Eur J Cardio-thorac

Surg (1992) 6: 655-659

surgery

0 Springer-Verlag 1992

Early evidence of beneficial effects of chordal preservation in mitral valve replacement on left ventricular dimensions P. K. Ghosh*, S. Shah, A. Das, M. Chandra, S. K. Agarwal, and P. K. Mittal Department of Cardiovascular and Thoracic Surgery, Sanjay Gandhi Postgraduate Raebareli Rd., Lucknow-226001, India

Institute of Medical Sciences, P.O. 375,

Abstract. Earlier authors have shown the improved left ventricular (LV) function after chordae-preserving mitral valve replacement (MVR) in follow-up studies. Seventy-nine consecutive patients undergoing MVR were studied preoperatively and predischarge with M-mode and two-dimensional Color Doppler echocardiography for early LV morphometric changes. Conventional MVR was performed in 42 patients (Group 1) and the posterior leaflet-chordae-papillary muscle complex was preserved in 37 patients (Group 2). Both cohorts were similar in age, sex, preoperative NYHA class and valve pathology. Four St. Jude bioprostheses, 9 Medtronic and 66 Sorin prostheses were implanted. The intraoperative and perioperative management protocol was uniform for both groupsThe median left atria1dimension in both groups decreased to better physiological levels (53 to 46 mm in group 1,52.5 to 46 mm in group 2). The median LV enddiastolic dimension increased from 47 to 48 mm in group 1 while it decreased from 56.5 to 49 mm in group 2. The median LV endsystolic dimension remained unchanged in group 1 but decreased in group 2 (37.6 to 36 mm). Echocardiographic documentation of such early changes in the LV dimensions after modified MVR indicates that the beneficial effects of chordal preservation become evident early in the postoperative period and may explain the improved perioperative LV function after modified MVR compared to conventional MVR. [Eur J Cardio-thorac Surg (1992) 6:655-6591 Key words: Mitral

valve replacement

- Chordal preservation

The concept of preserving the posterior mitral leaflet and subvalvar apparatus during mitral valve replacement (MVR) was introduced in the early 1960s [7, 271. Two decades later the revival of the concept and its widespread practice [lo, 411 have shown improved mortality and postoperative performance after modified MVR (mMVR) in the short- and medium-term follow-up. Left ventricular (LV) performance studied 2 months or later [12,22,28] after mMVR have been shown to be superior to that after conventional MVR (cMVR) where the entire native valve with subvalvar apparatus has been excised. David and colleagues [l l] reported early hemodynamic studies 7- 12 postoperative days after MVR and MV reconstruction and demonstrated better-preserved ejection fraction (EF) and decreased LV enddiastolic pressure (LVEDP) after mMVR and MV reconstruction. The pur-

* Present address: Harav Zinger 8, Rishon

Le Zion 75255, Israel

Presented at the Poster Session of the 5th Annual Meeting of the European Association for Cardio-thoracic Surgery, London, UK, September 23-25, 1991 Correspondence

to: Prof. Probal

K. Ghosh, MS, MCh, FRCSE

- Left ventricular

dimensions - Echocardiography

pose of this study was to evaluate echocardiographically if early beneficial LV dimension changes become apparent in the pre-discharge period, which may explain the better postoperative performance after mMVR.

Patients and methods All patients undergoing isolated MVR for rheumatic MV disease in our institute from January 1989 through April 1991 were included in this study. Associated tricuspid valve repair was undertaken in 9 of them. The clinical and echocardiographic work-up was the same in all of them. Preoperative heart catheterization was carried out in 25 patients, mostly to rule out associated coronary artery disease in patients over 40 years of age, and to quantitate the extent of regurgitation and/or pulmonary hypertension. The surgical technique of MVR undertaken in any particular patient was decided randomly without any reference to their clinical, echocardiographic or hemodynamic status. Group 1 (n 42) patients underwent cMVR where the entire mitral valve with subvalvar apparatus was excised and replaced with a prosthesis, In Group 2 (n 37) patients, mMVR was performed whereby the anterior mitral leaflet (AML) and its chordae were excised but the entire posterior mitral leaflet (PML) with all the chordae and papillary muscles was retained. Table 1 summarizes the clinical data of both groups.

656 Table 2. Techniques MVR

Table 1. Clinical data Group 1 conventional MVR

Group 2 modified MVR

Number Mean age in years (range) Men/Women Mean weight in kg Mean BSA in m2

42 28.5 (13-57) 16126 42.8 1.36

31 22.9 (10-54) 21116 40.3 1.46

Preoperative NYHA II III IV mean class AF MS MR MS MR ReMS Calcification

11 27 4 2.6 15 13 10 19 7 12

9 20 8 3.1 14 5 15 17 3 I

BSA = Body surface area; NYHA = New York Heart Association; AF = Atria1 fibrillation; MS = Mitral stenosis; MR = Mitral regurgitation; Re MS = Mitral restenosis

Operative

details

The operative procedure and myocardial preservation followed the same protocol in both groups. Systemic hypothermia to 25 “C, topical cooling, one period of aortic cross-clamping, an initial single dose of cold crystalloid cardioplegia supplemented by multiple cardioplegic infusions at intervals were employed in all patients. The gross pathological status of the mitral valve complex and the ventricles were recorded according to the type of disease [30, 381. Table 2 summarizes the different techniques of preservation of papillo-annular continuity in MVR. In most of our patients type I, II or IV of the techniques of Asano and Furuse [I] was utilized. In technique I, the PML was cross-stitched for pleating and the elongated chordae were rendered tense. The prosthetic valve was then anchored with interrupted buttressed 2-O Ethibond sutures inserted from the left atria1 side. Technique II was suitable in cases with severe loss of the cuspal area of PML. Interrupted everting buttressed sutures placed in the annulus were passed through the PML near its free margin. Technique IV was employed in patients with a wide PML, seen usually in predominant or pure mitral regurgitation (MR). A crescent of cuspal tissue was excised from the PML avoiding injury to its free margin and the chordae. Buttressed sutures were then passed through the annulus and below the leaflet to put the chordae under tension. A tilting disc prosthesis (Sorin or Medtronic) was used in most patients and the greater orifice was oriented anteriorly. Table 3 details the surgical data of both groups. The intraoperative and perioperative management protocol remained essentially the same for both groups.

of preserving

papillo-annular

continuity

in

A. Preserving PML

Ref (1, 17, 22, 23, 27, 28)

B. In situ implantation

Ref (6, 14)

C. Preserving AML & PML

Ref (9, 13, 22, 27)

D. Suture-mediated

Ref (2, 8)

PML = Posterior

mitral leaflet; AML = Anterior mitral leaflet

Table 3. Operative data Group 1 conventional MVR

Group 2 modified MVR

2 20 20

I 16 14

0

5 31

4 4 29

15 25 2 0 0

10 14 9 1 3

Median aortic clamp time (min) range

&IO)

&63)

Median CPB time (mm) range

(K75)

(%180)

Severity of MVD Type I II III Prosthesis SJM MH Sorin

used

Size of prosthesis 25 21 29 28 30

Associated

TV repair

Initial attempt of MV repair

2

I

2

5

MVD = Mitral valve disease; SJM = St. Jude; MH = Medtronic Hall; CPB = Cardiopulmonary bypass; TV = Tricuspid valve; MV = Mitral valve

muscles. The left ventricular enddiastolic dimension was measured at the R wave of a simultaneously recorded electrocardiogram and LVESD was measured at the nadir of septal motion. Each measurement represented an average value obtained over three to five consecutive cycles. In the postoperative period, when the septal motion was invariably flat, LVESD was assessed at endsystole of the electrocardiogram.

Data analysis Left ventricular dimensions Left ventricular studies were performed with Color Doppler echocardiography (ATL UM9) using a 2.5 MHz probe. In each patient apical, parastemal, suprastemal and long axis views were studied. All patients were studied preoperatively and pre-discharge on the IO-12th postoperative day. Left ventricular enddiastolic (LVEDD), endsystolic (LVESD) and left atrial dimensions were measured. The M-mode measurements of LV transverse dimensions were obtained at the level just cephalad to the tip of the papillary

The significance of the change between the preoperative and postoperative means of each category of parameters was determined by paired t-test and two-sample t-test analysis with a level of significance at 0.05. Additionally, the median values of each category with quartile and interquartile ranges as a measure of dispersion were also compared and a sign test and Mann-Whitney tests were carried out to elicit significance. In the subsets of each group, the non-parametric test, i.e., the sign test for paired comparison, and the MannWhitney tests for two independent samples were carried out. All tests led to similar conclusions.

CONV PRE

MVR POST

53\46

LA 60 5o 40

PRE

MOD. MVR

CONV MVR

MOD. MVR

PRE

POST

POST

LVEDD

PRE

6o 50

62\54

POST

52.5 146

i

30'

50 40

LVESD 50

1

30

33

1 20'

1

33

fj

‘*\46

MR

50 40

]

30 LVEOD

60

40

1 47y48

1 30'

60 50 1

56.5 149

40 30 j

MSMR

601

601 50

50

50 47.49.5 40 1

40

30'

30'

1

‘44

Fig. 1. Median values of all preoperative (Pre) and pre-discharge (Post) dimensions in mm of left atrium (LA), left ventricular enddiastole (LVEDD) and left ventricular end-systole (LVESD) in both groups

Fig. 2. Median values of left ventricular end-diastolic dimensions (LVEDD) in mm of both groups at preoperative (Pre) and predischarge (Post) period according to subsets of mitral stenosis (MS), regurgitation (MR) and mixed lesion (MSMR)

Results

Table 4. Left ventricular

There was no significant difference in the demographic or preoperative status between the two groups. Most patients were in NYHA class 3, though the mean functional class of the mMVR group was slightly higher. The duration of cardiopulmonary bypass time was similar in both groups. The mean ischemia time was less in the mMVR group though more patients had associated tricuspid valve (TV) reconstruction and attempt at MV reconstruction in this group. However, this difference was not considered statistically significant. Left atria1 (LA) dimensions changed significantly in both groups (Table 4, Fig. 1). In group 1 the median LA dimensions changed from 53 to 46 mm, while in group 2 it decreased from 52.5 to 46 mm after surgery. The median LVESD in group 1 remained unchanged at 33 mm while it decreased slightly in group 2 from 37.5 to 36 mm postoperatively. This difference was not considered significant in either group. A minor difference in trend between the 2 groups was also not considered significant. The median LVEDD increased in group 1 from 47 to 48 mm but it decreased in group 2 from 56.5 to 49. This reduction in the mMVR group was significant (P=O.OOOl). These dimension changes were further analyzed according to the subsets of preoperative lesions, namely dominant mitral stenosis (MS), dominant mitral regurgitation (MR) and mixed mitral stenosis and regurgitation (MSMR) (Table 4, Fig. 2,3). In the MS subset Mann-Whitney tests indicate

dimension

Group 1 conventional MVR

changes Group 2 modified MVR

Preoperative

Postoperative

Preoperative

Post operative

LA LVESD LVEDD

53.4* 1.6 34.5 &-1.3 47.0 + 1.5

46.8fl.8 34.Okl.2 47.5 + 1.4

55.6+ 1.7 39.1 f 1.5 56.6kl.7

46.5 f 2.8 38.4k2.36 50.4kl.8

LVEDD MS MR MSMR

42.Ok2.3 55.Ok3.1 47.7k2.1

47.1 f 1.5 45.Ok2.1 50.2If2.1

48.2kl.7 63.8k2.4 52.1 k2.2

43.6& 1.8 55.5 k2.4 47.1 k2.7

LVESD MS MR MSMR

28.0& 1.9

38.6k2.5 34.1+ 1.8

32.1 &I.7 31.Ok2.1 36.2* 1.8

35.3kl.8 44.7k2.0 36.2k2.4

31.OkO.5 42.7k3.1 35.4k3.8

All values are expressed in Mean+SEM (in mm) LA = left atrium; LVEDD = Left ventricular enddiastolic sions; LVESD = Left ventricular endsystolic dimensions

dimen-

that the median of the changes differs slightly for both groups with respect to LVEDD and LVESD. In the MR patients reductions in LVEDD occurred in both groups but the difference was not significant. Similarly the median LVESD decreased in both groups. In the MSMR sub-

658

LVESD

CONV MVR PRE 50

POST

1

MS 50

MOD MVR PRE

POST

1

30 35\3, 40 1 20’

30 27/33 40 1 20’ MR

50

50 42

40 30

40 \

29.5

44-

43.5

1

30 20 1

20

MSMR 50 40 30

1 35-37

1 2oJ

50 40 30 20’

1 33.32 1

Fig. 3. Median values of left ventricular end-systolic dimensions (LVESD) in mm of both groups at preoperative (Pre) and pre-discharge (post) period according to subsets of mitral stenosis (MS), regurgitation (MR) and mixed lesion (MSMR)

creased only in patients with chordae-preserving MVR. Our data indicated that LVEDD increased after conventional MVR while it decreased after modified MVR. Similarly, LVESD decreased only in patients with PML preservation. In fact, our clinical observation validates the experimental data of Gams and co-workers [15,16] showing that excision of the subvalvar apparatus increases LVEDD. This early clinical evidence of LV dimensional changes due to chordal preservation may explain the improved clinical behavior in patients after mMVR. These differences were pronounced in the patients with MS and MSMR. In the MR subsets, the decrease in both LVEDD and LVESD was noticed in our patients. This may reflect pre-existent LV decompensation where the correction of chronic regurgitation, irrespective of the technique, demonstrated recovery of the LV dimensions [3, 12, 26, 311. As a result of experimental and clinical observations, some authors [19, 421 have suggested preservation of both leaflets rather than only the PML. Hennein et al. [22] have compared PML-preserving MVR with bileaflet-preserving MVR and observed no difference in the postoperative echocardiographic dimension changes or hemodynamic, radionuclide or functional recovery data. In conclusion, the present study indicates that reduction in LVEDD and LVESD after PML-preserving MVR becomes apparent even as early as in the pre-discharge period, which may explain the improved perioperative clinical behavior in the patients treated. Acknowledgement. We are grateful to Dr. Mynda Salzburg University, Austria, for the data analysis.

the LVEDD and LVESD changes were not considered significant in group 1, but in group 2 with MVR the reduction in LVEDD was significant (p = 0.05). However, the LVESD changes in group 2 were not significant.

Schreur

of

set

Discussion The geometry of the left ventricle is altered in MVR because of the loss of anchoring of the subvalvar apparatus. This in turn, changes the mode of LV contraction [18,20, 40,431. Absence of improvement of the LV performance has been noticed after cMVR [3, 5,24,25, 31,32, 371. In experimental models, severe impairment of LV systolic function has been reported by several authors [18,35,36, 391 after severance of the chordae. Recently, in elegant experiments, Gams et al. [15, 161 have demonstrated marked changes in the shape and size of the LV after the loss of the subvalvar apparatus. Both the systolic and diastolic LV functions were altered as the major axis diameter and LV enddiastolic volume increased after the loss of papillo-annular continuity, in their experiments. In the perioperative stage, despite septal dyskinesia or akinesia, LVEDD has been shown to be the most reliable index of LV function. A reduction in LVEDD has been found uniformly to correlate well with the level of clinical improvement after successful valve surgery [4, 31, 371. Recently the NIH group [22] reported a decrease in LVEDD after both types of MVR, while LVESD de-

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