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Midterm Outcomes and Quality of Life of Aortic Root Replacement: Mechanical vs Biological Conduits
Canadian Journal of Cardiology 27 (2011) 262.e15–262.e20 www.onlinecjc.ca
Clinical Research
Midterm Outcomes and Quality of Life of Aortic Root Replacement: Mechanical vs Biological Conduits Eric J. Lehr, MD, PhD,a Peter Z. T. Wang, MD,b Antigone Oreopoulos, MScPT, PhD,b Hussein Kanji, MD,b Colleen Norris, PhD,b and Roderick MacArthur, MDb a
From the Division of Cardiac Surgery, The University of Maryland School of Medicine, Baltimore, MD, USA b
Division of Cardiac Surgery, The University of Alberta, Edmonton, Alberta, Canada
ABSTRACT
RÉSUMÉ
Background: Aortic root replacement is a complex operation for severe aortic root pathology such as aneurysms and dissections with concomitant aortic valve disease. Biological and mechanical valve conduits are available. Methods: Early and midterm results were analyzed in patients undergoing aortic root replacement. From January 1, 1998, to May 31, 2007, 144 patients underwent aortic root replacement (Bentall procedures) with either a mechanical (n ⫽ 51) or a biological (n ⫽ 93) valve conduit. Cox proportional hazard analysis was used to determine whether valve type was an independent predictor of all-cause mortality, and analysis of covariance was used to compare general and disease-specific health-related quality-of-life scores. Results: Operative mortality was 2.1%. Median follow-up time was 40 months; 1- and 5-year survival rates for the mechanical group were 96.0% and 89.0%, respectively, vs 93.0% and 84.0% for the biological group. Valve type was not predictive of all-cause mortality, and valve-related complications were not significantly different between groups. At follow-up, 31.5% of patients in the biological group were on anticoagulant. General and disease-specific healthrelated quality-of-life scores were not significantly different between groups.
Introduction : Le remplacement de la racine aortique est une opération complexe dans les pathologies sévères de la racine aortique comme les anévrismes et les dissections aortiques concomitantes. Des conduits de valves biologiques et mécaniques sont disponibles. Méthodes : Des résultats précoces et à moyen terme étaient analysés chez les patients subissant un remplacement de la racine aortique. Du 1er janvier 1998 au 31 mai 2007, 144 patients ont subi un remplacement de la racine aortique (opérations de Bentall) soit avec un conduit de valve mécanique (n ⫽ 51) ou un conduit de valve biologique (n ⫽ 93). Le modèle des risques proportionnels de Cox était utilisé pour déterminer si le type de valve était un indicateur indépendant de toutes les causes de mortalité, et l’analyse de la covariance était utilisée pour comparer les scores de la qualité de vie liée à la santé, généraux et spécifiques, à la maladie. Résultats : La mortalité opératoire était de 2,1 %. Le temps médian de suivi était de 40 mois; le taux de survie à 1 an et à 5 ans pour le groupe portant des valves mécaniques était de 96,0 % et 89,0 %, respectivement, versus 93,0 % et 84,0 % pour le groupe portant des valves biologiques. Le type de valve n’était pas un indicateur de toutes les causes de mortalité, et les complications associées à la valve n’étaient pas significativement différentes entre les groupes. Durant le
Aortic root pathologies involving the aortic valve and ascending aorta in adults predominantly include aortic aneurysms and type A dissections, having a yearly incidence of 10.4 and 2 per 100,000, respectively.1 Replacement of the aortic root and ascending aorta is usually the treatment of choice to prevent progressive dilation, aortic insufficiency, rupture, and death. Composite mechanical valve conduits2,3 are traditionally used in replacement of the aortic root and ascending aorta but expose patients to the risks of thrombo-
embolism and anticoagulation. Biological valve conduits, including stented,4 stentless,5 allograft, and autograft, are available and avoid the risks of thromboembolism and anticoagulation. In aortic valve replacement, stentless biological valves may provide superior coronary perfusion and hemodynamics and lower myocardial oxygen demand than their mechanical counterparts do.6 Although the choice of prosthesis in standard aortic valve replacement has been well studied, evidence guiding the decision of which prosthesis to use in aortic root replacement is less established. Stentless valve conduits have been shown to have good long-term durability,7 but health-related quality-of-life (HRQOL) outcomes in patients receiving mechanical (MECH) vs biological (BIO) valve conduits have not been well studied.
Received for publication February 11, 2010. Accepted May 5, 2010. Dr Corresponding author: Dr Roderick MacArthur, 3H2.17 Walter Mackenzie Centre, 8440 112th Street, Edmonton, Alberta T6G 2B7, Canada. E-mail: [email protected] See page 262.e20 for disclosure information.
0828-282X/$ – see front matter © 2011 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.cjca.2010.12.034
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Canadian Journal of Cardiology Volume 27 2011
Conclusions: Aortic root replacement with either mechanical or biological valved conduits is a safe procedure. Morbidity, mortality, and adverse quality of life were not associated with the type of valve conduit. Further studies are required to assess long-term durability of biological valve conduits used for aortic root replacement.
suivi, 31,5 % des patients du groupe portant des valves biologiques prenaient un anticoagulant. Les scores de la qualité de vie liée à la santé, généraux et spécifiques, à la maladie n’étaient pas significativement différents entre les groupes. Conclusions : Le remplacement de la racine aortique tant avec des conduits de valves mécaniques qu’avec des conduits de valves biologiques est une procédure sécuritaire. La morbidité, la mortalité et une qualité de vie médiocre n’étaient pas associées au type de conduit de valve utilisé. D’autres études sont requises pour évaluer la durabilité à long terme des conduits de valves biologiques utilisés pour le remplacement de la racine aortique.
Methods
ease. Four domains were measured: anginal frequency, physical limitation, treatment satisfaction, and disease perception. SAQ scores range from 0 to 100, and higher scores indicate fewer symptoms and better quality of life.10 The HADS is a 14-item questionnaire measuring depression and anxiety. Scores range from 0 to 21 for both anxiety and depression, with a score of 11 or higher indicating a mood disorder and a score of 8 to 10 suggesting a mood disorder.11 Postoperative complications such as stroke, bleeding, reoperation, and endocarditis were verified by telephone interview. Definitions for postoperative complications followed Society of Thoracic Surgeons and American Association for Thoracic Surgery guidelines.
Patient population Data were obtained from the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) registry and patient medical records. The registry is a population-based database that prospectively captures all cardiac catheterizations performed in the province of Alberta, Canada (population ⬃ 3.3 million), since 1995. Details of the database and methods of data collection have been previously described.8 All patients undergoing aortic root replacement from January 1, 1998, to May 31, 2007, were included in this study. Patients who had simple aortic valve replacement, stentless valve replacement without coronary reimplantation, and Ross procedures were excluded. Approval for this study was granted by the University of Alberta Health Research Ethics Board. Operative technique The operative technique used for aortic root replacement with either a mechanical1,2 or a biological valve conduit has been previously described.5 Briefly, aortic root replacement was performed using the modified Bentall technique with complete resection of the ascending aorta through a sternotomy. Myocardial protection was achieved with retrograde and antegrade cardioplegia during standard hypothermic cardiopulmonary bypass and circulatory arrest as required. The aorta was transected at the sino-tubular junction and the coronary ostia excised with a cuff of aortic wall. The aortic root and valve were then replaced by suture of either a mechanical or a biological conduit onto the annulus with the use of interrupted pledgeted polyester 2-0 suture, the coronary ostia were reimplanted, and the distal aorta anastomosed. All patients received anticoagulation for a minimum of 3 months postoperatively. Follow-up Survival data were obtained by merging records with data from the Alberta Bureau of Vital Statistics. Valve-related morbidity and HRQOL scores were obtained by mailed, self-administered questionnaires. The HRQOL questionnaires included the EuroQoL instrument, the Seattle Angina Questionnaire (SAQ), and the Hospital Anxiety and Depression Scale (HADS). The EuroQoL instrument is a 5-item general questionnaire assessing 5 health domains, mobility, self-care, usual activity, pain and discomfort, and anxiety and depression, from which the “EQ Index” is then calculated, producing a score from 0 to 1.0, with a higher score indicating better quality of life.9 The SAQ is a 19-item health status measure specific to patients with coronary artery dis-
Statistical analysis Patient characteristics, operative variables, and short- and midterm postoperative outcomes were compared by means of the Student t test for continuous variables and the chi-square test or Fisher exact test, as appropriate, for categorical variables. Significance was set at P ⬍ .05. Crude survival was analyzed by the Kaplan-Meier method and the log-rank test. Adjusted survival was analyzed with a Cox proportional hazards model. We chose covariates to enter into the model by selecting variables from the univariate analysis with P ⬍ .05, in addition to age, sex, and valve type. These variables included concurrent coronary artery bypass graft procedure and diabetes mellitus. HRQOL scores were reported as mean ⫾ standard deviation. Analysis of covariance was used to create adjusted scores for the mechanical and biological valve groups. Covariates were chosen on the basis of patient characteristics that were significantly different (P ⬍ .05) between the two groups defined in the section titled Preoperative characteristics, below. These characteristics included age, gender, chronic obstructive pulmonary disease, hyperlipidemia, and presence of coronary artery disease. Statistical analysis was conducted with SPSS software (SPSS for Windows, version 16.0, SPSS Inc, Chicago, IL). Results Preoperative characteristics We studied 144 consecutive patients who underwent aortic root replacement with a Bentall procedure or modified Bentall technique and a mechanical (MECH; n ⫽ 51) or biological (BIO; n ⫽ 93) valve conduit. In the MECH group, 98.0% of patients received a St Jude Medical Masters and 2.0% received a St Jude Medical Regent mechanical valve conduit (St Jude Medical, Inc, St Paul, MN). In the BIO group, 94.6% of the patients received a Medtronic Freestyle biological valve conduit (Medtronic, Inc, Minneapolis, MN). The remaining pa-
Lehr et al. Mechanical vs Biological Valve Conduits
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Table 1. Preoperative patient characteristics
Variables Age Gender (female) Body mass index Hypertension Diabetes mellitus Hyperlipidemia Smoking Prior cardiac surgery Marfan syndrome Infective endocarditis Chronic obstructive pulmonary disease Prior myocardial infarct Prior coronary artery disease Prior stroke Ejection fraction (banded) ⱕ35% 36%-55% ⬎55% Preoperative dialysis Preoperative NYHA class I II III IV
Table 2. Operative details
Mechanical stent (n ⫽ 51)
Biological stent (n ⫽ 93)
P value
47.7 ⫾ 14.1 3 (5.9) 28.0 ⫾ 5.1 28 (54.9) 4 (7.8) 15 (29.4) 19 (37.3) 10 (19.6) 8 (16.0) 2 (3.9)
60.9 ⫾ 13.9 31 (33.3) 27.2 ⫾ 4.9 59 (63.4) 8 (8.6) 45 (48.4) 45 (48.4) 36 (38.7) 5 (5.4) 9 (9.7)
⬍.001 ⬍.001 .347 .374 ⬎.999 .034 .223 .025 .063 .328
4 (7.8) 4 (7.8) 7 (13.7) 1 (2.0)
23 (24.7) 14 (15.1) 34 (36.6) 4 (4.3)
5 (15.2) 20 (60.6) 8 (24.2) 1 (2.0)
12 (15.8) 34 (44.7) 30 (39.5) 0 (0.0)
3 (25.0) 6 (50.0) 2 (16.7) 1 (8.3)
5 (11.6) 14 (32.6) 15 (34.9) 9 (20.9)
.014 .294 .004 .656 .258
.357 .288
Continuous data are reported as mean ⫾ DS; categorical data are presented as number (%). NYHA, New York Heart Association.
tients received a Medtronic Mosaic Porcine (1.1%), Toronto SPV (1.1%; St Jude Medical, Inc, St Paul, MN), CarpentierEdwards porcine xenograft (1.1%; Edward Lifesciences, Irvine, CA), or cryopreserved aortic homograft (2.2%; CryoLife, Inc, Kennesaw, GA). Indications for aortic root replacement included aortic root aneurysm, acute type A aortic dissection, and complicated valvular heart disease. Preoperative patient characteristics are presented in Table 1. Patients in the BIO group were significantly older than the patients in the MECH group (60.9 ⫾ 13.9 years vs 47.7 ⫾ 14.1 years, P ⬍ .001), and the MECH group contained a higher proportion of males (94.1% vs 66.7%, P ⬍ .001). Hyperlipidemia, coronary artery disease, and chronic obstructive pulmonary disease were significantly more common in the BIO group, but there was no significant difference in body mass index or number of patients with Marfan syndrome. Operative details Operative details are summarized in Table 2. Cardiopulmonary bypass (221 ⫾ 59 vs 198 ⫾ 67 min, P ⫽ .039) and cross-clamp (165 ⫾ 44 vs 141 ⫾ 40 min, P ⫽ .001) times were significantly longer for the BIO group than for the MECH group, but a higher number of patients in the BIO group underwent concomitant procedures. Early complications Early complications are shown in Table 3. Postoperative ventilation time was significantly longer for the BIO group (55 ⫾ 107 vs 22 ⫾ 32 hours, P ⫽ .037). No other significant differences in early postoperative complications were identified between the BIO and MECH groups. One patient (2.0%) in
Variables Indications for surgery Aortic aneurysm Aortic dissection Valvular disease Implanted valve size Surgical incidence First operation Reoperation Aortic explant type Mechanical Biological None Size of annulus Size of sinotubular junction Concurrent coronary artery bypass graft Concurrent mitral replacement Concurrent mitral repair Concurrent tricuspid replacement Concurrent tricuspid repair Cross-clamp time (min) Cardiopulmonary bypass time (min) Circulatory arrest time (min) Cooling temperature (°C) Cooling time (min) Rewarming time (min) Total operative time (min)
Mechanical stent (n ⫽ 51)
Biological stent (n ⫽ 93)
42 (84.0) 12 (23.5) 38 (74.5) 26.6 ⫾ 2.2
60 (65.2) 11 (11.8) 76 (81.7) 25.9 ⫾ 2.5
41 (80.4) 10 (19.6)
61 (65.6) 32 (34.4)
2 (3.9) 4 (7.8) 45 (88.2) 26.9 ⫾ 3.8 45.9 ⫾ 12.0
11 (11.8) 9 (9.7) 73 (78.5) 26.4 ⫾ 5.8 44.1 ⫾ 14.2
6 (11.8) 0 (0.0) 2 (3.9) 0 (0.0) 1 (2.0) 141 ⫾ 40
38 (40.9) 5 (5.4) 11 (11.8) 0 (0.0) 4 (4.3) 165 ⫾ 44
198 ⫾ 67 28.6 ⫾ 15.0 18.1 ⫾ 5.2 68.5 ⫾ 17.1 147.9 ⫾ 71.3 340.5 ⫾ 124.8
221 ⫾ 59 26.9 ⫾ 18.6 19.9 ⫾ 4.5 69.5 ⫾ 21.1 134.0 ⫾ 50.0 365.0 ⫾ 119.4
P value .020 .095 .391 .065 .084 .248
.741 .689 .065 .161 .138 ⬎.999 .656 .001 .039 .779 .321 .880 .570 .257
Continuous data are reported as mean ⫾ SD; categorical data are presented as frequency (%).
the MECH group and 6 patients (6.5%) from the BIO group experienced postop bleeding requiring surgical intervention (P ⫽ not significant). There were 12 (23.5%) patients in the MECH group and 33 (35.5%) patients in the BIO group with postoperative atrial fibrillation (P ⫽ not significant). Survival Overall operative mortality (death within 30 days of surgery) was 2.1% (n ⫽ 3). The operative mortality was 2.2% Table 3. Early postoperative complications
Variables Reoperation for bleeding AICD Pacemaker Inotropic support IABP Myocardial infarction Pneumonia Postoperative ventilation time Pleural effusion Dialysis Stroke Anticoagulation complication Pericardial effusion Atrial fibrillation Mortality
Mechanical stent (n ⫽ 51)
Biological stent (n ⫽ 93)
P value
1 (2.0) 1 (2.0) 1 (2.0) 21 (41.2) 2 (3.9) 1 (2.0) 3 (5.9) 22 ⫾ 32 3 (6.0) 3 (5.9) 0 (0.0) 2 (3.9) 2 (4.0) 12 (23.5) 1 (2.0)
6 (6.5) 1 (1.1) 9 (9.7) 41 (44.1) 5 (5.4) 0 (0.0) 9 (9.7) 55 ⫾ 107 11 (11.8) 5 (5.4) 5 (5.4) 1 (1.1) 5 (5.4) 33 (35.5) 2 (2.2)
.422 ⬎.999 .165 .860 ⬎.999 .354 .540 .037 .379 ⬎.999 .161 .286 ⬎.999 .188 ⬎.999
Continuous data are reported as mean ⫾ SD; categorical data are presented as frequency (%). AICD, automated implantable cardio-defibrillator; IABP, intra-aortic balloon pump.
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Canadian Journal of Cardiology Volume 27 2011 Table 4. Midterm postoperative complications
Variable
Mechanical stent (n ⫽ 32)
Biological stent (n ⫽ 58)
P value
2 (6.3) 1 (3.1) 0 (0.0) 1 (3.1) 1 (3.1) 3 (9.4) 3 (9.4)
4 (6.9) 2 (3.4) 0 (0.0) 2 (3.4) 5 (8.6) 2 (3.4) 5 (8.6)
⬎.999 ⬎.999 ⬎.999 ⬎.999 .416 .343 ⬎.999
Redo Bentall postoperative Nonstructural dysfunction Structural dysfunction Thromboembolic Endocarditis Bleeding events Late postoperative stroke
Continuous data are reported as mean ⫾ SD; categorical data are presented as frequency (%).
Figure 1. Comparison of aortic root replacement with a mechanical (blue) and a biological (purple) valved conduit for all-cause mortality (P ⫽ not significant).
(n ⫽ 2) in the BIO group and 2.0% (n ⫽ 1) in the MECH group, (P ⫽ not significant). All 3 operative deaths occurred in patients who underwent emergent or urgent operations. Median length of follow-up was 40 months. All-cause mortality of the entire cohort was 11.1% (n ⫽ 16) and is shown in Figure 1. There was no significant difference between the groups at 1 year (log-rank test P ⫽ .2). One-year and 5-year survival for the MECH group was 96.0% and 89.0%, respectively, compared with 93.0% and 84.0%, respectively, for the BIO group. Valve-related survival, defined as deaths related to valvular surgery and including cardiovascular mortality (shown in Fig. 2), did not differ between groups (log-rank test P ⫽ 0.9). Cox regression revealed that valve type was not an independent predictor of mortality after adjustment for age, sex, concurrent coronary artery bypass graft procedure, and diabetes (hazard ratio, 0.56; 95% confidence interval, 0.13-2.31). Midterm valve-related complications Median duration of follow-up was 40 months. Midterm complications are shown in Table 4. Two patients (6.3%) from the MECH group and 4 (6.9%) patients from the BIO group required a “redo” aortic root replacement. Complications related to structural valve dysfunction were not noted in any
patient. Three patients experienced thromboembolic complications, 1 patient from the MECH group (3.1%) and 2 patients from the BIO group (3.4%). Endocarditis occurred in 1 patient (3.1%) from the MECH group and 5 patients (8.6%) from the BIO group. There were no significant differences in midterm valve-related complications between groups. Thirty-one patients (96.9%) from the MECH group were receiving anticoagulation therapy (Coumadin) at follow-up; the remaining patient was noncompliant). Twenty-two patients (31.5%) from the BIO group were receiving anticoagulation at follow-up. Health-related quality-of-life analysis The overall response rate for the quality-of-life questionnaire among the 118 surviving patients who were sent questionnaires was 62.7%. Results of the HRQOL analysis are shown in Table 5. No statistically significant differences in adjusted means were found between the MECH and BIO groups in any of the HRQOL scales (SAQ, EuroQoL instrument, and HADS). Discussion Biological valve conduits provide an attractive alternative to mechanical valve conduits for aortic root replacement in paTable 5. Adjusted HRQOL scores HRQOL Measure HADS Anxiety* HADS Depression† SAQ Physical limitation‡ SAQ Anginal Frequency§ SAQ Treatment satisfaction¶ SAQ QOL储 EQ Index**
Figure 2. Comparison of aortic root replacement with a mechanical (blue) and a biological (purple) valved conduit for valve-related mortality (P ⫽ not significant).
Mechanical stent (n ⫽ 24)
Biological stent (n ⫽ 50)
P value
5.3 ⫾ 1.2 2.8 ⫾ 1.8 84.7 ⫾ 5.9 99.9 ⫾ 5.2 93.7 ⫾ 4.1 76.8 ⫾ 11.5 0.92 ⫾ 0.05
4.8 ⫾ 0.6 3.9 ⫾ 1.2 72.2 ⫾ 3.6 90.8 ⫾ 2.6 92.6 ⫾ 2.1 80.7 ⫾ 5.6 0.89 ⫾ 0.03
.7 .6 .1 .2 .8 .8 .6
Continuous data are reported as mean ⫾ SE. EQ, EuroQoL-5D; HADS, Hospital Anxiety and Depression Score; HRQOL, health-related quality of life; QOL, quality of life; SAQ, Seattle Angina Questionnaire. * Adjusted for age, sex, prior percutaneous coronary intervention. † Adjusted for age, sex, type 2 diabetes, chronic obstructive pulmonary disease, congestive heart failure, ejection fraction. ‡ Adjusted for age, sex, hyperlipidema, prior cardiovascular surgery, chronic obstructive pulmonary disease, peripheral vascular disease. § Adjusted for age, sex, hyperlipidemia. ¶ Adjusted for age, sex, hypertension, smoking. 储 Adjusted for age, sex. ** Adjusted for age, sex, type 2 diabetes, peripheral vascular disease, ejection fraction.
Lehr et al. Mechanical vs Biological Valve Conduits
tients who wish to avoid chronic anticoagulation or who otherwise meet criteria for biological aortic valves. The surgical literature has already demonstrated the safety and benefits of biological valve conduits. This study compared the midterm mortality, morbidity, and HRQOL outcomes between aortic root replacements performed with mechanical and biological valve conduits and focused predominantly on biological valves (primarily the Medtronic Freestyle valve) in aortic root replacement, including complex patients admitted with endocarditis, acute dissection, and emergency operation. Patients receiving biological valve conduits were older and had more comorbidities than the mechanical valve conduit group did. In addition, patients receiving biological valve conduits more frequently underwent concomitant coronary artery bypass grafting. There is a positive correlation between older age and concurrent coronary arterial bypass grafting in patients undergoing aortic root replacement.12 Despite these differences, both groups had similar operative mortality, morbidity, and HRQOL outcomes. In the early postoperative period, patients receiving biological valve conduits required a longer period of mechanical ventilation, likely resulting from older age and comorbid factors. In addition, they had an increased rate of reintervention, which was primarily driven by a nearly 10% rate of heart block requiring pacemaker insertion. Further study examining incidence of postoperative heart block with valve conduits is needed. There were no significant differences in valve-related complications at approximately 3 years. Compared with other series, the duration of cardiopulmonary bypass was prolonged, which was attributable to the high rate of redo procedures, long cooling and rewarming times, and concomitant procedures. Despite the prolonged bypass times, the complication rates and mortality remained fairly low. Nearly one-third (31.3%) of patients receiving a biological valve prosthesis were maintained on anticoagulation. Reasons for this finding are unclear. Atrial fibrillation is common and occurs in approximately one-third of patients undergoing aortic valve replacement.13 Our study displayed similar findings. A total of 45 patients (31.3%), 12 patients (23.5%) from the MECH group and 33 patients (35.5%) from the BIO group, experienced postoperative atrial fibrillation after undergoing aortic root replacement. It is not known how many of these patients remained in atrial fibrillation in the long term. It may also be that the patients have other indications for anticoagulation or that their physicians are not comfortable stopping anticoagulation after aortic root surgery. The mortality and valve-related complications in this study were similar to those previously described. The overall operative mortality of 2.1% found in this study was similar to the rate of 1.8% reported by Byrne et al.14 Our 5-year survival rates of 89.0% and 84.0% for the MECH and BIO groups, respectively, were slightly better than the mean 5-year survival rate of 84.6% and 81.2% found in the literature.14,15 Complications related to structural valve dysfunction were not seen in any patient. The HRQOL analysis showed no statistically significant differences in the postoperative quality of life perceived by patients in the BIO or MECH groups. However, there were 5-point differences in SAQ outcome scores, which suggest clinically meaningful differences.10 Patients who received mechanical valves reported fewer physical limitations and less angina frequency at 1 year, compared with the patients who received a
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biological valve. Stadler and colleagues used the Short Form-36 to assess HRQOL outcomes between clinical outcomes of mechanical and biological valve conduits in aortic root replacement16 and were also unable to detect significant differences between groups. On the other hand, Florath et al demonstrated that elderly patients receiving a mechanical valve had a 2-fold increased risk of an impaired emotional reaction.17 The difference in findings could be related to the increased use of deep hypothermic circulatory arrest in their mechanical valve group, which has been identified as a factor contributing to lower HRQOL in aortic surgery, whereas antegrade cerebral perfusion minimizes the adverse effect on HRQOL.18 There was no difference between our groups with respect to duration of hypothermic circulatory arrest. A major strength of our study is that we present quantitative and qualitative data from procedures over a 10-year period from one of the larger cardiac surgery centres in Canada. There are some limitations, however, that should be noted. As with all retrospective studies, observational data provide associative, not causal, evidence, and therefore the possibility of selection bias and residual confounding factors cannot entirely be ruled out. Postoperative echocardiographic data were not available; therefore, subclinical valve dysfunction could not be confirmed. HRQOL scores were collected at 1 year after cardiac catheterization; therefore, the follow-up time between surgery and HRQOL measurement was not uniform for all patients. However, we adjusted for differences in comorbidities and clinical factors likely to affect HRQOL. Approximately onethird of patients did not respond to the HRQOL surveys. Analysis of the nonrespondents showed no difference in survival compared with respondents; however, the nonrespondents required more inotropic support (53% vs 32%, P ⫽ .01) and reoperation due to bleeding (13% vs 3%, P ⫽ .03). Our sample size was relatively small, and a large multicentre trial is required to confirm our results. The choice of valve prosthesis in aortic root replacement includes a number of patient-specific factors, including age, comorbidities, and the risk of bleeding and thromboembolism. Our data suggest that aortic root replacement with biological valve conduits is safe and gives operative and midterm survival and HRQOL outcomes that are similar to those of patients receiving mechanical valve conduits. Thus, within the limits of this retrospective study, our data support the application of current guidelines for aortic valve replacement to the choice of prosthesis for aortic root replacement. Our results also suggest that it is reasonable to consider a biological valve conduit in patients whose lifestyle would be adversely affected by anticoagulation. In addition, stentless xenogenic biological valves have been shown to provide superior coronary perfusion and hemodynamics and lower myocardial oxygen demand than do their mechanical counterparts19,20 and may provide additional benefits over mechanical valve conduits that our study was not designed to examine. Further study of this patient population is required to assess long-term durability of biological valve conduits used for aortic root replacement.
Acknowledgements The authors wish to thank Dawne Colwell for her preparation of the graphics.
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Funding Sources E.J.L. received funding as a Canadian Institutes of Health Research Strategic Training Fellow in Tomorrow’s Research Cardiovascular Health Professionals. Additional funding was received from Edmonton Civic Employees’ Charitable Assistance Fund. Disclosures None of the authors have any potential conflicts of interest to disclose. References 1. Cherry C, DeBord S, Hickey C. The modified Bentall procedure for aortic root replacement. AORN J 2006;1:52-70. 2. Bentall H, De Bono A. A technique for complete replacement of the ascending aorta. Thorax 1968;4:3388-9. 3. Dossche KM, Schepens MA, Morshuis WJ, et al. A 23-year experience with composite valve graft replacement of the aortic root. Ann Thorac Surg 1999;4:1070-7. 4. Hilgenberg AD, Mora BN. Composite aortic root replacement with a bovine pericardial valve conduit. Ann Thorac Surg 2003;4:1338-9. 5. Kon ND, Cordell AR, Adair SM, Dobbins JE, Kitzman DW. Aortic root replacement with the freestyle stentless porcine aortic root bioprosthesis. Ann Thorac Surg 1999;6:1609-15.
Canadian Journal of Cardiology Volume 27 2011 9. The EuroQol Group. Euro-Qol: a new facility for the measurement of health-related quality of life. Health Policy 1990;199208. 10. Spertus JA, Winder JA, Dewhurst TA, et al. Development and evaluation of the Seattle Angina Questionnaire: a new functional status measure for coronary artery disease. J Am Coll Cardiol 1995;2:333-41. 11. Zigmond AS, Snaith RP. The hospital anxiety and depression scale. Acta Psychiatr Scand 1983;6:361-70. 12. Byrne JG, Karavas AN, Leacche M, et al. Impact of concomitant coronary artery bypass grafting on hospital survival after aortic root replacement. Ann Thorac Surg 2005;2:511-6. 13. Almassi GH, Schowalter T, Nicolosi AC, et al. Atrial fibrillation after cardiac surgery: a major morbid event? Ann Surg 1997;4:501-11. 14. Byrne JG, Gudbjartsson T, Karavas AN, et al. Biological vs. mechanical aortic root replacement. Eur J Cardiothorac Surg 2003;3:305-10. 15. Lima B, Hughes GC, Lemaire A, et al. Short-term and intermediate-term outcomes of aortic root replacement with St. Jude mechanical conduits and aortic allografts. Ann Thorac Surg 2006;2:579-85. 16. Stalder M, Staffelbach S, Immer FF, et al. Aortic root replacement does not affect outcome and quality of life. Ann Thorac Surg 2007;3:775-80. 17. Florath I, Albert A, Rosendahl U, et al. Mid term outcome and quality of life after aortic valve replacement in elderly people: mechanical versus stentless biological valves. Heart 2005;8:1023-9.
6. Lim E, Ali A, Theodorou P, et al. Longitudinal study of the profile and predictors of left ventricular mass regression after stentless aortic valve replacement. Ann Thorac Surg 2008;6:2026-9.
18. Immer FF, Lippeck C, Barmettler H, et al. Improvement of quality of life after surgery on the thoracic aorta: effect of antegrade cerebral perfusion and short duration of deep hypothermic circulatory arrest. Circulation 2004;11(suppl 1):II250-5.
7. El Hamamsy I, Clark L, Stevens LM, et al. Late outcomes following freestyle versus homograft aortic root replacement: results from a prospective randomized trial. J Am Coll Cardiol 2010;4:368-76.
19. Bakhtiary F, Abolmaali N, Dzemali O, et al. Impact of mechanical and biological aortic valve replacement on coronary perfusion: a prospective, randomized study. J Heart Valve Dis 2006;1:5-11.
8. Ghali WA, Knudtson ML. Overview of the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease. On behalf of the APPROACH investigators. Can J Cardiol 2000;10:1225-30.
20. Ninet J, Tronc F, Robin J, et al. Mechanical versus biological isolated aortic valvular replacement after the age of 70: equivalent long-term results. Eur J Cardiothorac Surg 1998;1:84-9.
Clinical Research
Midterm Outcomes and Quality of Life of Aortic Root Replacement: Mechanical vs Biological Conduits Eric J. Lehr, MD, PhD,a Peter Z. T. Wang, MD,b Antigone Oreopoulos, MScPT, PhD,b Hussein Kanji, MD,b Colleen Norris, PhD,b and Roderick MacArthur, MDb a
From the Division of Cardiac Surgery, The University of Maryland School of Medicine, Baltimore, MD, USA b
Division of Cardiac Surgery, The University of Alberta, Edmonton, Alberta, Canada
ABSTRACT
RÉSUMÉ
Background: Aortic root replacement is a complex operation for severe aortic root pathology such as aneurysms and dissections with concomitant aortic valve disease. Biological and mechanical valve conduits are available. Methods: Early and midterm results were analyzed in patients undergoing aortic root replacement. From January 1, 1998, to May 31, 2007, 144 patients underwent aortic root replacement (Bentall procedures) with either a mechanical (n ⫽ 51) or a biological (n ⫽ 93) valve conduit. Cox proportional hazard analysis was used to determine whether valve type was an independent predictor of all-cause mortality, and analysis of covariance was used to compare general and disease-specific health-related quality-of-life scores. Results: Operative mortality was 2.1%. Median follow-up time was 40 months; 1- and 5-year survival rates for the mechanical group were 96.0% and 89.0%, respectively, vs 93.0% and 84.0% for the biological group. Valve type was not predictive of all-cause mortality, and valve-related complications were not significantly different between groups. At follow-up, 31.5% of patients in the biological group were on anticoagulant. General and disease-specific healthrelated quality-of-life scores were not significantly different between groups.
Introduction : Le remplacement de la racine aortique est une opération complexe dans les pathologies sévères de la racine aortique comme les anévrismes et les dissections aortiques concomitantes. Des conduits de valves biologiques et mécaniques sont disponibles. Méthodes : Des résultats précoces et à moyen terme étaient analysés chez les patients subissant un remplacement de la racine aortique. Du 1er janvier 1998 au 31 mai 2007, 144 patients ont subi un remplacement de la racine aortique (opérations de Bentall) soit avec un conduit de valve mécanique (n ⫽ 51) ou un conduit de valve biologique (n ⫽ 93). Le modèle des risques proportionnels de Cox était utilisé pour déterminer si le type de valve était un indicateur indépendant de toutes les causes de mortalité, et l’analyse de la covariance était utilisée pour comparer les scores de la qualité de vie liée à la santé, généraux et spécifiques, à la maladie. Résultats : La mortalité opératoire était de 2,1 %. Le temps médian de suivi était de 40 mois; le taux de survie à 1 an et à 5 ans pour le groupe portant des valves mécaniques était de 96,0 % et 89,0 %, respectivement, versus 93,0 % et 84,0 % pour le groupe portant des valves biologiques. Le type de valve n’était pas un indicateur de toutes les causes de mortalité, et les complications associées à la valve n’étaient pas significativement différentes entre les groupes. Durant le
Aortic root pathologies involving the aortic valve and ascending aorta in adults predominantly include aortic aneurysms and type A dissections, having a yearly incidence of 10.4 and 2 per 100,000, respectively.1 Replacement of the aortic root and ascending aorta is usually the treatment of choice to prevent progressive dilation, aortic insufficiency, rupture, and death. Composite mechanical valve conduits2,3 are traditionally used in replacement of the aortic root and ascending aorta but expose patients to the risks of thrombo-
embolism and anticoagulation. Biological valve conduits, including stented,4 stentless,5 allograft, and autograft, are available and avoid the risks of thromboembolism and anticoagulation. In aortic valve replacement, stentless biological valves may provide superior coronary perfusion and hemodynamics and lower myocardial oxygen demand than their mechanical counterparts do.6 Although the choice of prosthesis in standard aortic valve replacement has been well studied, evidence guiding the decision of which prosthesis to use in aortic root replacement is less established. Stentless valve conduits have been shown to have good long-term durability,7 but health-related quality-of-life (HRQOL) outcomes in patients receiving mechanical (MECH) vs biological (BIO) valve conduits have not been well studied.
Received for publication February 11, 2010. Accepted May 5, 2010. Dr Corresponding author: Dr Roderick MacArthur, 3H2.17 Walter Mackenzie Centre, 8440 112th Street, Edmonton, Alberta T6G 2B7, Canada. E-mail: [email protected] See page 262.e20 for disclosure information.
0828-282X/$ – see front matter © 2011 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.cjca.2010.12.034
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Canadian Journal of Cardiology Volume 27 2011
Conclusions: Aortic root replacement with either mechanical or biological valved conduits is a safe procedure. Morbidity, mortality, and adverse quality of life were not associated with the type of valve conduit. Further studies are required to assess long-term durability of biological valve conduits used for aortic root replacement.
suivi, 31,5 % des patients du groupe portant des valves biologiques prenaient un anticoagulant. Les scores de la qualité de vie liée à la santé, généraux et spécifiques, à la maladie n’étaient pas significativement différents entre les groupes. Conclusions : Le remplacement de la racine aortique tant avec des conduits de valves mécaniques qu’avec des conduits de valves biologiques est une procédure sécuritaire. La morbidité, la mortalité et une qualité de vie médiocre n’étaient pas associées au type de conduit de valve utilisé. D’autres études sont requises pour évaluer la durabilité à long terme des conduits de valves biologiques utilisés pour le remplacement de la racine aortique.
Methods
ease. Four domains were measured: anginal frequency, physical limitation, treatment satisfaction, and disease perception. SAQ scores range from 0 to 100, and higher scores indicate fewer symptoms and better quality of life.10 The HADS is a 14-item questionnaire measuring depression and anxiety. Scores range from 0 to 21 for both anxiety and depression, with a score of 11 or higher indicating a mood disorder and a score of 8 to 10 suggesting a mood disorder.11 Postoperative complications such as stroke, bleeding, reoperation, and endocarditis were verified by telephone interview. Definitions for postoperative complications followed Society of Thoracic Surgeons and American Association for Thoracic Surgery guidelines.
Patient population Data were obtained from the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) registry and patient medical records. The registry is a population-based database that prospectively captures all cardiac catheterizations performed in the province of Alberta, Canada (population ⬃ 3.3 million), since 1995. Details of the database and methods of data collection have been previously described.8 All patients undergoing aortic root replacement from January 1, 1998, to May 31, 2007, were included in this study. Patients who had simple aortic valve replacement, stentless valve replacement without coronary reimplantation, and Ross procedures were excluded. Approval for this study was granted by the University of Alberta Health Research Ethics Board. Operative technique The operative technique used for aortic root replacement with either a mechanical1,2 or a biological valve conduit has been previously described.5 Briefly, aortic root replacement was performed using the modified Bentall technique with complete resection of the ascending aorta through a sternotomy. Myocardial protection was achieved with retrograde and antegrade cardioplegia during standard hypothermic cardiopulmonary bypass and circulatory arrest as required. The aorta was transected at the sino-tubular junction and the coronary ostia excised with a cuff of aortic wall. The aortic root and valve were then replaced by suture of either a mechanical or a biological conduit onto the annulus with the use of interrupted pledgeted polyester 2-0 suture, the coronary ostia were reimplanted, and the distal aorta anastomosed. All patients received anticoagulation for a minimum of 3 months postoperatively. Follow-up Survival data were obtained by merging records with data from the Alberta Bureau of Vital Statistics. Valve-related morbidity and HRQOL scores were obtained by mailed, self-administered questionnaires. The HRQOL questionnaires included the EuroQoL instrument, the Seattle Angina Questionnaire (SAQ), and the Hospital Anxiety and Depression Scale (HADS). The EuroQoL instrument is a 5-item general questionnaire assessing 5 health domains, mobility, self-care, usual activity, pain and discomfort, and anxiety and depression, from which the “EQ Index” is then calculated, producing a score from 0 to 1.0, with a higher score indicating better quality of life.9 The SAQ is a 19-item health status measure specific to patients with coronary artery dis-
Statistical analysis Patient characteristics, operative variables, and short- and midterm postoperative outcomes were compared by means of the Student t test for continuous variables and the chi-square test or Fisher exact test, as appropriate, for categorical variables. Significance was set at P ⬍ .05. Crude survival was analyzed by the Kaplan-Meier method and the log-rank test. Adjusted survival was analyzed with a Cox proportional hazards model. We chose covariates to enter into the model by selecting variables from the univariate analysis with P ⬍ .05, in addition to age, sex, and valve type. These variables included concurrent coronary artery bypass graft procedure and diabetes mellitus. HRQOL scores were reported as mean ⫾ standard deviation. Analysis of covariance was used to create adjusted scores for the mechanical and biological valve groups. Covariates were chosen on the basis of patient characteristics that were significantly different (P ⬍ .05) between the two groups defined in the section titled Preoperative characteristics, below. These characteristics included age, gender, chronic obstructive pulmonary disease, hyperlipidemia, and presence of coronary artery disease. Statistical analysis was conducted with SPSS software (SPSS for Windows, version 16.0, SPSS Inc, Chicago, IL). Results Preoperative characteristics We studied 144 consecutive patients who underwent aortic root replacement with a Bentall procedure or modified Bentall technique and a mechanical (MECH; n ⫽ 51) or biological (BIO; n ⫽ 93) valve conduit. In the MECH group, 98.0% of patients received a St Jude Medical Masters and 2.0% received a St Jude Medical Regent mechanical valve conduit (St Jude Medical, Inc, St Paul, MN). In the BIO group, 94.6% of the patients received a Medtronic Freestyle biological valve conduit (Medtronic, Inc, Minneapolis, MN). The remaining pa-
Lehr et al. Mechanical vs Biological Valve Conduits
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Table 1. Preoperative patient characteristics
Variables Age Gender (female) Body mass index Hypertension Diabetes mellitus Hyperlipidemia Smoking Prior cardiac surgery Marfan syndrome Infective endocarditis Chronic obstructive pulmonary disease Prior myocardial infarct Prior coronary artery disease Prior stroke Ejection fraction (banded) ⱕ35% 36%-55% ⬎55% Preoperative dialysis Preoperative NYHA class I II III IV
Table 2. Operative details
Mechanical stent (n ⫽ 51)
Biological stent (n ⫽ 93)
P value
47.7 ⫾ 14.1 3 (5.9) 28.0 ⫾ 5.1 28 (54.9) 4 (7.8) 15 (29.4) 19 (37.3) 10 (19.6) 8 (16.0) 2 (3.9)
60.9 ⫾ 13.9 31 (33.3) 27.2 ⫾ 4.9 59 (63.4) 8 (8.6) 45 (48.4) 45 (48.4) 36 (38.7) 5 (5.4) 9 (9.7)
⬍.001 ⬍.001 .347 .374 ⬎.999 .034 .223 .025 .063 .328
4 (7.8) 4 (7.8) 7 (13.7) 1 (2.0)
23 (24.7) 14 (15.1) 34 (36.6) 4 (4.3)
5 (15.2) 20 (60.6) 8 (24.2) 1 (2.0)
12 (15.8) 34 (44.7) 30 (39.5) 0 (0.0)
3 (25.0) 6 (50.0) 2 (16.7) 1 (8.3)
5 (11.6) 14 (32.6) 15 (34.9) 9 (20.9)
.014 .294 .004 .656 .258
.357 .288
Continuous data are reported as mean ⫾ DS; categorical data are presented as number (%). NYHA, New York Heart Association.
tients received a Medtronic Mosaic Porcine (1.1%), Toronto SPV (1.1%; St Jude Medical, Inc, St Paul, MN), CarpentierEdwards porcine xenograft (1.1%; Edward Lifesciences, Irvine, CA), or cryopreserved aortic homograft (2.2%; CryoLife, Inc, Kennesaw, GA). Indications for aortic root replacement included aortic root aneurysm, acute type A aortic dissection, and complicated valvular heart disease. Preoperative patient characteristics are presented in Table 1. Patients in the BIO group were significantly older than the patients in the MECH group (60.9 ⫾ 13.9 years vs 47.7 ⫾ 14.1 years, P ⬍ .001), and the MECH group contained a higher proportion of males (94.1% vs 66.7%, P ⬍ .001). Hyperlipidemia, coronary artery disease, and chronic obstructive pulmonary disease were significantly more common in the BIO group, but there was no significant difference in body mass index or number of patients with Marfan syndrome. Operative details Operative details are summarized in Table 2. Cardiopulmonary bypass (221 ⫾ 59 vs 198 ⫾ 67 min, P ⫽ .039) and cross-clamp (165 ⫾ 44 vs 141 ⫾ 40 min, P ⫽ .001) times were significantly longer for the BIO group than for the MECH group, but a higher number of patients in the BIO group underwent concomitant procedures. Early complications Early complications are shown in Table 3. Postoperative ventilation time was significantly longer for the BIO group (55 ⫾ 107 vs 22 ⫾ 32 hours, P ⫽ .037). No other significant differences in early postoperative complications were identified between the BIO and MECH groups. One patient (2.0%) in
Variables Indications for surgery Aortic aneurysm Aortic dissection Valvular disease Implanted valve size Surgical incidence First operation Reoperation Aortic explant type Mechanical Biological None Size of annulus Size of sinotubular junction Concurrent coronary artery bypass graft Concurrent mitral replacement Concurrent mitral repair Concurrent tricuspid replacement Concurrent tricuspid repair Cross-clamp time (min) Cardiopulmonary bypass time (min) Circulatory arrest time (min) Cooling temperature (°C) Cooling time (min) Rewarming time (min) Total operative time (min)
Mechanical stent (n ⫽ 51)
Biological stent (n ⫽ 93)
42 (84.0) 12 (23.5) 38 (74.5) 26.6 ⫾ 2.2
60 (65.2) 11 (11.8) 76 (81.7) 25.9 ⫾ 2.5
41 (80.4) 10 (19.6)
61 (65.6) 32 (34.4)
2 (3.9) 4 (7.8) 45 (88.2) 26.9 ⫾ 3.8 45.9 ⫾ 12.0
11 (11.8) 9 (9.7) 73 (78.5) 26.4 ⫾ 5.8 44.1 ⫾ 14.2
6 (11.8) 0 (0.0) 2 (3.9) 0 (0.0) 1 (2.0) 141 ⫾ 40
38 (40.9) 5 (5.4) 11 (11.8) 0 (0.0) 4 (4.3) 165 ⫾ 44
198 ⫾ 67 28.6 ⫾ 15.0 18.1 ⫾ 5.2 68.5 ⫾ 17.1 147.9 ⫾ 71.3 340.5 ⫾ 124.8
221 ⫾ 59 26.9 ⫾ 18.6 19.9 ⫾ 4.5 69.5 ⫾ 21.1 134.0 ⫾ 50.0 365.0 ⫾ 119.4
P value .020 .095 .391 .065 .084 .248
.741 .689 .065 .161 .138 ⬎.999 .656 .001 .039 .779 .321 .880 .570 .257
Continuous data are reported as mean ⫾ SD; categorical data are presented as frequency (%).
the MECH group and 6 patients (6.5%) from the BIO group experienced postop bleeding requiring surgical intervention (P ⫽ not significant). There were 12 (23.5%) patients in the MECH group and 33 (35.5%) patients in the BIO group with postoperative atrial fibrillation (P ⫽ not significant). Survival Overall operative mortality (death within 30 days of surgery) was 2.1% (n ⫽ 3). The operative mortality was 2.2% Table 3. Early postoperative complications
Variables Reoperation for bleeding AICD Pacemaker Inotropic support IABP Myocardial infarction Pneumonia Postoperative ventilation time Pleural effusion Dialysis Stroke Anticoagulation complication Pericardial effusion Atrial fibrillation Mortality
Mechanical stent (n ⫽ 51)
Biological stent (n ⫽ 93)
P value
1 (2.0) 1 (2.0) 1 (2.0) 21 (41.2) 2 (3.9) 1 (2.0) 3 (5.9) 22 ⫾ 32 3 (6.0) 3 (5.9) 0 (0.0) 2 (3.9) 2 (4.0) 12 (23.5) 1 (2.0)
6 (6.5) 1 (1.1) 9 (9.7) 41 (44.1) 5 (5.4) 0 (0.0) 9 (9.7) 55 ⫾ 107 11 (11.8) 5 (5.4) 5 (5.4) 1 (1.1) 5 (5.4) 33 (35.5) 2 (2.2)
.422 ⬎.999 .165 .860 ⬎.999 .354 .540 .037 .379 ⬎.999 .161 .286 ⬎.999 .188 ⬎.999
Continuous data are reported as mean ⫾ SD; categorical data are presented as frequency (%). AICD, automated implantable cardio-defibrillator; IABP, intra-aortic balloon pump.
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Canadian Journal of Cardiology Volume 27 2011 Table 4. Midterm postoperative complications
Variable
Mechanical stent (n ⫽ 32)
Biological stent (n ⫽ 58)
P value
2 (6.3) 1 (3.1) 0 (0.0) 1 (3.1) 1 (3.1) 3 (9.4) 3 (9.4)
4 (6.9) 2 (3.4) 0 (0.0) 2 (3.4) 5 (8.6) 2 (3.4) 5 (8.6)
⬎.999 ⬎.999 ⬎.999 ⬎.999 .416 .343 ⬎.999
Redo Bentall postoperative Nonstructural dysfunction Structural dysfunction Thromboembolic Endocarditis Bleeding events Late postoperative stroke
Continuous data are reported as mean ⫾ SD; categorical data are presented as frequency (%).
Figure 1. Comparison of aortic root replacement with a mechanical (blue) and a biological (purple) valved conduit for all-cause mortality (P ⫽ not significant).
(n ⫽ 2) in the BIO group and 2.0% (n ⫽ 1) in the MECH group, (P ⫽ not significant). All 3 operative deaths occurred in patients who underwent emergent or urgent operations. Median length of follow-up was 40 months. All-cause mortality of the entire cohort was 11.1% (n ⫽ 16) and is shown in Figure 1. There was no significant difference between the groups at 1 year (log-rank test P ⫽ .2). One-year and 5-year survival for the MECH group was 96.0% and 89.0%, respectively, compared with 93.0% and 84.0%, respectively, for the BIO group. Valve-related survival, defined as deaths related to valvular surgery and including cardiovascular mortality (shown in Fig. 2), did not differ between groups (log-rank test P ⫽ 0.9). Cox regression revealed that valve type was not an independent predictor of mortality after adjustment for age, sex, concurrent coronary artery bypass graft procedure, and diabetes (hazard ratio, 0.56; 95% confidence interval, 0.13-2.31). Midterm valve-related complications Median duration of follow-up was 40 months. Midterm complications are shown in Table 4. Two patients (6.3%) from the MECH group and 4 (6.9%) patients from the BIO group required a “redo” aortic root replacement. Complications related to structural valve dysfunction were not noted in any
patient. Three patients experienced thromboembolic complications, 1 patient from the MECH group (3.1%) and 2 patients from the BIO group (3.4%). Endocarditis occurred in 1 patient (3.1%) from the MECH group and 5 patients (8.6%) from the BIO group. There were no significant differences in midterm valve-related complications between groups. Thirty-one patients (96.9%) from the MECH group were receiving anticoagulation therapy (Coumadin) at follow-up; the remaining patient was noncompliant). Twenty-two patients (31.5%) from the BIO group were receiving anticoagulation at follow-up. Health-related quality-of-life analysis The overall response rate for the quality-of-life questionnaire among the 118 surviving patients who were sent questionnaires was 62.7%. Results of the HRQOL analysis are shown in Table 5. No statistically significant differences in adjusted means were found between the MECH and BIO groups in any of the HRQOL scales (SAQ, EuroQoL instrument, and HADS). Discussion Biological valve conduits provide an attractive alternative to mechanical valve conduits for aortic root replacement in paTable 5. Adjusted HRQOL scores HRQOL Measure HADS Anxiety* HADS Depression† SAQ Physical limitation‡ SAQ Anginal Frequency§ SAQ Treatment satisfaction¶ SAQ QOL储 EQ Index**
Figure 2. Comparison of aortic root replacement with a mechanical (blue) and a biological (purple) valved conduit for valve-related mortality (P ⫽ not significant).
Mechanical stent (n ⫽ 24)
Biological stent (n ⫽ 50)
P value
5.3 ⫾ 1.2 2.8 ⫾ 1.8 84.7 ⫾ 5.9 99.9 ⫾ 5.2 93.7 ⫾ 4.1 76.8 ⫾ 11.5 0.92 ⫾ 0.05
4.8 ⫾ 0.6 3.9 ⫾ 1.2 72.2 ⫾ 3.6 90.8 ⫾ 2.6 92.6 ⫾ 2.1 80.7 ⫾ 5.6 0.89 ⫾ 0.03
.7 .6 .1 .2 .8 .8 .6
Continuous data are reported as mean ⫾ SE. EQ, EuroQoL-5D; HADS, Hospital Anxiety and Depression Score; HRQOL, health-related quality of life; QOL, quality of life; SAQ, Seattle Angina Questionnaire. * Adjusted for age, sex, prior percutaneous coronary intervention. † Adjusted for age, sex, type 2 diabetes, chronic obstructive pulmonary disease, congestive heart failure, ejection fraction. ‡ Adjusted for age, sex, hyperlipidema, prior cardiovascular surgery, chronic obstructive pulmonary disease, peripheral vascular disease. § Adjusted for age, sex, hyperlipidemia. ¶ Adjusted for age, sex, hypertension, smoking. 储 Adjusted for age, sex. ** Adjusted for age, sex, type 2 diabetes, peripheral vascular disease, ejection fraction.
Lehr et al. Mechanical vs Biological Valve Conduits
tients who wish to avoid chronic anticoagulation or who otherwise meet criteria for biological aortic valves. The surgical literature has already demonstrated the safety and benefits of biological valve conduits. This study compared the midterm mortality, morbidity, and HRQOL outcomes between aortic root replacements performed with mechanical and biological valve conduits and focused predominantly on biological valves (primarily the Medtronic Freestyle valve) in aortic root replacement, including complex patients admitted with endocarditis, acute dissection, and emergency operation. Patients receiving biological valve conduits were older and had more comorbidities than the mechanical valve conduit group did. In addition, patients receiving biological valve conduits more frequently underwent concomitant coronary artery bypass grafting. There is a positive correlation between older age and concurrent coronary arterial bypass grafting in patients undergoing aortic root replacement.12 Despite these differences, both groups had similar operative mortality, morbidity, and HRQOL outcomes. In the early postoperative period, patients receiving biological valve conduits required a longer period of mechanical ventilation, likely resulting from older age and comorbid factors. In addition, they had an increased rate of reintervention, which was primarily driven by a nearly 10% rate of heart block requiring pacemaker insertion. Further study examining incidence of postoperative heart block with valve conduits is needed. There were no significant differences in valve-related complications at approximately 3 years. Compared with other series, the duration of cardiopulmonary bypass was prolonged, which was attributable to the high rate of redo procedures, long cooling and rewarming times, and concomitant procedures. Despite the prolonged bypass times, the complication rates and mortality remained fairly low. Nearly one-third (31.3%) of patients receiving a biological valve prosthesis were maintained on anticoagulation. Reasons for this finding are unclear. Atrial fibrillation is common and occurs in approximately one-third of patients undergoing aortic valve replacement.13 Our study displayed similar findings. A total of 45 patients (31.3%), 12 patients (23.5%) from the MECH group and 33 patients (35.5%) from the BIO group, experienced postoperative atrial fibrillation after undergoing aortic root replacement. It is not known how many of these patients remained in atrial fibrillation in the long term. It may also be that the patients have other indications for anticoagulation or that their physicians are not comfortable stopping anticoagulation after aortic root surgery. The mortality and valve-related complications in this study were similar to those previously described. The overall operative mortality of 2.1% found in this study was similar to the rate of 1.8% reported by Byrne et al.14 Our 5-year survival rates of 89.0% and 84.0% for the MECH and BIO groups, respectively, were slightly better than the mean 5-year survival rate of 84.6% and 81.2% found in the literature.14,15 Complications related to structural valve dysfunction were not seen in any patient. The HRQOL analysis showed no statistically significant differences in the postoperative quality of life perceived by patients in the BIO or MECH groups. However, there were 5-point differences in SAQ outcome scores, which suggest clinically meaningful differences.10 Patients who received mechanical valves reported fewer physical limitations and less angina frequency at 1 year, compared with the patients who received a
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biological valve. Stadler and colleagues used the Short Form-36 to assess HRQOL outcomes between clinical outcomes of mechanical and biological valve conduits in aortic root replacement16 and were also unable to detect significant differences between groups. On the other hand, Florath et al demonstrated that elderly patients receiving a mechanical valve had a 2-fold increased risk of an impaired emotional reaction.17 The difference in findings could be related to the increased use of deep hypothermic circulatory arrest in their mechanical valve group, which has been identified as a factor contributing to lower HRQOL in aortic surgery, whereas antegrade cerebral perfusion minimizes the adverse effect on HRQOL.18 There was no difference between our groups with respect to duration of hypothermic circulatory arrest. A major strength of our study is that we present quantitative and qualitative data from procedures over a 10-year period from one of the larger cardiac surgery centres in Canada. There are some limitations, however, that should be noted. As with all retrospective studies, observational data provide associative, not causal, evidence, and therefore the possibility of selection bias and residual confounding factors cannot entirely be ruled out. Postoperative echocardiographic data were not available; therefore, subclinical valve dysfunction could not be confirmed. HRQOL scores were collected at 1 year after cardiac catheterization; therefore, the follow-up time between surgery and HRQOL measurement was not uniform for all patients. However, we adjusted for differences in comorbidities and clinical factors likely to affect HRQOL. Approximately onethird of patients did not respond to the HRQOL surveys. Analysis of the nonrespondents showed no difference in survival compared with respondents; however, the nonrespondents required more inotropic support (53% vs 32%, P ⫽ .01) and reoperation due to bleeding (13% vs 3%, P ⫽ .03). Our sample size was relatively small, and a large multicentre trial is required to confirm our results. The choice of valve prosthesis in aortic root replacement includes a number of patient-specific factors, including age, comorbidities, and the risk of bleeding and thromboembolism. Our data suggest that aortic root replacement with biological valve conduits is safe and gives operative and midterm survival and HRQOL outcomes that are similar to those of patients receiving mechanical valve conduits. Thus, within the limits of this retrospective study, our data support the application of current guidelines for aortic valve replacement to the choice of prosthesis for aortic root replacement. Our results also suggest that it is reasonable to consider a biological valve conduit in patients whose lifestyle would be adversely affected by anticoagulation. In addition, stentless xenogenic biological valves have been shown to provide superior coronary perfusion and hemodynamics and lower myocardial oxygen demand than do their mechanical counterparts19,20 and may provide additional benefits over mechanical valve conduits that our study was not designed to examine. Further study of this patient population is required to assess long-term durability of biological valve conduits used for aortic root replacement.
Acknowledgements The authors wish to thank Dawne Colwell for her preparation of the graphics.
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Funding Sources E.J.L. received funding as a Canadian Institutes of Health Research Strategic Training Fellow in Tomorrow’s Research Cardiovascular Health Professionals. Additional funding was received from Edmonton Civic Employees’ Charitable Assistance Fund. Disclosures None of the authors have any potential conflicts of interest to disclose. References 1. Cherry C, DeBord S, Hickey C. The modified Bentall procedure for aortic root replacement. AORN J 2006;1:52-70. 2. Bentall H, De Bono A. A technique for complete replacement of the ascending aorta. Thorax 1968;4:3388-9. 3. Dossche KM, Schepens MA, Morshuis WJ, et al. A 23-year experience with composite valve graft replacement of the aortic root. Ann Thorac Surg 1999;4:1070-7. 4. Hilgenberg AD, Mora BN. Composite aortic root replacement with a bovine pericardial valve conduit. Ann Thorac Surg 2003;4:1338-9. 5. Kon ND, Cordell AR, Adair SM, Dobbins JE, Kitzman DW. Aortic root replacement with the freestyle stentless porcine aortic root bioprosthesis. Ann Thorac Surg 1999;6:1609-15.
Canadian Journal of Cardiology Volume 27 2011 9. The EuroQol Group. Euro-Qol: a new facility for the measurement of health-related quality of life. Health Policy 1990;199208. 10. Spertus JA, Winder JA, Dewhurst TA, et al. Development and evaluation of the Seattle Angina Questionnaire: a new functional status measure for coronary artery disease. J Am Coll Cardiol 1995;2:333-41. 11. Zigmond AS, Snaith RP. The hospital anxiety and depression scale. Acta Psychiatr Scand 1983;6:361-70. 12. Byrne JG, Karavas AN, Leacche M, et al. Impact of concomitant coronary artery bypass grafting on hospital survival after aortic root replacement. Ann Thorac Surg 2005;2:511-6. 13. Almassi GH, Schowalter T, Nicolosi AC, et al. Atrial fibrillation after cardiac surgery: a major morbid event? Ann Surg 1997;4:501-11. 14. Byrne JG, Gudbjartsson T, Karavas AN, et al. Biological vs. mechanical aortic root replacement. Eur J Cardiothorac Surg 2003;3:305-10. 15. Lima B, Hughes GC, Lemaire A, et al. Short-term and intermediate-term outcomes of aortic root replacement with St. Jude mechanical conduits and aortic allografts. Ann Thorac Surg 2006;2:579-85. 16. Stalder M, Staffelbach S, Immer FF, et al. Aortic root replacement does not affect outcome and quality of life. Ann Thorac Surg 2007;3:775-80. 17. Florath I, Albert A, Rosendahl U, et al. Mid term outcome and quality of life after aortic valve replacement in elderly people: mechanical versus stentless biological valves. Heart 2005;8:1023-9.
6. Lim E, Ali A, Theodorou P, et al. Longitudinal study of the profile and predictors of left ventricular mass regression after stentless aortic valve replacement. Ann Thorac Surg 2008;6:2026-9.
18. Immer FF, Lippeck C, Barmettler H, et al. Improvement of quality of life after surgery on the thoracic aorta: effect of antegrade cerebral perfusion and short duration of deep hypothermic circulatory arrest. Circulation 2004;11(suppl 1):II250-5.
7. El Hamamsy I, Clark L, Stevens LM, et al. Late outcomes following freestyle versus homograft aortic root replacement: results from a prospective randomized trial. J Am Coll Cardiol 2010;4:368-76.
19. Bakhtiary F, Abolmaali N, Dzemali O, et al. Impact of mechanical and biological aortic valve replacement on coronary perfusion: a prospective, randomized study. J Heart Valve Dis 2006;1:5-11.
8. Ghali WA, Knudtson ML. Overview of the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease. On behalf of the APPROACH investigators. Can J Cardiol 2000;10:1225-30.
20. Ninet J, Tronc F, Robin J, et al. Mechanical versus biological isolated aortic valvular replacement after the age of 70: equivalent long-term results. Eur J Cardiothorac Surg 1998;1:84-9.