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(Circulation. 2000;101:1940.)
© 2000 American Heart Association, Inc.

Clinical Investigation and Reports

Severe Aortic Stenosis With Low Transvalvular Gradient and Severe Left Ventricular Dysfunction

Result of Aortic Valve Replacement in 52 Patients

Heidi M. Connolly, MD; Jae K. Oh, MD; Hartzell V. Schaff, MD; Veronique L. Roger, MD; Sara L. Osborn, CCRA; David O. Hodge, MS; A. Jamil Tajik, MD

From the Division of Cardiovascular Diseases and Internal Medicine (H.M.C., J.K.O., V.L.R., S.L.O., A.J.T.), the Section of Cardiovascular Surgery (H.V.S.), and the Section of Biostatistics (D.O.H.), Mayo Clinic and Mayo Foundation, Rochester, Minn.

	Abstract

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Background—The outcome of aortic valve replacement in patients with severe aortic stenosis, low transvalvular gradient, and severe left ventricular dysfunction is not well known.

Methods and Results—Between 1985 and 1995, 52 patients with left ventricular ejection fraction (EF) 35% and aortic stenosis with transvalvular mean gradient <30 mm Hg underwent aortic valve replacement. The mean (±SD) preoperative characteristics included EF, 26±8%; aortic valve mean gradient, 23±4 mm Hg; aortic valve area, 0.7±0.2 cm²; and cardiac output, 3.7±1.2 L/min. Simultaneous coronary artery bypass graft surgery was performed in 32 patients (62%). Perioperative (30-day) mortality was 21% (11 of 52 patients). Ten additional patients died during follow-up. Advanced age (P=0.048) and small aortic prosthesis size (P=0.03) were significant predictors of hospital mortality by univariate analysis. By multivariate analysis, the only predictor of surgical mortality was smaller prosthesis size. The only predictor of postoperative survival was improvement in postoperative functional class (P=0.04). Postoperative functional improvement occurred in most patients. Postoperative EF was assessed in 93% of survivors; 74% demonstrated improvement. Positive change in EF was related to smaller preoperative aortic valve area and female sex.

Conclusions—Despite severe left ventricular dysfunction, low transvalvular mean gradient, and increased operative mortality, aortic valve replacement was associated with improved functional status. Postoperative survival was related to younger patient age and larger aortic prosthesis size, and medium-term survival was related to improved postoperative functional class.

Key Words: prognosis • stenosis • valves • ventricles

	Introduction

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Severe aortic stenosis carries a dismal prognosis when associated with congestive heart failure, with an expected survival of <2 years when treated medically.¹ Aortic valve replacement is the only effective treatment, but the operative risk² increases with the development of left ventricular (LV) systolic dysfunction.^{3 4 5 6 7}

The results of aortic valve replacement are uncertain among patients with severe aortic stenosis, reduced LV ejection fraction (LVEF), and low transvalvular mean gradient. Although these patients represent <5% of patients with aortic stenosis, they also represent the most controversial subset. Increased perioperative risk and reduced late outcome compared with controls have been reported in patients with reduced LVEF.⁷ LV dysfunction may be secondary to long-standing severe aortic stenosis with superimposed myocardial fibrosis, extensive coronary artery disease, or prior myocardial infarction, and in this situation, the LV dysfunction is not likely to improve after aortic valve replacement. Some have therefore suggested that aortic valve replacement should not be considered in this subgroup of patients.⁸

Few data are available on the clinical outcome of patients with aortic stenosis, decreased LVEF, and low transvalvular mean gradient who undergo aortic valve replacement. Therefore, we tested the hypothesis that aortic valve replacement in patients with aortic stenosis, LVEF 35%, and transvalvular mean gradient <30 mm Hg can be performed at an acceptable operative and medium-term risk and that clinical and EF improvement occur in the majority of surgical survivors.

	Methods

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Study Population
From the Mayo Clinic surgical database, we identified all patients who had aortic valve replacement for native aortic stenosis in the presence of severe LV systolic dysfunction (EF 35%) and associated low transvalvular mean gradient (mean gradient <30 mm Hg) between 1985 and 1995. We previously reported the outcome of aortic valve replacement in patients with aortic stenosis and reduced LVEF.⁷ Twenty-nine of the patients included in the present series were included in our previous report. Patients were excluded if they had concomitant valvular operations other than aortic valve replacement, previous aortic valve replacement, or more than moderate aortic valve regurgitation or were <18 years old. Preoperative clinical, echocardiographic, cardiac catheterization, hemodynamic, coronary artery (Table 1), and operative (Table 2) data were reviewed in 52 consecutive patients who fulfilled entry criteria.

View this table: [in this window] [in a new window]   Table 1. Clinical and Hemodynamic Data Gathered From the Medical Records of 52 Patients

View this table: [in this window] [in a new window]   Table 1A. Continued

View this table: [in this window] [in a new window]   Table 2. Surgical Data Gathered From the Records of 52 Patients

Echocardiography
Comprehensive 2D and Doppler echocardiographic assessment³⁰ was performed at the Mayo Clinic in 50 patients (96%) 30 days before aortic valve replacement. The EF was calculated by 2D echocardiography with a modification of the method of Quinones et al^{10 11} in 17 patients, by the volumetric method¹² in 25 patients, and by visual estimate^{13 14} in 10 patients.

Hemodynamic assessment of aortic stenosis was performed by 2D/Doppler methodology, and AVA was calculated by the continuity equation.¹⁵

Cardiac Catheterization
Forty patients (77%) had preoperative hemodynamic assessment by cardiac catheterization. With fluid-filled catheters, LV and systemic arterial pressures were recorded simultaneously. Cardiac output and index were measured, and AVA was calculated from the Gorlin equation.¹⁶

Coronary angiography was performed in 50 patients (96%) (mean age±SD, 72±9 years). Coronary artery stenosis was defined as a luminal diameter narrowing of 70% in 1 of the major epicardial coronary arteries or 50% luminal diameter narrowing of the left main coronary artery.

When >1 method was used to define preoperative EF, mean pressure gradient, or AVA, the result of the echocardiographic Doppler method was used when it was performed up to 30 days before aortic valve replacement. The mean AVA (Table 1) was obtained by echocardiographic Doppler technique in 42 patients and by cardiac catheterization in 10 patients.¹⁷

Surgical Procedures
The surgical data are outlined in Table 2.

Statistical Analysis
The data are reported as mean±SD. The relationship, univariate and multivariate, of potential risk factors with operative mortality (ie, death within 30 days after operation) was assessed by logistic regression analysis. Overall survival was estimated by the Kaplan-Meier method, and the predictors were analyzed by the Cox proportional hazards model. The relationship of preoperative variables to postoperative EF was assessed by simple and multiple linear regression.

	Results

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The preoperative clinical and hemodynamic data are outlined in Table 1. The surgical procedures and data are outlined in Table 2.

Clinical Outcome
Hospital Mortality
The 30-day mortality was 21% (11 of 52 patients). Univariate analysis for operative mortality identified 2 significant preoperative risk factors: a smaller prosthesis size (P=0.03) and advanced age at operation (P=0.048) (Table 3). The mean aortic prosthesis size was 23.1±1.8 mm in survivors and 21.6±2.1 mm in patients who died perioperatively. The mean age was 70±11 years for survivors and 77±8 years for patients who died perioperatively. Multivariate analysis identified prosthesis size as the only predictor of hospital mortality. Body surface area was not significantly related to hospital mortality.

View this table: [in this window] [in a new window]   Table 3. Perioperative Mortality and Prosthesis Size, Patient Age, and Preoperative NYHA Class

Overall Survival
Ten patients (Table 4) died during a median follow-up of 1.5 years (up to 3.9 years). Two patients were lost to follow-up. Two of the late deaths were from noncardiac causes. The survival of this patient group was 62% at 3 years (Figure 1). The survival in the study group was significantly lower (P=0.04) than survival among the 128 patients who underwent aortic valve replacement for aortic stenosis, with mean gradient 30 mm Hg previously reported.⁷

View this table: [in this window] [in a new window]   Table 4. Data on 10 Late Deaths

View larger version (15K): [in this window] [in a new window]   Figure 1. A, Kaplan-Meier survival curve for patients with aortic stenosis, decreased LV function, and low transvalvular mean gradient (MG) compared with expected survival. B, Kaplan-Meier survival curve for patients with aortic stenosis, decreased LV function, and low MG (<30 mm Hg) compared with patients with aortic stenosis, decreased LV function, and MG 30 mm Hg.

The 3- and 5-year survival rates among patients without coronary artery disease were 71% compared with 58% and 29%, respectively, among patients with coronary artery disease (P=NS because of small sample size). This is in contrast to our previous report.⁷

The relationship between the number of perioperative and late deaths and the preoperative mean gradient is outlined in Table 5.

View this table: [in this window] [in a new window]   Table 5. Data on Perioperative and Late Deaths Related to Mean Gradient

Symptomatic improvement was noted in most of the survivors of surgery. Thirty patients had functional status noted before and after operation. Of these, 85% were severely symptomatic (NYHA class III or IV) before and only 23% were severely symptomatic after operation (Figure 2): 77% of patients (23 of 30 patients) improved by 1 NYHA functional class at follow-up. Twenty-three patients (77%) were NYHA class I or II at follow-up.

View larger version (39K): [in this window] [in a new window]   Figure 2. Comparison of preoperative (preop) and postoperative (postop) NYHA functional class.

The year and urgency of operation as well as a history of coronary artery bypass graft surgery or myocardial infarction did not significantly affect survival in this series. Additional factors, including age, sex, preoperative EF, aortic valve area (AVA), cardiac output, mean aortic gradient, prosthesis size, and aortic annular patch enlargement, were not related to survival.

Postoperative EF
EF was assessed echocardiographically in 93% of the 30-day survivors (38 of 41 patients) at a mean interval of 18 months after operation. Of the patients in whom LVEF was assessed after operation, 28 (74%) showed a positive change. The mean change was an increase of 10±14 EF units (P<0.001) (mean preoperative EF, 24±7%; mean postoperative EF, 32±14%) (Figure 3). The postoperative EF ranged from 12% to 65%. AVA was significantly related to a change in EF after operation (P=0.03) (r=0.36). Sex was significantly related to postoperative EF (P=0.009); women had higher postoperative EF. There was no significant preoperative sex difference in EF.

View larger version (16K): [in this window] [in a new window]   Figure 3. Comparison of preoperative (preop) and postoperative (postop) LVEF. Solid horizontal line indicates mean EF; hatched box, 1 SD; and vertical line, highest and lowest mean values.

	Discussion

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In severe aortic stenosis, the left ventricle compensates for chronic pressure overload by hypertrophy in an attempt to normalize wall stress. Initially, EF and cardiac output are maintained. When wall stress exceeds the compensating mechanism, LV systolic function declines secondary to afterload mismatch, and the mean pressure gradient generated by the LV may be low despite the presence of severe aortic stenosis. Thus, when LV dysfunction is due to afterload mismatch,⁴ as seen in severe aortic stenosis, aortic valve replacement results in improvement in EF symptoms and survival.⁷

LV function and mean aortic valve gradient are prognostic indicators of outcome among patients undergoing aortic valve replacement for aortic stenosis.¹⁸ However, the outcome of aortic valve replacement among patients with LV dysfunction and low transvalvular mean gradient has not been well characterized. These patients represent the most controversial and clinically challenging patients with aortic stenosis. Two series reported the outcome of aortic valve replacement in patients with low transvalvular pressure gradient.^{19 20} However, these 2 series combined described only 22 patients with transvalvular mean gradient <30 mm Hg, and no EF data were reported for 14 of them. When our present series was compared with the 125 patients with aortic stenosis and reduced LVEF but mean gradient >30 mm Hg previously reported,⁷ there was a significant difference in survival (P=0.04) (Figure 1B). Thus, we undertook to define the outcome and to further stratify risk in this group of patients.

The paucity of data on the outcome of aortic valve replacement in patients with aortic stenosis and LV dysfunction with low mean gradient led us to review 52 such patients in an attempt to determine perioperative mortality, overall survival, and predictors of outcome. By multivariate analysis, we found that 30-day mortality was related to aortic prosthesis size. All patients had LV dysfunction and low mean gradient; therefore, further EF and mean gradient analysis alone were not related to survival. Improved postoperative EF was related to preoperative AVA and female sex.

In the present study, smaller aortic prosthesis size was associated with increased surgical mortality, as previously reported.¹⁸ This remained an important predictor of perioperative survival even though 17% had undergone simultaneous aortic root enlargement to allow placement of a larger prosthesis. Of the 11 patients who died perioperatively, 5 received an aortic prosthesis <23 mm. There was no relationship between body surface area and perioperative mortality, but small prosthesis size reflects small annulus dimension. The body surface area of the patient who received the 17-mm aortic prosthesis was 1.32 m², and the mean±SD of body surface area of the 3 patients who received 19-mm prostheses was 1.52±0.03 m². Small valve prostheses have higher transvalvular gradients than larger prostheses.^{21 22} The failure to decrease afterload effectively with smaller aortic prostheses in these patients with low preoperative mean transvalvular gradient may influence surgical outcome.

The problem of valve-prosthesis–patient mismatch is also potentially important regarding this series of patients. The effective orifice area of a prosthesis is less than that of a normal human valve. Occasionally, the reduced prosthetic valve area further confounds the clinical situation, resulting in symptomatic and hemodynamic deterioration. This occurs when the decrease in afterload is less than expected because of small prosthesis size. This may account, in part, for the increased mortality noted among patients with the smallest prostheses.^{23 24}

Small aortic prostheses have also been associated with increased late mortality among patients undergoing simultaneous coronary artery bypass graft surgery.²⁵ This association was not appreciated among the patients we report.

It remains uncertain whether annular enlargement²⁶ to accommodate a prosthesis 1 or 2 sizes larger will improve mortality.

Effect of Aortic Valve Replacement on Postoperative EF
Aortic valve replacement for aortic stenosis decreases ventricular afterload.²⁷ EF is expected to improve after aortic valve replacement among patients with severe aortic stenosis and decreased preoperative EF.^{5 6 27 28} Those who do not improve probably have permanent myocardial fibrosis. Previous studies showed that decreased preoperative EF, previous myocardial infarction, and low preoperative aortic valve gradient are associated with decreased postoperative EF.²⁹

An improvement in postoperative LVEF of 10 EF units (Figure 3) was noted in our study. The relationship of sex differences in LV adaptation to aortic stenosis has been described.^{30 31 32} A substantial sex-associated difference in regression of LV adaptation to chronic pressure and volume overload has also been reported.¹⁸ The factors accounting for these sex differences have not been characterized. The sex difference in our series (improved postoperative EF in women) was an isolated sex-related finding (ie, preoperative EF and mean gradient were not significantly different between men and women). Excessive hypertrophy has been reported in some patients with aortic stenosis.^{31 32} This finding was not noted among the 52 patients reported in this series.

Smaller preoperative AVA was significantly related to a change in postoperative EF. The smaller preoperative AVA may suggest a more severe degree of aortic stenosis in these patients with low preoperative mean gradient. Preoperative identification of appropriate surgical candidates may be improved by the use of dobutamine infusion³³ and/or transesophageal imaging.³⁴ These modalities may aid in optimizing surgical and overall survival.

An important variable that we were unable to assess was the true degree of aortic valve stenosis. Estimation of AVA in patients with low cardiac output and low transvalvular gradient is difficult, and in several patients in this series, the surgeon noted less than severe aortic stenosis at operation. Thus, some patients may have had another cause for LV dysfunction in conjunction with aortic valve stenosis of moderate severity. In our current practice, we use dobutamine during hemodynamic assessment; however, this was not performed in a sufficient number to allow risk stratification in the current series.

Limitations
Lack of Power
This series has limited power to stratify risk and identify statistical predictors of outcome. However, no larger series of such patients is available in the literature.

Follow-Up
The postoperative EF was determined for 93% of survivors of surgery (38 of 41 patients). This should be considered in the interpretation of results, because the performance of echocardiography may have been an indicator for better outcome. Comparison of baseline characteristics between survivors with and without determination of postoperative EF indicated no differences in proportion of female patients, preoperative NYHA functional class, age, and percentage of patients with coronary artery disease in this assessment.

EF Analysis
Echocardiographic estimates of LVEF may be a cause for concern; the use of echocardiography in this clinical setting, however, is standard clinical practice. Previous studies from our institution and others have documented acceptable correlations with angiography³⁵ and have confirmed reproducibility.^{36 37 38}

Other Causes of LV Dysfunction
Causes of LV dysfunction related to factors other than aortic stenosis and coronary artery disease cannot be excluded in this patient population.

Lack of Control Group
All of the patients included in this study underwent aortic valve replacement; thus, the clinical dilemma of differentiating LV systolic dysfunction due to aortic stenosis from moderate aortic stenosis with a coexistent cardiomyopathic process cannot be addressed.

Cardiac Output Determination
Cardiac output determination may be unreliable when measured by the thermodilution technique, particularly in low-output states. In our series, however, only 6 of the 50 patients in whom cardiac output was measured (12%) had measurement by thermodilution, so this technique should not have adversely affected our data.

Dobutamine Hemodynamic Assessment
Intravenous administration of dobutamine has been proposed as a method to determine surgical outcome in patients with low-output low-gradient aortic stenosis, when there is uncertainty about the severity of aortic stenosis.³³ Hemodynamic evaluation during dobutamine infusion was not performed in enough patients to allow risk stratification in this series.

Conclusions
Patients with low-gradient aortic stenosis represent a small but controversial subset. In our patients with decreased LVEF, low mean gradient, advanced age, and high prevalence of coronary artery disease, surgical mortality was lower than previously reported and was related to aortic prosthesis size and patient age. The early and intermediate follow-up results are acceptable compared with those of age- and sex-matched controls. Marked improvement in symptoms and LVEF occurred in >70% of the survivors. Improved postoperative EF was influenced considerably by female sex and a small preoperative AVA. We submit that patients with severe aortic stenosis, reduced LV function, and low mean gradient, contrary to previous recommendations⁸ and despite increased operative mortality, should not be denied aortic valve replacement, given the substantial potential clinical benefit.

	Footnotes

 
Reprint requests to Heidi M. Connolly, MD, Mayo Clinic, 200 First St SW, Rochester, MN 55905.

Received September 9, 1999; revision received November 19, 1999; accepted December 2, 1999.

	References

Top Abstract Introduction Methods Results Discussion References

 

1. Ross J Jr, Braunwald E. Aortic stenosis. Circulation. 1968;38(suppl 1):61–67.
   
2. Christakis GT, Weisel RD, Fremes SE, Teoh KH, Skalenda JP, Tong CP, Azuma JY, Schwartz L, Mickleborough LL, Scully HE, Goldman BS, Baird RJ. Can the results of contemporary aortic valve replacement be improved? J Thorac Cardiovasc Surg. 1986;92:37–46.[Abstract]
   
3. Rahimtoola SH. Early valve replacement for preservation of ventricular function? Am J Cardiol. 1977;40:472–475.[Medline] [Order article via Infotrieve]
   
4. Carabello BA, Green LH, Grossman W, Cohn LH, Koster JK, Collins JJ Jr. Hemodynamic determinants of prognosis of aortic valve replacement in critical aortic stenosis and advanced congestive heart failure. Circulation. 1980;62:42–48.[Free Full Text]
   
5. Kennedy JW, Doces J, Stewart DK. Left ventricular function before and following aortic valve replacement. Circulation. 1977;56:944–950.[Abstract/Free Full Text]
   
6. Smith N, McAnulty JH, Rahimtoola SH. Severe aortic stenosis with impaired left ventricular function and clinical heart failure: results of valve replacement. Circulation. 1978;58:255–264.[Abstract/Free Full Text]
   
7. Connolly HM, Oh JK, Orszulak TA, Osborn SL, Roger VL, Hodge DO, Bailey KR, Seward JB, Tajik AJ. Aortic valve replacement for aortic stenosis with severe left ventricular dysfunction: prognostic indicators. Circulation. 1997;95:2395–2400.[Abstract/Free Full Text]
   
8. Carabello BA. Timing of surgery in mitral and aortic stenosis. Cardiol Clin. 1991;9:229–238.[Medline] [Order article via Infotrieve]
   
9. Tajik AJ, Seward JB, Hagler DJ, Mair DD, Lie JT. Two-dimensional real-time ultrasonic imaging of the heart and great vessels: technique, image orientation, structure identification, and validation. Mayo Clin Proc. 1978;53:271–303.[Medline] [Order article via Infotrieve]
   
10. Quinones MA, Waggoner AD, Reduto LA, Nelson JG, Young JB, Winters WL Jr, Ribeiro LG, Miller RR. A new, simplified and accurate method for determining ejection fraction with two-dimensional echocardiography. Circulation. 1981;64:744–753.[Abstract/Free Full Text]
    
11. Quinones MA, Pickering E, Alexander JK. Percentage of shortening of the echocardiographic left ventricular dimension: its use in determining ejection fraction and stroke volume. Chest. 1978;74:59–65.[Abstract/Free Full Text]
    
12. Naik MM, Diamond GA, Pai T, Soffer A, Siegel RJ. Correspondence of left ventricular ejection fraction determinations from two-dimensional echocardiography, radionuclide angiography and contrast cineangiography. J Am Coll Cardiol. 1995;25:937–942.[Abstract]
    
13. Stamm RB, Carabello BA, Mayers DL, Martin RP. Two-dimensional echocardiographic measurement of left ventricular ejection fraction: prospective analysis of what constitutes an adequate determination. Am Heart J. 1982;104:136–144.[Medline] [Order article via Infotrieve]
    
14. Rich S, Sheikh A, Gallastegui J, Kondos GT, Mason T, Lam W. Determination of left ventricular ejection fraction by visual estimation during real-time two-dimensional echocardiography. Am Heart J. 1982;104:603–606.[Medline] [Order article via Infotrieve]
    
15. Oh JK, Taliercio CP, Holmes DR Jr, Reeder GS, Bailey KR, Seward JB, Tajik AJ. Prediction of the severity of aortic stenosis by Doppler aortic valve area determination: prospective Doppler-catheterization correlation in 100 patients. J Am Coll Cardiol. 1988;11:1227–1234.[Abstract]
    
16. Gorlin R, Gorlin SG. Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves, and central circulatory shunts, I. Am Heart J.. 1951;41:1–29.[Medline] [Order article via Infotrieve]
    
17. Lewis JF, Kuo LC, Nelson JG, Limacher MC, Quinones MA. Pulsed Doppler echocardiographic determination of stroke volume and cardiac output: clinical validation of two new methods using the apical window. Circulation. 1984;70:425–431.[Abstract/Free Full Text]
    
18. Morris JJ, Schaff HV, Mullany CJ, Rastogi A, McGregor CG, Daly RC, Frye RL, Orszulak TA. Determinants of survival and recovery of left ventricular function after aortic valve replacement. Ann Thorac Surg. 1993;56:22–29.[Abstract]
    
19. Brogan WC III, Grayburn PA, Lange RA, Hillis LD. Prognosis after valve replacement in patients with severe aortic stenosis and a low transvalvular pressure gradient. J Am Coll Cardiol. 1993;21:1657–1660.[Abstract]
    
20. Blitz LR, Gorman M, Herrmann HC. Results of aortic valve replacement for aortic stenosis with relatively low transvalvular pressure gradients. Am J Cardiol. 1998;81:358–362.[Medline] [Order article via Infotrieve]
    
21. Reisner SA, Meltzer RS. Normal values of prosthetic valve Doppler echocardiographic parameters: a review. J Am Soc Echocardiogr. 1988;1:201–210.[Medline] [Order article via Infotrieve]
    
22. Iwasaka T, Naggar CZ, Sugiura T, Tarumi N, Takayama Y, Inada M. Doppler echocardiographic assessment of prosthetic aortic valve function: findings in normal valves. Chest. 1991;99:399–403.[Abstract/Free Full Text]
    
23. Rahimtoola SH. The problem of valve prosthesis-patient mismatch. Circulation. 1978;58:20–24.[Abstract/Free Full Text]
    
24. Rahimtoola SH. Valve prosthesis-patient mismatch: an update. J Heart Valve Dis. 1998;7:207–210.[Medline] [Order article via Infotrieve]
    
25. He GW, Grunkemeier GL, Gately HL, Furnary AP, Starr A. Up to thirty-year survival after aortic valve replacement in the small aortic root. Ann Thorac Surg. 1995;59:1056–1062.[Abstract/Free Full Text]
    
26. Piehler JM, Danielson GK, Pluth JR, Orszulak TA, Puga FJ, Schaff HV, Edwards WD, Shub C. Enlargement of the aortic root or anulus with autogenous pericardial patch during aortic valve replacement: long-term follow-up. J Thorac Cardiovasc Surg. 1983;86:350–358.[Abstract]
    
27. Harpole DH, Jones RH. Serial assessment of ventricular performance after valve replacement for aortic stenosis. J Thorac Cardiovasc Surg. 1990;99:645–650.[Abstract]
    
28. Pantely G, Morton M, Rahimtoola SH. Effects of successful, uncomplicated valve replacement on ventricular hypertrophy, volume, and performance in aortic stenosis and in aortic incompetence. J Thorac Cardiovasc Surg. 1978;75:383–391.[Medline] [Order article via Infotrieve]
    
29. Hwang MH, Hammermeister KE, Oprian C, Henderson W, Bousvaros G, Wong M, Miller DC, Folland E, Sethi G. Preoperative identification of patients likely to have left ventricular dysfunction after aortic valve replacement: participants in the Veterans Administration Cooperative Study on Valvular Heart Disease. Circulation. 1989;80(suppl I):I-65–I-76.
    
30. Villari B, Campbell SE, Hess OM, Mall G, Vassalli G, Weber KT, Krayenbuehl HP. Influence of the collagen network on left ventricular systolic and diastolic function in aortic valve disease. J Am Coll Cardiol. 1993;22:1477–1484.[Abstract]
    
31. Carroll JD, Carroll EP, Feldman T, Ward DM, Lang RM, McGaughey D, Karp RB. Sex-associated differences in left ventricular function in aortic stenosis of the elderly. Circulation. 1992;86:1099–1107.[Abstract/Free Full Text]
    
32. Aurigemma GP, Silver KH, McLaughlin M, Mauser J, Gaasch WH. Impact of chamber geometry and gender on left ventricular systolic function in patients >60 years of age with aortic stenosis. Am J Cardiol. 1994;74:794–798.[Medline] [Order article via Infotrieve]
    
33. deFilippi CR, Willett DL, Brickner ME, Appleton CP, Yancy CW, Eichhorn EJ, Grayburn PA. Usefulness of dobutamine echocardiography in distinguishing severe from nonsevere valvular aortic stenosis in patients with depressed left ventricular function and low transvalvular gradients. Am J Cardiol. 1995;75:191–194.[Medline] [Order article via Infotrieve]
    
34. Hoffmann R, Flachskampf FA, Hanrath P. Planimetry of orifice area in aortic stenosis using multiplane transesophageal echocardiography. J Am Coll Cardiol. 1993;22:529–534.[Abstract]
    
35. Enriquez-Sarano M, Tajik AJ, Schaff HV, Orszulak TA, Bailey KR, Frye RL. Echocardiographic prediction of survival after surgical correction of organic mitral regurgitation. Circulation. 1994;90:830–837.[Abstract/Free Full Text]
    
36. Fast J, Jacobs S. Limits of reproducibility of cross-sectional echocardiographic measurement of left ventricular ejection fraction. Int J Cardiol. 1990;28:67–72.[Medline] [Order article via Infotrieve]
    
37. Amico AF, Lichtenberg GS, Reisner SA, Stone CK, Schwartz RG, Meltzer RS. Superiority of visual versus computerized echocardiographic estimation of radionuclide left ventricular ejection fraction. Am Heart J. 1989;118:1259–1265.[Medline] [Order article via Infotrieve]
    
38. Mueller X, Stauffer JC, Jaussi A, Goy JJ, Kappenberger L. Subjective visual echocardiographic estimate of left ventricular ejection fraction as an alternative to conventional echocardiographic methods: comparison with contrast angiography. Clin Cardiol. 1991;14:898–902.[Medline] [Order article via Infotrieve]
    

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				J.-L. Monin, M. Monchi, M. E.W. Kirsch, H. Petit-Eisenmann, S. Baleynaud, C. Chauvel, D. Metz, C. Adams, J.-P. Quere, P. Gueret, et al. Low-gradient aortic stenosis: impact of prosthesis-patient mismatch on survival Eur. Heart J., November 1, 2007; 28(21): 2620 - 2626. [Abstract] [Full Text] [PDF]

				J. Bergler-Klein, G. Mundigler, P. Pibarot, I. G. Burwash, J. G. Dumesnil, C. Blais, C. Fuchs, D. Mohty, R. S. Beanlands, Z. Hachicha, et al. B-Type Natriuretic Peptide in Low-Flow, Low-Gradient Aortic Stenosis: Relationship to Hemodynamics and Clinical Outcome: Results From the Multicenter Truly or Pseudo-Severe Aortic Stenosis (TOPAS) Study Circulation, June 5, 2007; 115(22): 2848 - 2855. [Abstract] [Full Text] [PDF]

				M. Mazzoni, R. De Maria, F. Bortone, M. Parolini, R. Ceriani, C. Solinas, V. Arena, and O. Parodi Long-Term Outcome of Survivors of Prolonged Intensive Care Treatment After Cardiac Surgery Ann. Thorac. Surg., December 1, 2006; 82(6): 2080 - 2087. [Abstract] [Full Text] [PDF]

				R. O. Bonow, B. A. Carabello, K. Chatterjee, A. C. de Leon Jr, D. P. Faxon, M. D. Freed, W. H. Gaasch, B. W. Lytle, R. A. Nishimura, P. T. O'Gara, et al. 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 (Writing Committee to Revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease) Developed in Collaboration With the Society of Cardiovascular Anesthesiologists Endorsed by the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons J. Am. Coll. Cardiol., August 1, 2006; 48(3): e1 - e148. [Full Text] [PDF]

				R. O. Bonow, B. A. Carabello, K. Chatterjee, A. C. de Leon Jr, D. P. Faxon, M. D. Freed, W. H. Gaasch, B. W. Lytle, R. A. Nishimura, P. T. O'Gara, et al. ACC/AHA 2006 Practice Guidelines for the Management of Patients With Valvular Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease) Developed in Collaboration With the Society of Cardiovascular Anesthesiologists Endorsed by the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons J. Am. Coll. Cardiol., August 1, 2006; 48(3): 598 - 675. [Full Text] [PDF]

				P Pibarot and J G Dumesnil Prosthesis-patient mismatch: definition, clinical impact, and prevention Heart, August 1, 2006; 92(8): 1022 - 1029. [Abstract] [Full Text] [PDF]

				A. Kulik, I. G. Burwash, V. Kapila, T. G. Mesana, and M. Ruel Long-Term Outcomes After Valve Replacement for Low-Gradient Aortic Stenosis: Impact of Prosthesis-Patient Mismatch Circulation, July 4, 2006; 114(1_suppl): I-553 - I-558. [Abstract] [Full Text] [PDF]

				J. G. Dumesnil and P. Pibarot Prosthesis-patient mismatch and clinical outcomes: The evidence continues to accumulate J. Thorac. Cardiovasc. Surg., May 1, 2006; 131(5): 952 - 955. [Full Text] [PDF]

				R. A. Lange and L. D. Hillis Dobutamine Stress Echocardiography in Patients With Low-Gradient Aortic Stenosis Circulation, April 11, 2006; 113(14): 1718 - 1720. [Full Text] [PDF]

				J.-P. Quere, J.-L. Monin, F. Levy, H. Petit, S. Baleynaud, C. Chauvel, C. Pop, P. Ohlmann, C. Lelguen, P. Dehant, et al. Influence of Preoperative Left Ventricular Contractile Reserve on Postoperative Ejection Fraction in Low-Gradient Aortic Stenosis Circulation, April 11, 2006; 113(14): 1738 - 1744. [Abstract] [Full Text] [PDF]

				J. Chambers Low "gradient", low flow aortic stenosis. Heart, April 1, 2006; 92(4): 554 - 558. [Full Text] [PDF]

				D. P. Taggart Prosthesis patient mismatch in aortic valve replacement: possible but pertinent? Eur. Heart J., March 2, 2006; 27(6): 644 - 646. [Full Text] [PDF]

				P. A. Grayburn Assessment of Low-Gradient Aortic Stenosis With Dobutamine Circulation, February 7, 2006; 113(5): 604 - 606. [Full Text] [PDF]

				A. Chukwuemeka, V. Rao, S. Armstrong, J. Ivanov, and T. David Aortic valve replacement: a safe and durable option in patients with impaired left ventricular systolic function Eur. J. Cardiothorac. Surg., February 1, 2006; 29(2): 133 - 138. [Abstract] [Full Text] [PDF]

				H Baumgartner What influences the outcome of valve replacement in critical aortic stenosis? Heart, October 1, 2005; 91(10): 1254 - 1256. [Abstract] [Full Text] [PDF]

				B Vaquette, H Corbineau, M Laurent, B Lelong, T Langanay, C de Place, C Froger-Bompas, C Leclercq, C Daubert, and A Leguerrier Valve replacement in patients with critical aortic stenosis and depressed left ventricular function: predictors of operative risk, left ventricular function recovery, and long term outcome Heart, October 1, 2005; 91(10): 1324 - 1329. [Abstract] [Full Text] [PDF]

				P. A. Pellikka, M. E. Sarano, R. A. Nishimura, J. F. Malouf, K. R. Bailey, C. G. Scott, M. E. Barnes, and A. J. Tajik Outcome of 622 Adults With Asymptomatic, Hemodynamically Significant Aortic Stenosis During Prolonged Follow-Up Circulation, June 21, 2005; 111(24): 3290 - 3295. [Abstract] [Full Text] [PDF]