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Ann Thorac Surg 1995;59:1056-1062
© 1995 The Society of Thoracic Surgeons
The Albert Starr Academic Center for Cardiac Surgery, St. Vincent Hospital and Medical Center, Portland, Oregon
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Abstract |
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Introduction |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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Aortic valve replacement (AVR) in the small aortic root may be associated with residual obstruction to left ventricular outflow. There have been reports of results with regard to survival up to 3 to 5 years after AVR in a small aortic root using Björk-Shiley, Carpentier-Edwards, Ionescu-Shiley, or Hancock prostheses [1–5]. In addition, the results of the Lillehei-Kaster aortic valve prosthesis have been demonstrated to be satisfactory in the large sizes, but this valve was not recommended in the small sizes [6]. Most recently, reports on the St. Jude prosthesis [7, 8] have suggested its advantages to be used in a small aortic root. Kratz and colleagues [7] have recommended that in patients with a body surface area (BSA) greater than 1.9 m2 and with a 19-mm or 21-mm annulus, St. Jude valve should be used or an aortic annulus-enlarging procedure should be performed. However, late survival longer than 15 years needs to be examined. This study reports our experience in patients who had a small aortic root and received small prostheses (21 mm or less) during the past 30 years, in an attempt to investigate the determinants for their long-term survival.
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Material and Methods |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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Operative Technique
An AVR was performed under the usual methods of cardiopulmonary bypass. After 1980, myocardial protection during operation was achieved by cardioplegia and moderate hypothermia. Core temperature was lowered to 25 to 30°C. Between 1990 and 1993, retrograde cardioplegia introduced through a coronary sinus cannula was used in some patients. The heart was maintained at approximately 20°C or less by use of intermittent cardioplegia every 20 to 30 minutes. The technique of aortic valve replacement has been described previously [9]. After the aortic valvular leaflets were excised the prosthetic valve was implanted with interrupted sutures. Selection of valve prosthesis was based on patient's age, availability of postoperative anticoagulant therapy, and surgeon's preference. Prosthesis use included early Starr-Edwards (other than model 1260) in 130 (32.2%), current Starr-Edwards (model 1260 since 1969) in 50 (12.4%), Carpentier-Edwards (porcine) in 113 (28%), and other prostheses in 111 patients (27.5%) (see Table 1
for details).
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Statistical Methods
Our primary concern is long-term survival and freedom from complications, therefore, we based the analyses primarily on operative survivors only.
Univariate analysis used nonparametric actuarial survival [10] for estimating actuarial event-free rates, and the log-rank statistic for comparisons [11]. Eleven variables (age divided as above, sex, preoperative functional class, BSA, small BSA [less than 1.6, 1.7, 1.8, or 1.9 m2], period of operation, previous AVR, type of prosthesis, size of prosthesis, concomitant CABG, and re-replacement) were investigated with regard to the long-term survival by the Kaplan-Meier method.
To determine the simultaneous effects of multiple risk factors, we used semiparametric multivariable proportional hazards regression [12]. Risk factors that were significant or nearly so (p < 0.2) by univariate analysis were entered into a forward stepwise regression; entry into the model was based on the likelihood-ratio statistic based on the maximum partial likelihood estimates (SPSS, Inc, Chicago, IL). A p value of less than 0.05 was considered significant.
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Results |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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These variables were also examined in the two subsets of the patients (those without concomitant CABG and those with concomitant CABG). Variables that were not significant for the entire group of the patients may be significant in subsets of patients as described below.
INFLUENCE OF AGE ON LONG-TERM SURVIVAL.
The influence of older age is reflected by decreased survival (Fig 1). In patients younger than 49 years, the survival was 70.6% ± 7.0% at 10 years and 49.0% ± 8.9% at 20 years. In patients aged between 50 and 59 years, the survival was 71.4% ± 6.9% at 10 years and 27.6% ± 7.9% at 20 years. However, in patients aged 60 to 69 years, the survival was 52.6% ± 6.1% at 10 years and only 12.9% ± 4.9% at 20 years. In old patients, the survival was reduced to 44.5% ± 7.4% at 10 years for the patients aged between 70 and 79 years and there were no survivors at 10 years for the patients older than 80 years (p = 0.0003). Note: The Kaplan-Meier curves for each subgroup terminate at the time of the last death (or event) in that subgroup, and patients surviving beyond that time are not indicated. But in fact, such patients could be shown by extending the last point on the curve horizontally to the duration of the longest survivor in the subgroup (compare Fig 5 and Table 1
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). However, in the subset of the patients who had concomitant CABG, female patients had better long-term survival (p = 0.026; Fig 3).
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). However, those who had concomitant CABG were older (74.9 ± 8.2 versus 67.9 ± 13.5 years, p = 0.0004) and operated on more recently (61.8% versus 40.4% since 1987).
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shows the influence of the type of valve prostheses on long-term survival. In patients who received current Starr-Edwards prosthesis, the 10-year survival was 48.8% ± 7.6%. In comparison, the 10-year survival was 67.0% ± 4.5% for previous Starr-Edwards prostheses, 50.3% ± 9.1% for Carpentier-Edwards porcine prosthesis, and 34.3% ± 11.4% for other types of prostheses (p = 0.047).
INFLUENCE OF BODY SURFACE AREA ON LONG-TERM SURVIVAL.
The effect of BSA (less than, equal to, or more than 1.5, 1.6, 1.7, 1.8, and 1.9 m2) on long-term survival was examined. However, none of these variables was significant. These variables were also examined in two subsets of the patients [ie, in those who had concomitant CABG (n = 102) and those who did not (n = 302)]. A BSA less than 1.7 m2 was a significant variable in the subset of patients (n = 102) who had concomitant CABG (p = 0.014; Fig 6).
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COMPARISON BETWEEN SMALL AND LARGE AORTIC ROOTS.
With regard to the long-term survival, there were no significant differences between the patients who received small prostheses (21 mm or less) and the patients who received large prostheses (more than 21 mm, n = 2,391) (p = 0.210). Similarly, there were no differences between these two groups of patients as to the freedom from reoperation (p = 0.804) or the freedom from thromboembolism (p = 0.972).
Multivariate Analysis
Three regression analyses were performed using the Cox proportional hazard regression.
The first regression was performed for the entire group of patients (n = 404, with or without concomitant CABG). Eight variables were included in a Cox hazard regression. These variables were age as a continuous variable, gender, BSA as a continuous variable, time frame of the operation, the type of valve prostheses, concomitant CABG, re-replacement of the valve, and the size of the prostheses (21 mm versus 17 to 20 mm). This regression analysis revealed that concomitant CABG and age are independent variables to determine the long-term survival after AVR in a small aortic root (Table 2).
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The third regression was performed in the subgroup of the patients (n = 102) with concomitant CABG. The variables included in the regression analysis were the same as in the second regression except that BSA was included in the analysis as less than versus equal to or greater than 1.7 m2 (because this variable was significant in the univariate analysis). This regression analysis reveals that a BSA of less than 1.7 m2 is the only independent variable to determine the long-term survival after AVR in a small aortic root with concomitant CABG (Table 2).
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Comment |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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Despite the fact that transvalvular pressure gradients existed for small size aortic prostheses such as Ionescu-Shiley [2] or other pericardial valves [1], and Lillehei-Kaster [6] prosthesis, excellent clinical results, with certain limitations, have been reported in patients who underwent AVR with small size prostheses [1, 2, 5, 7]. For example, Teoh and associates [1] suggest that a 19-mm pericardial valve may have excellent hemodynamic results if inserted in patients with a BSA of less than 1.3 m2. Bojar and colleagues [2] have reported excellent clinical improvement from the use of small Ionescu-Shiley valves in elderly patients. Kratz and associates [7] have suggested that in patients with a 19-mm or 21-mm annulus, consideration should be given to using the Hemodynamic Plus series of St. Jude valves or performing an annulus-enlarging procedure.
In the present study, although the long-term survival for the patients who received small prostheses (21 mm or less) is not different from that for the patients who received large prostheses (more than 21 mm), this does not imply that in the patients with small aortic root the determinants of long-term survival are the same as in the patients with large aortic root. In fact, we have found from the present study that in patients with small aortic root the determinants of long-term survival are different among subsets of the patients.
Risk Factors for Long-Term Survival
In general, the influence of age on the long-term survival is obvious. However, this study shows that even in patients between 70 and 79 years old, the 10-year survival reached 44.5% ± 7.4%. This demonstrates that such patients may still benefit from AVR for their late life. Others Au: cite ref 13 in order[14–16] and ourselves [17–20] have demonstrated previously the benefit of valve operations in older patients. The present study has further demonstrated such a benefit in older patients who receive small aortic prostheses.
The influence of concomitant CABG on survival is shown in Figure 4. Although the patients who had concomitant CABG were older and operated on more recently, in the Cox regression CABG was an independent risk factor for long-term survival (Table 2).
The influence of sex on long-term survival in patients with small aortic root is rather complicated. This is reflected by the fact that in all of the patients who had small aortic root (n = 404) and in the patients who only had AVR, without concomitant CABG, sex is not a significant variable in regard to the long-term survival (Fig 2). However, in the subset of patients who had concomitant CABG, sex is a significant factor and female patients had better long-term results (p = 0.026; Fig 3). It has been well documented that female patients, after CABG, have poorer long-term results than male patients [20]. Our results that women had better long-term survival in this particular subgroup are perhaps related to the fact that female patients have smaller body size than men and therefore, they have less problems with mismatch between body size and prosthesis size. In fact, mismatch between body size and prosthesis size was the only determinant found to be significant for long-term survival in this particular group of patients (ie, the patients with concomitant CABG). The third Cox regression analysis, which was performed in the subset of patients who had concomitant CABG, showed that BSA, but not female sex, is the independent risk factor for the long-term survival (Table 2).
In general, size of the prostheses for AVR is correlated to the body size of the patient, that is, the larger the patient is, the bigger is the size of the prosthesis that may be implanted into the aortic root because the size of the root is larger. In all of our AVR patients (n = 2,977), the size (mm) of the implanted prosthesis was related to the BSA (m2) (y = 4.78x + 14.71, p < 0.0001). In those patients who received larger prostheses (21 mm or more) the BSA is not a factor influencing long-term survival. In fact, in these patients, there were no differences in the long-term survival (p > 0.05) between the patients whose BSA was greater than 1.7 m2 and those whose BSA was less than 1.7 m2. Even in the patients who received a small (21 mm or less) prosthesis, only in those patients who had concomitant CABG did the mismatch reach statistical significance. One explanation for this may be that in these patients cardiac reserve was compromised further by concomitant coronary disease and, therefore, the influence of a possible mismatch is more obvious in these patients than in those without coronary disease. Another possible explanation may be that in most of these patients coronary artery atherosclerosis was the primary indication for the operation and the aortic valve lesion in these patients was less severe than in those who underwent AVR without concomitant CABG and therefore, these patients were more sensitive to the mismatch. In fact, multivariable analysis (Cox regression) has revealed that in this subset of patients, this is the only independent variable influencing the long-term survival as described above. Thus, at least in this subset of patients, aortic root enlargement perhaps has a place and should be considered more often. In this experience, however, aortic root enlargement was only performed in 2 patients.
Type of Prosthesis
With regard to the type of valve used in patients with a small aortic root, although there have been a number of studies that suggest to use a particular type of prosthesis, a universally accepted opinion has not been formed. Stewart and colleagues [6] in their study on the Lillehei-Kaster aortic valve prosthesis suggested that this valve is not recommended in the smaller sizes because of an unfavorable ratio of effective orifice area to tissue diameter. Teoh and colleagues [1] have suggested that 19-mm pericardial prostheses (Ionescu-Shiley) may produce prohibitive gradients during exercise; therefore, they should not be used in active patients and only reserved for very small patients. In contrast, Bove and associates [5] commented that procedures to enlarge the aortic annulus are usually unnecessary if Ionescu-Shiley pericardial valves are used. Bojar and associates [2] also reported that small (17- and 19-mm) Ionescu-Shiley valves in elderly patients achieve excellent results. As aforementioned, Kratz et al [7]Au: ref 7 OK? have suggested that in patients with a BSA greater than 1.9 m2 and with a 19- or 21-mm annulus, either using St. Jude valve or performing an annulus-enlarging procedure may be favorable to the patient. New designs of prostheses such as the Hemodynamic Plus series of St. Jude valves (19 mm) [21], Medtronic-Hall [22], or Carpentier-Edwards pericardial valve [23] may increase the flow area in small sizes and therefore, further improve the hemodynamic effect when implanted in a small aortic root. However, no long-term survival data on these newly developed prostheses are available.
In the present study, we examined long-term survival in small patients who received 19- or 21-mm Starr-Edwards silicone ball valve prostheses. We found that in patients with a small aortic root the type of prosthesis is not an independent determinant of long-term survival. Although the survival with the previous Starr-Edwards prosthesis seems to be slightly better than that with other prostheses (p = 0.047; Fig 5), this factor is not an independent determinant as indicated by the Cox hazard regression, in which the valve type did not enter into the final equation. This suggests that the slight difference seen among the different types of the prostheses regarding the long-term survival may be related to other factors such as age. In fact, the patients who received the current model of Starr-Edwards prosthesis or other types of prostheses were operated on more recently than those who received the previous Starr-Edwards prosthesis. It is not surprising that, with increased surgical experience, the age of patients in more recent years was greater and this may also account for the slight difference in survival seen among the types of the prostheses. Nevertheless, the results of the Cox proportional hazard regression shows that the type of valve prostheses does not independently affect the long-term survival.
With regard to the differences between the patients who received the 21-mm and the patients who received the 17- to 20-mm prostheses, this study does not detect further significance as to the long-term survival.
Incidence of Re-replacement and Thromboembolic Complications
We have also found that the incidence of re-replacement for the patients who received small aortic prostheses (21 mm or less) is not higher than that for the patients who received larger size (more than 21 mm) prostheses (Fig 9)Au: no Fig 9, or 7 & 8. This finding suggests the tolerance of most patients to the implantation of small aortic valve prostheses. One of the reasons for this may be that most of our patients with small aortic root are older than 60 years (71.9% compared with 59.7% of patients with large aortic root; p < 0.00001). Older people are usually more tolerant to small size of aortic valve prostheses owing to less physical activity than younger patients [1]. Similarly, there were no differences between the patients who received small size and the patients who received large size prostheses with regard to thromboembolic complications. This observation further demonstrates that in the majority of patients who have small aortic root AVR may achieve satisfactory long-term results.
In conclusion, patients with small aortic root may have satisfactory long-term results after isolated AVR without aortic root enlargement procedures. Old age and concomitant CABG are the risk factors for the long-term survival in those patients. Au/Ed: paper ms: ``Neither the type of prosthesis nor other factors studied independently influence the long-term survival.'' ;please check it appears that sentence have been rearranged and not put on diskNeither the type of prosthesis nor other factors studied independently influence the long-term survival. In the subgroup of patients who require concomitant CABG, mismatch between body size and prosthesis size is a negative determinant for long-term survival. In these patients, aortic root enlargement may be advantageous. However, the benefit and the risk of this procedure should be evaluated carefully in these high-risk patients.
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Acknowledgments |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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We gratefully acknowledge the assistance of Vicki Christiansen and Bernita Wood for dedicated work at patient follow-up, of Vicki Anderson for database services, and of Maria Wesley, Rebecca Lu, and Tina Sobey for help in reviewing charts.
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Footnotes |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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Address reprint requests to Dr He, Cardiovascular Research, The Albert Starr Academic Center for Cardiac Surgery, St. Vincent Hospital & Medical Center, 9155, Barnes Rd, Suite 240, Portland, OR 97225.
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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V. Rao, G. T. Christakis, J. Sever, S. E. Fremes, G. Bhatnagar, G. Cohen, M. A. Borger, L. Abouzahr, and B. S. Goldman A NOVEL COMPARISON OF STENTLESS VERSUS STENTED VALVES IN THE SMALL AORTIC ROOT J. Thorac. Cardiovasc. Surg., March 1, 1999; 117(3): 431 - 438. [Abstract] [Full Text] [PDF]
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U. Hvass, G. M. Palatianos, R. Frassani, C. Puricelli, and M. O'Brien MULTICENTER STUDY OF STENTLESS VALVE REPLACEMENT IN THE SMALL AORTIC ROOT J. Thorac. Cardiovasc. Surg., February 1, 1999; 117(2): 267 - 272. [Abstract] [Full Text] [PDF]
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 R. Vijayanagar, G. Chan, R. Musunuru, N. Sastry, I. Siegman, N. Rattehalli, and M. Cortelli Aortic Valve Replacement Without Annular Enlargement in Patients with Small Aortic Roots Asian Cardiovasc Thorac Ann, December 1, 1998; 6(4): 279 - 284. [Abstract] [Full Text] [PDF]
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B. Medalion, B. W. Lytle, P. M. McCarthy, R. W. Stewart, K. L. Arheart, J. H. Arnold, F. D. Loop, and D. M. Cosgrove III Aortic valve replacement for octogenarians: are small valves bad? Ann. Thorac. Surg., September 1, 1998; 66(3): 699 - 706. [Abstract] [Full Text] [PDF]
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F. C. Spencer The Development of Valvular Heart Surgery Over the Past 50 Years (1947-1997): Personal Recollections Ann. Thorac. Surg., November 1, 1997; 64(5): 1549 - 1554. [Abstract] [Full Text]
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R. De Paulis, L. Sommariva, G. M. De Matteis, E. Caprara, F. Tomai, A. P. de Peppo, P. Polisca, C. Bassano, and L. Chiariello EXTENT AND PATTERN OF REGRESSION OF LEFT VENTRICULAR HYPERTROPHY IN PATIENTS WITH SMALL SIZE CARBOMEDICS AORTIC VALVES J. Thorac. Cardiovasc. Surg., May 1, 1997; 113(5): 901 - 909. [Abstract] [Full Text]
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G. T. Christakis and B. S. Goldman Do Small Aortic Valves Influence Long-Term Survival? Ann. Thorac. Surg., April 1, 1997; 63(4): 933 - 934. [Full Text]
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D. Sawant, A. K. Singh, W. C. Feng, A. A. Bert, and F. Rotenberg Nineteen-Millimeter Aortic St. Jude Medical Heart Valve Prosthesis: Up to Sixteen Years' Follow-up Ann. Thorac. Surg., April 1, 1997; 63(4): 964 - 970. [Abstract] [Full Text]
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A. C. Moulijn, H. A. Verheul, E. Dekker, B. J. Amsel, G.-W. He, G. L. Grunkemeier, and A. Starr Background Mortality and Aortic Valve Replacement in the Elderly Ann. Thorac. Surg., January 1, 1997; 63(1): 300 - 301. [Full Text]
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G. T. Christakis, C. D. Joyner, C. D. Morgan, S. E. Fremes, K. J. Buth, J. Y. Sever, V. Rao, K. P. Panagiotopoulos, P. M. Murphy, and B. S. Goldman Left Ventricular Mass Regression Early After Aortic Valve Replacement Ann. Thorac. Surg., October 1, 1996; 62(4): 1084 - 1089. [Abstract] [Full Text]
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