Ann Thorac Surg 2011;92:866-872. doi:10.1016/j.athoracsur.2011.04.028
© 2011 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Operative Risks and Survival in Veterans With Severe Aortic Stenosis: Surgery Versus Medical Therapy
Sam Chitsaz, MD,
Nicolas Jaussaud, MD,
Edward Chau, MD,
Kimberly S. Yan, BS,
Ali N. Azadani, PhD,
Mark B. Ratcliffe, MD,
Elaine E. Tseng, MD*
Department of Surgery, University of California San Francisco Medical Center, and San Francisco Veterans Affairs Medical Center, San Francisco, California
Accepted for publication April 4, 2011.
* Address correspondence to Dr Tseng, UCSF Medical Center and San Francisco VAMC, Division of Cardiothoracic Surgery, 500 Parnassus Ave, Ste W405, Box 0118, San Francisco, CA 94143-0118 (Email: elaine.tseng{at}ucsfmedctr.org).
 |
Abstract
|
|---|
Background: Transcatheter aortic valves were developed as an alternative to surgery for the one third to two thirds of patients with severe aortic stenosis who do not undergo aortic valve replacement. In this study, we examined reasons for medical management of aortic stenosis in relation to operative risks and outcomes for veterans with and without valve replacement.
Methods: The echocardiography database was screened from 2000 to 2007 for severe aortic stenosis. The Society of Thoracic Surgeons risk scores and survival were determined for patients with and without aortic valve replacement.
Results: Of 132 severe aortic stenosis patients included, 42% were medically managed. Predicted operative mortality risk was lower for surgical patients than for medical patients (4.5% ± 4.2% versus 6.8% ± 5.1%, p = 0.002). Overall, the most common reason for medical management of aortic stenosis was assumption that the patient was high risk for surgery (30.4%). The surgery group had significantly higher median survival (92.2 versus 32.4 months) and 5-year survival (71% versus 37%, p < 0.001) than the medical group. Cardiac surgery was not consulted in 61% of medically managed patients, of whom only 18% had Society of Thoracic Surgeons risk score of 10 or greater. Aortic valve replacement was an independent predictor of lower mortality (hazard ratio 0.43, p = 0.008).
Conclusions: Although operative risk was higher among patients who did not undergo surgery, most were not the 10% or greater required for transcatheter valves. Given the significantly lower survival with medical therapy, aortic valve replacement should be carefully considered for most severe aortic stenosis patients whereas transcatheter aortic valves should be reserved for patients with high operative risks.
|
Introduction
|
|---|
Aortic valve replacement (AVR) is the gold standard for treatment of severe aortic stenosis (AS), the most frequent pathology for which AVR is performed [1, 2]. Although severe AS with symptoms, concomitant coronary artery bypass graft surgery (CABG) or open heart surgery, or left ventricular systolic dysfunction are class I indications for AVR [2], one third to two thirds of such patients are deprived of AVR because of age, comorbidities, high operative risk, or lack of indicative symptoms [3–5].
Development of transcatheter aortic valve implantation (TAVI) has opened a new chapter for inoperable AS patients, and may radically change the patients denied or referred for surgery in the future [6]. Limitations of the technology include paravalvular leak and unknown long-term durability, but the technology is evolving [7]. As life expectancy increases, the elderly AS population is expected to increase. To understand the role of TAVI within the context of current clinical decision making, it is important to have a clear perspective of clinical course and survival characteristics of severe AS patients, particularly those managed without surgery.
Medical therapy for severe AS has a poor natural history, with low survival rates for patients without surgery [4, 8]. However, few studies have predicted AVR operative risk for AS patients not operated on and primarily relied on less predictive European System for Cardiac Operative Risk Evaluation (EuroSCORE) risk assessments [3, 9]. In this study, our goal was to calculate The Society of Thoracic Surgeons (STS) risk scores of severe AS veterans diagnosed by echocardiography and uncover reasons why patients did not undergo surgery. We compared risk scores and survival of patients with and without AVR.
|
Material and Methods
|
|---|
Patient Population and Clinical Data
The San Francisco Veterans Affairs Medical Center echocardiography database was reviewed to identify patients with documented severe AS from January 2000 to July 2007. We chose to have at least 3 years' follow-up for all patients to observe patients with questionable symptoms and patients who refused surgery, and to allow AVR for patients gradually referred to surgery. Inclusion criteria for the study were patients with severe AS, defined as aortic valve area less than 1.0 cm2 calculated by either echocardiography or cardiac catheterization, or mean transvalvular gradient of 40 mm Hg or more. Medical records were reviewed to determine if patients had symptoms referable to AS. Patients were classified as symptomatic if they had angina, dyspnea on exertion, shortness of breath, or at least one episode of syncope. Patients being medically treated with diuretics with relief of shortness of breath were considered symptomatic. Patients who during follow-up did not undergo AVR were reviewed to assess reasons and to determine if surgeons were consulted. Telephone follow-up was performed for medically managed patients to determine if AVR was performed elsewhere and their status updated. The study was approved by the Veterans Affairs (VA) Institutional Review Board and the University of California Committee on Human Research. Informed consent was waived owing to the retrospective nature of the study, but for patients undergoing telephone follow-up, informed consent was obtained.
Two independent investigators reviewed in detail echocardiography, angiography, clinical, and surgical data to extract patient risk factors. Risk factors, including coronary artery disease, heart failure, hypertension, diabetes mellitus, and renal insufficiency, were defined based on the STS risk calculator. Pulmonary artery hypertension was defined as mean pulmonary artery pressure of 30 mm Hg or greater. Liver disease was defined as having cirrhosis, positive serologic markers of viral hepatitis, serum albumin less than 3.0 g/dL, total serum bilirubin greater than 50 µmol/L, and prothrombin time greater than 2.3 s.
The primary endpoint of the study was all-cause mortality. Death was determined by the Social Security Death Index, and follow-up data were obtained from the VA Computerized Patient Record System. Follow-up data were available for all patients. Survival was calculated in months.
Risk Score Calculation
The STS risk score for operative mortality was calculated by the online STS risk calculator (dataset 2.61; available at: http://209.220.160.181/stswebriskcalc261/de.aspx) [10]. For patients with AVR, STS risk scores were calculated using clinical data at time of surgery. For nonsurgically managed patients, anticipated STS risk scores were calculated for isolated AVR based on data recorded at time of first diagnosis of severe AS. If a patient had an isolated CABG or percutaneous coronary intervention within 1 year after diagnosis of severe AS, STS risk score was calculated for AVR/CABG. Given our exclusive veteran population and to validate our STS risk scores, we calculated VA risk scores for operative mortality using the online VA Surgical Quality Improvement Program patient risk calculator (version 19; available at: https://vhadennsqipweb.v19.med.va.gov/NSQIP/risk/index.htm).
Statistical Analysis
Normally and nonnormally distributed continuous variables are presented as mean ± SD, and median and range, respectively. Independent sample Student's t test, Mann-Whitney U test, and Fisher's exact test were used to compare normally distributed, nonnormally distributed, and categorical variables, respectively. Linear regression analysis and paired t test were used to compare calculated STS and VA risk scores. Survival was estimated using Kaplan-Meier method and log rank test was used to test for differences between survival curves. The Statistical Package for the Social Sciences version 15.0 (SPSS, Chicago, IL) was used for graphic plots, statistical analyses, and tests. Differences were considered statistically significant at p values of less than 0.05.
|
Results
|
|---|
Baseline Patient Characteristics
Search of the echocardiography database yielded a total number of 147 patients diagnosed with severe AS (Fig 1
). Thirteen surgical patients underwent concomitant procedures other than CABG, including mitral valve repair, aortic aneurysm repair, tricuspid repair, and Maze procedures that precluded STS risk calculation. Two medical patients underwent AVR at an outside institution and were excluded owing to lack of clinical information from the outside hospital at time of AVR. Of the 132 remaining patients, 56 (42%) were managed without AVR, 1 of whom later underwent isolated CABG. Forty-two AVR patients (55%) received concomitant CABG.
View larger version (41K):
[in this window]
[in a new window]
|
Fig 1. Patients diagnosed with severe aortic stenos (AS) and their treatment. (AVR = aortic valve replacement; CT = cardiothoracic; STS = The Society of Thoracic Surgeons.)
|
|
Patients' baseline characteristics are summarized in Table 1. The AVR group was significantly younger than the nonsurgical group (p < 0.001), had a higher proportion of white patients (p < 0.05), higher prevalence of coronary artery disease (p < 0.001), and lower prevalence of renal insufficiency (p = 0.001). The entire study population was male. Mean aortic pressure gradient was significantly lower for the medical group than for the surgical group; however, gradients rose to 37.1 ± 15.9 mm Hg at a median of 3.42 months (range, 0 to 81.9 months) for nonsurgical patients, not significantly different from the AVR group (p = 0.084).
Decision on Surgery
Of 56 severe AS patients without AVR, the most frequent reasons for medical management included the assumptions that the patient was at high risk for AVR (17 patients, 30%) and that the patient was asymptomatic (13 patients, 23%), followed by patient refusal of AVR (11 patients, 20%). Of 13 patients deemed asymptomatic, 4 were symptomatic. Only 22 patients (39%) medically managed were referred for surgery consultation (Fig 1). Of 34 patients (61%) not referred to cardiac surgery, 5 patients refused referral for AVR evaluation. For the remaining 29 patients, surgery was not recommended—the primary reason was assumption that the patient was asymptomatic (29%), followed by the assumption that symptoms were exclusively due to another etiology, namely, coronary artery disease (26.5%), and assumption that the patient was high risk for surgery due to comorbidities (23.5%). Among patients seen by cardiac surgery and recommended AVR, 6 patients refused surgery. Of the remaining 16 patients, estimated high perioperative mortality risk was by far the most frequent reason for refusing AVR (41%). Reasons for medical management are summarized in Table 2.
Of 9 medical patients seen by surgeons and assumed to be high risk, 5 had 10% or greater STS risk and 2 patients had 8% risk, 1 was an active intravenous drug abuser, and 1 was a frail elderly patient at high risk of aspiration; the remaining 2 patients had 5% risk, and both had pulmonary rehabilitation concerns as well as 1 with morbid obesity. Among 8 patients not referred to cardiac surgery and assumed to be high risk, 5 had 10% or greater risk, 1 had 6.5% risk with end-stage renal disease, and 2 had 3.5% risk, 1 with dementia. Overall, among patients deemed high risk by either surgery or cardiology, 1 patient had cirrhosis and hepatitis C, 1 had metastatic cancer, and 3 had dementia as risk factors not accounted for by the STS calculator. One of the patients in the medical group underwent isolated CABG later. The reason behind not performing concomitant AVR was that results of consecutive echocardiography examinations were borderline and varied between moderate and severe AS, while transvalvular gradient on cardiac catheterization demonstrated moderate AS.
STS Risk Score for Operative Mortality
The STS risk score for perioperative mortality was significantly lower for the AVR group than for the medical group (4.5% ± 4.2% versus 6.8% ± 5.1%, respectively, p = 0.002; median 3.35% versus 5%, respectively). Of 56 medically managed patients, only 12 (21%) had a risk score of 10% or greater. For patients undergoing AVR, 7% (5 patients) had risk score of 10% or greater. Risk scores for different medical subgroups are presented in Table 3.
View this table:
[in this window]
[in a new window]
|
Table 3 The Society of Thoracic Surgeons (STS) Operative Mortality Risk Scores for Aortic Valve Replacement (AVR) and Medical Groups
|
|
The VA risk score for operative mortality was directly correlated to the STS score with a correlation coefficient of 0.86 (R2 = 0.73, p < 0.001; Fig 2
); however, the VA score was higher than the STS score on average (6.9% ± 6.2% versus 5.4% ± 4.7%, respectively, p < 0.001). Twenty-six patients (20%; 15 patients in the medical group and 11 patients in the AVR group) had a VA risk score of 10% or greater for operative mortality, compared with 17 patients (13%) with an STS risk score of 10% or greater (p < 0.001).
View larger version (22K):
[in this window]
[in a new window]
|
Fig 2. Scatter plot of relationship between calculated Society of Thoracic Surgeons (STS) and Veterans Affairs (VA) risk scores for operative mortality.
|
|
Follow-Up and Survival
Eighteen patients (24%) in the AVR group and 38 patients (68%) in the nonsurgery group died during follow-up. Operative mortality for isolated AVR was 3% (1 of 34) whereas operative mortality was 0% for AVR plus CABG, for a total of 1.3% combined mortality. The patient who died after AVR had hemodynamically deteriorated before AVR, so that he received a left ventricular assist device for stabilization, and subsequently underwent AVR but died postoperatively. Median survival rate was higher in the AVR group than in the medical group (92.2 months versus 32.4). Moreover, the AVR group showed higher survival rates than the nonsurgery group at 1 year, 88% (95% confidence interval [CI], 81% to 95%) versus 78% (95% CI, 68% to 88%); at 3 years, 81% (95% CI, 72% to 90%) versus 44% (95% CI, 31% to 57%); and at 5 years, 71% (95% CI, 58% to 85%) versus 37% (95% CI, 23% to 50%; log-rank test p < 0.001; Fig 3
). Cox proportional hazards regression model showed that refusing AVR was a predictor of mortality, as well as older age, higher level of serum creatinine, and liver disease. The AVR group had a hazard ratio for mortality of 0.43 (95% CI, 0.23 to 0.80, p = 0.008; Table 4).
View larger version (27K):
[in this window]
[in a new window]
|
Fig 3. Kaplan-Meier survival curves for severe aortic stenosis (AS) patients treated medically (solid line) versus surgically (broken line). (AVR = aortic valve replacement.)
|
|
Two patients in the surgical group died before AVR. One patient, a post-CABG 80-year-old man was diagnosed with severe AS and coronary artery disease but lacked sufficient conduit. He was offered minimally invasive reoperative AVR after percutaneous coronary intervention, but he delayed his hybrid procedure for family reasons. Before percutaneous coronary intervention, he suffered a hip and humerus fracture and died at an outside institution. The second patient, a 59-year-old veteran with severe AS and coronary artery disease, chronic obstructive pulmonary disease, and pulmonary hypertension was offered AVR/CABG after medical treatment of an episode of decompensated heart failure and pulmonary edema. Despite recommendations of his physicians, he went home to get his affairs in order before surgery and died before his scheduled surgery.
Two patients with AS assumed not to be severe died within a year, with echocardiograms that showed valve areas less than 1.0 cm2 and mean gradients of 33 and 35 mm Hg. Two other patients are alive but with discrepancies in mean gradients and calculated valve areas between repeated echocardiograms and cardiac catheterization.
|
Comment
|
|---|
In this study based on an echocardiography database, we present the proportion of surgical versus nonsurgical treatment, STS calculated risk scores, and survival outcomes for veterans with severe AS. We found approximately 40% of veterans were medically managed and 60% underwent AVR. This proportion of medically managed severe AS is consistent with results from the Michael E. DeBakey Veterans Affairs Medical Center in Texas [11] and the EuroHeart Survey [12]; however, frequency of nonsurgical therapy has been significantly higher in other academic institutions, ranging from 52% to 69% [4, 9, 13]. In our population, the AVR group was younger than the medical group, which reduced operative risk. However, age is not a contraindication to surgery [2], and in a study of octogenarians who refused AVR, mortality increased more than 12-fold over that for patients who underwent AVR [14].
We found a higher incidence of coronary disease among AVR patients. Whether patients not considered surgical candidates by their referring physicians are also not being referred for cardiac catheterization is not known but is a potential source of bias. However, our operative mortality for AVR/CABG was lower than for isolated AVR even though according to the STS executive summary, unadjusted overall mortality of AVR/CABG is greater than isolated AVR (approximately 5% versus 3% nationally). We examined severe AS patients, including AVR and AVR/CABG patients; thus, our predicted STS risk score for the operated group was significantly higher (4.5%) than that reported by Bach and colleagues [9], of 1.8%, which most likely represents isolated AVR. In our hands, AVR/CABG had no increase in mortality over AVR alone. Including both AVR/CABG and AVR, while not necessarily examined in previous studies of nonoperative AS, is important as patients not referred for severe AS often have unknown status of coronary disease that would be discovered during preoperative AVR workup.
Another difference in the AVR population that reduced risk of postoperative mortality was a lower serum creatinine and incidence of renal dysfunction compared with medical patients. Medically treated patients had lower gradients and slightly larger valve area at the time of AS diagnosis but within a median of 3.4 months, hemodynamics were not statistically different from those of their AVR counterparts.
In our center, clinicians' assessment of high operative mortality risk was the primary reason for medical management of severe AS, and overall correlated well with mean predicted STS risk for mortality of 10.3% to 11.7%. However, approximately 40% of those patients had predicted STS risks of less than 10%. Careful evaluation by a surgeon is required to assess AVR eligibility. The second most frequent reason for nonoperative management was the assumption that the patient was asymptomatic; however, nearly a third of those patients were symptomatic, and the proportion may have been greater if standardized routine exercise testing had been performed. Patients may unconsciously decrease their level of activity gradually to below their symptom threshold. Understanding how a patient's activity has changed from a broader perspective is important in assessing true asymptomatic status. Given the higher risk of the symptomatic versus the asymptomatic subgroup and the excellent surgical outcomes of AVR, consideration should be given to AVR for asymptomatic patients. Unlike the Texas VA study, patient refusal of AVR was not the primary reason for medical treatment, but was third. Lastly, the assumption that symptoms were not due to AS and the assumption that AS was not severe were the final reasons for refraining from surgery.
Approximately 60% of nonoperative patients in this study were not referred for cardiac surgery consultation, similar to the study by Bakaeen and associates [11]. Within this unreferred subgroup, the most frequent reasons for medical management were the assumption that the patient was asymptomatic, whereas 30% were symptomatic upon careful medical record review; and the assumption that a patient's symptoms were caused by other conditions, namely, coronary artery disease or chronic obstructive pulmonary disease. Overall, the assumption that a patient was a high surgical risk was third, accounting for a small population of patients eligible for transcatheter valves. In the unreferred population, the median predicted STS risk of operative mortality was 5%, and less than 20% patients had a risk score of 10% or greater.
The STS and VA risk score assessments showed very good correlation in our population. The VA risk estimation examines factors not included in the STS calculator such as patient functional status, use of diuretics, presence of cardiomegaly, and American Society of Anesthesiologists (ASA) classification. On average, our VA risk scores were 1.5% higher than estimated STS scores. Nevertheless, 80% of our study population had a VA risk score of less than 10%.
Although EuroSCORE risk assessment overestimates mortality risk compared with the STS calculator [15], our operative mortality of 1.3% was less than the 4.5% predicted by the STS. Consideration of AVR in asymptomatic patients may be warranted in our population based on these results. Short-term and long-term survival was significantly longer for the AVR group than for the medical group. Kvidal and coworkers [16] showed that after AVR, patient symptoms diminish considerably, quality of life improves, and long-term survival approaches that expected for an aged-matched population. Thus, it is crucial to clarify reasons for high mortality risk and carefully assess symptomatology. Certainly, some patients with low risk scores are poor surgical candidates because of frailty and comorbidities not assessed by current scoring systems. Therefore, clinical judgment remains the mainstay for determining whether patients are at high risk for surgery [17]. Given surgeons' experience with postoperative recovery of borderline patients, the 60% of patients not referred to surgery should at least be evaluated by cardiac surgeons. Multidisciplinary evaluation by cardiology and cardiac surgery are essential to assess patient symptoms and underlying disorders for an accurate estimation of the risk of postoperative complications and mortality.
Transcatheter aortic valve implantation has emerged as an alternative to treat inoperable patients with severe AS [6, 7]. Approved in Europe and utilized in Canada and Asia, TAVI will play a greater role in treating high-risk AS patients in the future. However, since only 30% of patients denied AVR were considered high risk clinically and only 21% had 10% or greater STS risk, better definition of the population for TAVI will be required. Despite TAVI, not all patients referred undergo TAVI, with 15% of patients undergoing AVR and 30% of patients considered ineligible [18]. Paravalvular leak and unknown durability remain important pitfalls; however, as transcatheter valve designs and implantation techniques evolve, they will be an important alternative to AVR in select patients [7]. Multidisciplinary teams and improved estimation of operative risk will be necessary to determine the role of TAVI in the current paradigm of managing severe AS patients.
Study Limitations
This retrospective single-center study of veterans was all male, so results cannot be generalized to both sexes. Review of our surgical database, which began in 2001, revealed that the number of AVRs performed at our center was significantly greater than those found from the echocardiography database. A large proportion of veterans undergoing surgery at our hospital was referred from numerous remote sites in Northern California and Nevada. Because we did not have access to echocardiography databases for all referring sites, we could not accurately assess whether we have overestimated or underestimated the proportion of nonsurgical veterans in the VA system overall. It is possible that local sites not associated with an academic institution may refer even less frequently to cardiac surgery, given a lack of cardiac surgeon on site. We, therefore, limited this study to results based on our echocardiography database. Another limitation was that we were not able to evaluate patients' frailty based on the Cardiovascular Health Study frailty index or the Study of Osteoporotic Fractures frailty index, among others, because they included variables that should be assessed prospectively during a clinic visit or hospitalization. The Morse fall scale and the Braden risk assessment scale were measured only for hospitalized surgical patients and were not recorded for any patients in the medical group.
In conclusion, owing to the significantly lower survival rate of medically managed patients, AVR should be carefully considered for the majority of severe AS patients with TAVI reserved for those with high operative risks. Cardiologists and cardiac surgeons should be involved jointly in multidisciplinary decision making to assess symptomatology, operative risk, and evaluation of appropriate candidates for AVR.
|
Acknowledgments
|
|---|
This work was supported by the American Heart Association, the Northern California Institute for Research and Education, and the Fédération Française de Cardiologie/Société Française de Cardiologie, and Société Française de Chirurugie Thoracique et Cardio-Vasculaire.
|
References
|
|---|
- Bach DS, Radeva JI, Birnbaum HG, Fournier AA, Tuttle EG. Prevalence, referral patterns, testing, and surgery in aortic valve disease: leaving women and elderly patients behind? J Heart Valve Dis 2007;16:362-369.[Medline]
- Bonow RO, Carabello BA, Chatterjee K, et al. 2008 Focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines J Am Coll Cardiol 2008;52:e1-e142.[Medline]
- Bach DS, Cimino N, Deeb GM. Unoperated patients with severe aortic stenosis J Am Coll Cardiol 2007;50:2018-2019.[Medline]
- Varadarajan P, Kapoor N, Bansal RC, Pai RG. Clinical profile and natural history of 453 nonsurgically managed patients with severe aortic stenosis Ann Thorac Surg 2006;82:2111-2115.[Abstract/Free Full Text]
- Iung B, Cachier A, Baron G, et al. Decision-making in elderly patients with severe aortic stenosis: why are so many denied surgery? Eur Heart J 2005;26:2714-2720.[Abstract/Free Full Text]
- Leon MB, Smith CR, Mack M, et al. Transcatheter aortic-valve implantation for aortic stenosis in patients who cannot undergo surgery N Engl J Med 2010;363:1597-1607.[Medline]
- Vahanian A, Alfieri O, Al-Attar N, et al. Transcatheter valve implantation for patients with aortic stenosis: a position statement from the European Association of Cardio-Thoracic Surgery (EACTS) and the European Society of Cardiology (ESC), in collaboration with the European Association of Percutaneous Cardiovascular Interventions (EAPCI) Eur Heart J 2008;29:1463-1470.[Abstract/Free Full Text]
- Iivanainen AM, Lindroos M, Tilvis R, Heikkila J, Kupari M. Natural history of aortic valve stenosis of varying severity in the elderly Am J Cardiol 1996;78:97-101.[Medline]
- Bach DS, Siao D, Girard SE, et al. Evaluation of patients with severe symptomatic aortic stenosis who do not undergo aortic valve replacement: the potential role of subjectively overestimated operative risk Circ Cardiovasc Qual Outcomes 2009;2:533-539.[Abstract/Free Full Text]
- O'Brien SM, Shahian DM, Filardo G, et al. The Society of Thoracic Surgeons 2008 cardiac surgery risk models: part 2—isolated valve surgery Ann Thorac Surg 2009;88(Suppl):23-42.[Abstract/Free Full Text]
- Bakaeen FG, Chu D, Ratcliffe M, et al. Severe aortic stenosis in a veteran population: treatment considerations and survival Ann Thorac Surg 2010;89:453-458.[Abstract/Free Full Text]
- Iung B, Baron G, Butchart EG, et al. A prospective survey of patients with valvular heart disease in Europe: the Euro Heart Survey on Valvular Heart Disease Eur Heart J 2003;24:1231-1243.[Abstract/Free Full Text]
- Freed BH, Sugeng L, Furlong K, et al. Reasons for nonadherence to guidelines for aortic valve replacement in patients with severe aortic stenosis and potential solutions Am J Cardiol 2010;105:1339-1342.[Medline]
- Kojodjojo P, Gohil N, Barker D, et al. Outcomes of elderly patients aged 80 and over with symptomatic, severe aortic stenosis: impact of patient's choice of refusing aortic valve replacement on survival Q J Med 2008;101:567-573.[Abstract/Free Full Text]
- Dewey TM, Brown D, Ryan WH, et al. Reliability of risk algorithms in predicting early and late operative outcomes in high-risk patients undergoing aortic valve replacement J Thorac Cardiovasc Surg 2008;135:180-187.[Abstract/Free Full Text]
- Kvidal P, Bergstrom R, Horte LG, Stahle E. Observed and relative survival after aortic valve replacement J Am Coll Cardiol 2000;35:747-756.[Medline]
- Vahanian A, Otto CM. Risk stratification of patients with aortic stenosis Eur Heart J 2010;31:416-423.[Abstract/Free Full Text]
- Otten AM, van Domburg RT, van Gameren M, et al. Population characteristics, treatment assignment and survival of patients with aortic stenosis referred for percutaneous valve replacement EuroIntervention 2008;4:250-255.[Medline]
Top
Abstract
Introduction
