initiated this prospec-ively randomized trial. During early follow-up, im-roved hemodynamic function and regression of LVHas documented in both groups.There are three important hemodynamic findings from

his study. At midterm follow-up, the SAV provides, first,ower transvalvular blood flow velocities with lower trans-alvular pressure gradients; second, a similar level of LVHegression; and third, similarly good LV function in com-arison with conventional stented xenograft implantation.In general, mechanisms of valve deterioration were

elated to leaflet tear, with only 3 cases involving calcifi-ation. The absence of significant calcification may beue to long-term follow-up not being available atresent, but it may also be a reflection of the stentlessalve design or the fixation process, or a combination ofhese factors. Other reports have described aortic regur-itation and structural valve failure caused by progres-ive dilation of the sinotubular junction occurring 5.8 to 7ears after complete subcoronary implantation of theoronto SPV [21, 22]. We did not observe such compli-ations in our present experience.

At echocardiographic follow-up, comparable hemody-amic results with no dilatation of the sinotubular junc-

ion was documented after either Toronto SPV or Free-tyle SAV implantation. In comparison with the seriesrom David, we included older patients in the presenttudy. Maybe patient age, perhaps together with differ-nces in aortic wall calcification or a change in extracel-ular matrix composition, is a potential factor for theccurrence of late dilatation of the sinotubular junction.In this study, after SAV implantation, the reoperation

ate was 1 after Freestyle AVR and 0 after Toronto SPVmplantation. Owing to these low event rates at 8 years,e cannot draw any definitive conclusions at the present

ime. Longer follow-up is required.Hemodynamic results were in favor of stentless valves.

his finding can be easily explained by the larger effec-ive orifice areas resulting from the lack of an obstructingtent and larger valve size selection at a given annulus

iameter. From an echocardiographic perspective, stent-

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ess valves resemble native aortic valve function and cane considered close to an ideal artificial heart valve.aravalvular leakage was not a major issue in this series.here were no relevant differences between the tworoups in overall hospital outcome. Intraoperative aorticross-clamp time was longer in the stentless group, buthe overall duration was acceptable because it did notesult in any excess morbidity.

The overall mortality was acceptable when consideringatient age and comorbidities. During the follow-uperiod of 6 to 9 years, 21.9% of the patients after SAV and3.3% of the patients after CSB died of different—mostlyonvalve-related—causes. There was no difference inurvival between the SAV group and an age-matchederman population [23]. However, there was a signifi-

ant difference in survival after CSB and the age-matchederman population (Fig 2) [23].Although there was no difference in atrial fibrillation

nd anticoagulation therapy between the two groups, thencidence of neurologic events was higher in the CSBroup. At most recent echocardiographic examinations inhose patients, normal valve function had been docu-

ented, and there was no evidence for intracardiachrombus formation.

In summary, a good clinical outcome with acceptableurvival was documented at medium-term follow-upfter randomized stentless versus conventional xenograftVR. We did not observe any valve-related mortality as

ar as the information obtained from the family physi-ians is concerned. The patients perceived an improveduality of life after AVR; however, no cause and effectelationship was found with lower transvalvular pressureradient. Fewer thrombembolic events and better sur-ival were proved by this study.

eferences

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DOI: 10.1016/j.athoracsur.2007.02.017 2007;84:467-472 Ann Thorac Surg

Volkmar Falk and Friedrich W. Mohr Sven Lehmann, Thomas Walther, Jörg Kempfert, Sergey Leontjev, Ardawan Rastan,

Results of a Prospectively Randomized TrialStentless Versus Conventional Xenograft Aortic Valve Replacement: Midterm

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