Chordal preservation during mitral valve replacement: basis ... - medIND

IJTCVS Review 2005; 21: 45–52

Talwar et al 45 Chordal preservation

Chordal preservation during mitral valve replacement: basis, techniques and results Sachin Talwar, M.Ch., Honnakere Venkataiya Jayanthkumar, MS, Arkalgud Sampath Kumar, M.Ch., Department of Cardiothoracic & Vascular Surgery, Cardiothoracic Centre, All India Institute of Medical Sciences, New Delhi Introduction The aim of mitral valve (MV) surgery is to provide a competent, non-obstructed valve without compromising the left ventricular (LV) function. To a large extent, these aims are met with valve conservation and repair rather than valve replacement1, 2 . However, a large number of patients require mitral valve replacement (MVR) when repair is not feasible and in this subgroup of patients preservation of left ventricular function is an important concern. As the awareness of the deleterious effects of the loss of annulo-ventricular continuity has increased, chordal preservation has gained popularity and is now a standard procedure during MVR 3 . A wide variety of techniques are available. The aim of this article is to systematically review the basis, historical aspects, techniques, concerns and long-term results of MVR with chordal preservation. Anatomy and physiology The bicuspid design of the mitral valve along with its subvalvular apparatus has evolved over millions of years and it is not by accident, rather it is by nature’s design. In normal hearts, the orifice which results from a bicuspid configuration of the MV is round in diastole and ellipsoidal in systole. In systole, the mitral orifice decreases by almost 25% and the circumference of the mitral annulus reduces by 30%4. The chordae of the mitral valve insert either into the free edge or into the rough zone on the ventricular surface of the anterior and posterior mitral leaflets. The Address for correspondence: Dr. A Sampath Kumar Professor, Department of Cardiothoracic & Vascular Surgery Cardiothoracic Centre All India Institute of Medical Sciences, Ansari Nagar New Delhi – 110 029 Telefax : 91-11-26588889 E-mail : [email protected] @IJTCVS 097091342110305/118 Received - 25/10/04; Review Completed - 19/11/04; Accepted - 19/11/04.

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chordae of the anterior leaflet insert on either side of a central clear zone. There are two papillary muscles antero-lateral and postero-medial. Each of these gives chordae to both the anterior and posterior mitral leaflets. In 1922, Wiggers and Katz5 and later Rushmer et al6,7 proposed the concept of annulo-ventricular continuity. According to this concept, the left ventricular geometry and function are a result of a dynamic interaction between the mitral annulus and the LV wall. The attachments between the mitral annulus and the LV wall moderate the LV distension during diastole and wall tension during systole. When the papillary muscles contract during the isometric phase of the cardiac cycle, the closed MV is drawn into the LV cavity thus reducing the longitudinal axis of the LV and increasing its short axis8. The bulbo-spiral muscles play an important role in this9. As a result of this interaction, the myocardial fibres stretch additionally and generate more tension, leading to greater contraction and an increase in stroke volume (SV). During systole, the ventricle undergoes counterclockwise torsional deformation of the apex with respect to base; during isometric relaxation and in early diastole, this is reversed (diastolic recoil)10. Disruption of the papillary-annular continuity impairs this torsional deformation thereby causing abnormal diastolic function and disruption of normal LV stress-strain patterns 11. Historical aspects and animal experiments In 1964, Lillehei introduced the concept of chordal preservation during MVR to reduce the problem of postoperative low cardiac output syndrome12. However very soon there emerged strong opposition to this idea13-16. The concept was re-introduced by David in 1981 after an experimental study of MVR in dogs17. This study showed that LV function deteriorated if the chordae were transected but remained unchanged when the chordae were intact. David also compared resting preoperative and post-operative LV function and exercise induced changes after MVR with or without chordal preservation in patients with chronic mitral regurgitation. LV function showed a decline in those

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who had chordal transection but not in those with chordal preservation. Left ventricular end-diastolic volume (LVED), end-systolic volume (LVESV) and stroke volume (SV) reduced significantly in both groups. With exercise, cardiac output increased in both the groups primarily by an increase in the heart rate, but only those patients in whom the chordae had been spared could increase the LV ejection fraction (EF) and stroke volume index. Also in the chordal preservation group, there was better long-term systolic function and LV performance both at rest and during exercise. They also demonstrated increased LV end-diastolic pressures after chordal transection and conventional MVR whereas these decreased after MVR with chordal preservation18. Effects of chordal transection Canine experiments have been performed to assess the effects of chordal transection on the LV mechanics. Gams et al19demonstrated that chordal transection in a working dog heart led to an increase in the long axis of the LV followed by a reduction in contractility. The LV stroke volume could then be maintained only by a higher preload and up to 30% increase in fibre force. Hansen20 demonstrated that transection of chordae to the anterior mitral leaflet (AML) reduced the LV function to a greater degree as compared to the transection of chordae to the posterior mitral leaflet (PML). He hypothesized that preservation of the subvalvular apparatus improved LV systolic performance by reduction of the LV afterload; He further proposed that the detrimental effect of transection of the chordae to the AML was because of regional afterload reduction. Because the AML is larger than the PML, the development of tension in the chordae to this leaflet should be greater at a given LV pressure. Chordal transection also appeared to shorten the long axis of the LV with an increase in the minor axis and dilatation of the chamber. However when the chordae were intact, the chamber shape remained same during isometric contraction. In addition to this, transection of the chordae produced dyskinetic areas at the insertion of severed papillary muscles. Rastelli14 after his canine experiments indicated that preservation or excision of the chordae did not affect the cardiac performance after replacement with StarrEdwards prosthesis. However, Doces and Kennedy21 have reported reduction in ejection fraction after conventional MVR. Sarris and colleagues22 demonstrated that in an openchest swine experimental model, the changes induced


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by chordal transection could be completely reversed by reattaching the papillary muscles. This forms the basis for neo-chordal reconstruction at re-operation in those patients in whom chordae have been transected previously. These effects were described in a simplified manner in a recent editorial on the issue23. The function of the chordae and papillary muscles was eloquently compared to a pair of gymnasts on parallel bars (Fig. 1 & 2). As the gymnasts (chordae) move towards the parallel bars (mitral annulus), they bring the floor (LV wall) with them and in addition prevent overstretching of the LV cavity. When either of the chordae are transected, only one gymnast works, and the unsupported portion of the LV thins and dilates. When both the anterior and posterior chordae are divided, the gymnasts do not have the arms to pull themselves up

Fig. 1. The parallel bars are the mitral annulus. (b) The arms of the gymnasts are chordae and their bodies the papillary muscles. The floor is the left ventricular wall. (Reproduced with permission from : Kumar AS. Heart strings. Ind J Thorac Cardiovasc Surg 2004;20:115-16.)

Fig. 2. Effect of chordal resection- Note dilatation & ventricular wall thickness where chordae are resected partially or completely (a)Partial chordal resection (b) Complete chordal resection. (Reproduced with permission from : Kumar AS. Heart strings. Ind J Thorac Cardiovasc Surg 2004;20:115-16.)

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and in an attempt to reach the bars, they have to jump higher and higher, but with each attempt they sink lower, resulting in dilatation of the LV cavity and thinning of its walls. When all the chordae are intact, the gymnasts are free to do their work. Physiologic alterations in mitral valve disease In chronic mitral regurgitation (MR), the LV function gradually declines. This can be easily demonstrated by selective angiography where the LV contractility is poor in successive films and also by an elevated LV filling pressure. The regurgitation into the left atrium during systole (regurgitatnt stroke volume) is added to the forward stroke volume and tends to increase the total forward output and ejection fraction (EF) in the early phase. However, progressive LV dilatation increases the wall tension as per the Laplace law which leads to increased systolic wall stress and also increases the afterload. After MVR, there is a rapid increase in the LV afterload and the adaptation of LV to this change depends upon the annulo-ventricular continuity9,24. Fixation of the mitral annulus with a rigid prosthesis interferes with the distension and contraction of the basoconstrictors. Also, after MVR, the LV volume decreases because of elimination of the regurgitant volume. After MVR with chordal transection, the EF is determined by contractility, preload and after-load. Because there is elimination of the low impedance pathway into the left atrium, it increases the after-load and at the same time reduces the preload. This may be further worsened by some residual gradient across the prosthesis and may be responsible for the syndrome of “low output” in many of these patients despite a satisfactory prosthesis function. It has been demonstrated that post-operative low output syndrome

Fig. 3. David’s technique: (a) Normal Mitral valve. AML = anterior mitral leaflet, PML = posterior mitral leaflet (b)A triangular portion of the AML and a crescent of PML are excised.


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is less common after mitral valve repair as compared to conventional MVR without chordal preservation which possibly explains the role of subvalvular apparatus in preserving LV function2. In patients undergoing surgery for mitral stenosis (MS), the LV is small and because of severe subvalvular fusion and often fused, rigid and calcified leaflets, the annulus loses it sphincter-like function. Excision of this valve with chordae does not produce the picture of reduced preload and increased after-load as observed after MVR for chronic MR. Nevertheless, the loss of annulo-ventricular continuity still leads to progressive LV dilatation with eventual decline of LV function in the long-term9,23. Techniques of chordal preservation PML preservation In the original technique as described by Lillehei12, the posterior leaflet was bound to the annulus with a running stitch. In 2 of the 23 patients, this stitch was continued around the entire annular circumference and chordae to both the AML and PML were preserved. In the remaining 21 patients, only the PML was preserved because it was thought that the AML would interfere with the ball of the caged ball valve prosthesis used for MVR. Using this technique, Lillehei reported reduction in operative mortality from 37% to 14% 12. Total chordal preservation With the development of low profile bi-leaflet mechanical valves, and refinements in surgical technique, various methods of total chordal preservation have been described to preserve the LV systolic function and to avoid interference with the mechanical prosthesis function by portions of the retained subvalvular apparatus and also to prevent left ventricular outflow tract obstruction (LVOTO). In addition to these considerations, it is important to adjust tension on the chordae during chordal preservation as too much stress on the chordae can lead to chordal rupture and entanglement with the prosthesis. Also the method of AML preservation should avoid the systolic anterior motion of the AML which has the potential to produce LVOTO. David’s technique25 (Figure 3) The AML is incised at its base, 2-3 mm from its attachment. The incision is carried to both the sides and brought down centrally towards the free edge of the leaflet and a triangular segment of the AML is thus excised leaving the chordae attached to the remaining

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AML which is re-suspended to the mitral annulus by sutures used to secure the prosthetic valve. The PML with its chordae is left intact. In patients with myxomatous MR undergoing MVR, the chordae are shortened by imbricating the PML in the mitral annulus using the sutures used for prosthetic valve fixation. Alternatively, a part of the posterior leaflet is excised and reattached to the mitral annulus during fixation of the prosthetic valve. Advantages of the David technique are the maintenance of the chordae in their natural anatomic orientation, reduced risk of LVOTO and reduction in the bulk of leaflet tissue. 26

Feikes technique (Figure 4) The AML is split from the centre of the free edge towards the annulus. Incisions are made on either side of this split towards the two commissures to detach the AML from the annulus. The resulting two halves of the leaflet along with the intact chordae are trimmed to remove thickened and calcific areas and then rotated posteriorly and sutured to the posterior mitral annulus. This technique has been reported to be specially useful while implanting tilting disc prosthesis where disc entrapment by the subvalvular apparatus is a concern. The chordal continuity to the AML is well maintained. A theoretical disadvantage of this technique is that it disturbs the normal geometric relationships of the mitral subvalvular apparatus which could alter the distribution of regional LV wall stresses and disturb chordal tension during papillary muscle contraction thereby reducing global LV systolic and diastolic function11. Khonsari Technique 27 (Figure 5) After the AML is detached from the annulus between the two commissures, an ellipse of tissue is excised and the rim of the leaflet tissue containing the chordae is reattached to the anterior annulus (Khonsari I technique). If the leaflet is thick or calcified, it is divided into 2-5 chordal segments which are re-attached to the annulus (Khonsari II technique). The PML is retained completely and the redundant leaflet tissue is folded up into the annulus by passing the valve sutures through the annulus and bringing them through the leading edge of the leaflet tissue. They also advocate construction of artificial chordae using 4-0 polytetrafluoroethylene (PTFE) sutures if there is considerable thickening and fusion of chordae and papillary muscles. With this technique, there has been no reported incidence of LVOTO or interference with prosthetic


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Fig. 4. Feikes technique: (a)The AML is incised in the midline and the incision is extended sideways (b)The 2 segments of the AML are turned backwards and sutured to the posterior mitral annulus.

Fig. 5. Khonsari technique: (a) The AML is separated from the mitral annulus (b)The two chordal buttons are re-attached to the anterior mitral annulus (Khonsari I) in such a way that the point 1 is approximated with 2 and the point 3 is sutured to point 4. (c) Multiple buttons of AML with chordae are attached to the anterior mitral annulus (Khonsari II)

valve function. It is believed that with the use of this technique, myocardial rupture is prevented by maintaining the tethering effect of the intact subvalvular apparatus28. A concern with the Khonsari technique is that the chordae could become stretched around the struts of the bioprostheses thereby exerting more stress on the retained chordae. Miki’s technique29 (Figure 6) This is the most commonly used technique as it is thought to maintain more normal chordal tension as the direction of the chordal force is more anterior than the Fiekes technique. The AML is separated from the annulus and incised in centre. The anterior and posterior

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Fig. 6. Miki’s technique: The PML is incised in the midline (b) & (c) The two papillary muscles are split and the two halves of the PML are reattached to the commissures.

commissures are incised and papillary muscles are split. Excessive cuspal tissue and fibrous and calcific nodules are excised. The two chordal segments thus created are sutured to the respective antero-lateral and posteromedial commissures. The PML is incised in the centre and the prosthetic valve is sutured in position plicating the PML and including the AML and chordae in valve sutures. The technique is simple, and LVOTO is uncommon with good preservation of LV function. This technique is particularly suitable for patients with rheumatic mitral valve disease and thickened, deformed and calcific cusps 30. Also this technique allows placement of a larger prosthesis. The use of a low profile prosthesis further reduces the incidence of leaflet obstruction from retained chordae. Rose and Oz technique 31 (Figure 7)

Fig. 7. Rose and Oz technique : (a) An ellipse of AML is removed, (b)The defect in AML is closed is closed with a running polypropylene suture and valve sutures are placed.


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The AML is stretched posteriorly and its central portion is excised. The rim of the remaining leaflet tissue contains the marginal chordae. The defect in the AML is then closed with a running suture placed parallel to the annulus. This tacks the marginal chordae to the fibrous triagones and displaces the anterior leaflet chordae to the periphery of the mitral orifice. Valve sutures are placed to reinforce the previously running suture line. The prosthetic valve is sutured to orient the leaflets perpendicular to the native annulus. In this way, restriction of the prosthetic leaflet motion is minimized. Reported advantages of this technique are reduced bulk of the AML which reduces the possibility of impairment of valve function, low risk of LVOTO, and reduced risk of thrombosis on the redundant leaflet tissue. Miscellaneous techniques Vander-Salm32 and Yu33 have described procedures for complete retention of valve leaflets and subvalvular apparatus without the risk of LVOTO or interference with prosthetic valve function. In these techniques the central part of the AML is incised from the edge to the base and pledgeted horizontal mattress sutures are passed from the left atrium through the mitral annulus avoiding the papillary muscles and chordae around the free edge of the leaflet and up through the prosthetic sewing ring. If the AML is large, it is reefed within the sutures and the prosthetic valve is seated and tied. This has the advantage that the native leaflet is reefed and compressed between the prosthesis and the native annulus and also chordal tension is evenly maintained. Safeguards In choosing the technique to be used for chordal preservation, the factors to be considered are the simplicity and reproducibility of the technique, prevention of post-operative LVOTO due to systolic anterior motion of the remaining AML and risk of interference with the prosthetic valve function. The technique used should allow for implantation of an adequate size prosthesis to prevent post-operative patient-prosthesis mismatch. In MVR with chordal preservation, the function of the native valve leaflets is replaced by the prosthetic mitral valve and the preserved chordae and the papillary muscles assist the myocardium during systole and diastole. Care should therefore be taken to ensure that these attachments are of sufficient length to moderate left ventricular distension during diastole and wall tension during systole. Care should be taken to prevent excessive shortening of the chordae as it may

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cause rupture of a papillary muscle head34. In patients with pure MS, the papillary muscles should be incised. This allows the anterior and posterior chordae to fall away and ensures free movement of the discs. Further, incision of the PML in the middle allows a larger prosthesis to be seated30. Results of partial or complete chordal preservation Experiments by Hansen and associates20 have clearly demonstrated that LV function was superior with an intact subvalvular apparatus, intermediate with preservation of either the AML or PML and poorest with loss of all chordae. Horskotte et al35 showed that partial chordal preservation preserving the PML alone improved the event-free survival, but they did not attempt total chordal preservation. Hennein et al36 showed that after chordal excision, exercise capacity, LV systolic dimensions and cardiac index did not improve and the LV function declined. In contrast, after preservation of the entire subvalvular apparatus, the exercise capacity improved markedly, LV function improved and resting ejection fraction was preserved. However there was no significant difference between posterior chordal preservation alone or the total chordal preservation group. In an experimental evaluation of different chordal preservation methods during MVR, there was no statistically significant difference between the results of anterior (Khonsari)27 and posterior (Feikes)26 technique in terms of global LV systolic and diastolic function11. The pioneering work in this field has been reported from David’s centre. The late results of a randomized trial comparing chordal preservation with no chordal preservation indicated that even 7 years after operation, patients with chordal preservation had better LV function than those without it37. In a recent randomized trial from the same centre38, comparing partial versus complete chordal sparing MVR, it was clearly demonstrated that complete retention of the subvalvular apparatus confers a significant early advantage by reducing the chamber size and systolic after-load as compared with partial chordal preservation. Also the LV ejection fraction improved with time in the complete preservation group because of favourable LV remodeling. David went on to study 241 patients undergoing redo-MVR 1-22 years after initial MVR39. 54 of these had intact chordae after re-operation. The chordae and papillary muscles which had been preserved in some patients as early as 22 years prior to re-operation were intact and non-atrophic suggesting good function. 4-0 PTFE sutures were used to create new


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chordae if these had been transected at previous operation. 187 patients did not have any form of chordal preservation. The incidence of low-output syndrome and operative mortality were less in patients in whom chordae were preserved as compared to the non-chordal group. Based on these results, the authors recommended re-preservation of chordae in patients undergoing MVR if the chordae had been transected earlier 40 . The technique of chordal reconstruction using PTFE sutures was described in detail recently 41. Chowdhary et al42 reported on 451 patients who underwent mitral valve replacement for rheumatic disease. The entire valve was excised in 70 patients while 124 had preservation of the posterior mitral apparatus and 257 had partial anterior leaflet resection with preservation of both anterior and posterior chordae. Clinical improvement was observed in all three groups of patients but echochardiographically determined indices of left ventricular size, shape, and function were superior in patients with complete preservation of the mitral apparatus42. Hetzer’s study43 clearly lists the major advantages of chordal preservation – (a) reduction in operative mortality (b) improvement in early and late ventricular function (c) improvement in long-term survival and (d) elimination of risk of ventricular rupture. Despite the clear advantages of complete chordal preservation as detailed above, many surgeons still retain only the posterior leaflet because of greater technical complexity, longer operating time, and fear of potential interference with mechanical leaflet motion, need to undersize the mitral prosthesis and the possibility of LVOTO. However, with application of the correct surgical technique tailored to suit the individual patient, preservation of the entire subvalvular structures is feasible in all patients with an adequate sized prosthesis43. Although these techniques can be easily learnt and reproduced, it is probably still not adopted by some as it involves a change in behaviour which has always been met with by skepticsm and increased resistance from critics44. Effects of chordal preservation on right ventricular (RV) function Improvement of LV function is automatically expected to lead to an improvement in the RV function. However, a study from Sweden 45 has shown a statistically significant improvement in right ventricular function after LV chordal preservation. This improvement in RV function has been clearly

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documented by radionuclide studies and is an area of future investigation as this is very important in patients with severe pulmonary arterial hypertension who may have significant RV dysfunction prior to surgery and may benefit from LV chordal preservation. Conclusion Complete chordal preservation during MVR confers several advantages as compared to conventional MVR without chordal preservation or partial chordal preservation. It preserves LV geometry and function, reduces the operative mortality, improves early and long-term survival and reduces the risk of ventricular rupture. With appropriate surgical technique even large size prosthetic valves can be implanted and the risk of prosthetic valve dysfunction and LV outflow tract obstruction can be eliminated. There is emerging evidence which suggests that RV function may improve significantly after LV chordal preservation. References 1. Crawford MH, Souchek J, Oprian CA, Miller Dc, Rahimtoola S, Giacomini JC, et al. Determinants of survival and left ventricular performance after mitral valve replacement. Circulation 1990; 81: 1173-81. 2. Goldman ME, Mora F, Guarino T, Fuster V, Mindich BP. Mitral valvuloplasty is superior to valve replacement for preservation of ventricular function: An intraoperative two-dimensional echocardiographic study. J Am Coll Cardiol 1981; 10: 568-75. 3. Carabello BA. The mitral valve apparatus:is there still room to doubt the importance of its preservation? J Heart Valve Dis 1993; 2: 250-52. 4. Orniston JA, Shah PM, Tei C, Wong M. Size and motion of the mitral valve annulus in man. I. A two-dimensional echocardiographic method and findings in normal subjects. Circulation 1981; 64: 113-20. 5. Wiggers CS, Katz LM. Contour of the ventricular volume cur ves under different conditions. Am J Physiol 1922; 58: 439-75. 6. Rushmer RF. Initial phase of the ventricular systole: asynchronous contraction. Am J Physiol 1956; 184: 188-94. 7. Rushmer RF, Finlayson BL, Nash AA. Movements of the mitral valve. Circ Res 1956; 4: 337-42. 8. David TE, Uden DE, Strauss HD. The importance of the mitral apparatus in left ventricular function after correction of mitral regurgitation. Circulation 1983; 68: II76-82. 9. Westaby S. Preservation of left ventricular function in mitral valve surgery. Heart 1996; 75: 326-29. 10. Moon MR, DeAnda A Jr, Daughters GT II, Ingels NB, Miller DC. Effects of chordal disruption on regional left ventricular torsional deformation. Circulation 1996; 94 (Suppl): II143-51. 11. Moon MR, DeAnda A Jr, Daughters GT II, Ingels NB Jr, Miller DC. Experimental evaluation of different chordal preservation methods during mitral valve replacement. Ann Thorac Surg 1994; 58: 931-43. 12. Lillehei CW, Levy MJ, Bonnabeau RC. Mitral valve replacement with preservation of papillary muscles and chordae tendinae. J Thorac Cardiovasc Surg 1964; 47: 532-43.


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13. Bjork VO, Bjork L, Malers L. Left ventricular function after resection of the papillary muscles in patients with total mitrl valve replacement. J Thorac Cardiovasc Surg 1964; 48; 635-39. 14. Rastelli GC, Tsakiris AG, Banchero N, Wood EH, Kirklin JW. Cardiac performance after replacement of the dog mitral valve with Starr-Edwards prosthesis with and without preservation of the chordae tendinae. Surg Forum 1966; 17: 178-79 15. Cohen LH, Reis RL, Morrow AG. Left ventricular function after mitral valve replacement. J Thorac Cardiovasc Surg 1968; 56: 1115. 16. Rouleau CA, Frye RL, Ellis FH. Haemodynamic state after open mitral valve replacement and reconstruction. J Thorac Cardiovasc Surg 1969; 58: 870-78. 17. David TE, Straus HD, Mesher E, Anderson MJ, MacDonald IL, Buda AJ. Is it important to preserve the chorde tendinae and papillary muscles during mitral valve replacement? Can J Surg 1981; 24: 236-39. 18. David TE, Burns RJ, Bacchus CM, Druck MN. Mitral valve replacement for mitral regurgitation with and without preservation of chordae tendineae. J Thorac Cardiovasc Surg 1984; 88(5 Pt 1): 718-25. 19. Gams E, Hagl S, Schad H, Heimisch W, Mendler N, Sebening F. Significance of the subvalvular apparatus for left ventricular dimensions and systolic function: experimental replacement of the mitral valve. Thorac Cardiovasc Surg 1991; 39: 5-12. 20. Hansen DE, Cahill PD, Derby GC, Miller DC. Relative contributions of the anterior and posterior mitral chordae tendineae to canine global left ventricular function. J Thorac Cardiovasc Surg 1987; 93: 45-55. 21. Doces J, Kennedy JW. Quantitative assessment of left ventricular function following successful mitral valve surgery. Am J Cardiol 1975; 35: 132. 22. Sarris GE, Cahill PD, Hansen DE, Derby GC, Miller DC. Restoration of left ventricular systolic performance after reattachment of the mitral chordae tendineae. The importance of valvular-ventricular interaction. J Thorac Cardiovasc Surg 1988; 95: 969-79. 23. Kumar AS. Heart strings. Ind J Thorac Cardiovasc Surg 2004; 20: 115-16. 24. David TE. A rational approach to the surgical treatment of mitral valve disease. In : Karp RD, ed. Advances in cardiac surgery, vol 2. Chicago : Mosby year book 1990; P 63-84. 25. David TE. Mitral valve replacement with preservation of chordae tendineae. Rationale and technical considerations. Ann Thorac Surg 1986; 41: 680-82. 26. Feikes HL, Daugharthy JB, Perry JE, Bell JH, Hieb RE, Johnson GH. Preservation of all chordae tendineae and papillarymuscles during mitral valve replacement with a tilting disc valve. J Card Surg 1990; 5: 81-5. 27. Sintek CF, Pfeffer TA, Kchamba TA, Khonsari SR. Mitral valve replacement: technique to preserve the subvalvular apparatus. Ann Thorac Surg 1995; 59: 1027-29. 28. Okita Y, Miki S, Ueda Y, Tahata T, Sakai T, Matsuyama K. Mitral valvereplacement with maintenance of mitral annulopapillary muscle continuity inpatients with mitral stenosis. J Thorac Cardiovasc Surg 1994; 108: 42-51. 29. Miki S, Kusuhara K, Ueda Y, Komeda M, Ohkita Y, Tahata T. Mitral valve replacement with preservation of chordae tendineae and papillary muscles. Ann Thorac Surg 1988; 45: 28-34. 30. Wasir H, Choudhary SK, Airan B, Srivastava S, Kumar AS. Mitral valve replacement with chordal preservation in a rheumatic population. J Heart Valve Dis 2001; 10: 84-89. 31. Rose EA, Oz MC. Preservation of the anterior leaflet chordae tendineae during mitral valve replacement. Ann Thorac Surg 1994; 57: 768-69.

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32. Vander Salm TJ, Pape LA, Mauser JF. Mitral valve replacement with complete retention of native leaflets. Ann Thorac Surg 1995; 59: 52-55. 33. Yu Y, Gao C, Li G, Zhu L, Wang D, Liu M. Mitral valve replacement with complete mitral leaflet retention: operative techniques. J Heart Valve Dis 1999; 8: 44-46. 34. Trites PN, Kiser JC, Johnson C, Tycast FJ, Gobel FL. Occlusion of Medtronic-Hall mitral valve prosthesis by ruptured papillary muscle and chordae tendineae. J Thorac Cardiovasc Surg 1984; 88: 301. 35. Horstkotte D, Hager D, Schulte WB, Strauer BE. The effect of chordal preservation on late outcome after mitral valve replacement: A randomized study. J Heart Valve Dis 1993; 2: 150-58. 36. 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: 828-36. 37. Komeda M, David TE, Rao V, Sun Z, Weisel RD, Burns RJ. Late hemodynamic effects of the preserved papillary muscles during mitral valve replacement. Circulation 1994; 90: II190-4. 38. Yun KL, Sintek CF, Miller DC, Pfeffer TA, Kochamba GS, Khonsari S, Zile MR. 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. 39. Rao V, Komeda M, Weisel RD, Ivanov J, Ikonomidis JS, Shirai T,


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