Mitral valve remodeling: Long-term results with posterior pericardial annuloplasty

Mitral valve remodeling: Long-term results with posterior pericardial annuloplasty

Mitral Valve Remodeling: Long-Term Results With Posterior Pericardial Annuloplasty Roberto Scrofani, MD, Stefano Moriggia, MD, Maurizio Salati, MD, Pi...

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Mitral Valve Remodeling: Long-Term Results With Posterior Pericardial Annuloplasty Roberto Scrofani, MD, Stefano Moriggia, MD, Maurizio Salati, MD, Pino Fundaro, MD, Paolo Danna, MD, and Carmine Santoli, MD Divisions of Thoracic and Cardiovascular Surgery and Cardiology, Ospedale "L. Sacco," Milan, Italy

Background. We studied the long-term results of a technique of mitral annuloplasty using autologous pericardium. Methods. Between June 1989 and December 1994, 113 mitral valvuloplasties were performed for myxomatous degenerative disease. Repair of isolated anterior leaflet prolapse was performed in 26 patients (23%), posterior leaflet prolapse in 38 (33.6%), and prolapse of both leaflets in 49 (43.4%). Posterior pericardial annuloplasty was performed in all patients. In 20 patients, the pericardial graft was marked with metal clips for postoperative cinefluoroscopic assessment of annulus motion. Results. The operative mortality rate was 2.7% (3/113). One patient died of a myocardial infarction and 2 of low cardiac output syndrome. One patient required replacement of the mitral valve 2 days after operation because of dehiscence of the annular plication. Follow-up (average length, 32.41 ± 20.09 months; range, 1 to 71 months) was 97% complete and revealed good clinical and functional

results: 95 patients (84.1%) were in New York Heart Association class I and had no regurgitation or only m i l d residual regurgitation. Postoperative transmitral flow indices were almost normal (mitral valve area = 3.7 ± 0.4 cm2; peak flow velocity = 1.06 ± 0.2 m/s). O n l y 3 patients had reoperation w i t h i n 3 years (actuarial 5-year reoperation-free rate, 89.7%) and event-free survival at 5 years was 91%. In patients with metal clips marking autologous pericardium, p l a n i m e t r y of the area derived by fluoroscopic examination showed systolic narrowing of annulus size (8.5% ± 6.4%; p < 0.01) and a slight systolic fall in the anteroposterior diameter of the annulus contour (5.9% + 3.8%; p < 0.01). Conclusions. Posterior pericardial annuloplasty seems to be a safe, effective, and easily performed technique and a more physiologic correction that preserves mitral annulus motion.

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Echocardiographic Evaluation

rosthetic annuloplasty rings are currently used in mitral reconstruction. Recently, flexible rings have b e e n introduced to preserve mitral annulus function [1-3]. In 1991, we [4] r e p o r t e d a technique for r e m o d e l i n g of the posterior mitral valve annulus using autologous pericardium. The p u r p o s e of this study was to evaluate long-term results in patients who u n d e r w e n t mitral valve repair with this technique.

Material and M e t h o d s Between June 1989 a n d D e c e m b e r 1994, 113 consecutive patients u n d e r w e n t an open heart operation for mitral regurgitation caused by m y x o m a t o u s degenerative disease. Autologous p e r i c a r d i u m was u s e d for the posterior annuloplasty in all patients. Sixty-eight patients were m e n a n d 45, women; the m e a n age was 58.1 _+ 12.09 years (range, 22 to 84 years). Seven patients (6.2%) were in N e w York Heart Association class IV, 78 (69.0%) were in class III, 24 (21.2%) were in class II, a n d 4 (3.5%) were in class I. Forty-seven patients (41.6%) were in chronic atrial fibrillation. Accepted for publication Nov 19, 1995. Address reprint requests to Dr Scrofani,Divisione di Chirurgia Toracica e Cardiovascolare, Ospedale "L. Sacco," Via G. B. Grassi n. 74, 20157 Milano, Italy. © 1996 by The Society of Thoracic Surgeons Published by Elsevier Science Inc

(Ann Thorac Surg 1996;61:895-9)

All patients u n d e r w e n t t w o - d i m e n s i o n a l echocardiographic examination before operation, at the time of discharge from the h o s p i t a l and then yearly. C h a m b e r size was obtained from M - m o d e findings. The grade of mitral regurgitation was evaluated b y m e a n s of the ratio b e t w e e n the regurgitant jet area a n d the left atrial area: values ranging from 0% to 20% were considered grade 1; b e t w e e n 20% and 40%, grade 2; a n d higher than 40%, grade 3 [5]. The mitral valve area was m e a s u r e d both by the half-time pressure m e t h o d and by short-axis planimetry. Transmitral flow characteristics were defined in terms of p e a k velocity and m e a n velocity. Preoperatively, all patients h a d severe (grade 3+) rnitral incompetence. Isolated anterior leaflet p r o l a p s e was o b s e r v e d in 26 patients (23%), posterior leaflet prolapse in 38 (33.6%), and prolapse of both leaflets in 49 (43.4%).

Operative Technique After sternotomy and before aortic a n d caval cannulation, the p e r i c a r d i u m was o p e n e d longitudinally. A strip of p e r i c a r d i u m (0.5 to 0.6 cm × 5 to 6 cm) was freed of adipose and extrapleural tissue, treated with a 10-minute i m m e r s i o n in 0.0625% g l u t a r a l d e h y d e solution, a n d r i n s e d in physiologic solution. In the first 20 patients, metal clips were attached to the midline of the external surface of the pericardial strip. The m a r k e d strip was 0003-4975/96/$15.00 SSDI 0003-4975(95)01139-0

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Results

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Fig 1. Five-year freedom from reoperation for patients who underwent mitral valvuloplasty.

rolled up in a tubular fashion with the serosal surface outside. Moderate systemic hypothermia (28°C) and cold cardioplegia were employed for myocardial protection. The mean aortic cross-clamp time was 71 -+ 18 minutes. Posterior leaflet prolapse was managed by a wide quadrangular resection (38 patients). Anterior or bilateral leaflet prolapse was treated by quadrangular resection of the posterior leaflet and transposition of the chordae to the anterior leaflet (75 patients). The annulus beneath the excised or transposed portion of the mural leaflet was plicated with interrupted stitches (2-0 polyester). The procedure was completed by closing the residual cleft of the mural leaflet with interrupted sutures. The pericardial graft was placed along the posterior annulus just beyond the anatomic commissures, fixed with mattress sutures (4-0 polyester), and spaced to restrict the posterior annulus. The optimal diameter of the annulus was determined, stitch by stitch, by digital control, so as to obtain an orifice measuring two fingerbreadths. Myocardial revascularization was performed in 12 patients (10.6%) and a De Vega annuloplasty for functional tricuspid regurgitation, in 11 patients (9.7%). All patients were placed on a regimen of anticoagulant therapy for 3 months postoperatively. Then they were switched to antiplatelet therapy.

Clinical Results There were three hospital deaths (2.7%). One patient died suddenly 4 days after operation of posterior papillary muscle rupture caused by intraoperative myocardial infarction, and 2 patients died of low cardiac output syndrome. One patient required early reoperation for severe mitral regurgitation caused by dehiscence of the annular plication. Myocardial infarction occurred in 2 patients and gastric hemorrhage in 1 patient. No patient experienced thromboembolism or endocarditis during the postoperative course. At a mean postoperative interval of 32.41 -+ 20.09 months (range, 1 to 71 months), follow-up was 97% complete. Ninety-five patients (84.17%) were in New York Heart Association functional class ! or II. Three patients died during follow-up (1 of aortic dissection, 1 of renal failure, and 1 of gastric cancer). Three patients had reoperation within 3 years. The condition of 1 patient deteriorated slowly because of associated aortic regurgitation, and double-valve replacement was performed after 51 months. The other 2 patients underwent reoperation after 12 and 18 months because of unsatisfactory mitral repair. Freedom from reoperation at 1 year and 5 years was 97% and 89.7%, respectively (Fig 1). At reoperation, each pericardial prosthesis appeared completely endothelialized and was indistinguishable from the atrial endocardium. No evidence of calcification was observed. A sample of pericardium was taken from I patient for histologic study (Fig 2), which revealed only a mild inflammatory reaction. Event-free survival (freedom from death, thrornboembolism, reoperation, myocardial infarction, endocarditis, and anticoagulation-related hemorrhage) at 5 years was 91% (Fig 3). Thromboembolic complications occurred during follow-up in 2 patients; only 1, in whom a right carotid artery occlusion was found, sustained a major neurologic sequela. Both patients were in sinus rhythm

Fluoroscopy

In the 20 patients whose pericardial strip had the metal clips, cinefluoroscopic recordings at 50 frames per second were obtained in the left anterior oblique projection 10 days after operation and then at 1 year and 5 years. Systolic and diastolic annulus contours, displayed by the metal clips, were entered into a computer, and the respective areas were calculated by means of suitable software. The distance between the posterior annulus and the midpoint of the line joining the two commissures was recorded and assumed to be the anteroposterior radius. Statistical Analysis All data are expressed as the mean +- the standard deviation. The paired t test was used to compare the results before and after operation. Fisher's exact test and the life-table method were used when appropriate.

Fig 2. Photomicrograph of histologic section of autologous pericardium. There is no evidence of calcification, and only a mild, aspecific inflammatory reaction is present. (Hematoxylin and eosin; XlO before 44% reduction.)

Ann Thorac Surg 1996;61:895-9

SCROFANI ET AL POSTERIOR PER1CARDIAL ANNULOPLASTY

Annulus Motion

100 95 90 85 %

80 75 70 65 60

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Fig 3. Five-year freedom from events (death, thromboembolism, reoperation, myocardial infarction, endocarditis, and anticoagulationrelated hemorrhage) for patients who underwent mitral valvuloplasty.

and on a regimen of aspirin therapy; no evidence of intraatrial thrombosis was detected at transesophageal echocardiography.

Echocardiographic Results At intraoperative a n d in-hospital echocardiographic evaluation, residual mitral regurgitation was absent or mild on color-flow Doppler analysis in 95 patients (84.1%), moderate in 17 patients (15.0%), and severe in 1 patient (0.9%). The left ventricular end-diastolic diameter decreased significantly after operation from 66.38 m m _+ 9.12 m m to 55.46 m m + 6.65 m m (p < 0.01) (Table 1). The relationship b e t w e e n residual mitral regurgitation a n d left ventricular d i m e n s i o n s is shown in Figure 4. The reduction in mitral valve area was substantial (from 6.8 _+ 2.2 cm 2 to 3.7 + 0.4 c m 2 ; p < 0.01). Postoperatively, the transmitral peak flow velocity was 1.06 _+ 0.2 m/s (range, 0.61 to 1.26 m/s). In 8 patients, the echocardiographic w i n d o w allowed reliable visualization of the pericardial prosthesis. In these patients, the m e a s u r e m e n t s of the posterior perimeter showed a significant reduction during systole from 3.4 +_ 0.6 cm to 2.9 ± 0.5 cm (p < 0.01) (mean reduction, 13.4% ± 6.6%). Neither systolic anterior motion of the mitral valve nor any left ventricular outflow tract gradient was observed (mean velocity in left ventricular outflow tract, 0.81 _+ 0.66 m/s).

Planimetry of the area derived by fluoroscopic examination revealed a mild but significant narrowing during ventricular systole. The m e a n reduction was 8.5% + 6.4% (range, 0.1% to 25%) (p < 0.01). At I year postoperatively, the reduction was 7.7% +_ 6.0% (p < 0.05) a n d at 5 years, 14.7% + 10.2% (p < 0.05). This change is similar to that observed for the a n n u l u s of healthy h u m a n s [5]. The anteroposterior diameter of the a n n u l u s contour exhibited a slight systolic fall of 5.9% -- 3.8% (p < 0.01). At 1 year postoperatively, the decrease was 6.7% ± 4.7% (p < 0.05) a n d at 5 years, 16.6 ± 12.5% (p < 0.05). There was no difference between patients in sinus rhythm a n d those with atrial fibrillation. Comment In the surgical repair of mitral incompetence, a n n u l o plasty is performed for four reasons: (1) to correct the dilatation of the annulus, (2) to increase the leaflet coaptation, (3) to reinforce the a n n u l u s sutures w h e n part of the valve has been resected, a n d (4) to prevent future dilatation of the annulus. Stabilization of the posterior a n n u l u s with a ring or other type of support seems important for the reinforcement of the posterior leaflet a n d creates a buttress against which the anterior leaflet can open and close [6-9]. In deciding what type of annuloplasty to use, a complete u n d e r s t a n d i n g of the function of the mitral a n n u l u s is essential. The mitral a n n u l u s is an elliptic portion of a hyperbolic paraboloid ("saddle shape") and it has a sphincterlike function that reduces the area by approximately 26% during systole [10]. During the cardiac cycle, it changes its s h a p e - - b e c o m i n g circular during diastole a n d elliptic in systole. These changes in size a n d shape result from relaxation and contraction of the basoconstrictor muscles [11, 12]. In patients with degenerative mitral regurgitation, dilatation of the a n n u l u s involves only the posterior mitral annulus, as the anterior portion of the mitral a n n u l u s is part of the fibrous skeleton of the heart. Our aim was to restore a normal a n n u l u s shape by selectively shortening the a n n u l u s segments that had been dilated by the pathologic process with a technique that best preserves the physiologic contractile properties of the mitral annulus. In the first part of our experience (73 patients), the usual valvuloplasty procedures [3] were associated with a

Table 1. Results of Echocardiographic Study Variable End-diastolic diameter (ram) End-systolic diameter (mm) Shortening fraction Mitral valve area (cm2) E/A ratioc a Significance: p < 0.01 versus Preop. E/A = protodiastofic/telesystolic.

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Postop

66.38 ± 9.12 44.69 _+9.12 33.75 + 6.23 6.8 ± 2,2 .-.

55.46 ± 6.65"~ 39.11 ± 7.84a 30.34 _+6.79b 3.7 + 0.4a 1.05 ± 0.5

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1 Year 53.9 + 37.80 + 31.09 ± 3.15 ± 1.03 ±

7.05"~ 6.38" 7.18b 0.90a 0.27

L-Ratio was d e t e r m i n e d for patients in sinus rhythm.

5 Years 53.4 _+5.61'~ 37.83 _+4.43~ 28.91 + 5.72t" 3.24 ± 0.61"~ 1.11 ± 0.59

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A n n Thorac Surg 1996;61:895--9

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Fig 4. Comparison between (A) left ventricular end-diastolic diameter and (B) end-systolic dimneter measurements and various degrees of residual mitral regurgitation (MR). There are no signifT"cant differences, even in patients with moderate residual MR. See Echocardiographic Evaluation section for M R grading.

selective posterior annuloplasty performed with a conduit of expanded polytetrafluoroethylene. Since 1989, we have substituted autologous pericardium for the polytetrafluoroethylene conduit to obtain a softer prosthesis that conforms to the natural geometry of the annulus [13, 14]. The efficacy of this technique is demonstrated by our clinical results (postoperative New York Heart Association class I or II, 84.1% of patients, and 5-year reoperation-free rate, 89.7%) and echocardiographic results. Postoperative sequential Doppler echocardiographic studies showed that most patients (84.1%) had mild or no mitral regurgitation at the late postoperative studies and significant reduction in left ventricular dimensions. Even in the 17 patients (15.0%) with moderate mitral regurgitation postoperatively, there was a significant fall in left ventricular end-diastolic diameter, and, more important, the left ventricular dimensions were unchanged after 12 months. Only 1 (5.9%) of them needed mitral valve replacement after reconstruction because of progression of mitral regurgitation, but this patient had associated aortic valve regurgitation that probably contributed to the repeat dilatation of the annulus. The other patients with moderate mitral regurgitation did not exhibit a clinically significant increase in the severity of mitral valve insufficiency during follow-up, a finding indicating that autologous pericardium is strong enough to prevent dilatation of the annulus. In our experience, no patient exhibited left ventricular outflow tract obstruction. This abnormality, which is due to systolic anterior motion of the rnitral valve, has been

described as a complication of rigid-ring annuloplasty, and the reported incidence ranges from 4.5% to 10% [15-18]. Systolic anterior motion has been described in only 1 patient having annuloplasty without a rigid ring [19]. We believe that confining the annuloplasty to the posterior portion of the annulus and using a pliable annulus graft are effective in avoiding systolic anterior motion. The method of preserving autologous pericardium is extremely important in determining tissue durability and preventing calcification. The scientific procedure of using autologous tissue treated with a brief immersion in glutaraldehyde solution was established by Chauvaud and colleagues in 1991 [20]. On the basis of this experimental study, the clinical use of glutaraldehyde-pretreated pericardium became established in our institution for all mitral valve reconstructive procedures. In our experience, we have observed no evidence of calcification or tearing of the pericardial graft; no instance of calcification was detected in our 113 patients followed by echocardiographic evaluation, and this result was confirmed by microscopic examination of autologous pericardium from 1 patient (see Fig 2). Pericardium has been attractive to the cardiac surgeon for a long time. Its ready availability, its ease of handling, and its pliability make it an obvious choice when a defect must be eliminated. We believe that there is sufficient evidence to support the use of autologous pericardium, as its long-term durability and low thrombogenicity offer several advantages. The benefits conferred by autologous

Ann Thorac Surg 1996;61:895-9

tissue, the easily a c c o m p l i s h e d surgical t e c h n i q u e , effective f u n c t i o n i n g of t h e r e m o d e l e d valve, a n d p r e s e r v a t i o n of the n a t u r a l s h a p e of the v a l v e m a k e t e c h n i q u e a useful surgical a l t e r n a t i v e for e x t e n s i v e tral v a l v e r e c o n s t r u c t i v e p r o c e d u r e s .

SCROFANI ET AL POSTERIOR PERICARDIALANNULOPLASTY

the the this mi-

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