Recommendations for prosthesis type in older patients who underwent surgical aortic valve replacement (SAVR) are established, albeit undervalidated. The purpose of this study is to compare outcomes after bioprosthetic versus mechanical SAVR across various age groups. This was a retrospective study using an institutional SAVR database. All patients who underwent isolated SAVR were compared across valve types and age strata (<65 years, 65 to 75 years, >75 years). Patients who underwent concomitant operations, aortic root interventions, or previous aortic valve replacement were excluded. Objective survival and aortic valve reinterventions were compared. Kaplan–Meier survival estimation and multivariate regression were performed. A total of 1,847 patients underwent SAVR from 2010 to 2023. A total of 1,452 patients (78.6%) received bioprosthetic valves, whereas 395 (21.4%) received mechanical valves. Of those who received bioprosthetic valves, 349 (24.0%) were aged <65 years, 627 (43.2%) were 65 to 75 years, and 476 (32.8%%) were older than 75 years. For patients who received mechanical valves, 308 (78.0%) were aged <65 years, 84 (21.3%) were between 65 and 75 years, and 3 (0.7%) were >75 years. The median follow-up in the total cohort was 6.2 (2.6 to 8.9) years. No statistically significant differences were observed in early-term Kaplan–Meier survival estimates between SAVR valve types in all age groups. However, the cumulative incidence estimates of aortic valve reintervention were significantly higher in patients aged under 65 years who received bioprosthetic than those who received mechanical valves, with 5-year reintervention rates of 5.8% and 3.1%, respectively (p = 0.002). On competing risk analysis for valve reintervention, bioprosthetic valves were significantly associated with an increased hazard of aortic valve reintervention (hazard ratio 3.35, 95% confidence interval 1.73 to 6.49, p <0.001). In conclusion, SAVR with bioprosthetic valves (particularly, in patients aged <65 years) was comparable in survival to mechanical valve SAVR but significantly associated with increased valve reintervention rates.
Graphical Abstract
Despite the expanding use of transcatheter interventions, surgical aortic valve replacement (SAVR) remains a highly effective tool in the treatment of aortic stenosis (AS). Moreover, with innovation in valvular prostheses and surgical techniques over recent decades, prosthesis selection during SAVR is a critical point of consideration. The current 2020 American College of Cardiology/American Heart Association guidelines for the management of valvular heart disease cite flexibility in prosthesis choice for patients aged 50 to 65 years, with concomitant IIa recommendations of bioprosthetic valves for patients with AS aged >65 years and mechanical valves for patients with AS aged <50 years. Although valve choice is often streamlined in the youngest and oldest patients with AS who underwent SAVR because of the burdens of structural valve degeneration and anticoagulation regimens, evidence regarding valve choice in middle-aged patients remains lacking. Various studies have reported decreased mortality in young patients receiving mechanical valves, whereas other analyses demonstrate early drop-offs in survival benefits. Incorporation of individual patient preferences and co-morbidities is a necessary component of preoperative evaluation; however, age can often be one of the most valuable objective metrics in the determination of prosthesis type. This study aimed to examine a single-center experience of patients across separate age strata who underwent isolated SAVR by comparing short- and midterm outcomes based on prosthesis type.
Methods
This was a retrospective, observational study using an institutional database of SAVR operations performed at our center (University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania) from 2010 to 2023. Definitions and terminology were consistent with those used in the Society of Thoracic Surgeons database. All patients who underwent isolated SAVR were included in the study. Patients who required SAVR for infective endocarditis, underwent concomitant operations, aortic root interventions, or had previous aortic valve replacement procedures were excluded. This study was approved by the institutional review board of the University of Pittsburgh on April 17, 2019 (STUDY18120143), with written consent waived.
This study aimed to compare the clinical outcomes of patients across various age groups who underwent first-time SAVR with bioprosthetic versus mechanical prostheses. The primary outcome investigated was long-term survival. Additional outcomes of interest included postoperative clinical outcomes. All follow-up data were obtained from a clinical warehouse that contains long-term survival data for patients who underwent cardiac operations at the University of Pittsburgh Medical Center.
Primary stratification was between SAVR valve type (bioprosthetic vs mechanical), with secondary stratification by age group. Continuous variables were presented as mean ± SD for normally distributed data or median and interquartile range for nonnormally distributed data. Categorical data were reported by frequency and percentage. Normally distributed continuous variables were analyzed by analysis of variance, whereas nonnormally distributed continuous variables were analyzed with the nonparametric Kruskal–Wallis test. A chi-square test was used to compare categorical variables between groups, as appropriate.
Unadjusted survival estimates were generated using Kaplan–Meier methods and compared using log-rank statistics. Cumulative incidence estimates for aortic valve reintervention were compared between prosthesis types across age groups. Finally, competing risk and logistic regression analyses were performed to identify factors associated with valve reintervention. Variable selected for consideration in the model included valve type, age category, long-term dialysis, hypertension, valvular insufficiency, New York Heart Association class, preoperative arrhythmia, and operative ischemic time. All statistical analyses were performed with SAS/STAT version 15.2 software (SAS Institute). All tests were 2-sided with an α level of 0.05 designated to indicate statistical significance.
Results
A total of 1,847 patients who underwent SAVR were included in the study, with 1,452 (78.6%) receiving bioprosthetic aortic valves and 395 (21.4%) receiving mechanical valves. Patients were categorized into 3 age strata: <65 years, 65 to 75 years, and >75 years. Of those aged <65 years who underwent SAVR (n = 657), 349 (53.1%) received bioprosthetic valves, whereas 308 (46.9%) received mechanical valves. For patients aged between 65 and 75 years (n = 711), 627 (88.2%) received bioprosthetic valves and 84 (11.8%) received mechanical valves. Similarly, of the patients aged >75 years (n = 479), 476 (99.4%) received bioprosthetic valves, whereas only 3 (0.6%) received mechanical valves. Baseline characteristics were reported and compared between bioprosthetic and mechanical valves groups across different the age groups ( Table 1 ). In patients aged under 65 years, those who received bioprosthetic valves were statistically significantly more likely to have lower ejection fractions (p = 0.002) and lower glomerular filtration rates (p = 0.047) but less likely to have preoperative hypertension when than similarly aged patients who received mechanical valves (p = 0.008). In patients aged 65 to 75 years, patients who received bioprosthetic valves had significantly higher preoperative Society of Thoracic Surgeons mortality risk scores (p = 0.047) but lower ejection fractions (p = 0.019) and rates of previous coronary artery bypass surgery (p = 0.020). Lastly, significantly higher rates of preoperative arrhythmia (p = 0.009) but lower pulmonary artery systolic pressures (p = 0.047) were seen in patients who underwent mechanical versus biologic SAVR over the age of 75 years.
| <65 Years | 65-75 Years | >75 Years | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Variable | Bioprosthetic (n=349) | Mechanical (n=308) | P-Value | Bioprosthetic (n=627) | Mechanical (n=84) | P-Value | Bioprosthetic (n=476) | Mechanical (n=3) | P-Value |
| Age (years) | 59.0 [54.0-62.0] | 56.0 [49.0-60.5] | 0 | 70.0 [68.0-73.0] | 68.0 [66.0-70.0] | 0 | 81.0 [78.0-84.0] | 76.0 [76.0-81.0] | 0.080 |
| Sex: Female | 103 (29.5%) | 102 (33.1%) | 0.320 | 268 (42.7%) | 30 (35.7%) | 0.220 | 216 (45.4%) | 0 (0.0%) | 0.115 |
| Race | 0.122 | 0.631 | 0.898 | ||||||
| White | 250 (71.6%) | 198 (64.3%) | 440 (70.2%) | 56 (66.7%) | 444 (93.3%) | 3 (100%) | |||
| Black | 11 (3.2%) | 14 (4.5%) | 8 (1.3%) | 2 (2.4%) | 9 (1.9%) | 0 (0.0%) | |||
| Other | 88 (25.2%) | 96 (31.2%) | 179 (28.5%) | 26 (31.0%) | 23 (4.8%) | 0 (0.0%) | |||
| Body surface area (m 2 ) | 2.1 [1.9- 2.2] | 2.0 [1.9- 2.2] | 0.529 | 2.0 [1.8-2.2] | 2.0 [1.9-2.2] | 0.274 | 1.9 [1.7-2.0] | 2.3 [1.9-2.3] | 0.079 |
| Calculated STS Operative Mortality Risk (%) | 1.0 [0.7-1.7] | 0.9 [0.7-1.6] | 0.060 | 1.5 [1.1-2.4] | 1.3 [1.0-2.0] | 0.047 | 3.2 [2.1-4.9] | 1.8 [1.4-3.4] | 0.128 |
| Prior CABG | 5 (1.4%) | 3 (1.0%) | 0.593 | 44 (7.0%) | 12 (14.3%) | 0.020 | 62 (13.0%) | 0 (0.0%) | 0.503 |
| Previous history of heart failure | 106 (30.4%) | 86 (27.9%) | 0.491 | 207 (33.0%) | 33 (39.3%) | 0.254 | 156 (32.8%) | 0 (0.0%) | 0.227 |
| Prior MI | 53 (15.2%) | 36 (11.7%) | 0.191 | 101 (16.1%) | 15 (17.9%) | 0.684 | 78 (16.4%) | 1 (33.3%) | 0.430 |
| Cerebrovascular disease | 45 (12.9%) | 33 (10.7%) | 0.389 | 108 (17.2%) | 9 (10.7%) | 0.131 | 103 (21.6%) | 0 (0.0%) | 0.363 |
| Peripheral vascular disease | 33 (9.5%) | 17 (5.5%) | 0.058 | 92 (14.7%) | 12 (14.3%) | 0.925 | 86 (18.1%) | 0 (0.0%) | 0.416 |
| Stroke/TIA | 12 (3.4%) | 11 (3.6%) | 0.926 | 40 (6.4%) | 3 (3.6%) | 0.311 | 45 (9.5%) | 0 (0.0%) | 0.576 |
| Hypertension | 236 (67.6%) | 237 (76.9%) | 0.008 | 553 (88.2%) | 68 (81.0%) | 0.061 | 419 (88.0%) | 3 (100%) | 0.523 |
| Diabetes mellitus | 112 (32.1%) | 90 (29.2%) | 0.426 | 231 (36.8%) | 29 (34.5%) | 0.679 | 140 (29.4%) | 1 (33.3%) | 0.882 |
| Dyslipidemia | 167 (47.9%) | 125 (40.6%) | 0.061 | 360 (57.4%) | 45 (53.6%) | 0.504 | 351 (73.7%) | 3 (100%) | 0.302 |
| Long-term dialysis | 10 (2.9%) | 12 (3.9%) | 0.464 | 5 (0.8%) | 1 (1.2%) | 0.712 | 5 (1.1%) | 0 (0.0%) | 0.858 |
| Chronic lung disease | 89 (25.5%) | 62 (20.1%) | 0.103 | 150 (23.9%) | 17 (20.2%) | 0.454 | 111 (23.3%) | 1 (33.3%) | 0.683 |
| NYHA class | 0.630 | 0.102 | 0.611 | ||||||
| I | 232 (66.5%) | 212 (68.8%) | 415 (66.2%) | 53 (63.1%) | 296 (62.2%) | 3 (100%) | |||
| II | 34 (9.7%) | 35 (11.4%) | 66 (10.5%) | 16 (19.0%) | 51 (10.7%) | 0 (0.0%) | |||
| III | 58 (16.6%) | 43 (14.0%) | 119 (19.0%) | 11 (13.1%) | 110 (23.1%) | 0 (0.0%) | |||
| IV | 25 (7.2%) | 18 (5.8%) | 27 (4.3%) | 4 (4.8%) | 19 (4.0%) | 0 (0.0%) | |||
| Ejection Fraction (%) | 58.0 [53.0-60.0] | 58.0 [55.0-63.0] | 0.002 | 58.0 [55.0-63.0] | 60.0 [58.0-63.0] | 0.019 | 58.0 [55.0-63.0] | 58.0 [53.0-65.0] | 0.943 |
| Arrhythmia | 19 (5.4%) | 28 (9.1%) | 0.070 | 68 (10.8%) | 14 (16.7%) | 0.117 | 66 (13.9%) | 2 (66.7%) | 0.009 |
| Status | 0.157 | 0.187 | 0.685 | ||||||
| Elective | 254 (72.8%) | 244 (79.2%) | 510 (81.3%) | 75 (89.3%) | 380 (79.8%) | 3 (100%) | |||
| Urgent | 92 (26.4%) | 62 (20.1%) | 114 (18.2%) | 9 (10.7%) | 95 (20.0%) | 0 (0.0%) | |||
| Preoperative GFR (mL/min/1.73m 2 ) | 75.0 [63.3-87.6] | 78.7 [64.3-90.6] | 0.047 | 70.9 [57.8-83.0] | 67.2 [58.4-79.9] | 0.535 | 63.5 [48.1-78.9] | 54.2 [52.1-61.2] | 0.417 |
| Preoperative creatinine (mg/dL) | 1.0 [0.8- 1.1] | 0.9 [0.8-1.1] | 0.089 | 0.9 [0.8- 1.1] | 1.0 [0.9-1.1] | 0.105 | 1.0 [0.8- 1.2] | 1.3 [1.2-1.3] | 0.130 |
| GFR category | 0.833 | 0.032 | 0.860 | ||||||
| >45 | 325 (93.1%) | 283 (91.9%) | 571 (91.1%) | 75 (89.3%) | 380 (79.8%) | 3 (100%) | |||
| 30-44 | 10 (2.9%) | 8 (2.6%) | 42 (6.7%) | 5 (6.0%) | 80 (16.8%) | 0 (0.0%) | |||
| 15-29 | 6 (1.7%) | 7 (2.3%) | 13 (2.1%) | 2 (2.4%) | 13 (2.7%) | 0 (0.0%) | |||
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