(Circulation. 1997;95:899-904.)
© 1997 American Heart Association, Inc.
Articles |
Time-Related Changes in Left Ventricular Function After Double Valve Replacement for Combined Aortic and Mitral Regurgitation in a Young Rheumatic Population
Predictors of Postoperative Left Ventricular Performance and Role of Chordal Preservation
the Department of Cardiology, Baragwanath Hospital, Johannesburg, South Africa.
Correspondence to Daniel Skudicky, MD, Department of Cardiology, Baragwanath Hospital, PO Bertsham 2013, Johannesburg, South Africa. E-mail psareli@iafrica.com.
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Abstract |
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Background The long-term effects of double valve replacement on left ventricular function in patients with combined severe rheumatic aortic and mitral regurgitation have not been reported previously. Furthermore, the importance of chordal preservation in this group of patients is unknown.
Methods and Results Serial clinical and echocardiographic evaluations were performed prospectively in 44 patients who underwent double valve replacement for combined aortic and mitral regurgitation. Chordae to the posterior mitral leaflet were preserved in 27 patients. Mean follow-up was 40±19 months. Left ventricular end-diastolic diameter decreased significantly 3 months after surgery (from 66±10 to 52±11 mm; P<.001) without a substantial change in end-systolic diameter, resulting in a significant decline in ejection fraction (from 60±9% to 48±15%; P<.001). At 1 year, a significant reduction in end-systolic dimension was observed without a concomitant decline in end-diastolic diameter, thus normalizing the ejection fraction (55±12%; P=.17 versus baseline). No further changes were seen at latest follow-up. Multivariate regression analysis identified baseline end-systolic diameter and ejection fraction as independent predictors of postoperative systolic performance. Chordal preservation did not emerge as a univariate or multivariate predictor.
Conclusions After an initial postoperative decline in ejection fraction, normalization in left ventricular systolic function may be expected 1 year after double valve replacement for combined rheumatic mitral and aortic regurgitation. End-systolic diameter and ejection fraction are the only independent predictors of postoperative left ventricular performance.
Key Words: valves • regurgitation • echocardiography
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Introduction |
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Aortic and mitral regurgitation frequently occur in combination.1 2 Although myxomatous degeneration with leaflet prolapse of both valves accounts for some cases,3 rheumatic disease is the most common cause.2 The hemodynamics and loading conditions for isolated mitral or aortic regurgitation have been well documented,4 5 6 and their effect on postoperative left ventricular function has been established.7 8 9 Although previous studies have looked at the clinical outcome of patients undergoing double valve replacement for combined severe aortic and mitral regurgitation,10 11 few data are available on postoperative left ventricular function in these patients.7 12 Furthermore, whether chordal preservation has any salutary effect on left ventricular function in patients having surgery for concomitant mitral and aortic valve regurgitation has never been investigated. In this study, we sought to analyze long-term changes in left ventricular function after double valve replacement and to determine preoperative predictors of postoperative ejection performance.
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Methods |
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Patient Enrollment
In September 1989, a registry was initiated at Baragwanath Hospital to prospectively monitor patients who underwent prosthetic heart valve replacement for the first time and survived operation and hospitalization. Between September 1989 and January 1995, 502 patients were entered into this registry. Forty-four patients who underwent simultaneous aortic and mitral valve replacement for combined severe pure aortic insufficiency and pure or predominant mitral regurgitation (mitral valve area
1.8 cm2) were identified and make up the study population. Two patients died within 30 days of surgery and were not included in the present analysis. Valvular regurgitation was judged to be severe on the basis of physical examination and Doppler color flow mapping. The origin of the valve lesions was considered to be rheumatic in all cases, on the basis of clinical and echocardiographic criteria and as confirmed by surgical evaluation. None of the patients had concomitant coronary bypass surgery or repair of associated congenital heart abnormalities. The baseline characteristics of the 44 patients are described in Table 1
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Surgery
Operations were performed with the standard techniques of cardiopulmonary bypass, including hemodilution and moderate systemic hypothermia and myocardial protection with cold crystalloid cardioplegia. Chordae to the posterior mitral leaflet were preserved in 27 patients. This was not done in a randomized fashion. In 9 patients (20%), a modified De Vega tricuspid annuloplasty was performed. Implanted valve prostheses included St Jude Medical, Medtronic Hall, and Carbomedics.
Patient Follow-up and Doppler Echocardiography
All patients were followed up at our hospital at a dedicated prosthetic valve follow-up clinic. Patients were seen at 2 weeks and 1, 2, and 3 months after surgery and thereafter every 3 months or more frequently if clinically indicated. At each visit, a clinical examination plus anticoagulation level determination were performed. Doppler two-dimensional echocardiography with color flow mapping was performed in every patient before surgery with the use of a Hewlett-Packard Sonos model 500 or 1000 attached to a commercially available 2.5- or 3.5-MHz transducer. All studies were recorded on videotape. Serial follow-up studies were performed on the same tape by use of the same equipment. Echocardiographic studies were routinely performed at 3 and 12 months and then yearly or at more frequent intervals whenever feasible or when a complication was suspected. Although echocardiograms were recorded prospectively by multiple observers, the present analysis was performed retrospectively by a single observer (D.S.) using the two-dimensional images recorded on tape. Linear regression analysis showed an excellent correlation (r=.94, P<.001) for intraobserver variability.
Two-dimensional images were used to avoid problems with M-mode beams that were not directed perpendicular to the endocardium.13 Left ventricular end-diastolic and end-systolic diameters and wall thickness were measured just above the papillary muscles in the parasternal long-axis view. The left ventricular ejection fraction was calculated as previously described.14 Paradoxical septal motion was not noted on M-mode or two-dimensional imaging in any of the postoperative studies, although the septum appeared hypokinetic in six patients and akinetic in one. Left atrial dimension was measured in systole.
End-systolic pressure was estimated from noninvasive blood pressure measurements15 by use of a Dinamap (Critikon monitor),16 and end-systolic stress was calculated by use of the following formula17 :
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For left ventricular measurements, an average of 3 beats for patients in sinus rhythm and 5 beats in those with atrial fibrillation was obtained.
The severity of regurgitant lesions was assessed in multiple orthogonal parasternal and apical views by Doppler color flow mapping. Mitral insufficiency was considered severe when the regurgitant jet to left atrial ratio was >50%. Severe aortic regurgitation was defined as an aortic regurgitant jet height to left ventricular outflow height ratio 60%. The accuracy of these methods and the correlation with left ventricular angiography have been described previously.18 19 20 The presence of ring leaks was investigated with color flow mapping from the transthoracic and transesophageal approaches.
All patients were treated with diuretics preoperatively, whereas only 3 patients received ACE inhibitors and 2 digoxin. After surgery, all patients were treated with warfarin and dipyridamole. Digoxin (n=4), diuretics (n=20), and ACE inhibitors (n=11) were used at the discretion of the physician caring for the patient.
Statistical Analysis
Data are presented as mean±SD. Group comparisons were made by use of the unpaired Student's t test or 
2 analysis as appropriate. ANOVA with the post hoc Tukey test was used for comparison of echocardiographic data before surgery, at 3 and 12 months after surgery, and at latest follow-up. All clinical, surgical, and echocardiographic variables listed in Table 1
were entered into a forward and backward stepwise multivariate regression analysis to identify independent predictors of postoperative left ventricular performance. Logistic regression analysis was used to predict the probability of postoperative left ventricular dysfunction (defined as an ejection fraction <50%) at latest follow-up for each patient. Data were analyzed on a personal computer by use of a commercially available statistical program (Systat 5). Significance was assumed at a two-tailed value of P<.05.
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Results |
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Mean follow-up was 40±19 months (range, 4 to 73 months). One patient was lost to follow-up. There were three deaths (6.8%): one patient died of heart failure due to severe left ventricular dysfunction (postoperative ejection fraction 14%) with a normally functioning mechanical prosthesis, and two were noncardiovascular deaths (one motor vehicle accident and one pneumonia). All but one patient were in sinus rhythm at latest follow-up. New York Heart Association functional class improved significantly after surgery, from 3.2 to 1.2 (P<.0001).
Serial Echocardiographic Assessment
Results obtained at baseline, 3 and 12 months after surgery, and at latest echocardiographic follow-up (34±14 months) are shown in Table 2. Left ventricular end-diastolic diameter decreased significantly at 3 months without a substantial change in end-systolic diameter, resulting in a significant decline in ejection fraction. At 1 year, there was a significant reduction in end-systolic dimension without a concomitant decline in end-diastolic diameter, thus resulting in normalization of the ejection fraction. No additional changes in left ventricular dimensions or systolic function were observed at latest follow-up.
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End-systolic stress declined significantly from baseline to latest follow-up (from 171±46 to 139.4±39 mm Hg; P<.001). Six patients (14%) had a preoperative ejection fraction <50%. In this subgroup of patients, the ejection fraction dropped from 42±7% preoperatively to 35±5% at 3 months after surgery (P=.24). At 1 year, it improved to 42±5%, and no further changes were noted at latest follow-up, a trend that was similar to the total group. Baseline end-systolic stress was significantly higher in the six patients with preoperative left ventricular dysfunction than in the rest of the patients (217±71 versus 164±38 mm Hg; P<.0001). At latest follow-up, there was a significant reduction in end-systolic stress in the group of patients with normal preoperative left ventricular function (from 164±38 to 132±29 mm Hg; P=.007), with a nonsignificant trend toward reduction in the group with preoperative left ventricular impairment (from 217±71 to 188±60 mm Hg; P=.28). A significant reduction in left atrial diameter from baseline to latest follow-up was also noted (from 50±11 to 40±9 mm; P<.0001).
Compared with the rest of the patients, postoperative left ventricular ejection fraction was significantly lower in patients receiving ACE inhibitors (49.5±16% versus 60.5±6%; P=.004) or diuretics (51.7±14% versus 62.1±5%; P=.003) because they were used preferentially in the patients with poor postoperative ventricular function. However, therapy with ACE inhibitors or diuretics did not emerge as significant predictors of postoperative left ventricular function in the multivariate analysis.
Valve-Related Complications
Valve obstruction occurred in two patients, both on the mitral prosthesis, at 24 and 28 months after the operation. The International Normalized Ratio at presentation was 1.1 and 1.3, respectively, and both patients were referred for emergency surgery and survived reoperation. In these two cases, the last echocardiogram before the valve obstruction was used for the present analysis. Mild ring leaks (
2+) were detected on the mitral position in three cases and on the aortic in two. There were no other valve-related complications during the follow-up period. Only one patient required admission for anticoagulation-related bleeding.
Predictors of Postoperative Left Ventricular Function and Role of Chordal Preservation
Of all the baseline clinical, echocardiographic, and intraoperative variables analyzed, only end-systolic diameter (P=.006) and ejection fraction (P=.003) emerged as independent predictors of postoperative ejection fraction in the multivariate analysis. The Figure shows the computed probability of postoperative left ventricular dysfunction at latest follow-up by use of the logistic model for a given preoperative ejection fraction and end-systolic diameter. The risk of postoperative left ventricular dysfunction was 2.2% when the preoperative ejection fraction was 70% and rose to 95.7% for an ejection fraction of 29%. Similarly, a preoperative end-systolic diameter of 29 mm predicted a 2.1% probability of left ventricular dysfunction at latest follow-up, and predictive ability increased to 95% for an end-systolic diameter of 80 mm (Table 3). Left ventricular end-systolic diameter and ejection fraction in the two patients who died during the perioperative period were 53 and 57 mm and 49% and 38%, respectively.
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Chordal preservation was not a significant predictor of postoperative outcome in a univariate or multivariate model. Baseline characteristics of patients with and without chordal preservation were similar except for age (Table 4). Patients in the chordal preservation group were younger (19±17 versus 30±12 years; P<.001). Clinical and echocardiographic data at latest follow-up comparing both groups are shown in Table 5. No differences in functional class, left ventricular dimensions, or systolic function were detected among the two groups.
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Discussion |
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Aortic and mitral regurgitation frequently occur in combination.1 2 The first report of simultaneous mitral and aortic valve replacement was published by Cartwright and coworkers in 1963.21 Although there have been several subsequent publications emphasizing the clinical outcome of double valve replacement for combined valve regurgitation,10 11 few data are available regarding postoperative left ventricular function in these patients.7 8 9 10 11 12
Serial Changes in Left Ventricular Function
Boucher et al22 reported a significant reduction in ejection fraction 2 to 4 weeks after isolated aortic or mitral valve replacement for aortic or mitral regurgitation because of a decrease in end-diastolic volume. However, late postoperative analysis (1 to 2 years after surgery) showed normalization of the ejection fraction in the aortic insufficiency group owing to a reduction in end-systolic volume, whereas in the mitral regurgitation group, ejection fraction remained subnormal. There is a paucity of data examining the effect of double valve replacement on left ventricular ejection performance in patients with combined mitral and aortic regurgitation. In a short-term evaluation of 13 young patients with active rheumatic carditis in whom the chordae tendineae were uniformly resected, Essop et al12 found relatively well-preserved fractional shortening 3 months after surgery. In contrast, the present study demonstrated subnormal left ventricular systolic function 3 months after surgery owing to a reduction in the end-diastolic diameter with no change in the end-systolic diameter. Normalization of the ejection fraction was only observed at 1 year. This discrepancy may be due to the fact that patients in the current study were older (23±9 versus 13±0.8 years; P<.0001), with more long-standing valvular regurgitation and therefore less contractile reserve.
The phenomenon of late fall in end-systolic dimension and recovery of systolic function in our group of patients with double valve replacement is similar to that reported for patients with isolated aortic regurgitation.9 22 The elevated afterload measured preoperatively and its significant reduction postoperatively are also similar to the data reported for isolated aortic regurgitation.23 It would appear, therefore, that the hemodynamics of combined valve regurgitation more closely approximate those of isolated aortic regurgitation than isolated mitral regurgitation. Although the postoperative increase in ejection fraction is most likely due to a substantial reduction in afterload, a concomitant improvement in contractility cannot be excluded. These results would also suggest that the detrimental loading conditions created by mitral valve replacement are more than offset by the favorable hemodynamics of aortic valve replacement.
Predictors of Postoperative Left Ventricular Function
Similar to previous reports24 25 26 27 28 on isolated aortic or mitral insufficiency, left ventricular end-systolic diameter and ejection fraction were significant independent predictors of postoperative ejection performance in the present study. It would appear from these data that to optimize postoperative left ventricular function in patients undergoing simultaneous aortic and mitral valve replacement for regurgitant lesions, surgery should be considered before the ejection fraction drops below 55% or the end-systolic diameter exceeds 50 mm. The fact that both patients who died in the perioperative period had values for end-systolic diameter and ejection fraction that were beyond the recommended cutoff values would serve to further validate these guidelines. Because this was a noninvasive study, we cannot exclude the role of other potential predictors, such as pulmonary artery pressure or left ventricular volumes.
Role of Chordal Preservation
Although several studies15 29 30 31 have shown that retaining the submitral apparatus during mitral valve replacement may enhance preservation of left ventricular function, most of these studies have not been randomized and were performed in a predominantly nonrheumatic population. In a small (n=16) but randomized trial, Komeda et al32 showed a greater ejection fraction 4 to 5 years after mitral valve replacement with chordal preservation than with mitral valve replacement with chordal transection (degenerative disease of the mitral valve in all cases). By contrast, in a large, nonrandomized study,16 preservation of chordae tendineae was not an independent predictor of postoperative outcome in 61 patients with rheumatic mitral regurgitation. The role of chordal preservation in rheumatic mitral insufficiency, therefore, is as yet uncertain. The role, if any, of chordal preservation during double valve replacement for combined aortic and mitral regurgitation has never been investigated. Although the decision regarding preservation of the submitral apparatus was left to the operating surgeon and therefore was nonrandomized, the similar baseline characteristics of the patients with and without chordal preservation in the present analysis suggest that a comparison between them would be valid. The results of the present study would indicate that chordal preservation does not have a significant impact in the outcome of rheumatic patients undergoing double valve replacement.
Study Limitations
The use of echocardiography for the assessment of left ventricular ejection fraction may be a concern. However, the method of assessment of ejection that we used in the present study has been validated14 and has been shown to be highly reproducible.33
Conclusions
After an initial postoperative decline in ejection fraction, normalization of left ventricular function may be expected 1 year after double valve replacement for combined rheumatic mitral and aortic regurgitation. Left ventricular end-systolic diameter and ejection fraction are the only independent predictors of postoperative left ventricular performance. Chordal preservation does not appear to affect the outcome of these patients, although results of randomized studies are still needed to confirm these data.
Received July 8, 1996; revision received September 26, 1996; accepted October 5, 1996.
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