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Ann Thorac Surg 2000;69:1459-1465
© 2000 The Society of Thoracic Surgeons
a Departments of Department of Thoracic and Cardiovascular Surgery, Aarhus University Hospital - Skejby Sygehus, Aarhus, Denmark
b Department of Cardiology, Skejby Sygehus, Aarhus University Hospital, Aarhus, Denmark
Address reprint requests to Dr Lund, Department of Cardio-Thoracic Surgery, Copenhagen University Hospital in Gentofte, Niels Andersens Vej 65, DK-2900 Hellerup, Denmark
e-mail: olund{at}thorax.dk
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Abstract |
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Methods. A detailed follow-up was performed to a maximum of 18.6 years in 694 patients aged 15 to 83 years who undervent aortic valve replacement (AVR) with the standard St. Jude valve during 1980 to 1993. The Cox regression analysis was used to identify independent determinants of outcome in the aortic stenosis (n = 490) and regurgitation (n = 204) groups.
Results. Overall survival was 58%, 39%, and 37% at 10, 15, and 18 years, respectively. Only 12% of deaths (0.60%/patient-year) were related to the valve with a 15-year freedom of 91%. Embolism (1.18%/patient-year) and anticoagulant-related bleeding (2.24%/patient-year) were the dominant complications with 10-year/15-year freedoms of 90%/80% and 85%/72%, respectively. Only 24% of bleeding events were classified as major. Valve thrombosis occurred in 2 patients (0.04%/patient-year): 1 did not receive vitamin K antagonist treatment and International Normalized Ratio was below target level in the other. There were no mechanical failures. Endocarditis (0.42%/patient-year) and paravalvular leak (0.42%/patient-year) occurred with 15-year freedoms of 92% and 96%, respectively, with a relation between the latter (but not the former) and preoperative endocarditis in the regurgitation group. Freedom from serious complications (2.33%/patient-year) and all complications joined (4.33%/patient-year) were 72% and 54%, respectively, at 15 years with a 96% freedom from redo AVR (0.36%/patient-year). Age- and heart-related variables were independent risk factors for mortality, thromboembolism, bleeding, serious complications, and all complications joined. Small valve (19 and 21 mm) adversely affected serious and all complications in the regurgitation group.
Conclusions. With a follow-up approaching 2 decades and exhibiting a low rate of valve-related deaths, acceptable low thrombogenicity, and abscence of mechanical failure, the standard aortic St. Jude disc valve sets the standard for contemporary mechanical valves.
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Introduction |
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TopAbstractIntroductionMaterial and methodsResultsCommentAppendixReferences |
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The still available "pioneer valve," the Starr-Edwards silastic ball valve (Baxter Healthcare Corporation, Edwards CVS Division, Irvine, CA), has passed 30 years of clinical follow-up [2]. Published aortic St. Jude valve series with a maximum follow-up of 15 years are available [3, 4]. The present large and homogenous series of 694 patients with a first-time aortic valve replacement (AVR) using the standard St. Jude disc valve with a maximum follow-up of nearly 19 years may thus indicate important outcome data at 15 years and beyond. With this in mind, we aimed to give a detailed account of the long-term performance profile of the standard St. Jude valve and to elucidate independent determinants of outcome.
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Material and methods |
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TopAbstractIntroductionMaterial and methodsResultsCommentAppendixReferences |
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There were 427 men and 267 women aged 15 to 83 years. The clinical profile is given in Table 1 and the Appendix. Left-sided heart catheterization was performed in 612 patients combined with echocardiography in 563, whereas 82 were evaluated exclusively with echocardiography. The primary indication for AVR was aortic stenosis in 481 patients, chronic aortic regurgitation in 90, combined stenosis and regurgitation in 58, active bacterial endocarditis in 55, and ascending aortic aneurysm or dissection in 10. The predominant valve lesion was aortic stenosis in 490 patients, aortic regurgitation in 145, and combined stenosis and regurgitation in 59. The patients with regurgitation or combined lesion had at least moderate (grade 3 of 4) regurgitation. Of the total of 549 patients with stenosis or combined lesion, 434 had a catheter passed into the left ventricle: the peak-to-peak gradient across the valve was at least 30 mm Hg (average, 85 mm Hg; maximum, 186 mm Hg); the remaining 115 patients had a Doppler (peak instantaneous) gradient of at least 35 mm Hg (average, 87 mm Hg). The peak-to-peak gradient was estimated (average, 83 mm Hg; range, 51 to 128 mm Hg) in these 115 patients using linear regression in 303 patients with both measurements (peak-to-peak gradient = 29 + 0.62 · Doppler gradient; r = 0.57, p < 0.001). Left ventricular failure was defined as an episode of pulmonary edema or vascular congestion [5] within a year before the operation. Secondary kidney failure was recorded when S-creatinine exceeded the upper reference level of our laboratory [5] in two successive preoperative blood samples.
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All patients except one was started on a regimen of lifelong anticoagulant treatment with vitamin K antagonists aiming at maintaining Owren’s prothrombin-proconvertin index within the 10% to 20% range. For our laboratory this translates into an International Normalized Ratio (INR) corridor of 2.5 to 5.0. During 1997 the target INR was lowered to 2.0 to 3.0 [8]. One patient received lifelong treatment with low-dose acetylsalicylic acid and dipyridamole because of a hemangioma of the colon and another was shifted to the same treatment 1 year after operation because of bleeding from colon diverticulosis.
Follow-up and valve-related complications
A detailed account of database construction, definitions of variables, and follow-up involving direct contact with all patients who were still alive, with the general practitioner of all patients, and with all hospitals where patients had been admitted throughout follow-up has been given previously [6]. All of the present 694 patients were accounted for at the end of study: 42 had died during the first 30 days after AVR (early mortality), 190 had died late, and 462 were still alive. Death certificates were available for all deaths; autopsy was performed in 25 (60%) of early deaths and 52 (27%) of late deaths. A total of 4,502 patient-years at risk were accumulated with a mean follow-up of 6.5 years and a maximum of 18.6 years.
Registration of valve-related complications followed internationally accepted guidelines [9] as previously detailed [6, 10, 11]. Embolism was recorded if a systemic vascular event could not be proved to be thrombotic or hemorrhagic. Embolic and hemorrhagic events were recorded as minor if symptoms subsided within 48 hours or as major if they did not. Valve thrombosis and paravalvular leak were recorded in the absence of infective endocarditis, and hemolysis if B-hemoglobin in a patient with serologic signs of chronic hemolysis [7, 12] could not be kept normal with iron, vitamin B12, and folic acid medication.
Statistical analysis
All analyses were computerized by means of the BMDP Dynamic version 7.0 software package [13]. Simple comparisons were done using a one-way analysis of variance or a Pearson 
2 test. Cumulative survival and complication freedom curves were made using the Kaplan-Meier product-limit method and differences between curves were tested with a log-rank test and a Gehan test. Multivariable analyses of long-term survival and valve-related complications were done using a Cox proportional hazard regression analysis employing a comprehensive formalized analysis sequence as previously described [5, 6]. The odds ratio (multiplication factor for risk increase relative to a basic risk of 1) was calculated [6] for each independent risk factor. The Cox analyses were performed on two patient groups: the 490 patients with aortic stenosis and the 204 patients with regurgitation including those with combined stenosis and regurgitation (Table 1). All variables of Table 1 and the Appendix were entered into the Cox analyses including valve size index (valve size divided by body surface area) in both test groups and peak-to-peak aortic valve gradient in the tests of the stenosis group. The long-term survival of a sex-, age-, and operative year-matched Danish background population was calculated using the annually published Danish life-tables; the relative survival for each postoperative year of the patients was calculated as the ratio between the conditional survival probability of the patients and of the matched background population [6, 14]. Survival, complication freedoms, relative survival, and linearized incidence rates are given with 95% confidence intervals [6, 15], whereas quantitative data are given with ±1 standard deviation (SD). The level of statistical significance was 0.05.
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Results |
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The causes of the 42 early deaths are given in Table 2: 71% were cardiogenic. Two valve-related deaths were caused by a cerebral embolus in 1 patient and a cerebral hemorrhage in another (12 and 21 days after AVR). Early mortality was 5.5% in 434 patients with isolated chronic aortic valve disease, 6.6% in 183 with associated CAD, 7.3% in 55 with active endocarditis, and 9.1% in 22 with ascending aorta replacement of which 5 also had CAD (p > 0.05). Early mortality was 5.1% in 532 patients aged 69 years or younger and 9.3% in 162 patients aged 70 years or older (p = 0.05).
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Thromboembolism
There were 53 embolic events in 42 patients (Tables 3, 4; Fig 2): 75% of the events were major or fatal. The incidence rate did not change significantly over time. There were two valve thromboses: one occurred in a female patient with associated CAD 8.2 years after AVR when she was 77 years old and who did not receive vitamin K antagonist treatment (but acetylsalicylic acid and dipyridamole) because of a sigmoid hemangioma; one of the two valve leaflets was immobilized in a semiopen position, and she did not undergo redo AVR because of high age and severe universal atherosclerosis but was alive at the end of study 1.1 year after the valve thrombosed. The other valve thrombosis occurred during vitamin k antagonist treatment in a female patient 5.9 years after AVR when she was 49 years old; her INR had been below target range just before the thrombosis, and she underwent a successful redo AVR with another disc valve and was alive at the end of study 1 year later. The independent risk factors for thromboembolism are given in Table 6. Age was a strong risk factor in both test groups, whereas high peak-to-peak gradient reduced the risk of thromboembolism in the stenosis group (odds ratio < 1).
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Endocarditis
Prosthetic valve endocarditis occurred in 19 patients (Table 3) with a 15-year and 18-year freedom of 92% (Table 4; Fig 2). Eight patients underwent redo AVR with 3 deaths within 1 month and none during the ensuing 2 months; the remaining 11 patients were treated conservatively with 4 deaths during the 1st month after start of antibiotics treatment and a further 2 deaths during the 2nd and 3rd months. There was no relation between preoperative native endocarditis and postoperative prosthetic endocarditis in any of the two groups (Table 6).
Paravalvular leak, hemolysis and structural failure
Paravalvular leak occurred in 19 patients (Tables 3, 4; Fig 2): 11 were diagnosed within 1 year after operation and another 4 before the 5-year date. Seven of these 19 patients also had hemolysis with chronic anemia and 1 patient had hemolysis without paravalvular leak (Table 3); his 25 mm St. Jude valve appeared normal during redo AVR 1.6 years after the primary operation. There were no risk factors for paravalvular leak in the stenosis group, whereas preoperative native endocarditis (odds ratio 5.92, p = 0.01) was an independent risk factor in the regurgitation group. There were no instances of structural or mechanical failure.
Composite complication rates and redo AVR
All complications joined gave 195 events in 140 patients (Tables 3, 4; Fig 3). The incidence rate did not change significantly over time. The independent risk factors are shown in Table 6; they included small valve size in the regurgitation group. Serious complications (Tables 3, 4; Fig 3) occurred with 10-year and 15-year freedoms of 86% and 72%, respectively. Age (odds ratio for a 10-year age increase: 1.57, p = 0.01) was the independent risk factor in the stenosis group, whereas preoperative native endocarditis (odds ratio 3.50, p < 0.01) and valve size less than or equal to 21 mm (odds ratio 3.65, p < 0.01) were the risk factors in the regurgitation group. Valve-related deaths (Tables 3, 4; Fig 3) were independently related to secondary kidney failure (odds ratio 3.87) and cardiothoracic index (odds ratio of an index increase of 0.1:2.14, p < 0.05) in the stenosis group and to New York Heart Association (NYHA) class IV (odds ratio 7.07, p < 0.01) and atrioventricular conduction block (odds ratio 8.83, p = 0.01) in the regurgitation group. Redo AVR (Tables 3, 4; Fig 3) was performed in 16 patients, mainly for endocarditis and paravalvular leak. The 18-year freedom was as high as 96%. The replacement valves included nine St. Jude disc valves, two other bileaflet disc valves, three Starr-Edwards silastic ball valves, and two stented xenografts. The independent risk factors (none in the stenosis group) are given in Table 6.
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Comment |
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TopAbstractIntroductionMaterial and methodsResultsCommentAppendixReferences |
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Valve-related death is an important measure of prosthetic valve performance. Only 13% of the present late deaths were valve related, but another 6% were "sudden and unexpected" and potentially valve related. However, it has been shown that less than 10% of sudden deaths are related to the prosthetic valve or anticoagulant treatment [1, 16]. It should be stressed that the present long-term survival (with early mortality excluded) was only marginally different from the survival of a matched background population.
We have recently published the long-term results of a large series of patients with the traditional "mechanical valve of comparison," the Starr-Edwards aortic model 1260 silastic ball valve, with a clinical follow-up to 32 years [2]. The Starr-Edwards ball valve patients were comparable with the present St. Jude valve patients regarding age, but the prevalence of complicating diseases and procedures was only 22% compared with 38% in the present series and the ball valves were on average 3 mm larger than the present St. Jude valves. With these differences in mind, a comparison between the two aortic valve series reveals a higher thrombogenicity of the Starr-Edwards ball valve, comparable rates of all complications and serious complications, complete absence of mechanical failure of both valves, and a 30% higher rate of valve-related deaths associated with the ball valve.
It is well established that the St. Jude disc valve, like any other mechanical valve, is thrombogenic and that vitamin K antagonist treatment is necessary [8, 17]. However, anticoagulant treatment reduced the present rate of embolism to and even below the rate associated with the aortic allograft valve with no anticoagulation but a high rate of primary valve degeneration especially late after AVR [11]. It is important to observe that the present very infrequent cases of valve thrombosis, as in other St. Jude disc valve series [4, 18], occurred in patients who did not receive vitamin K antagonist treatment or in whom INR was below target level. The present incidence rates of valve-related complications were comparable with or lower than previously reported levels from age and target INR comparable aortic St. Jude disc valve series with maximum follow-up of at least 10 years [3, 18]. A lower rate of bleeding was found only in series in which patients were significantly younger and had a significantly lower prevalence of CAD than the present patients [4, 19]. High age and CAD were major determinants of anticoagulant-related bleeding in the present as well as in other reports [10]. As these two variables were also the main risk factors for late mortality, it cannot surprise that survival at 10 years better than the present one was found only in St. Jude disc valve series in which prevalence of CAD (9% to 18%) and patient age (54 to 57 years) were lower than in the present patients [4, 18, 19]. A newer disc valve, the CarboMedics valve, with a maximum follow-up in reported series reaching 8 years, has shown incidence rates of thromboembolism and of all complications comparable with [20] or higher than [21] the present rates but with comparable bleeding rates.
Obviously, the target INR corridor is an important determinant of the incidence rates of thromboembolism and bleeding. The current trend, to lower target INR in patients with modern aortic disc valves, stems from observations by Horstkotte and coworkers [8]. A lowering of target INR to 1.8 to 2.8 in patients with an aortic St. Jude valve reduced the overall rate of bleeding with only a modest increase in the rate of major thromboembolism (but a significant increase of minor embolism) [8]. However, some of their minor events would have been classified as major according to the present criteria, and their overall rates of both thromboembolism and bleeding of their aortic St. Jude disc valve patients were about twice the present rates. The present distribution between major and minor events further indicates that low intensity anticoagulation may backfire: 75% of our embolic events were major compared with only 24% of our bleeding episodes. Our recent lowering of target INR to 2.0 to 3.0, complying with the international trend, may thus result in a decrease of the rate of a rather benign complication at the cost of an increased rate of a "malignant" complication. In another aortic St. Jude disc valve series it was noted that INR was below 2.5 in all embolic episodes wherein INR was known [18]. Perhaps a target INR corridor of 2.5 to 3.5 would be suitable.
Another mode of action other than lowering target INR may be valid in reducing the dominant complications of mechanical valves: thromboembolism and anticoagulant-related bleeding. High age was the dominant risk factor in the present just as in numerous other studies, but also CAD played a role. High age, CAD, and systemic hypertension have been shown previously to be the decisive risk factors [6, 10, 22]. Avoidance of a mechanical valve and anticoagulant treatment in patients with these risk factors may do the trick. A xenograft or allograft valve may be indicated primarily in patients aged, eg, 70 years and older and in patients in their 60s with concomitant CAD and hypertension.
A low aortic valve gradient preoperatively was associated with a high rate of thromboembolism in our patients with aortic stenosis. It has been shown previously that a low gradient is related to a poor left ventricle and a high death rate after AVR [5, 6]. A malfunctioning left ventricle also has been related to a poor hemodynamic function of the standard St. Jude disc valve and also to a higher degree of intravascular hemolysis and presumeably of platelet activation [7]. Other factors indicating poor preoperative heart status (high cardiothoracic index, CAD, left ventricular failure, antifailure medication) were related to a high bleeding rate in the present study. The implication is straightforward and cannot be repeated too often: operation before heart status deteriorates would reduce the risk of thromboembolism and bleeding as well as the rate of both cardiogenic and valve-related deaths after AVR.
The present incidences of prosthetic endocarditis and paravalvular leak were low and comparable with the rates of other St. Jude disc valve series [3, 4, 18, 19]. The majority of the present paravalvular leaks were detected within a few years after AVR and were related to preoperative native endocarditis in our aortic regurgitation group. These factors may be related to a certain weakness of aortic annular tissue (even though the primary infection seemed to be eradicated) that underlines the importance of a meticulous suturing technique. Prosthetic endocarditis seemed to occur more at random with no relation to preoperative native endocarditis and with an 18-year freedom as high as 92%. It has been shown that the standard aortic St. Jude disc valve is less susceptible to infection than aortic allografts and xenografts [23].
The two smallest (19 and 21 mm) of the aortic St. Jude disc valves independently increased the risk of serious complications and of all complications joined in the present patients with aortic regurgitation. The latter is usually associated with a volume loaded and dilated left ventricle, and it has been shown that mismatch between valve size and end-diastolic dimension of the left ventricle significantly impairs the hemodynamic function of the standard aortic St. Jude disc valve [7]. Aortic root enlargement or use of a modified valve with a larger inner opening area [24] may be the available remedies.
With a maximum follow-up of nearly 19 years the present low rate of valve-related deaths, acceptably low thrombogenicity, and absence of mechanical failure are indicators of a sound valve design. We conclude that the standard aortic St. Jude disc valve sets the standard for contemporary mechanical valves.
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Acknowledgments |
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Appendix |
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TopAbstractIntroductionMaterial and methodsResultsCommentAppendixReferences |
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References |
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TopAbstractIntroductionMaterial and methodsResultsCommentAppendixReferences |
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