Asian Cardiovasc Thorac Ann 2005;13:233-237
© 2005 Asia Publishing EXchange Ltd
Effect of Chordal Preservation on Left Ventricular Function
Nagarajan Muthialu, DNB,
Shashi K Varma, MCh,
Sundar Ramanathan, MCh,
Chandrasekar Padmanabhan, DNB,
K Madhusudana Rao, MCh,
Muralidharan Srinivasan, MCh
Department of Cardiothoracic & Vascular Surgery, G. Kuppuswamy Naidu Memorial Hospital, Coimbatore, India
For reprint information contact: Nagarajan Muthialu, DNB Tel: 91 80 2349 4649 Fax: 91 80 2349 1212 Email: prathi_naga{at}hotmail.com, 318, 13th Cross, West of Chord Road, Mahalakshmipuram, Bangalore 560086, India.
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ABSTRACT
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Chordopapillary apparatus preservation was compared with valve-excising mitral valve replacement in a retrospective analysis of 360 patients, of whom 98 had total or partial chordal preservation and 262 had the conventional operation. No significant differences were seen in age, sex, pathology, crossclamp or cardiopulmonary bypass times between the 3 groups. Left ventricular fractional shortening decreased significantly in patients whose valves had been excised completely, whereas it remained unchanged in patients with either partial or total chordal conservation. There was a survival benefit for patients undergoing leaflet preservation (92% vs. 80% for conventional excision at 5 years; p = 0.001). Chordal preservation during valve replacement for mitral valve disease improves survival, enhances functional status, preserves left ventricular geometry and function, and improves overall cardiac performance. Preservation of the posterior leaflet alone offers excellent results that are comparable to those of patients with total chordal preservation.
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INTRODUCTION
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Mitral valve replacement (MVR) for mitral valve disease continues to be associated with long-term morbidity and mortality.1 Despite improvements in myocardial protection and prosthetic valves, the rate of morbidity has not decreased significantly over the years. The most common cause of death following MVR is cardiac failure. This study compares various aspects of chordopapillary apparatus preservation (both total preservation and selective preservation of the posterior mitral leaflet alone) with conventional valve-excising MVR.
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PATIENTS AND METHODS
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All patients who underwent MVR from May 1996 to August 2002 were analyzed retrospectively from the data available from the registry. Mitral valve disease was diagnosed using transthoracic echocardiography supplemented with transesophageal echocardiography and cineangiography, which included left ventriculography in selected patients (mostly those with equivocal findings on transthoracic echocardiography). Mitral regurgitation was the main valve pathology; pure mitral stenosis was so small in each subgroup that it was not analyzed separately. Of 467 patients who underwent MVR in this period, 360 satisfied the inclusion criteria: isolated mitral disease with no evidence of coronary artery disease (both clinical and angiographic if over the age of 45 years), no previous open heart operation, and no concomitant cardiac procedures. Twenty-two patients underwent MVR with preservation of the entire chordal apparatus and the native valve (bileaflet preservation group), 76 patients underwent MVR with preservation of the posterior mitral leaflet and attached chordae (posterior leaflet preservation group), and the remaining 262 patients underwent MVR with excision of the entire native valve and chordae tendineae (conventional excision group). The preoperative variables and operative data are given in Table 1
. Blood cardioplegia and continuous aortic crossclamping with mild systemic hypothermia were used.
To accommodate the valve and prevent the possibility of prosthetic interference by the native leaflets, a central crescent of valve tissue was excised, and instead of re-suspending the chordae, the sutures were passed through the leaflet remnant and then through the annulus in an everting fashion. Additional procedures such as commissurotomy and splitting of the anterior leaflet from its free edge to the annulus and re-suspension using 4/0 polypropylene were carried out as required intraoperatively. Two patients who had chordopapillary conservation had to undergo valve excision during the same operation, because of possible valve interference. Most patients with conventional MVR or posterior leaflet preservation had a Starr-Edwards mechanical valve (model no. 6120; Baxter Healthcare, Edwards CVS Division, Santa Ana, CA, USA) as the prosthesis of choice; this was mainly due to surgeon preference. The types of valve used in the two study groups are shown in Table 2.
The preoperative and postoperative history, clinical examinations, and investigations were complete in all patients. New York Heart Association (NYHA) functional class was recorded at the time of operation and at follow-up. Perioperative death was defined as occurring within 30 days of operation or during the hospital stay. Death after discharge was ascribed to congestive heart failure if the patient died after experiencing symptoms of failure such as orthopnea, paroxysmal nocturnal dyspnea, or pulmonary edema. Sudden death was assumed to be of arrhythmogenic origin unless proved otherwise. Noninvasive testing during follow-up included periodic clinical examination at 6–12-month intervals and transthoracic echocardiography. Invasive monitoring and radionuclide scintigraphy were not routinely performed without clinical indication of structural valve dysfunction or a new cardiac disease, as these would eliminate the patient from our study, they were not performed in any of the studied patients.
Statistical analysis of preoperative and postoperative data was carried out using the paired Student t test. Actuarial survival curves were constructed by the Kaplan-Meier method.
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RESULTS
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There were no significant differences in age, sex, pathologic diagnosis, and crossclamp or cardiopulmonary bypass times between the patient groups. There was a slight female preponderance in the posterior preservation group, and more males in the total conservation group. In all groups, the majority of patients were in NYHA functional class III preoperatively. The preoperative echocardiographic profile and the performance status of the patients in the postoperative period are shown in Table 3.
All 3 groups had left ventricular (LV) systolic and diastolic dilatation and moderate contractile dysfunction. Postoperative echocardiographic data are given in Table 3
. There were no statistically significant differences between the posterior chordal and bileaflet preservation groups. Patients in all 3 groups had decreases in LV diastolic dimensions, although they were not statistically significant. A significant decrease in mean LV dimension was seen in the combined preservation groups (preoperative, 47 ± 1.5 mm vs. postoperative, 35 ± 1.8 mm; p = 0.001). When the mean LV systolic dimension of the combined preservation group was compared with that of the conventional group (preoperative, 40 ± 1.7 mm vs. postoperative, 38 ± 1.5 mm), the differences in the postoperative data were significant ( p = 0.001). Conversely, LV fractional shortening decreased significantly in patients whose valve had been excised completely, whereas it remained unchanged in patients with valve conservation, either partial or total. The relative preservation of fractional shortening in patients with chordal preservation was due to the comparable decreases in LV systolic and diastolic dimensions in these two groups, compared with a decrease in LV diastolic dimension only in patients undergoing conventional MVR. Left atrial dimensions decreased comparably in all 3 groups.
Follow-up was 98% complete for patients in the conventional MVR group at a mean of 22 months postoperatively, and 98% complete in the preservation groups at 15 months postoperatively. There were 29 (8%) deaths: 6 (6%) in the combined preservation group; 3 each in the bileaflet (13.6%) and posterior preservation (4%) groups, and 23 (8.7%) in the conventional group. The various causes included low cardiac output or congestive heart failure (as determined by the timing of presentation after surgery; low cardiac output in the postoperative period, and congestive heart failure in the follow-up period) in 22 (6%): 2 (9%) in the bileaflet preservation group, 3 (4%) in the posterior preservation group, and 17 (6.5%) in the conventional group. Other causes were neurological (ischemic stroke) in 3 (0.8%): 1 who had bileaflet preservation and 2 in the conventional group; structural failure in the form of valve dysfunction secondary to noncompliance with anticoagulant therapy in 1 (0.3%) in the conventional group; and multi-organ failure probably due to sepsis in 3 (0.8%) who were all in the conventional group. Among these, 6 deaths (1.6%) occurred within 30 days postoperatively.
As the study was designed to evaluate the functional aspects of the left ventricle with respect to the role of chordal preservation, only those deaths due to either low cardiac output or cardiac failure were considered relevant to the study and the others were excluded from further analysis of actuarial survival. Thus, 22 deaths were analyzed further for the calculation of survival. Because the numbers in each preservation group were small, they were grouped together for further actuarial survival analysis. There was a survival benefit for patients undergoing leaflet preservation, either partial or total, which was significant when projected into an actuarial curve (Figure 1). Survival in the combined leaflet preservation group was 92% vs. 80% for conventional excision at 5 years; p = 0.001. As seen in Table 4, except for one patient who remained in NYHA class III, all other patients in the preservation group improved to either class I or II, whereas a substantial proportion of patients (21%) were still in NYHA class III or IV after conventional MVR.
The significance of the type of valve used to the changes found in the functional and echocardiographic data was limited to the Starr-Edwards mechanical ball valve prosthesis as the numbers were small with other valves used. By analysis of variance, the changes in fractional shortening and resting LV geometric changes were accounted for by the presence or absence of either posterior or total preservation of the chordae, and not by the prosthesis used (fractional shortening, 34% preoperatively vs. 26% postoperatively in the conventional group; and 31% vs. 29% in the preservation group; p = 0.06).
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DISCUSSION
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Mitral valve replacement has been associated with a high prevalence of postoperative LV dysfunction resulting in high postoperative morbidity, poor exercise tolerance, and high NYHA functional class.1 Perioperative strategies to decrease the prevalence of low output cardiac failure include revision of the indications for MVR, improvement of myocardial protection and type of mitral prosthesis used, mitral valve reconstruction to correct mitral regurgitation as far as possible, and chordopapillary apparatus preservation. Chordal preservation was initially introduced by Lillehei and colleagues2 in 1964 but did not gain popularity because of the potentially detrimental effects reported by Bjoerk and colleagues.3 Its re-emergence was largely due to David and colleagues4 who described it as an important method of preserving LV function after MVR.
This study demonstrates that MVR with bileaflet or posterior preservation is associated with better immediate results than conventional MVR. Improved operative and postoperative survival had been shown before in patients with acute MR following acute MI. In addition to improved survival, patients undergoing either posterior or bileaflet preserving MVR derived greater functional benefit than those undergoing chordae-resecting operations.5–7 This functional improvement is related to the fact that there is no postoperative dilatation of the left ventricle following MVR.5 Since the geometry of the ventricle is well preserved, overall stroke volume and ejection fraction are maintained, which helps to ensure freedom from symptoms.5 In the conventional group, 20% of patients were in class III or IV and incapacitated in contrast to the preservation group where all except one were within class I or II.
This study also demonstrates that the changes in LV dimensions differed significantly between the conventional and preservation groups. These changes primarily accounted for preservation of the fractional shortening in patients with chordae-sparing operations. This may in turn account for the better clinical outcome seen in these patients.
Preservation of the posterior leaflet alone has been shown to be effective in preventing postoperative LV dilatation.8 The intact chordal apparatus helps to maintain the geometry of the lateral and posterior left ventricle, and hence the functional class is better in these patients. As shown in our data, there was no statistical difference between the two major preservation groups. This further highlights the importance of maintaining at least the posterior leaflet apparatus in those individuals with widespread disease involving the mitral valve apparatus. Patients who have extensive disease of the annulus and leaflets can undergo excision and re-suspension by suturing to the annulus using interrupted polypropylene sutures.9
There were some limitations to this study: it was retrospective; there were multiple surgeons involved and hence, techniques varied; and the study groups were not case matched. The study groups were small, even though it was conducted in a tertiary care center, and the follow-up period was limited as awareness of chordal preservation was realized only lately. There is likely to have been a bias towards preservation or excision of the valve apparatus due to the different surgeons involved, and this cannot be assessed. A larger prospective trial, eliminating bias, is required to evaluate the advantage of chordal preservation. Nevertheless, it was concluded that chordal preservation during MVR improves survival, enhances functional capacity, preserves LV geometry and function, and improves overall cardiac performance. Chordal preservation can be used safely for ball-valve and tilting-disc mechanical prostheses as well as bioprostheses, and it should be the procedure of choice in patients with mitral regurgitation who require MVR.
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REFERENCES
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- Hennein HA, Swain JA, McIntosh CL, Bonow RO, Stone CD, Clark RE. Comparative assessment of chordal preservation versus chordal resection during mitral valve replacement. J Thorac Cardiovasc Surg 1990;99:828–-37.[Abstract]
- Lillehei CW, Levy MJ, Bonnabeau RC Jr. Mitral valve replacement with preservation of papillary muscles and chordae tendinea. J Thorac Cardiovasc Surg 1964;47:532–43.
- Bjoerk VO, Bjoerk L, Malers E. Left ventricular function after resection of the papillary muscles in patients with total mitral valve replacement. J Thorac Cardiovasc Surg 1964;48:635–9.
- David TE, Uden DE, Strauss HD. The importance of the mitral apparatus in left ventricular function after correction of chronic mitral regurgitation. Circulation 1983;68(3 Pt 2):II76–82.
- Straub U, Feindt P, Huwer H, Petzold T, Kalweit G, Volkmer I, et al. Postoperative assessment of chordal preservation and changes in cardiac geometry following mitral valve replacement. Eur J Cardiothorac Surg 1996;10:734–40.[Abstract]
- Natsuaki M, Itoh T, Tomita S, Furukawa K, Yoshikai M, Suda H, et al. Importance of preserving the mitral subvalvular apparatus in mitral valve replacement. Ann Thorac Surg 1996;61:585–90.[Abstract/Free Full Text]
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- Yun KL, Sintek CF, Miller DC, Pfeffer TA, Kochamba GS, Khonsari S, et al. Randomized trial comparing partial versus complete chordal-sparing mitral valve replacement: effects on left ventricular volume and function. J Thorac Cardiovasc Surg 2002;123:707–14.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
