Ann Thorac Surg 2002;74:1115-1119
© 2002 The Society of Thoracic Surgeons
Original article: cardiovascular
Is prophylactic aortic valve replacement indicated during mitral valve surgery for mild to moderate aortic valve disease?
Jong-Won Ha, MD, PhD*a,
Seung-Hyuck Choi, MDa,
Byung-Chul Chang, MD, PhDb,
Chung Mo Nam, PhDc,
Yangsoo Jang, MD, PhDa,
Namsik Chung, MD, PhDa,
Won-Heum Shim, MD, PhDa,
Seung-Yun Cho, MD, PhDa,
Sung-Soon Kim, MD, PhDa
c Department of Preventive Medicine and Public Health Yonsei University College of Medicine, Seoul, South Korea
a Divisions of Cardiology,Yonsei Cardiovascular Hospital, Yonsei University College of Medicine, Seoul, South Korea
b Division of Cardiovascular Surgery, Yonsei Cardiovascular Hospital, Yonsei University College of Medicine, Seoul, South Korea
Accepted for publication June 6, 2002.
* Address reprint requests to Dr Ha, Cardiology Division, Yonsei Cardiovascular Hospital, Yonsei University College of Medicine, CPO Box 8044, Seoul, South Korea
e-mail: jwha{at}yumc.yonsei.ac.kr
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Abstract
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Background. Determining the need for surgical treatment of coexisting mild to moderate aortic valve disease in patients referred for mitral valve surgery is often difficult. The purpose of this study was to assess long-term clinical outcome and the need for subsequent aortic valve replacement in patients with mild to moderate rheumatic aortic valve disease at the time of mitral valve surgery.
Methods. A total of 275 patients (90 men and 185 women, mean age 43 years) with rheumatic disease who underwent mitral valve surgery were followed up for an average of 9 years. Patients were classified into two groups: those with coexisting mild to moderate aortic valve disease at the time of mitral valve surgery (141 patients, group A) and those without (134 patients, group B). Primary outcomes (death and subsequent aortic valve surgery) were compared between the two groups.
Results. At the time of mitral valve surgery, 104 patients (74%) in group A had mild aortic regurgitation, 37 (26%) had moderate aortic regurgitation, 5 had (4%) mild aortic stenosis, and 2 (1%) had moderate aortic stenosis. At the end of follow-up, no patient had severe aortic valve disease. In all, 12 patients (5%) in group A had primary events (eight deaths and four subsequent aortic valve replacements), and 12 patients (9%) in group B had such events (12 deaths). According to Kaplan-Meier analysis, neither the survival rate nor the event-free survival rate differed significantly over the follow-up period between the two groups.
Conclusions. In most patients who have mild to moderate rheumatic aortic valve disease at the time of mitral valve surgery, the long-term outcome is comparable to that of subjects without aortic valve disease at the time of mitral valve surgery. Subsequent aortic valve replacement is rarely needed after a long follow-up period.
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Introduction
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Given that one-third of patients with rheumatic heart disease have simultaneous involvement of mitral and aortic valve [1–4], it would appear that a significant number of patients who are referred for mitral valve (MV) surgery have coexistent aortic valve (AV) disease that, alone, does not justify surgery. However, it is not clear whether these patients should undergo AV replacement at the time of MV surgery or whether AV replacement should be delayed until standard indications for replacement develop. The risks of any excessive perioperative morbidity and mortality from a combined procedure and of the long-term complications after an AV replacement must be weighed against the risk of progression of the AV disease to the point that surgery is required before the end of the expected benefit from MV surgery. Therefore, therapeutic decisions in these patients require a complete understanding of the natural history of rheumatic AV disease. The purpose of this study was to assess the long-term clinical outcome of a series of patients who had mild to moderate rheumatic AV disease at the time of MV surgery and to evaluate the need for subsequent AV surgery in these patients.
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Material and methods
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Study patients
Between 1983 and 1995, a total of 1,156 patients underwent MV surgery in our cardiovascular surgery division. After exclusion of patients with nonrheumatic valve disease, severe AV disease at the time of surgery, or double-valve replacement, 275 patients (mean age, 43; 90 men, 185 women) who underwent MV surgery were entered into the study. Patients were classified into two groups: those with coexisting mild to moderate AV disease at the time of MV surgery (141 patients, group A), and those without (134 patients, group B). Mean follow-up periods for groups A and B were 8.2 years and 10.2 years, respectively. Clinical data obtained from the hospital records included age, sex, rhythm, New York Heart Association (NYHA) functional class, and concomitant medical conditions (coronary artery disease, diabetes, and hypertension). Permanent anticoagulation with warfarin was started postoperatively and monitored, and the dosage was adjusted every 1 to 3 months on an outpatient basis. The target level of anticoagulation was an international normalized ratio of 3.0 to 3.5.
Echocardiographic studies
Echocardiographic studies were performed in a standard manner; these included parasternal long- and short-axis views, as well as two-, four-, and five-chamber and apical long-axis views. Mean and peak aortic pressure gradients were calculated with the modified Bernoulli equation [5] using continuous-wave Doppler recordings. Aortic valve area was computed with the continuity equation [5, 6] by standard methods when systolic function of the left ventricle was decreased. In patients with normal left ventricle systolic function, the mean gradient was used to define the severity of aortic stenosis (AS) (mild, <25 mm Hg; moderate, 25 to 50 mm Hg; severe, >50 mm Hg). In patients with systolic left ventricular dysfunction, an AV area of 1.5 cm2 or more was considered mild AS; 1.1 to 1.5 cm2 was considered moderate; and 1.0 cm2 or less was considered severe. Aortic regurgitation (AR) grade was estimated by integrating data from the continuous-wave Doppler velocity spectrum [7] and color flow mapping, as previously described [8, 9]. Progression of AV disease was defined as increases in more than one grade of disease severity.
Clinical follow-up
The two primary study end points were time to death from any cause and time to subsequent AV surgery due to severe AV disease. Follow-up data were obtained by hospital chart review, telephone interview, or search of the National Death Index. The decision to refer the subject for valve surgery was made by the patient’s own physician.
Statistical analysis
Descriptive base line characteristics were summarized by frequencies and percentages or by mean values and standard deviation. Differences in base line clinical characteristics between the two groups were compared by use of the t test for continuous variables and the 
2 or Fisher’s exact test for categorical variables. Survival was described using Kaplan-Meier life table analysis with the log-rank test to assess differences between groups. Results were considered to be statistically significant when the p value was less than 0.05.
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Results
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Patient characteristics
Patients in the two groups had similar base line characteristics, such as age, sex, frequency of atrial fibrillation, preoperative functional class, predominant MV disease, types of MV surgery, and left ventricular ejection fraction (Table 1).
The following prosthetic valves were used at time of mitral valve surgery: group A, St. Jude (St. Jude Medical, St. Paul, MN) 43 (31%), CarboMedics (Sulzer Carbomedics, Austin, TX) 42 (30%), Duromedics (Baxter Healthcare Corp, Irvine, CA) 28 (20%), tissue valves 22 (16%); group B, St. Jude 49 (37%), CarboMedics 30 (22%), Duromedics 20 (15%), tissue valves 26 (19%), and other mechanical valves 8 (6%). All patients in group A had AR mild in 104, and moderate in 37. Of the 141 patients in group A, 7 had mixed stenosis and regurgitation, 5 mild stenosis and regurgitation, 1 moderate stenosis and regurgitation, and 1 moderate stenosis and mild regurgitation. Coronary angiography, which was performed in 58 patients in group A and 47 in group B, showed significant coronary artery stenosis in 2 of the 58 patients in group A and in 2 of the 47 in group B. All 4 of these patients had single-vessel disease.
Progression of aortic valve disease
At least two echocardiographic studies were available for in 92 patients (65%) in group A and 41 (31%) in group B. During the follow-up period, 6 of 41 patients (15%) in group B had progression to AV disease; 5 had mild regurgitation, and 1 had mild stenosis. In contrast, 22 of 92 patients (24%) in group A had progression to AV disease. Nine patients had a progression of regurgitation: 8 patients from mild to moderate, and 1 patient from moderate to severe. In all, 19 patients had progression of stenosis: 13 patients, from none to mild; 3, from none to moderate; and 3, from mild to moderate. Three patients had progression of both stenosis and regurgitation. Severe AR was present in only 1 patient in group A at the end of follow-up. No patient in either group had severe AS at the end of follow-up. Only 3 patients in group A and 2 in group B were in NYHA functional class III or IV at the end of follow-up.
Clinical outcome
The duration of follow-up was 8.2 ± 3.3 years (range, 1 to 17 years) in group A and 10.2 ± 4.0 years (range 2 to 17 years) in group B. During follow-up, 20 patients had died (8 in group A, 12 in group B). Causes of death in group A were cardiac in 4 patients (progressive heart failure in 2, bacterial endocarditis in 1, sudden cardiac death in 1), noncardiac in 2 patients (suicide in 1, liver cirrhosis in 1), and unknown in 2. Causes of death in group B were cardiac in 1 (progressive heart failure), noncardiac in 5 (cerebral infarction in 2, cerebral hemorrhage in 1, renal failure 1, pneumonia and sepsis 1), and unknown in 6. Of the 141 patients in group A, 4 (3%) underwent AV surgery. Three patients with symptoms (NYHA III) who had moderate AS underwent AV replacement. One patient with prosthetic MV failure and moderate AR (grade III) had double-valve replacement. Of the 134 subjects in group B, no patient underwent AV surgery.
Figures 1 and 2
show Kaplan-Meier analyses of the probability of survival and event-free survival in the two groups during the follow-up periods. Ten-year survival rates in groups A and B were 96% and 93%, respectively (Fig 1). If death and AV surgery were considered as a composite endpoint, 10-year event-free survival rates in groups A and B were 93% and 93%, respectively (Fig 2). Neither the survival rate nor the event-free survival rate differed significantly over the follow-up period. Although the progression of AV disease is more frequent in patients with initial lesions, progression to severe disease is not common. There were no statistically significant differences between the two groups in complications such as thromboembolism and hemorrhage. In all, 25 patients had nonfatal complications (12 from group A, 13 from group B). In group A, 5 patients had hemorrhagic complications. Bleeding from the urogenital system occurred in 3 patients and 2 patients showed other bleeding. In group B, 11 patients had hemorrhagic complications. Gastrointestinal bleeding occurred in 1 patient and cerebral bleeding in another; bleeding from the urogenital system occurred in 6 patients and other bleeding was found in 3. Thromboembolic complications occurred in 14 patients (7 patients from each group). Cerebral infarction occurred in 6 patients from each group and renal infarction occurred in 1 patient from each group.
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Fig 1. Estimated overall survival rates for patients with (group A) and without (group B) mild to moderate aortic valve disease at the time of mitral valve surgery. Percent survival is plotted against years of follow-up. Time to death was not statistically different between the two groups.
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Fig 2. Estimated event-free survival for patients with (group A) and without (group B) mild to moderate aortic valve disease at the time of mitral valve surgery.
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Comment
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The current study demonstrates that (1) in most patients who have mild to moderate rheumatic AV disease at the time of MV surgery, the survival rate is high and is almost identical to that in patients without AV disease at the time of MV surgery; and (2) subsequent AV replacement is rarely needed after a long follow-up period. To our knowledge, this study reports the largest number of patients to date with mild to moderate rheumatic AV disease at the time of MV surgery who have been followed-up for clinical outcome. The results of this study may be important in the decision not to recommend premature AV replacement in these patients.
Because one-third of patients with rheumatic heart disease have simultaneous involvement of the MV and the AV, whether a mild to moderately diseased AV should be replaced or left alone during MV surgery is a common clinical dilemma. Now that intraoperative transesophageal echocardiographic monitoring has become an integral part of cardiovascular surgery, a mild to moderately diseased AV that was not the primary target for the operation at the time of MV surgery is more commonly observed. If significant mitral stenosis is associated with mild or moderate AS or with AR that does not of itself necessitate intervention, percutaneous balloon dilatation of MV, if feasible, provides excellent symptomatic improvement and long-term outcome. This approach may allow a surgical procedure on the MV to be delayed until AV disease requires surgical intervention. However, management of mild or moderate AV disease in patients with severe symptomatic mitral stenosis who are not candidates for percutaneous balloon dilatation is difficult. Because of the progressive course of valvular disease, failure to treat AV disease at the time of MV surgery is likely to necessitate reoperation on the AV, which is associated with increased risk. Conversely, the addition of an AV operation to an MV surgical procedure increases the immediate surgical risk, and multiple prosthetic valves have a higher long-term complication rate than single prostheses [10]. Although valve repair or debridement is sometimes feasible in patients with AR, it is less likely to be successful in those with rheumatic heart disease [11], which is the focus of the current study. Optimal management mandates understanding of long-term natural history of mild to moderate rheumatic AV disease.
A recent prospective study by Otto and colleagues [12] demonstrated that symptoms develop in about 75% of patients with initially asymptomatic AS, who then require valve replacement within the next 5 years. This observation has led to the suggestion that valve replacement be done at the time of coronary artery bypass surgery in patients with mild to moderate stenosis to obviate the need for repeat surgery in the next few years. Thus, prophylactic AV replacement at the time of coronary artery bypass surgery was recommended in older patients with moderate aortic stenosis with an aortic valve area of 1.2 cm2 or less and an aortic valve area index 0.8 cm2/m2 or less, provided that the patients are not at high risk for thromboembolism and thus can receive a bioprosthesis [13].
Unlike the progression of isolated AV disease or of coronary artery disease, the progression and long-term clinical outcome of AV disease in patients undergoing MV surgery for rheumatic heart disease are unknown. Rheumatic heart disease, unlike degenerative or congenital diseases, generally has a gradually progressive clinical course. Thus, a different course of AV disease might be expected in this population. Vaturi and colleagues [14] evaluated the long-term course of AV disease and the need for AV surgery in 131 patients undergoing MV surgery. Of the patients, 59 had mild AV disease at the time of surgery. After a mean follow-up of 21 years, AV replacement was needed in only 6 patients. Moreover, in 4 patients, the primary indication for the second operation was dysfunction of the prosthetic MV. Although the long-term outcome of moderate AV disease was not provided, these researchers concluded that hemodynamically significant AV disease rarely develops over a long follow-up period in patients with or without mild AV disease. The results of our study, which includes patients with moderate AV disease, agree with those of Vaturi and colleagues [14], demonstrating that AV replacement is rarely needed during a long follow-up period.
Study limitations
This study is limited by its retrospective nature. Insufficient echocardiographic follow-up of study patients precludes the assessment of AV disease progression in a more precise, quantitative manner. Therefore, the rate and the manner of progression of AV disease and factors determining more rapid progression could not be evaluated. However, although echocardiography is most frequently used for follow-up of patients with valvular disease, it is usually confined to patients with severe disease, according to the recommended guideline for clinical practice. Follow-up of patients with mild to moderate AV disease who have stable signs and symptoms is a class IIb recommendation ("usefulness or efficacy is less well established by evidence or opinion") [15].
In our study, AR was the more common coexisting lesion. Therefore, the progression of AV disease in this study was progression primarily of AR rather than of AS. Our data may not apply to patients with mild to moderate AV disease at the time of coronary artery bypass surgery, when the predominant associated lesion is stenosis rather than regurgitation.
In conclusion, in this study, patients with or without mild to moderate rheumatic AV disease at the time of MV surgery had a very low rate of clinical events (defined as either death or subsequent AV surgery). These results suggest that prophylactic AV replacement should not be recommended at the time of MV surgery in these patients.
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Acknowledgments
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We are very grateful to Fletcher A. Miller, MD, for reviewing the manuscript.
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Abstract
Introduction
