(Circulation. 1999;100:II-48.)
© 1999 American Heart Association, Inc.
Surgery for Valvular Heart Disease |
Predictors of the Long-Term Outcome After Combined Aortic and Mitral Valve Surgery
From the Cardiology Division, Department of Internal Medicine (J.T., T.S.), Clinic for Cardiovascular Surgery (M.T.), and Biostatistics Division, Institute for Social and Preventive Medicine (B.S.), University Hospital, Zurich, Switzerland.
Correspondence to Juraj Turina, MD, Cardiology Division, University Hospital, 8091 Zurich, Switzerland. E-mail juraj.turina{at}dim.usz.ch
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Abstract |
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Background—The influence of preoperative clinical, hemodynamic, and surgical procedures on long-term prognosis after combined aortic and mitral valve surgery is not well known.
Methods and Results—One hundred seventy patients (mean age, 50.5 years; 102 men and 68 women) who underwent surgery for chronic combined aortic and mitral valvular disease between 1975 and 1989 were followed up for an average of 10.6 years. Additional repair of tricuspid valve was performed in 29 patients (17%), and aortocoronary bypass graft surgery was performed in 7 patients (4.1%). The perioperative mortality rate was 4%, and 10- and 20-year survival rates were 61% and 33%. Only 12 of 94 deaths (11%) were non–cardiac related. At 10 and 20 years, 57% and 21% of patients were free of reoperation, respectively. The main predictors of late survival in univariate analysis were age at surgery (P=0.0002), preoperative left ventricular ejection fraction (P=0.002), cardiac index (P=0.007), tricuspid surgery (P=0.03), pulmonary vascular resistance (P=0.03), NYHA class (P=0.04), and additional aortocoronary bypass graft surgery (P=0.04). Duration of symptoms, gender, cause of valvular disease, and type of prosthesis were not predictive of postoperative outcome. In multivariate stepwise Cox analysis, ejection fraction (P=0.0008), age at surgery (P=0.0011), and tricuspid surgery (P=0.007) were independent predictors of late survival.
Conclusions—In combined aortic and mitral valve disease, preoperative myocardial function is the main predictor of long-term survival. Low operative mortality rates and good late outcome make valve replacement mandatory before deterioration of myocardial function occurs. Additional tricuspid valve disease requiring surgery significantly decreases the late survival rate.
Key Words: surgery • valves • survival • prognosis • transplantation
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Introduction |
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Surgery for combined aortic and mitral valve disease was introduced in the early 1960s; until the mid-1970s, it was associated with a high operative mortality rate and unsatisfactory late results.1 2 3 Despite well documented improvement in surgical techniques with a marked decrease in operative mortality rates and a considerable increase in late postoperative survival rates in the 1980s and 1990s, some reluctance remained to refer a patient with combined aortic and mitral disease to surgery.4 5 A paucity of experience due to the limited number of patients, a lack of good prospective clinical and hemodynamic studies in patients who have not undergone surgery, great differences in clinical presentation and hemodynamics between regurgitant and stenotic lesions, and changes in causes of valvular disease in developed countries aggravate the decision-making process for surgery in patients with combined aortic and mitral disease.1 6 7 This was the main reason for reassessment of preoperative clinical, hemodynamic, and surgical predictors for long-term survival after combined aortic and mitral valve surgery in patients operated on at our institution from the mid-1970s to the late 1980s.
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Methods |
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All 170 patients who underwent combined aortic and mitral valve surgery and associated procedures at the Cardiology Division of Medical Policlinic at the University Hospital in Zurich between 1975 and 1989 were included in the study. All except 2 patients underwent right and left heart catheterization, and all except 2 had left ventricular (LV) angiography. All patients >40 years old and those with angina pectoris underwent coronary angiography. For the calculation of LV volume and ejection fraction (EF), only high-quality angiograms were considered. Hence, preoperative EF and volume were reported in only 159 of 170 patients (94%). NYHA class was determined according to symptoms and functional impairment at the time of preoperative evaluation and operation regardless of previous symptoms and history.
Patients
The main characteristics of the study patients are
presented in Table 1
. The
age of the patients at the time of surgery ranged from 21 to 79 years
(mean, 50.5 years). The cause of valvular disease was rheumatic
in 41% of patients, and 18% had a history of bacterial endocarditis;
in other patients, the origin of valvular disease was not
specified and was assumed to be degenerative. None of the patients were
operated while they had acute endocarditis, and in the majority of
patients, endocarditis antedated surgery by several years. Previous
surgery of the heart and great vessels had been performed in 35
patients (21%).
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Clinical and Hemodynamic Data
Preoperative NYHA class was 2.9, whereas 24% of patients were
in class II, 62% were in class III, and 14% were in class IV (Figure 1). Heart failure was present or was
previously found in 45% of patients. The mean duration of cardiac
symptoms was 5.2 years; in 51% of patients, symptoms were present
for <4 years, and in 12% of patients, symptoms were present for
>12 years. The most important hemodynamic
variables are shown in Table 1
and Figure 1.
According to type and hemodynamic severity of aortic
and mitral disease, patients were divided into different groups (Figure 2). The combination of aortic
regurgitation and mitral regurgitation
was the most common disease (50%).
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Follow-Up
After surgery, all patients were seen at least once in
our outpatient clinic, generally 6 months after surgery. Additional
information was obtained through the use of standardized questionnaires
that were mailed to patients and their physicians. Causes of death and
cardiac complications were classified according to
guidelines8 and were obtained from medical reports, death
certificates, and telephone contact with physicians. The mean follow-up
was 10.6 years (1802 patient-years); in surviving patients, it was 14.5
years, with the longest follow-up being 22.3 years. During the
follow-up, 14 patients (8% of the entire group) were lost 1.7 to 15.6
years after the operation (mean follow-up, 7.2 years).
Statistical Analysis
Statistical evaluations and all calculations were performed with
StatView 4.5 software (Abacus Concepts, Inc). Survival was calculated
according to the Kaplan-Meier method. Univariate
analysis was performed for all data presented in Table 1 separately for cardiac survival and reoperation-free survival.
Multivariate analysis (Cox hazard regression)
was applied in a stepwise manner for all significant
parameters in univariate analysis in
both groups of data.
Surgical Procedures
All 170 patients had combined aortic and mitral valve surgery.
In 41 patients (24%), additional surgical procedures were performed:
reconstruction of the tricuspid valve due to significant
regurgitation [n=29 (17%)], aortocoronary
bypass graft surgery [n=7 (4%)], and surgery of the ascending aorta
[n=7 (4%)]. Replacement (n=280) and repair (n=60) of the aortic and
mitral valves were both performed (Figure 3). Mechanical prostheses (mainly
Björk-Shiley) were used in most patients; bioprostheses (mainly
Carpentier-Edwards) were used after 1977 until the mid-1980s, more
often in the aortic (32%) than in the mitral (18%) position (Table 2). Intraoperative myocardial protection
also evolved during this period. During the first years of the study,
ice-cold saline perfusion of the coronary arteries was used,
combined with intermittent aortic cross-clamping, moderate total body
hypothermia (26° to 28°C), and cold pericardial irrigation; after
1978, the use of cold potassium cardioplegia became the standard
method.
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Results |
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Survival
Ninety-four patients died and 14 were lost to follow-up (Table 3
); the early mortality rate (<1 month)
was 4%, and 10- and 20-year survival rates were 61% and 33%,
respectively (Figure 4). The mortality
rate remained stable during the entire follow-up period
(5%/patient-year). Most patients (72%) died of cardiac causes; heart
failure and sudden, unexpected death were the most frequent causes of
cardiac death (Table 3). Noncardiac death occurred in 12
patients, with malignancies (n=5) and infections (n=4) being the most
common causes. In 14 patients, the cause of death remained unknown;
these cases were regarded as probably cardiac related. In calculations,
they were grouped together with cardiac death. Due to the low number of
non–cardiac-related deaths, survival curves for general and cardiac
survival are very similar, especially during the first 10 years (Figure 4). The average NYHA class of long-term survivors was 2.1; 17%
were in class I, 65% were in class II, 13% were in class III, and 6%
were in class IV (Figure 1).
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Reoperations
During the follow-up, 46 cardiac reoperations were performed in 37
patients, with an early mortality rate of 7%. Prosthesis
replacement was performed in the aortic and mitral (n=12), aortic
(n=9), mitral (n=10), and tricuspid (n=2) positions. In 4 patients,
refixation of mitral prosthesis had to be performed; 4 heart
transplantations became necessary 8, 10, 11, and 12 years after initial
valve replacement due to intractable heart failure. Valvular
reoperations were combined with surgery of the ascending aorta (n=5),
aortocoronary bypass graft surgery (n=2), and tricuspid
reconstruction (n=2). Bioprosthesis degeneration was the reason
for reoperation in two thirds of the cases. Elective heart
transplantation was performed in 3 patients at 8, 10, and 12 years
after valve replacement, without early and late deaths; the only
emergency transplantation performed due to early postoperative
intractable myocardial failure after reoperation of aortic and mitral
prosthesis and aortocoronary bypass graft surgery was
not successful. Mean duration of function for bioprostheses was
10.2±0.3 years in aortic and 8.2±0.4 years in mitral position.
Reoperation-free survival rates were 57% after 10 years and only 21%
after 20 years (Figure 4).
Cardiac Complications
During the follow-up, 45 major complications other than
reoperation (death included) were encountered; the most common
were stroke (n=16), endocarditis (n=11), embolism (other than cerebral)
(n=7), myocardial infarction (n=6), and bleeding during
anticoagulation (n=5). Due to diagnostic difficulties, we
have not differentiated between embolic and hemorrhagic stroke as
causes. The incidence of all thromboembolic and bleeding complications
(stroke, embolism, and bleeding) was 1.6%/patient-year, whereas the
incidence of lethal complications was 0.3%/patient-year. The incidence
of bacterial endocarditis was 0.6%/patient-year, and that of lethal
outcome was 0.1%/patient-year.
Survival
The impact of different parameters on long-term
survival after combined aortic and mitral surgery is presented
in Table 4. Univariate
analyses were performed separately for overall and cardiac
survival and for operation-free survival. Age, duration of symptoms,
pressure, and volume parameters were calculated as
continuous variables; all other data were analyzed as
dichotomous variables. Higher age at surgery, higher preoperative
NYHA class, higher pulmonary artery resistance, lower cardiac
index, lower LVEF, additional tricuspid surgery, and
aortocoronary bypass graft surgery were significantly
(P<0.05) related to poorer late survival rates (Table 4). When preoperative NYHA classes are analyzed
separately, only NYHA class II was clearly related to better long-term
outcome, with the differences in survival curves for NYHA classes III
and IV being minimal during the entire follow-up period (Figure 5). Only a cohort of patients with the
lowest EF (<40%) had clearly decreased survival rates. The survival
rates for patients with moderately decreased EF (40% to 54%) and
normal EF (>54%) were very similar (Figure 5). Neither cause
of the valvular disease, duration of symptoms, nor previous
heart failure was a predictor of late outcome. A certain trend for
better late outcome was noted with lower preoperative right and left
atrial and pulmonary artery pressures; only pulmonary
vascular resistance was a significant survival predictor in
univariate analysis.
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The type of prosthesis (mechanical versus
bioprosthesis) had no major impact on long-term outcome; a
strong tendency for better long-term survival, falling short of
statistical significance (P<0.08), was seen for 55 patients
with mitral valve repair. Additional tricuspid
regurgitation requiring surgery decreased the late
survival rate (Figure 5). Despite bypass surgery, the outcome of
patients with coronary artery disease was poor.
In multivariate stepwise regression analysis of the foregoing parameters, only age {P=0.0011, exponential coefficient [Exp(Coef)]1.034}, LVEF [P=0.0008, Exp(Coef) 2.10], and additional tricuspid surgery [P=0.007, Exp(Coef) 0.966] arose as independent predictors of the late outcome.
In univariate analysis for reoperation-free survival, age, LV end-systolic volume, and the use of a bioprosthesis in the aortic and mitral position were major predictors of reoperation. In multivariate analysis, higher age, higher end-systolic volume, the use of a bioprosthesis in the aortic position, and tricuspid surgery were independent predictors of a higher risk of reoperation in long-term follow-up.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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The optimal timing of surgical treatment for combined aortic and mitral surgery is not well defined.9 The decreased operative mortality rates and improved late survival rates during the past decade require reassessment of indication for surgery in patients with combined valvular disease.3 4 10 This study summarizes the experience with combined aortic and mitral surgery during the late 1970s and 1980s, with an emphasis on preoperative clinical and hemodynamic data and the choice of surgical procedures as predictors of long-term survival.
Surgical Results
Our observations demonstrate that combined valvular
surgery can be performed with a low operative mortality rate of <5%
and good late results (10-year survival rate, 61%), whereas three
fourths of long-term survivors had a fair quality of life (NYHA classes
I and II). Similar results in comparable patient cohorts have been
reported.2 3 4 10 11 Nevertheless, the early operative
mortality rate is higher and the late survival rate is lower than those
after isolated aortic or mitral valve replacement.1 9 12
Heart failure and sudden, unexpected death are the major late causes of
death.3 4 10 Heart failure can occur slowly and
insidiously, many years after valve replacement, and heart
transplantation might become necessary when myocardial failure is
refractory to medical therapy. Thus, current late postoperative
survival rates do not exactly correspond to "survival of the
heart." In particular, patients with preoperative severe chronic
volume overload and reduced myocardial function might require heart
transplantation late after valve replacement.
Significant tricuspid regurgitation requiring surgical repair worsened the prognosis.3 The prognostic importance of preoperatively increased pulmonary vascular resistance points to the importance of chronic pressure load on the right ventricle for postoperative outcome. Thus, it is not only genuine tricuspid valve disease but also the chronic overload of the right ventricle with dilation and myocardial failure that burdens the late postoperative outcome. Tricuspid repair should be performed when hemodynamic significant regurgitation is present, because such disease does not disappear after correction of the left-side valvular disease.13 14 In our relatively young patient group, the incidence of coronary artery disease was very low, but the long-term prognosis of these patients was less favorable despite aortocoronary bypass graft surgery.
Influence of Surgery
The period between 1975 to 1989 is rather long, and surgical
techniques and valvular prostheses evolved considerably during
this time. In the 1970s and early 1980s, some older mechanical
prostheses and a higher number of bioprostheses were used. Two late
deaths were due to acute dysfunction of Björk-Shiley prostheses
in the mitral position, which was later a well recognized problem of
convex-concave modification of this prosthesis.15
The durability of bioprostheses, especially in the mitral position, is
limited, and two thirds of repeat operations in our patients were due
to prosthesis degeneration.16 The type of
prosthesis remained without major importance for long-term
survival due to the low mortality rates for reoperation, confirming the
results of randomized studies of aortic or mitral valve replacement
with mechanical prostheses or bioprostheses.17 The
reoperation for combined aorto-mitral replacement has a higher
operative mortality rate than that for isolated valve reoperation, so
we abandoned the use of bioprostheses for combined aortic and mitral
replacement during the late 1980s.
Repair of mitral valve was performed in one third of our patients. In isolated mitral regurgitation, valve repair is superior to valve replacement in cases with suitable valvular pathology.18 19 In our patients, we noted the trend for better long-term survival rates with mitral repair compared with replacement, but the difference did not reach the level of statistical significance.
Survival Predictors
Preoperative LVEF appeared to be the best single predictor of
survival after combined aorto-mitral valve surgery. Information on
preoperative myocardial function in combined valvular disease
is rare.10 Significantly decreased late outcome was
demonstrated only for patients with severely reduced EF (<40%). On
reflection of the experience with valve replacement in isolated aortic
or mitral regurgitation, the potential for recovery
after successful double valve replacement is equally limited when
preoperative systolic function is severely
decreased.9 20 21 The presence of severe tricuspid
regurgitation requiring surgery is the second important
predictor of late outcome. Preoperative clinical status is of only
limited predictive value for postoperative outcome. Lower late survival
rates for patients in preoperative NYHA class III or IV could be
demonstrated on univariate analysis, but neither
duration nor severity of previous symptoms had any major impact on late
survival.
Retrospectively, the indication for combined aortic and mitral surgery in our patients in the 1970s and 1980s appears to have been too conservative. Half of our patients had a reduced LVEF and cardiac index, three fourths of them were in NYHA class III or IV over a long period of time, and heart failure developed in the majority. In these patients, the potential for improvement of surgical outcome is indicated by earlier surgery, before severe decrease in myocardial function began.
Summary and Prospects for Future Development
With modern surgical perioperative treatment and
durable prostheses that have excellent hemodynamic
performance, late postoperative results in combined aortic and
mitral valve disease depends crucially on preoperative LV function. Low
operative mortality rates and good late results make valve replacement
mandatory even in moderately symptomatic patients before LV
function dysfunction ensues. Durable, modern mechanical substitutes
such as bileaflet prostheses should be chosen for valve replacement,
but when possible, mitral repair should be attempted. Close
surveillance of patients after successful valvular surgery
should be maintained, especially in patients with preoperatively
decreased myocardial function. Consequent modern medical treatment of
postoperative myocardial dysfunction should be provided. Elective heart
transplantation should be considered when refractory LV dysfunction
occurs. The implantation of an automatic defibrillator might become
necessary when malignant arrhythmias arise.
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