Ann Thorac Surg 2003;75:1808-1814
© 2003 The Society of Thoracic Surgeons
Original article: cardiovascular
Aortic valve replacement in patients with impaired ventricular function
Ram Sharony, MDa,
Eugene A. Grossi, MDa*,
Paul C. Saunders, MDa,
Charles F. Schwartz, MDa,
Giovanni B. Ciuffo, MDa,
F. Gregory Baumann, PhDa,
Julie Delianides, MAa,
Robert M. Applebaum, MDa,
Greg H. Ribakove, MDa,
Alfred T. Culliford,, MDa,
Aubrey C. Galloway, MDa,
Stephen B. Colvin, MDa
a Division of Cardiothoracic Surgery, Department of Surgery, New York University School of Medicine, New York, New York, USA
Accepted for publication January 7, 2003.
* Address reprint requests to Dr Grossi, New York University Medical Center, Suite 9-V, 530 First Ave, New York, NY 10016, USA.
e-mail: grossi{at}cv.med.nyu.edu
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Abstract
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BACKGROUND: Patients with reduced ventricular function undergoing aortic valve replacement have increased operative risks, but the impact of valvular pathophysiology and other risk factors has not been clearly defined.
METHODS: From June 1992 through June 2002, 1,402 consecutive patients underwent isolated aortic valve surgery with or without coronary artery bypass grafting; of these patients, 416 had an ejection fraction less than 40% and are the subject of this report. These patients (mean age, 68.6) had severe stenosis (62.5%), severe regurgitation (30.3%), or mixed disease (7.2%). Aortic valve replacement plus coronary artery bypass grafting was performed in 48.4% of patients, and 27% had previous cardiac surgery. Follow-up included echocardiography and survival analysis.
RESULTS: Hospital mortality was 10.1% (42 of 416), with no difference between aortic stenosis (9.6%) and regurgitation (11.1%). Multivariate analysis revealed that age (p = 0.002) and renal disease (odds ratio = 4.2; 95% confidence interval, 1.9 to 9.3; p = 0.001) were independently associated predictors of mortality. Valvular pathophysiology had no impact on mortality. Peripheral vascular disease, multivessel coronary disease, and renal disease were associated risks for any postoperative complication. Peripheral vascular disease (odds ratio = 12.3, p = 0.02), history of cerebrovascular disease (odds ratio = 4.8, p = 0.038), and diabetes (odds ratio = 2.7, p = 0.04) were associated risks for stroke. The ejection fraction was more than 40% in 52% of the patients who had postoperative echocardiography (mean follow-up, 6 months). Actuarial survival revealed no difference between pathophysiologic groups.
CONCLUSIONS: Aortic valve surgery in patients with impaired ventricular function carries an acceptable operative risk that can be stratified by age and comorbidities. The type of valvular pathophysiology does not significantly affect mortality.
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Introduction
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Chronic aortic stenosis increases left ventricular wall tension with subsequent ventricular hypertrophy, dilatation, and failure [1]. In longstanding aortic regurgitation (AR), volume overload causes left ventricular hypertrophy resulting in myocardial structural changes, including cellular hypertrophy, interstitial fibrosis, and subsequently depressed left ventricular (LV) contractility [2]. Early and conflicting reports have examined the perioperative risk of patients with reduced LV systolic function undergoing aortic valve surgery [3, 4]. Recently some authors have advocated avoiding surgical intervention in such patients because of prohibitively high risks [5]. However, other reports have demonstrated that aortic valve replacement in patients with aortic stenosis and reduced left ventricular function (LVF) has encouraging long-term survival with improved functional class [6, 7].
Although preoperative left ventricular function has been reported to provide risk stratification of perioperative prognosis and long-term survival in patients with aortic stenosis [8] and regurgitation [9, 10], no studies have compared the results for the different valvular pathophysiologies in the subgroup of patients with reduced ventricular function. In order to assess the outcomes of these patients after aortic valve replacement (AVR), we retrospectively evaluated the results of AVR performed at our institution in patients with impaired ejection fractions.
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Material and methods
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Between June 1992 and June 2002, 1,402 consecutive patients underwent isolated AVR with or without concomitant coronary artery bypass grafting (CABG) at the New York University Medical Center, Tisch Hospital (New York, NY). Of these, 416 patients (29.6%) had a LV ejection fraction less than 40% and are the principal subject of this report. Table 1
lists the preoperative characteristics of the groups of patients with normal and impaired LVF who underwent isolated AVR (with or without CABG). Among the patients with reduced LVF, there were significantly higher incidences of previous cardiac surgery, previous myocardial infarction, renal disease, congestive heart failure, peripheral vascular disease (PVD), urgent or emergent operations, and concomitant CABG. Table 2
presents the patient demographic and comorbid factors of the 416 patients with impaired LVF analyzed by valve pathophysiology. Of these patients, aortic stenosis (AS) was present in 62.5%, AR in 30.3%, and mixed disease (AS and AR) in 7.2%. The patients’ mean ± standard deviation age was 68.6 ± 6.5 years (range, 21 to 92 years); the AS patients on average were a decade older than the AR patients. In addition, the AS patients had higher incidences of concomitant CABG (p = 0.004), previous myocardial infarction (p = 0.001), and diabetes (p = 0.003). Left ventricular ejection fraction subgrouping analysis revealed that overall 22.3% of patients had an LV ejection fraction ≤ 25%. In addition, active endocarditis was more frequently associated with insufficiency (8.9% vs 1.2%; p < 0.001).
The majority of aortic procedures were performed with moderate hypothermia and cold blood cardioplegia. Transesophageal echocardiography (TEE) was used routinely for intraoperative assessment and to confirm the removal of air. Postoperative echocardiographic follow-up was available in 217 of the surviving patients (58%) with impaired LVF. The decision to perform an echocardiogram was at the discretion of the referring cardiologist. These echocardiograms were obtained at a mean interval of 6 months after surgery (range, 10 days to 9.5 years). The definitions used for preoperative risk factors and perioperative complications are those stated in the New York State Cardiac Surgery Reporting System, an audited cardiac risk and morbidity data collection instrument. Hospital mortality was defined as death at any time before discharge from the hospital. Data were prospectively collected by trained nurse clinicians. Follow-up survival was ascertained from the United States Social Security Death Index.
Statistical analysis was performed using the statistical software SPSS (SPSS Inc, Chicago, IL). Patient demographic and operative data were summarized as mean ± standard deviation, median, or prevalence, as appropriate. Continuous variables were analyzed by the Student’s t test and categorical variables by the 
2 test with continuity correction. Multivariate analyses of outcomes were performed with stepwise logistic regression. Survival analysis was performed by using life-table methodology; differences were tested with a Wilcoxon statistic. A p value of 0.05 or less was considered to be significant.
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Results
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Overall hospital mortality for the reduced LVF group was 10.1% (42 of 416) compared with 4.9% (48 of 986) in the normal LVF group (p < 0.001). Perioperative morbidity analysis (Table 3) revealed significantly higher overall complication rates in the impaired LVF group. Patients with impaired LVF had higher incidences of postoperative stroke, gastrointestinal complications, and any major complication, in addition to having longer hospital stays.
The analyses of risk factors for mortality and morbidity in AVR patients with impaired ventricular function are presented in Tables 4, 5, and 6.
Univariate risk factor analysis (Table 4) demonstrated that advanced age (> 70 years),
diabetes, renal failure, urgent or emergent operation, congestive heart failure, preoperative intraaortic balloon pump, PVD,
and ejection fraction ≤ 25% were associated with increased risk for hospital mortality. In the cohort of patients with predominant aortic stenosis, the presence of significant multivessel disease had no impact on hospital mortality (8.4% vs 10.6%; p = 0.543). Multivariate analysis revealed that age (p = 0.001) and renal disease (odds ratio [OR] = 4.2; p = 0.001; 95% confidence interval [CI] = 1.9 to 9.3) were independently associated risks of hospital mortality. Of note, valvular pathophysiology had no significant impact on mortality in either univariate or multivariate risk analysis (Fig 1).
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Table 4. Univariate Risk Factor Analysis for Hospital Mortality for Patients With Impaired Left Ventricular Function Undergoing Aortic Valve Replacement
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Table 6. Univariate Risk Factor Analysis for Major Complications in Patients With Impaired Left Ventricular Function
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Fig 1. Cumulative survival according to valvular pathophysiology (aortic stenosis and aortic regurgitation, without mixed disease) (p = 0.12). (• = predominant aortic stenosis;  = predominant aortic regurgitation.)
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Seventy-six percent of the patients with impaired LVF were free from mortality and any major morbidity. Analysis of AS and AR patient subgroups for postoperative morbidity (Table 5) revealed no significant differences between these pathologic subtypes. Univariate analysis of major morbidity in patients with impaired LV ejection fraction showed increased complications with age ≥ 70 years, PVD, history of previous myocardial infarction, urgent or emergent operation, diabetes, renal disease, history of cerebrovascular disease, and the presence of concomitant CABG (Table 6). Multivariate analysis showed that PVD (OR = 2.8; p = 0.001; 95% CI = 1.6 to 5.0), multivessel coronary disease (OR = 1.8; p = 0.02; 95% CI = 1.1 to 3.0), and renal disease (OR = 2.0; p = 0.04; 95% CI = 1.1 to 3.8) were associated with increased postoperative complications.
Perioperative stroke occurred in 2.0% of patients with normal LV, but increased to 5.5% in patients with impaired LVF (p = 0.005). Univariate analysis of stroke (new neurologic deficit or positive CAT scan, or both) in those patients with impaired LV function showed that previous myocardial infarction (8.7% vs 3.3%; p = 0.02), diabetes (11.8% vs 4.3%; p = 0.02), age ≥ 70 years (7.8% vs 2.7%; p = 0.02), history of stroke or cerebrovascular disease (12.1% vs 4.3%; p = 0.01), PVD or carotid disease (10.4% vs 3.9%; p = 0.01), and concomitant CABG (8.5% vs 2.8%; p = 0.01) were associated risk factors. Multivariate analysis of the risks of stroke revealed (Table 7)
that PVD, history of stroke or cerebrovascular disease, and diabetes were independent risk factors.
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Table 7. Multivariate Analysis of Stroke for Patients With Impaired Left Ventricular Function Undergoing Aortic Valve Replacement
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Among the patients with impaired preoperative LV function, a postoperative ejection fraction greater than 40% was found in 52% of the patients who had postoperative echocardiography (mean follow-up, 6 months). Analysis of echocardiographic follow-up studies in the different valve pathophysiology subsets revealed that ejection fraction greater than 40% was found in 54.5% and 45.3% of patients with predominant AS and AR, respectively (p = 0.24).
Follow-up analysis (92.7% complete) revealed a 5-year survival rate of 65% for the predominant AS group and 70% for the predominant aortic insufficiency (AI) group (p = 0.12). Cox regression for all death revealed that age (p < 0.001), renal disease (OR = 2.0; p = 0.003; 95% CI = 1.3 to 3.1), previous cardiac surgery (OR = 1.7; p = 0.008; 95% CI = 1.1 to 2.4), and history of stroke or cerebrovascular disease (OR = 1.6; p = 0.031; 95% CI = 1.1 to 2.3) were significant predictors of death.
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Comment
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Impaired left ventricular function has been demonstrated to be an incremental risk factor for mortality after aortic valve replacement. For patients with impaired left ventricular function, mortality rates range between 8% and 21% in the presence of aortic stenosis [8, 11] and between 6% and 12% among patients with AR [9, 12]. However, Bloomstein and coworkers [13] did not find preoperative impaired LVF to be a predictor for operative mortality. They reported an overall mortality of 16.7%, but they studied only 23 patients with low ejection fraction, most of whom were undergoing elective procedures. Our current analysis shows that patients with impaired LVF who undergo AVR have higher mortality and postoperative morbidity compared with patients with normal LVF. This correlates with the majority of previous reports that demonstrate higher, but still acceptable, operative risks with AVR in patients with impaired ventricular function. Despite the increased operative risk, it has been recently demonstrated that for patients with AS and severe LV dysfunction, a surgical approach is superior to medical treatment with respect to 1-year and 4-year survival [14].
Increased operative mortality has been reported for aortic valve surgery in certain surgical candidates, including the elderly [13, 15], patients with dialysis-dependent renal failure [16], patients undergoing concomitant CABG [17], and those requiring urgent operation [18] or reoperation [19]. The present results demonstrate that in the subset of patients with impaired ventricular function, age and renal failure are independent risk factors for mortality. In comparison with a previous report of 55 nonconsecutive patients [5], we did not find that prior myocardial infarction was a risk factor for mortality. Also, a history of previous cardiac operation and concomitant CABG were not found to be significant independent risk factors in our study that focused on patients with impaired LV function. Although these two factors were reported as risks for early mortality when a mixed (normal and impaired LV function) population was studied [20], they may have been masked by other, more dominant factors that characterize patients with impaired LVF.
The overall stroke rate in our study (3.1%) is comparable with that previously reported for valve surgery [21]. However, the risk for stroke in the impaired LV function group is 2.75-fold higher than the risk that was observed in the normal LVF group. PVD, diabetes, and previous history of cerebrovascular disease were found to be independent risk factors for stroke. These factors have also been shown to be independent predictors of new postoperative neurological events after CABG [22]. Previously, age has been reported as a risk factor and predictor of neurologic events in patients undergoing AVR [23] and reoperative AVR [24]. However, the high stroke rate (11%) in the latter reoperative AVR report prevents comparison with the current study.
We believe that our study is one of the largest studies that focuses on AVR in the presence of impaired LVF. Of noteworthy importance, we did not find any significant differences in mortality and morbidity rates in patients with impaired LVF undergoing AVR for aortic stenosis compared with patients with AR. This is contrary to the conventional belief that AR is associated with higher operative mortality than that of aortic stenosis [15, 25]. This finding implies that in earlier studies, in which the incidence of impaired ventricular function was lower, valvular pathophysiology became a surrogate variable for ventricular function, with stenosis being associated with better function than regurgitation.
Limitations
This study is limited mainly by its retrospective nature, although the data were collected prospectively. However, the strength of this study is the fact that it reports a large, consecutive experience of a single university hospital. Left ventricular systolic function was assessed using echocardiographic measurements without additional complex volume calculations. However, all LVF assessments were performed at the same echocardiography department. In daily clinical practice, M-mode echocardiographic dimensions are regarded as sufficient for determination of LVF [10], and systolic volumes and dimensions are better predictors of postoperative outcome than diastolic measurements [26].
Conclusion
Aortic valve surgery in patients with impaired ventricular function results in higher operative morbidity and mortality than in patients with normal ventricular function. These patients also present with more comorbidity compared with patients with normal LV function. However, the operative risk is acceptable and can be stratified by age and comorbidities. Valvular pathophysiology does not have a significant impact on operative risk or long-term survival. Therefore, the type of aortic valvular pathophysiology should not be considered an independent risk factor in the presence of impaired ventricular function.
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Acknowledgments
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This paper is supported in part by The Foundation for Research in Cardiac Surgery and Cardiovascular Biology.
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Top
Abstract
Introduction
