Abstract
Objective
To define the indications and characteristics for redo aortic valve replacement (AVR) after primary mechanical AVR and to determine whether operative indication influences early and late outcomes.
Methods
We analyzed 379 consecutive patients undergoing redo AVR after previous mechanical AVR (2000-2023) at a single tertiary center. Baseline, operative, and outcomes data were obtained from a prospectively maintained database and electronic health records. Outcomes were compared across principal indications, with survival estimated by Kaplan-Meier analysis and predictors of mortality identified using multivariable Cox regression.
Results
Median age at redo surgery was 61.8 years (interquartile range, 52.4-69.4 years); 61.2% were male. The median interval to reoperation was 10.2 years (3.9-18.2). Indications included endocarditis (26.6%), pannus obstruction (18.7%), prosthesis-patient mismatch (11.6%), and elective replacement during aortic surgery (16.0%). Endocarditis cases were frequently nonelective and had longer operative times, greater complication rates, and greater operative mortality (13.0% vs 1.4% pannus and 3.4% others; P < .001). Independent predictors of all-cause mortality were older age, diabetes, dialysis dependence, previous myocardial infarction, and nonelective surgery. Indication, including endocarditis, and valve size were not independent predictors. Lower overall survival in endocarditis and bioprosthetic redo cases reflected excess early mortality; beyond 1 year, survival was similar across indications.
Conclusions
Redo AVR after previous mechanical AVR is uncommon and arises from heterogeneous indications. Early risk is greatest with endocarditis and nonelective presentation, whereas long-term survival is driven largely by comorbidities rather than indication or prosthesis type. These findings may guide risk assessment, prosthesis selection, and timing of intervention.
Key Words: redo aortic valve replacement, mechanical valve failure, prosthetic valve dysfunction, endocarditis, pannus formation
Landmark analysis shows similar survival across operative indications after 1 year.
Central Message.
Early risk of redo AVR after mechanical AVR is increased in patients with endocarditis, but after the first postoperative year, survival is similar to patients with other indications for reoperation.
Perspective.
Outcomes after redo AVR after primary mechanical AVR vary by indication, with endocarditis driving early mortality. However, beyond 1 year, survival converges across groups, and neither indication nor valve size independently predicts late mortality. These findings support individualized operative planning and risk counseling.
Mechanical prostheses are often preferred for younger patients undergoing aortic valve replacement (AVR) because of their durability and lower reoperation rate compared with bioprosthetic valves. Indeed, recent studies have shown a survival advantage of mechanical over biological valves for AVR in patients aged 60 to 65 years.1, 2, 3, 4 Although mechanical valves are designed to last a lifetime, a small proportion of patients still require reoperation for various structural and nonstructural causes, which, although rare, can lead to serious complications.
Redo AVR may be a complex and sometimes high-risk procedure associated with increased operative morbidity and mortality, as well as technical challenges and greater resource use.5,6 Large-scale, long-term data on outcomes of reoperation on mechanical heart valves are limited because of the relatively infrequent occurrence. Such information regarding late intervention on mechanical valves may be more challenging to obtain in the future because of the increasing use of transcatheter valve replacement in younger patients.7
This study aimed to identify the most common causes of redo AVR after mechanical valve implantation, compare baseline and operative characteristics according to the cause of reoperation, and evaluate long-term survival. These findings may provide valuable insights to inform improved management strategies and decision-making for prosthesis selection in patients undergoing AVR.
Methods
Patients and Data Collection
The Mayo Clinic Institutional Review Board in Rochester, Minnesota, approved the study (institutional review board no. 23-011633, February 7, 2025) with a waiver of informed consent. All patients authorized the use of their clinical data for research. Between 2000 and 2023, 379 patients underwent redo AVR at our institution after initial mechanical AVR. Reoperation was defined as repeat AVR via an open surgical approach. For patients who underwent more than one redo AVR, only the first redo procedure was included in the analysis.
Clinical and operative data were obtained from a prospectively maintained surgical database and a retrospective review of electronic health records. The primary outcomes were to describe characteristics of the overall cohort, compare baseline characteristics across the principal indications for redo AVR, and evaluate long-term all-cause mortality. Vital status was ascertained using information from the Mayo Clinic electronic medical record system and LexisNexis Accurint, which consolidates information from multiple sources, including the Social Security Death Master File and state death records.
Statistical Analysis
Categorical variables are reported as numbers (percentage) and continuous variables as medians (25th through 75th interquartile range) or mean (standard deviation). Group differences in baseline characteristics were assessed using the Kruskal-Wallis test for continuous variables and Pearson χ2 or Fisher exact test for categorical variables. A multivariable Cox regression model was used to estimate the adjusted hazard ratios (HRs) of all-cause mortality. Variable selection for this model was determined on the basis of clinical expertise, previous literature, and univariate analysis.
The Kaplan-Meier method was used for survival analysis, and differences between groups were analyzed using the 2-tailed log-rank test. All analyses were performed using R software (version 4.2.2; R Foundation for Statistical Computing).
Results
Patient Characteristics
Between 2000 and 2023, 379 patients underwent redo AVR after primary mechanical AVR. The median age at the time of reoperation was 61.8 (52.4-69.4) years, and 61.2% of the patients were male (Table 1). The median interval between initial AVR and reoperation was 10.2 years (3.9-18.2 years). Most primary operations (68%) were performed at other institutions.
Table 1.
Baseline characteristics of patients undergoing redo AVR after primary mechanical aortic valve replacement
| Variables | Overall (n = 379) |
|---|---|
| Male sex | 232 (61.2%) |
| Age at primary mechanical AVR, y | 48.6 (39.5-58.5) |
| Age at redo AVR, y | 61.8 (52.4-69.4) |
| Interval between primary/redo AVR, y | 10.2 (3.9-18.2) |
| Primary AVR performed at other hospital | 259 (68%) |
| Body mass index, kg/m2 | 29.9 (6.3) |
| NYHA class (n = 315) | |
| I | 63 (16.6%) |
| II | 70 (18.4%) |
| III | 122 (32.1%) |
| IV | 60 (15.8%) |
| Dyslipidemia | 263 (69.4%) |
| Hypertension | 254 (67.0%) |
| Diabetes mellitus | 77 (20.3%) |
| Cerebrovascular disease | 119 (31.4%) |
| History of atrial fibrillation/flutter | 91 (24.0%) |
| Current smoking | 37 (9.7%) |
| Dialysis | 11 (2.9%) |
| Previous myocardial infarction | 46 (12.1%) |
| Previous cerebrovascular accident | 77 (20.3%) |
| Preoperative echocardiogram | |
| LVEF (%) | 58.2 (11.6) |
| AV gradient, mm Hg (n = 330) | 29.0 (19.3) |
| AV stenosis | 213 (56.2%) |
| AV regurgitation | |
| None | 55 (14.3%) |
| Trivial | 135 (35.7%) |
| Mild | 77 (20.4%) |
| Moderate | 41 (10.8%) |
| Severe | 71 (10.8%) |
AVR, Aortic valve replacement; NYHA, New York Heart Association; LVEF, left ventricular ejection fraction; AV, aortic valve.
Hypertension (67%), dyslipidemia (69%), and cerebrovascular disease (31%) were common comorbidities; 20% of patients had diabetes mellitus. Nearly one half of the cohort (48%) presented with moderate-to-severe heart failure symptoms (New York Heart Association class III or IV). The mean preoperative left ventricular ejection fraction was 58±11.6%, and aortic stenosis, present in 56% of patients, was the predominant pathophysiologic finding on Doppler echocardiograph.
Patient Characteristics at the Time of Initial AVR
The main indications for mechanical AVR at the initial operation were bicuspid aortic valve (31.6%), rheumatic heart disease (15.5%), and endocarditis (11.8%). As shown in Table 2, slightly more than one half of the patients (52.3%) underwent a concomitant procedure at the time of initial AVR, including aortic surgery (19.2%), coronary artery bypass grafting (11.8%), or a mitral valve procedure (11.6%). The most common implanted prosthesis was the St Jude mechanical valve (54.6%), followed by the Carbomedics (CORCYM) valve (19.8%) and the Björk-Shiley valve (7.1%).
Table 2.
Characteristics of primary mechanical aortic valve replacement of patients undergoing redo AVR
| Variables | Overall (n = 379) |
|---|---|
| Main indications for primary mechanical AVR | |
| Bicuspid aortic valve | 120 (31.6) |
| Rheumatic heart disease | 59 (15.5%) |
| Bicuspid aortic valve/aortopathy | 41 (10.8%) |
| Endocarditis | 45 (11.8%) |
| Degenerative fibrocalcific valve disease | 24 (6.3%) |
| Stenosis/insufficiency etiology unknown | 24 (6.3%) |
| Aortic aneurysm/dissection | 15 (3.9%) |
| Marfan-related valvulopathy | 8 (2.1%) |
| Heart disease postradiation | 5 (1.3%) |
| Lupus-related valvulopathy | 2 (0.5%) |
| Other | 15 (3.9%) |
| Unknown | 21 (5.5%) |
| Concomitant procedure during primary AVR | |
| Isolated AVR | 181 (47.7%) |
| AVR + aortic surgery | 73 (19.2%) |
| AVR + CABG | 45 (11.8%) |
| AVR + mitral valve surgery | 44 (11.6%) |
| AVR + aortic surgery + CABG | 8 (2.1%) |
| AVR + myectomy | 7 (1.8%) |
| AVR + MV repair | 6 (1.5%) |
| AVR + MVR + TV surgery | 6 (1.5%) |
| AVR + CABG + MVR | 5 (1.3%) |
| Other | 4 (1.0%) |
| Mechanical valve implanted at primary AVR | |
| St Jude | 207 (54.6%) |
| Carbomedics | 75 (19.8%) |
| Björk-Shiley | 27 (7.1%) |
| Medtronic Hall | 20 (5.3%) |
| On-X | 17 (4.5%) |
| Starr-Edwards | 16 (4.2%) |
| Other/unknown | 17 (4.5%) |
Aortic surgery: root surgery, +/− ascending aorta, +/− arch. AVR, Aortic valve replacement; CABG, coronary artery bypass graft; MV, mitral valve; MVR, mitral valve replacement; TV, tricuspid valve.
Indications for Redo AVR
The predominant cause of redo AVR was endocarditis (26.6%), followed by pannus formation (18.7%), and prosthesis-patient mismatch (11.6%); in 16% of patients, the mechanical prosthesis was electively replaced at the time of repair of an ascending aortic aneurysm or dissection (Table 3). Other less-common cardiovascular problems leading to reoperation included perivalvular leak (8.4%), valve thrombosis (5.2%), and aortic graft dehiscence or contained rupture (4.2%). Among patients with endocarditis, 81% occurred late (>1 year) after the primary procedure.
Table 3.
Main indication and type of valve implanted at redo aortic valve replacement
| Variable | Overall (n = 379) |
|---|---|
| Endocarditis | 101 (26.6%) |
| Early endocarditis (<1 y) | 19 (18.8%) |
| Late endocarditis (≥1 y) | 82 (81.1%) |
| Nonstructural valve deterioration | |
| Pannus formation | 71 (18.7%) |
| PPM | 44 (11.6%) |
| Perivalvular leak | 32 (8.4%) |
| Aortic aneurysm/dissection | 61 (16%) |
| Thrombosis | 20 (5.2%) |
| Contained graft rupture/dehiscence | 16 (4.2%) |
| Other | 34 (8.9%) |
| Type of valve implanted | |
| On-X | 112 (29.5%) |
| Carbomedics | 84 (22.1%) |
| St Jude, mechanical | 61 (16.0%) |
| Homograft | 37 (9.7%) |
| Carpentier-Edwards | 20 (5.2%) |
| St Jude Medical Trifecta | 14 (3.6%) |
| Sorin Mitroflow | 12 (3.1%) |
| Hancock 2 | 8 (2.1%) |
| Magna Ease | 6 (1.5%) |
| Medtronic Freestyle | 6 (1.5%) |
| Other | 19 (5.0%) |
PPM, Prosthesis-patient mismatch.
Comparative Analysis by Cause of Redo AVR
Patients with endocarditis were more frequently male (79.2%), had shorter intervals between procedures (4.0 [1.3-11.1] years), were more likely to undergo nonelective operations (80%), and were older at primary AVR (54.5 [44.2-61.4] years) compared with those with pannus (45.7 [36.6-54.5] years) or other causes (47.2 [38.3-58.2] years) (P .002). Conversely, those with pannus were older at the time of redo surgery (64.2 [56.4-73.1] years), more frequently female (73.2%), and had the longest time interval between operations (15.8 [10.1-22.3] years).
Valve size also differed significantly. Small prostheses (<21 mm) were more common in pannus cases (65%) than in endocarditis (14.3%) or other causes (39.3%) (P < .001). Aortic or other concomitant procedures were significantly more frequent during the primary operation in patients with endocarditis (P < .001). Patients with pannus were more likely to have rheumatic valve disease (37.5%) as the initial etiology, whereas bicuspid aortic valve disease was predominant among other causes (35.4%) (Table 4).
Table 4.
Comparative characteristics according to the indication for redo AVR after primary mechanical AVR
| Variables | Endocarditis (n = 101) |
Pannus (n = 71) |
Others (n = 207) |
P value |
|---|---|---|---|---|
| Sex/male | 80 (79.2%) | 19 (26.8%) | 133 (64.4%) | <.001 |
| Age at primary surgery, y | 54.5 (44.2-61.4) | 45.7 (36.6-54.5) | 47.2 (38.3-58.2) | .002 |
| Age at redo surgery, y | 61.9 (51.8-69.4) | 64.2 (56.4-73.1) | 60.5 (51.9-68.9) | .129 |
| Time between surgeries | 4.0 (1.3-11.1) | 15.8 (10.1-22.3) | 11.0 (5.0-19.0) | <.001 |
| Type of explanted mechanical valve | .073 | |||
| Björk-Shiley | 2 (2.0%) | 10 (13.9%) | 15 (7.3%) | |
| Carbomedics | 24 (23.8%) | 10 (13.9%) | 41 (19.9%) | |
| Medtronic Hall | 3 (3.0%) | 6 (8.3%) | 11 (5.3%) | |
| On-X | 10 (9.9%) | 0 (0.0%) | 7 (3.4%) | |
| St Jude | 58 (57.4%) | 41 (56.9%) | 106 (51.5%) | |
| Valve size (n = 322) | <.001 | |||
| Large | 26 (31.0%) | 1 (1.7%) | 46 (25.7%) | |
| Medium | 46 (54.8%) | 20 (33.9%) | 62 (34.6%) | |
| Small | 12 (14.3%) | 39 (65.0%) | 70 (39.3%) | |
| Any concomitant procedure at primary AVR | 65 (64.4%) | 38 (52.8%) | 80 (38.9%) | <.001 |
| Aortic concomitant procedure at primary AVR | 37 (36.6%) | 5 (6.9%) | 40 (19.4%) | <.001 |
| Nonelective surgery | 81 (80.0%) | 16 (22.2%) | 59 (28.4%) | <.001 |
| Main indication for primary AVR | <.001 | |||
| Bicuspid valve | 29 (28.7%) | 18 (25.0%) | 73 (35.4%) | |
| Bicuspid valve/aortopathy | 21 (20.8%) | 5 (6.9%) | 15 (7.3%) | |
| Endocarditis | 6 (5.9%) | 9 (12.5%) | 30 (14.6%) | |
| Rheumatic valve disease | 5 (5.0%) | 27 (37.5%) | 27 (13.1%) | |
| Diabetes mellitus | 28 (27.7%) | 15 (20.8%) | 34 (16.5%) | .071 |
| Current smoking | 11 (10.9%) | 3 (4.2%) | 23 (11.2%) | .205 |
| Hypertension | 65 (64.4%) | 47 (65.3%) | 142 (68.9%) | .683 |
| Chronic kidney disease - dialysis | 6 (5.9%) | 0 (0.0%) | 5 (2.4%) | .060 |
| Body mass index, kg/m2 | 29.8 (6.4) | 28.3 (5.4) | 30.5 (6.5) | .044 |
| History of drug use within last year | 1 (1.0%) | 0 (0.0%) | 1 (0.5%) | .670 |
| Immunosuppression | 11 (10.9%) | 4 (5.6%) | 12 (5.8%) | .228 |
| Previously treated endocarditis (N = 368) | 10 (9.9%) | 7 (9.9%) | 33 (16.8%) | .152 |
Valve sizes: small ≤21 mm, medium 23-25 mm, and large >25 mm. AVR, Aortic valve replacement.
Perioperative Outcomes
As seen in Table 3, the most commonly implanted prosthesis at reoperation among patients with a previous mechanical aortic valve was another mechanical valve (69.2%), compared with bioprosthetic valves (30.8%). The On-X mechanical valve was used in approximately one third of patients (29.5%), followed by the Carbomedics valve (22.1%) and the St Jude valve (16.0%). A homograft was used in 9.7% of cases. Mean cardiopulmonary bypass and crossclamp times were longest in patients with endocarditis compared with patients with pannus formations and other causes (P < .001).
Postoperative outcomes are summarized in Table 5. Complications were more frequent in the endocarditis group, including acute kidney injury (26%), dialysis requirement (13%), and longer stay in the intensive care unit (181 ± 304 hours) compared with pannus formation and other causes. Operative (30-day) mortality was significantly greater among patients with endocarditis (12.9%) compared with pannus (1.4%) and other causes (3.4%) (P < .001).
Table 5.
Perioperative outcomes of patients undergoing redo AVR after primary mechanical AVR
| Variables | Endocarditis (n = 101) |
Pannus (n = 71) |
Others (n = 207) |
P value |
|---|---|---|---|---|
| Cardiopulmonary bypass time, min | 226.9 ± 85.7 | 158.2 ± 83.8 | 191.0 ± 92.1 | <.001 |
| Aortic crossclamp time, min | 168.1 ± 74.4 | 122.5 ± 71.5 | 147.7 ± 76.9 | .001 |
| Isolated AVR | 167.0 ± 70.9 | 107.9 ± 52.6 | 133.7 ± 52.6 | .019 |
| Length of ICU stay, h (n = 338) | 181.7 ± 303.9 | 82.7 ± 87.5 | 74.6 ± 72.9 | <.001 |
| Atrial fibrillation | 30 (29.7%) | 23 (31.9%) | 40 (20.1%) | .061 |
| Stroke | 2 (2.0%) | 0 (0.0%) | 3 (1.5%) | .514 |
| Acute kidney injury | 27 (26.7%) | 6 (8.3%) | 19 (9.5%) | <.001 |
| Dialysis required | 13 (13.0%) | 7 (9.7%) | 19 (9.5%) | .454 |
| Pneumonia | 12 (11.9%) | 3 (4.2%) | 12 (6.0%) | .095 |
| Permanent pacemaker | 30 (29.7%) | 16 (22.2%) | 43 (21.6%) | .279 |
| Re-exploration for bleeding | 9 (8.9%) | 3 (4.2%) | 14 (7.0%) | .483 |
| Postoperative tamponade | 0 (0.0%) | 0 (0.0%) | 1 (0.5%) | .648 |
| Length of in-hospital stay, d | 15.4 ± 13.6 | 10.1 ± 6.5 | 9.9 ± 7.4 | <.001 |
| Readmission within 30 d of dismissal | 11 (11.0%) | 10 (14.1%) | 22 (10.8%) | .743 |
| Operative mortality (30 d) | 13 (12.9%) | 1 (1.4%) | 7 (3.4%) | <.001 |
AVR, Aortic valve replacement; ICU, intensive unit care.
Clinical Variables Associated With Mortality
In the multivariable Cox regression analysis (Table 6), older age at redo surgery (HR, 1.03; 95% CI, 1.0-1.04; P < .001), diabetes mellitus (HR, 1.5, 95% CI, 1.0-2.1; P = .001), renal failure requiring dialysis (HR, 3.1, 95% CI, 1.4-7.0); P = .005), history of myocardial infarction (HR, 1.56, 95% CI, 1.0-2.3; P = .03), and nonelective surgery (HR, 1.7, 95% CI, 1.2-2.4; P < .001) were independently associated with increased mortality. Neither valve size nor endocarditis as the indication for redo surgery was independently associated with overall mortality.
Table 6.
Univariable and multivariable regression model analysis of predictors of long-term all-cause mortality
| Variables | Univariable |
Multivariable |
||
|---|---|---|---|---|
| HR (95% CI) | P value | HR (95% CI) | P value | |
| Female sex | 1.01 (0.7-1.3) | .96 | ||
| Body mass index, kg/m2 | 1.02 (0.9-1.0) | .15 | ||
| Age at redo AVR surgery | 1.03 (1.0-1.04) | <.001 | 1.03 (1.0-1.04) | <.001 |
| Diabetes | 2.07 (1.5-2.8) | <.001 | 1.5 (1.0-2.1) | .001 |
| Renal failure-dialysis | 3.40 (1.5-7.3) | .002 | 3.16 (1.4-7.0) | .005 |
| Current smoking | 1.46 (0.9-2.3) | .11 | ||
| Nonelective surgery | 1.71 (1.2-2.2) | <.001 | 1.7 (1.2-2.4) | <.001 |
| Valve size redo surgery | ||||
| Small | 1.14 (0.8-1.5) | .40 | 1.05 (0.7-1.4) | .78 |
| Pannus formation | 0.87 (0.6-1.2) | .47 | ||
| Endocarditis | 1.31 (0.9-1.8) | .09 | 1.02 (0.7 – 1.4) | .90 |
| Years between procedures | 1.00 (0.9-1.01) | .76 | ||
| Age at primary surgery | 1.02 (1.01-1.04) | <.001 | ||
| Any concomitant procedure at primary surgery | 1.02 (0.7-1.3) | .88 | ||
| Aortic surgery at primary surgery | 0.61 (0.3-0.9) | .02 | ||
| Aortic surgery at redo surgery | 0.59 (0.4-0.8) | <.001 | 0.75 (0.5-1.0) | .10 |
| Preoperative CVA | 0.89 (0.6-1.2) | .52 | ||
| Hypertension | 1.31 (0.9-1.7) | .08 | ||
| History of myocardial infarction | 1.78 (1.1-2.6) | .006 | 1.56 (1.0-2.3) | .03 |
| History of atrial fibrillation/flutter | 1.63 (1.2-2.2) | .002 | 1.23 (0.8-1.7) | .21 |
| Postoperative CVA | 1.75 (0.5-5.5) | .33 | ||
| Reoperation for bleeding | 1.52 (0.9-2.5) | .10 | ||
| Postoperative renal failure—dialysis | 2.62 (1.7-4.0) | <.001 | ||
Valve size: small ≤21 mm. HR, Hazard ratio; AVR, aortic valve replacement; CVA, cerebrovascular accident.
Survival Endocarditis Versus Other Causes
Patients who underwent redo AVR for endocarditis had lower overall survival trend compared with those undergoing reoperation for other indications; however, the difference between the groups did not reach statistical significance (log-rank P = .092) (Figure 1, A). Lower survival among patients with endocarditis was primarily attributable to greater early postoperative mortality. In a landmark analysis, excluding the first postoperative year, survival was virtually identical for patients with endocarditis versus those without infection (Figure 1, B).
Figure 1.
A, Unadjusted Kaplan-Meier survival curves comparing patients with and without endocarditis as the indication for redo AVR after mechanical valve implantation. Survival was also similar between groups in multivariable analysis (P = .90). B, Landmark Kaplan-Meier survival curves beginning 1 year postoperatively, demonstrating comparable late survival between groups after exclusion of early postoperative risk. C, Unadjusted Kaplan-Meier survival curves comparing patients who received a bioprosthetic versus a mechanical aortic valve at redo AVR. All curves include 95% CIs. AVR, Aortic valve replacement.
Prosthesis Type at Redo Surgery and Survival
In univariate analysis, overall survival was superior in patients receiving a mechanical valve rather than a bioprosthesis at the time of reoperation. However, as was seen in the analysis of patients with endocarditis, most of the difference in survival occurred during the first year, reflecting greater-risk patients, especially those receiving homograft, most of whom had endocarditis as an indication for reoperation (Figure 1, C). At 15 years, the estimated survival of patients receiving mechanical valves was 47%, compared with 29% for patients receiving bioprosthetic valves.
Discussion
During the period of this study, 16,989 patients underwent AVR at our Clinic, and 1181 procedures were redo AVRs; most reoperations were performed for bioprosthetic valve failure. In this study, we present a comprehensive analysis of redo AVR after primary mechanical AVR. Reoperation on mechanical heart valves is relatively uncommon in current practice, and large-scale, long-term data are limited.
Patients undergoing redo AVR after mechanical AVR were typically older than 60 years, and the interval between operations varied according to the underlying indication for reintervention. The most frequent cause of reoperation after mechanical AVR was endocarditis, and the interval between the primary procedure and reintervention was less than 5 years in most patients. Endocarditis as the primary indication for redo AVR was associated with a greater rate of aortic and other concomitant procedures during the initial operation, most commonly in patients with bicuspid aortic valve disease and aortopathy. The need for more extensive surgical reconstruction and the greater use of prosthetic material may have predisposed patients to infection, leading to a shorter interval between procedures.8 Host-related factors, such as procedural complexity and the virulence of the infecting microorganism, are known to play key roles in determining early outcomes after redo AVR for endocarditis.9,10
In the present series, operative mortality among patients undergoing redo AVR for endocarditis was approximately 4-fold greater than in those reoperated for noninfectious indications. This excess risk likely reflects the intrinsic severity of active infection, the greater frequency of urgent or emergent presentation, and the complexity of surgical reconstruction required in these cases, rather than redo status alone. These findings underscore the importance of prevention strategies, including appropriate antibiotic prophylaxis and early recognition of prosthetic valve infection, to mitigate the need for high-risk reintervention.
It is notable, however, that despite the often-acute presentation and greater perioperative morbidity and mortality, long-term survival of patients with mechanical valves undergoing reoperation for endocarditis was comparable with that of patients undergoing reoperation for other causes. Indeed, after the first postoperative year, late survival of patients having replacement of a mechanical valve due to endocarditis was virtually identical to that of patients having reoperation for noninfectious indications.
Pannus formation was the second most frequent indication for redo AVR. Li and colleagues11 reported that, in their experience, obstructing pannus and perivalvular leaks were the most common indications for reoperation among patients with mechanical aortic valve prostheses undergoing redo AVR. Referral patterns may explain the relatively higher incidence of endocarditis in the present series, as 68% of all patients in the study cohort had undergone initial mechanical AVR elsewhere.
In our experience, patients with mechanical valves who underwent reoperation for pannus formation were more often female, had a longer interval between procedures, and were therefore older at the time of reoperation. Pannus formation was significantly associated with rheumatic valve disease as the predominant initial indication for mechanical AVR; it was also associated with use of smaller prosthetic valve sizes during the primary surgery. Oh and colleagues12 suggested that pannus development may result from a chronic, ongoing inflammatory process associated with rheumatic heart disease. Further, pannus formation may be caused by turbulent flow forces concentrated within the smaller effective orifice areas of small aortic prostheses.12 This mechanism could explain both the delayed presentation and the hemodynamic predisposition to pannus overgrowth, which causes prosthetic obstruction.
Structural failure and thrombosis of the mechanical prosthesis were uncommon causes for reoperation in our cohort of patients with mechanical aortic valves. This observation is consistent with the known durability of the current generation mechanical heart valves and greater attention to adequate long-term anticoagulation therapy. In earlier years, thrombosis was a not uncommon and potentially catastrophic late complication of AVR with a mechanical prosthesis, particularly those with a single-disc design.13, 14, 15, 16 Other predisposing factors include patient noncompliance with warfarin anticoagulation and underlying prothrombotic diseases.17, 18, 19 Recognition of these issues and improvements in anticoagulation protocols, as well as the availability of thrombolytic therapy, have greatly reduced the incidence and severity of mechanical valve thrombosis and the need for reoperation.17, 18, 19
When a redo operation becomes necessary, the decision to implant a new mechanical or a bioprosthetic valve should consider patient age, comorbidities, life expectancy, and individual preferences. Although mechanical valves offer superior durability, bioprosthetic valves may be favored in older patients or in those for whom lifelong anticoagulation is undesirable. In our study, survival trends after the first year postoperatively were generally similar between patients receiving mechanical and bioprosthetic valves at redo surgery, suggesting that patient-related factors, such as diabetes, renal failure, advanced age at reoperation, previous myocardial infarction, and nonelective presentation, have a greater impact on late survival than the type of prosthesis itself.
These findings have several practical implications. First, although patients undergoing redo AVR for endocarditis are a high-risk subgroup in regards to early morbidity and mortality, late survival is satisfactory and outcomes support an aggressive approach to surgical management of infected mechanical aortic prostheses. Second, because long-term survival beyond the first postoperative year is largely determined by patient comorbidities rather than operative indication or prosthesis type, prosthesis selection at reoperation should be individualized on the basis of patient age, comorbidity burden, and preferences rather than concern for differential late survival. Finally, risk counseling should clearly distinguish between early operative risk, particularly in infectious or nonelective presentations and long-term prognosis, which appears comparable across indications once early risk is overcome.
Limitations
This retrospective study reflects the practice of a single center, and institutional location and referral patterns may introduce selection bias, limiting the generalizability of our findings. The number of redo cases, although among the largest reported for mechanical prostheses, is relatively small, which limits the statistical power to detect subtle but clinically meaningful differences between subgroups. In addition, health records may have been incomplete for some patients, and this prevented accurate stratification of endocarditis cases as active or treated. As with any observational study, unmeasured confounders and missing long-term follow-up data could have influenced the results, despite careful data collection and validation.
Conclusions
Although redo AVR after primary mechanical AVR is relatively uncommon, understanding its indications and patient characteristics may guide clinical decision-making when such cases arise. Patients with mechanical valves undergoing redo AVR are typically in their early sixties, with endocarditis and pannus formation as the leading causes of reoperation. The interval between procedures varies according to the underlying indication. Early mortality after redo AVR was strongly associated with endocarditis as the indication for operation. In contrast, overall late mortality was influenced more by patient age and comorbidities, such as diabetes and renal failure. Endocarditis as an indication for reoperation and the size and type of prosthesis used had minimal impact on overall late survival.
Conflict of Interest Statement
The authors reported no conflicts of interest.
The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest.
Audio
Audio 1. This is an audio recording of the presentation of the associated abstract and discussion.
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