Abstract
Background:
Societal guidelines suggest that aortic valve replacement (AVR) in patients age 50 to 70 years can be performed with either bioprosthetic or mechanical valves. This study reviewed outcomes between these valve types among patients aged 50 to 70 years undergoing AVR.
Methods:
We examined adult patients 50 to 70 years undergoing isolated AVR with a mechanical or bioprosthetic valve at a single institution between 2010 and 2018. Kaplan-Meier analysis was used to evaluate longitudinal survival and multivariable Cox regression analysis was used for risk adjustment. A propensity-matched analysis was performed as well.
Results:
A total of 723 patients underwent isolated AVR with 467 (64.6%) receiving a bioprosthetic valve. At baseline, patients undergoing bioprosthetic AVR were older (median 65 vs 60 years; P < .001). One-year survival was comparable, however, survival at 5 years was significantly higher among patients undergoing mechanical AVR (95.5% vs 82.6%; P = .010). Among the 196 matched pairs, bioprosthetic AVR was associated with an increased adjusted hazard for death (hazards ratio, 3.29; P < .001). Additionally, 5-year freedom from stroke and bleeding were similar following matching, though mechanical AVR was associated with a greater freedom from repeat valve intervention (97.5% vs 92.9%; P = .020).
Conclusion:
In patients age 50 to 70, mechanical AVR is associated with improved long-term survival and freedom from repeat aortic valve intervention. Further large cohort studies should be performed to explore the potential benefits of mechanical valve replacement in this age range.
Keywords: bioprosthetic valve, mechanical valve, survival analysis, valve repair/replacement
1 |. INTRODUCTION
Prosthesis selection for aortic valve replacement (AVR) has become increasingly complex for patients 50 to 70 years of age, particularly in the advent of transcatheter approaches. Current guidelines from the American Heart Association and American College of Cardiology call for individualized selection of valve types for patients 50 to 70 years and acknowledge the clinical equipoise in valve choice among this age group.1 European guidelines also published in 2017 similarly reflect uncertainty regarding the best valve choice for these patients, though they suggest a mechanical valve for patients <60 years and bioprosthetic valve for patients >65 years, albeit with a low level of evidence.2 Thus, aside from patient preference and anticoagulation considerations, there is insufficient data to guide valve selection for patients in this age range. Retrospective analyses specifically exploring patients 50 to 70 years of age have been conflicting. While some studies demonstrate comparable mortality between bioprosthetic and mechanical valves in this age group,3–5 others have reported improved survival associated with a mechanical valve.6,7 Thus, the relative mortality rates and associated adverse events for mechanical versus bioprosthetic AVR in this population are unknown. The purpose of this study was to examine our experience with patients 50 to 70 years of age undergoing isolated surgical AVR to compare both early and longitudinal outcomes based on prosthesis type.
2 |. METHODS
2.1 |. Study cohort
Patients aged 50 to 70 years undergoing isolated surgical AVR with a bioprosthetic or mechanical valve at a single institution between 2010–2018 were included. We excluded all patients undergoing concomitant procedures, including coronary artery bypass grafting or other concomitant valve procedures. We also excluded patients undergoing any ablation procedures, those undergoing aortic surgery, and those patients undergoing AVR for infective endocarditis. This study was approved by the Institutional Review Board at the University of Pittsburgh.
2.2 |. Statistical analysis
Pairwise comparison was performed utilizing the Student t test for gaussian data and Mann-Whitney U test for non-Gaussian data. Categorical data were compared using the χ2 test. Cox proportional hazards models were constructed to obtain hazard ratios for death associated with the valve types in both an unadjusted model and a model adjusted for relevant variables. Propensity score matching utilizing clinically-relevant baseline characteristics was performed to obtain matched groups of patients who underwent either bioprosthetic or mechanical AVR. Nearest neighbor matching was performed with a caliper distance of 0.20 the standard deviation of the logit of the propensity score. Appropriateness of matching was confirmed by an absolute standardized mean difference of <0.010. Cox regression analysis was utilized as previously described to obtain unadjusted and adjusted hazard ratios for death within the matched cohorts. Perioperative and 5-year outcomes were also compared in the unmatched and matched cohorts utilizing pairwise comparisons. Kaplan-Meier analysis was employed to model overall survival in patients undergoing either bioprosthetic or mechanical AVR, both before and after propensity score matching.
3 |. RESULTS
3.1 |. Baseline characteristics, outcomes, and survival
A total of 723 patients aged 50 to 70 years underwent isolated surgical AVR during the study period with 467 (64.6%) undergoing bioprosthetic AVR and 256 (35.4%) receiving a mechanical AVR (Table 1). Bioprosthetic valve types included: St. Jude Trifecta (n = 241, 51.6%), Carpentier-Edwards Perimount (n = 69, 14.8%), Carpentier-Edwards Magna Ease (n = 52, 11.1%), and other (n = 105, 22.5%). Mechanical valve types included: St. Jude Regent (n = 158, 61.7%), On-X (n = 51, 19.9%), and other (n = 47, 18.4%). Patients undergoing AVR with a bioprosthetic valve were significantly older (65 vs 60 years; P < .001). Both cardiopulmonary bypass time (99 vs 105 minutes; P = .035) and ischemic time (76 vs 83 minutes; P = .028) were significantly shorter in the bioprosthetic AVR group. Patients receiving a bioprosthetic valve were also significantly less likely to have had a prior valve operation (4.9% vs 13.7%; P < .001).
TABLE 1.
Baseline characteristics of patients 50 to 70 y old undergoing mechanical or bioprosthetic isolated aortic valve replacement
| Mechanical valve (N = 256) | Bioprosthetic valve (N = 467) | P value | |
|---|---|---|---|
| Age (y), median (IQR) | 60 (56–64) | 65 (60–68) | <.001 |
| Sex, no (%) | |||
| (1) Male | 170 (66.4) | 238 (60.6) | .123 |
| (2) Female | 86 (33.6) | 184 (39.4) | |
| Race, no (%) | |||
| (1) Caucasian | 236 (92.2) | 452 (96.8) | .006 |
| (2) African American | 15 (5.9) | 10 (2.1) | .009 |
| BMI (kg/m2), median (IQR) | 30.1 (26.4–35.7) | 30.0 (26.4–35.0) | .832 |
| Diabetes mellitus, no (%) | 76 (29.7) | 184 (39.4) | .009 |
| Hypertension, no (%) | 206 (80.5) | 387 (82.9) | .422 |
| Chronic lung disease, no (%) | 52 (20.3) | 113 (24.2) | .234 |
| Dialysis, no (%) | 7 (2.7) | 6 (1.3) | .240 |
| Immunosuppression, no (%) | 24 (9.4) | 36 (7.7) | .437 |
| Peripheral arterial disease, no (%) | 21 (8.2) | 72 (15.4) | .006 |
| Cerebrovascular disease, no (%) | 34 (13.3) | 59 (12.6) | .804 |
| Family history of CAD, no (%) | 39 (15.2) | 78 (16.7) | .608 |
| Previous heart failure, no (%) | 72 (28.1) | 133 (28.5) | .919 |
| Previous myocardial infarction, no (%) | 47 (18.4) | 69 (14.8) | .209 |
| Cardiac presentation, no (%) | <.001 | ||
| (1) Stable angina | 16 (6.3) | 52 (11.1) | |
| (2) Unstable angina | 19 (7.4) | 22 (4.7) | |
| (3) NSTEMI | 9 (3.5) | 7 (1.5) | |
| (4) STEMI | 0 | 1 (0.2) | |
| Arrhythmia, no (%) | 51 (19.9) | 59 (12.6) | .009 |
| Number of diseased vessels, no. (%) | .027 | ||
| (1) 0 | 197 (80.1) | 328 (71.6) | |
| (2) 1 | 30 (12.2) | 68 (14.9) | |
| (3) 2 | 6 (2.4) | 33 (7.2) | |
| (4) 3 | 13 (5.3) | 29 (6.3) | |
| Preoperative intra-aortic balloon pump, no. (%) | 0 | 3 (0.64%) | .560 |
| Positive stress test, no (%) | 12 (4.69%) | 16 (3.43%) | .401 |
| Status, no (%) | .628 | ||
| (1) Elective | 201 (78.5) | 363 (77.7) | |
| (2) Urgent | 54 (21.1) | 96 (20.6) | |
| (3) Emergent | 1 (0.4) | 6 (1.3) | |
| (4) Emergent salvage | 0 | 2 (0.4) | |
| Serum creatinine, mg/dL | 0.9 (0.8–1.1) | 0.9 (0.8–1.1) | .481 |
| Left ventricular ejection fraction (%) | 58 (55–63) | 58 (50–63) | .344 |
| Previous valve procedure, no. (%) | 35 (13.7) | 23 (4.9) | <.001 |
| Previous CABG, no (%) | 16 (6.3) | 30 (6.4) | .927 |
| Previous PCI, no. (%) | 24 (9.4) | 53 (11.4) | .411 |
| Cardiopulmonary bypass time, min | 105 (82–130) | 99 (82–117) | .035 |
| Ischemic time, min | 83 (63–102) | 76 (62–93) | .028 |
| Aortic insufficiency, no. (%) | <.001 | ||
| (1) None | 27 (10.8) | 103 (22.6) | |
| (2) Trace | 44 (17.5) | 76 (16.7) | |
| (3) Mild | 66 (26.3) | 134 (29.5) | |
| (4) Moderate | 61 (24.3) | 69 (15.2) | |
| (5) Severe | 53 (21.1) | 73 (16.0) | |
| Aortic stenosis, no. (%) | 227 (88.7) | 434 (93.5) | .023 |
| AV disease etiology, no. (%) | <.001 | ||
| (1) Degenerative (senile) | 43 (23.5) | 126 (45.7) | |
| (2) Bicuspid aortic valve | 110 (60.1) | 124 (44.9) | |
| (3) Rheumatic | 6 (3.3) | 7 (2.5) | |
| (4) Primary aortic disease | 3 (1.6) | 3 (1.1) | |
| (5) Other | 21 (11.5) | 16 (5.8) | |
| Pulmonary artery systolic pressure, mm Hg | 36 (29–46) | 36 (30–44) | .936 |
| Albumin, mg/dL | 3.9 (3.6–4.2) | 3.8 (3.5–4.1) | .018 |
| Total bilirubin, mg/dL | 0.6 (0.5–0.9) | 0.6 (0.4–0.8) | .196 |
Abbreviations: BMI, body mass index; CABG, coronary artery bypass grafting; CAD, coronary artery disease; IQR, interquartile range; NSTEMI, non ST elevation myocardial infarction; PCI, percutaneous coronary intervention; STEMI, ST elevation myocardial infarction.
Cox regression modeling demonstrated that a bioprosthetic valve was associated with increased unadjusted (hazards ratio [HR], 1.70; P = .030) and adjusted (HR, 2.31; P = .002) hazards for death when compared to mechanical AVR (Table 2). Diabetes (HR, 1.57; P = .030), chronic lung disease (HR, 1.79; P = .006), and cerebrovascular disease (HR, 3.26; P < .001) were also associated with increased adjusted hazards for death. At 5 years, there were no significant differences in freedom from stroke (92.6% vs 96.4%; P = .135), endocarditis (98.8% vs 97.1%; P = .137), and repeat aortic valve intervention (97.6 vs 94.1; P = .051) between patients undergoing mechanical as compared with bioprosthetic AVR (Table 3). Overall survival was significantly higher among patients undergoing mechanical AVR (log rank test P = .028) (Figure 1A).
TABLE 2.
Cox proportional hazards model for death in patients 50 to 70 y old undergoing mechanical or bioprosthetic aortic valve replacement, before propensity score matching
| Hazard ratio | 95% Confidence interval | P value | |
|---|---|---|---|
| Unadjusted | |||
| Valve type | |||
| (1) Mechanical valve | Reference | Reference | Reference |
| (2) Bioprosthetic valve | 1.70 | 1.05–2.75 | .030 |
| Adjusted | |||
| Valve type | |||
| (1) Mechanical valve | Reference | Reference | Reference |
| (2) Bioprosthetic valve | 2.31 | 1.35–3.96 | .002 |
| Serum creatinine, mg/dL | 1.43 | 1.21–1.70 | <.001 |
| Diabetes mellitus | 1.57 | 1.04–2.37 | .030 |
| Chronic lung disease | 1.79 | 1.18–2.72 | .006 |
| Immunosuppression | 2.85 | 1.69–4.81 | <.001 |
| Cerebrovascular disease | 3.26 | 2.04–5.21 | <.001 |
| Previous myocardial infarction | 2.04 | 1.27–3.29 | .003 |
| Arrhythmia | 1.93 | 1.19–3.15 | .008 |
TABLE 3.
Five-year outcomes among patients undergoing biologic or mechanical aortic valve replacement, before propensity score matching
| Mechanical valve (%) | Bioprosthetic valve (%) | P value | |
|---|---|---|---|
| Freedom from stroke | 92.6 | 96.4 | .135 |
| Freedom from bleeding | 99.3 | 100.0 | .036 |
| Freedom from heart failure readmission | 85.6 | 84.4 | .603 |
| Freedom from cardiac readmission | 61.9 | 62.2 | .762 |
| Freedom from endocarditis | 98.8 | 97.1 | .137 |
| Freedom from repeated aortic valve intervention | 97.6 | 94.1 | .051 |
FIGURE 1.
Kaplan-Meier analysis of overall survival in patients aged 50 to 70 years undergoing isolated mechanical or bioprosthetic aortic valve replacement before (A) and after (B) propensity score matching
3.2 |. Characteristics, survival, and outcomes in the matched cohort
Propensity score matching resulted in a well-matched cohort of 392 patients (Table 4). After matching, Cox analysis demonstrated increased unadjusted (HR, 2.71; P = .004) and adjusted (HR, 3.29; P = .001) hazards for death among those undergoing bioprosthetic AVR when compared to mechanical AVR (Table 5). Diabetes (HR,2.25; P = .011), immunosuppression (HR, 2.89; P = .005), previous heart failure (HR, 2.95; P = .001), and prior percutaneous coronary intervention (HR, 3.08; P = .006) also predicted death. At 5 years, freedom from repeat aortic valve intervention was significantly lower among those with mechanical AVR (97.5% vs 92.9%; P = .020), however there were no significant differences in freedom from stroke (93.7% vs 94.9%; P = .500) or freedom from bleeding (99.2% vs 100%; P = .300) (Table 6). After matching, survival was significantly higher among patients undergoing mechanical AVR (log rank test P = .040) (Figure 1B). Review of postoperative outcomes in the unmatched and matched cohorts revealed no significant differences in operative mortality or adverse events in either of the analyses (Table 7).
TABLE 4.
Baseline characteristics of patients 50 to 70 y old undergoing aortic valve replacement, following propensity score matching
| Mechanical valve (N = 196) | Bioprosthetic valve (N = 196) | P value | Standardized mean difference | |
|---|---|---|---|---|
| Age (y), median (IQR) | 61 (57–65) | 62 (57–66) | .349 | 0.081 |
| Sex, no. (%) | ||||
| (1) Male | 66 (33.67) | 66 (33.67) | 1.000 | <0.001 |
| (2) Female | ||||
| Race, no. (%) | ||||
| (1) Caucasian | 188 (95.9) | 187 (95.4) | .804 | 0.022 |
| (2) African American | 6 (3.1) | 8 (4.1) | .586 | 0.052 |
| BMI (kg/m2), median (IQR) | 30.1 (26.4–35.4) | 29.6 (26.4–34.3) | .583 | 0.005 |
| Diabetes mellitus, no. (%) | 64 (32.7) | 64 (32.7) | 1.000 | 0.000 |
| Hypertension, no. (%) | 153 (78.1) | 154 (78.6) | .903 | 0.013 |
| Chronic lung disease, no. (%) | 40 (20.4) | 41 (20.9) | .901 | 0.012 |
| Dialysis, no. (%) | 3 (1.5) | 3 (1.5) | 1.000 | <0.001 |
| Immunosuppression, no. (%) | 18 (9.1) | 17 (8.7) | .859 | 0.018 |
| Peripheral arterial disease, no. (%) | 18 (9.2) | 25 (12.8) | .258 | 0.111 |
| Cerebrovascular disease, no. (%) | 26 (13.3) | 21 (10.7) | .437 | 0.076 |
| Family history of CAD, no. (%) | 30 (15.3) | 30 (15.3) | 1.000 | <0.001 |
| Previous heart failure, no. (%) | 57 (29.1) | 53 (27.0) | .653 | 0.045 |
| Previous myocardial infarction, no. (%) | 31 (15.3) | 30 (15.8) | .889 | 0.014 |
| Cardiac presentation, no. (%) | ||||
| (1) Stable angina | 15 (7.7) | 21 (10.7) | .171 | 0.109 |
| (2) Unstable angina | 12 (6.1) | 7 (3.6) | 0.106 | |
| (3) NSTEMI | 6 (3.1) | 6 (3.1) | <0.001 | |
| (4) STEMI | 0 | 0 | … | |
| Arrhythmia, no. (%) | 31 (15.8) | 30 (15.3) | .889 | 0.014 |
| Number of diseased vessels, no. (%) | ||||
| (1) 0 | 153 (80.1) | 152 (78.8) | .829 | 0.012 |
| (2) 1 | 24 (12.6) | 25 (13.0) | 0.015 | |
| (3) 2 | 4 (2.1) | 7 (3.6) | 0.073 | |
| (4) 3 | 10 (5.2) | 9 (4.7) | 0.022 | |
| Positive stress test, no. (%) | 7 (3.6) | 10 (5.1) | .457 | 0.078 |
| Status, no. (%) | ||||
| (1) Elective | 159 (81.1) | 161 (82.1) | .896 | 0.025 |
| (2) Urgent | 36 (18.4) | 35 (17.9) | 0.013 | |
| (3) Emergent | 1 (0.5) | 0 | 0.056 | |
| (4) Emergent salvage | 0 | 0 | … | |
| Serum creatinine, mg/dL | 0.9 (0.8–1.1) | 1.0 (0.8–1.1) | .333 | 0.042 |
| Left ventricular ejection fraction (%) | 58 (55–63) | 58 (53–60) | .173 | 0.060 |
| Previous valve procedure, no. (%) | 21 (10.7) | 16 (8.2) | .388 | 0.090 |
| Previous CABG, no. (%) | 11 (5.6) | 11 (5.6) | 1.000 | <0.001 |
| Previous PCI, no. (%) | 17 (8.7) | 15 (7.7) | .712 | 0.033 |
| Cardiopulmonary bypass time, min | 105 (78–128) | 100 (84–122) | .535 | 0.037 |
| Ischemic time, min | 83 (63–102) | 77 (63–94) | .358 | 0.049 |
| Aortic insufficiency, no. (%) | ||||
| (1) None | 26 (13.6) | 32 (16.7) | .886 | 0.084 |
| (2) Trace | 35 (18.3) | 33 (17.2) | 0.027 | |
| (3) Mild | 51 (26.7) | 55 (28.7) | 0.046 | |
| (4) Moderate | 44 (23.0) | 40 (20.8) | 0.052 | |
| (5) Severe | 35 (18.3) | 32 (16.7) | 0.040 | |
| Aortic stenosis, no. (%) | 179 (91.3) | 179 (91.3) | 1.000 | <0.001 |
| AV disease etiology, no. (%) | ||||
| (1) Degenerative (senile) | 39 (22.4) | 40 (40.4) | .807 | 0.012 |
| (2) Bicuspid aortic valve | 77 (57.1) | 68 (40.7) | 0.098 | |
| (3) Rheumatic | 5 (3.6) | 6 (2.2) | 0.037 | |
| (4) Primary aortic disease | 0 (1.5) | 1 (1.0) | 0.054 | |
| (5) Other | 11 (11.7) | 12 (4.8) | 0.022 |
Abbreviations: AV, aortic valve; BMI, body mass index; CABG, coronary artery bypass grafting; CAD, coronary artery disease; IQR, interquartile range; NSTEMI, non ST elevation myocardial infarction; PCI, percutaneous coronary intervention; STEMI, ST elevation myocardial infarction.
TABLE 5.
Cox proportional hazards model for death following propensity score matching
| Hazard ratio | 95% Confidence interval | P value | |
|---|---|---|---|
| Unadjusted | |||
| Valve type | Reference | Reference | Reference |
| (1) Mechanical valve | 2.71 | 1.37–5.34 | .004 |
| (2) Bioprosthetic valve | |||
| Adjusted | |||
| Valve type | Reference | Reference | Reference |
| (1) Mechanical valve | 3.29 | 1.62–6.70 | .001 |
| (2) Bioprosthetic valve | |||
| Diabetes mellitus | 2.25 | 1.21–4.21 | .011 |
| Immunosuppression | 2.89 | 1.38–6.05 | .005 |
| Previous heart failure | 2.95 | 1.56–5.57 | .001 |
| Previous PCI | 3.08 | 1.39–6.84 | .006 |
Abbreviation: PCI, percutaneous coronary intervention.
TABLE 6.
Five-year outcomes for patients 50 to 70 y old undergoing mechanical or bioprosthetic aortic valve replacement, following propensity score matching
| Mechanical valve (%) | Bioprosthetic valve (%) | P value | |
|---|---|---|---|
| Freedom from stroke | 93.7 | 94.9 | .500 |
| Freedom from bleeding | 99.2 | 100.0 | .300 |
| Freedom from heart failure readmission | 85.7 | 83.5 | .500 |
| Freedom from cardiac readmission | 67.9 | 61.4 | .700 |
| Freedom from endocarditis | 98.5 | 95.8 | .100 |
| Freedom from repeat aortic valve intervention | 97.5 | 92.9 | .020 |
TABLE 7.
Postoperative outcomes stratified by valve type, before and after propensity score matching; data are shown as number (%)
| Before propensity score matching | After propensity score matching | |||||
|---|---|---|---|---|---|---|
| Mechanical valveN = 256 | Bioprosthetic valveN = 467 | P value | Mechanical valveN = 196 | Bioprosthetic valveN = 196 | P value | |
| Operative mortality | 1 (0.4) | 4 (0.9) | .661 | 0 | 1 (0.5) | 1.000 |
| Blood product transfusion | 49 (19.1) | 112 (24.0) | .131 | 36 (18.4) | 51 (26.0) | .068 |
| Prolonged ventilation >24 h | 12 (4.7) | 32 (6.9) | .244 | 10 (5.1) | 11 (5.6) | .823 |
| Deep sternal wound infection | 0 | 1 (0.2) | 1.000 | 0 | 1 (0.5) | 1.000 |
| Acute renal failure | 6 (2.3) | 10 (2.1) | .860 | 5 (2.6) | 5 (2.6) | 1.000 |
| Sepsis | 1 (0.4) | 3 (0.6) | 1.000 | 1 (0.5) | 1 (0.5) | 1.000 |
| Pneumonia | 4 (1.6) | 14 (3.0) | .236 | 3 (1.5) | 4 (2.0) | 1.000 |
| Permanent stroke | 4 (1.6) | 9 (1.9) | 1.000 | 3 (1.5) | 3 (1.5) | 1.000 |
| Reoperation | 18 (7.0) | 23 (4.9) | .242 | 16 (8.2) | 15 (7.7) | .852 |
| New-onset atrial fibrillation | 84 (32.8) | 169 (36.2) | .363 | 64 (32.7) | 58 (29.6) | .513 |
4 |. CONCLUSIONS
The landscape of AVR continues to evolve. The introduction of transcatheter options has resulted in an exponential shift to utilizing more bioprosthetic valves.8 The primary advantages of bioprosthetic valves are the avoidance of anticoagulation and the option for transcatheter valve-in-valve replacement in the presence of valve failure. Despite these drastic trends, it is unclear what the optimal prosthesis should be for surgical AVR among middle-aged patients. Prior studies examining the use of bioprosthetic versus mechanical valves have yielded conflicting results which is reflected in the lack of clarity in current consensus guidelines.1,2 In this cohort of patients aged 50 to 70 years, we found that the use of a mechanical valve was associated with improved 5-year survival, a finding that persisted after risk adjustment and after propensity matching. There were also lower rates of repeat aortic valve intervention among those patients receiving a mechanical valve. We believe these data collectively support the use of mechanical valves in patients aged 50 to 70 undergoing isolated AVR.
Others have similarly reported improved survival and lower rates of reoperation with mechanical prostheses in the aortic position, with most other outcomes being comparable, as was observed in our analysis.6,7 In contradistinction, a randomized trial of 310 patients aged 55 to 70 demonstrated no differences in survival between mechanical and bioprosthetic AVR up to 13 years with similar rates of adverse events.9 Similarly, a retrospective study of over 4000 patients between 50 and 69 years of age also found no differences in survival out to 15 years although there were higher risks of bleeding with mechanical valves.4 A statewide study of the California database demonstrated much higher utilization of bioprosthetic valves for AVR in recent years despite a long-term mortality benefit of mechanical valves in patients aged up to 55 years.3 The risks of reoperation with bioprosthetic valves was found to be higher in their analysis as well.
In addition to age and predicted life expectancy of the patient, other factors that are important in deciding between bioprosthetic versus mechanical valves are anticoagulation-associated complication risks, including long-term risks of bleeding and stroke. We found no differences in significant bleeding out to 5 years in either valve type, which is underscored by our prior work demonstrating comparable readmission rates following bioprosthetic or mechanical AVR up to 5 years.10 Additionally, we demonstrated similar rates of freedom from stroke following matching, which is in agreement with prior studies finding comparable thromboembolism rates regardless of valve type.11 Patients with contraindications to anticoagulation or with anticipated poor compliance with regular testing may not derive the same benefit from mechanical valve use. This is supported by data demonstrating that patients with less time with a therapeutic international normalized ratio (INR) have a higher risk of thromboembolic events and that anticoagulation variability may decrease survival.12,13 Thus, though the overall risk of anticoagulation-related complications is relatively low, patient factors must be heavily weighted particularly in the selection of mechanical valve replacement to maintain the mortality benefit.
In our practice, we are aggressive about attaining therapeutic anticoagulation levels in the early postoperative period and retaining control of anticoagulation management in our patients for the first postoperative month. Most of the patients undergoing mechanical AVR receive warfarin therapy the night of surgery and intravenous heparin is not typically initiated unless the INR remains sub-therapeutic on postoperative day 4. Our trained outpatient staff regularly monitor INRs of our patients for the first postoperative month. In addition, we try to utilize home monitoring technology to further augment time in the therapeutic range for anticoagulation. We believe that with retaining close control of anticoagulation in these patients that the adverse events related to mechanical valves can be minimized over time, and that the advantages, namely durability, can have greater weight on how patients fare over the long-term.
Mechanical valve placement affords lifelong durability which is supported by our finding of a lower need for repeat aortic valve intervention at 5 years. Reoperation, with a reported associated 30-day mortality of around 7%, may be the primary driver contributing to reduced long-term survival among patients undergoing bioprosthetic AVR as we found no other significant differences in long-term complications.3 Preliminary data suggests that valve-in-valve approaches may offer an alternative to redo sternotomy among patients with a bioprosthetic valve with indications for reoperation, though long-term outcomes of this strategy have yet to be established.14 The previously-mentioned California-based study of patients undergoing AVR cited the mortality benefit for mechanical valves up to age 55 related to avoidance of reoperation which outweighed the relatively low risks of stroke and bleeding.3 Nevertheless, Potter et al15 found no differences in early mortality rates between those undergoing index or re-operative AVR and thus, taking into account the likelihood of valve degeneration, suggested that a bioprosthetic valve was a safe option in younger patients. These conflicting reports highlight the complexities of decision-making for prosthesis type in this age cohort.
The important role of the Heart Team is underscored in both the United States and European guidelines on valvular disease and the Heart Team remains particularly beneficial among this cohort of patients in which prosthesis selection remains controversial.1,2 Interestingly, a study of cardiothoracic surgeons and cardiologists found that surgeons more heavily weighted patient involvement in decision-making for valve type and displayed a significantly greater preference for bioprosthetic valves in six hypothetical cases.16 Thus, multidisciplinary discussions may assist in mitigating inherent biases among different types of providers to ensure individualized selection based on both patient wishes and the best available evidence.
This study has several limitations. Due to the retrospective study design, we were unable to account for all aspects of decision-making for bioprosthetic versus mechanical AVR including multidisciplinary decisions made by the Heart Team. Some factors that are important in this decision-making, such as patient preference or intolerance to anticoagulation, were also not included. We did not have cause of death in our data registry, and it is unclear if the differences in survival were directly related to the valve type or not. Finally, it is unclear if our results are generalizable to other practices.
In conclusion, we demonstrate in over 700 patients aged 50 to 70 undergoing isolated AVR that use of a mechanical prosthesis was associated with improved survival and lower rates of reoperation as compared to bioprosthetic valves, with no differences in other relevant clinical outcomes. This experience adds further evidence to the body of literature evaluating outcomes of valve types in this age cohort, which remains controversial. Further research is needed to identify nuances in patient selection, surgical technique, and postoperative management of middle-aged patients receiving mechanical valves that may lead to improved outcomes in certain patient subsets or centers.
ACKNOWLEDGMENTS
Dr. Arman Kilic serves on a Medical Advisory Board for Medtronic, Inc. Dr. Thomas Gleason serves on a Medical Advisory Board for Abbott, Inc. All other authors have nothing to disclose with regard to commercial support.
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