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OPEN MITRAL COMMISSUROTOMY.
THE GOLDEN STANDARD

Antunes M J; Vieira H; Ferrão de Oliveira J

Cardiothoracic Surgery. University Hospital
Coimbra. Portugal

Abstract
Introduction
Patients and Methods
Results
Discussion
Conclusion

ABSTRACT
Objective:
Percutaneous balloon mitral commissurotomy (PBMC) has recently emerged as an alternative to surgical commissurotomy for the treatment of rheumatic mitral valve stenosis. However, this blind procedure may result in incomplete separation of the commissures which could lead to accelerated restenosis. Hence, open mitral commissurotomy (OMC), which is a visually oriented procedure remains our method of choice. This work aimed at assessing its long-term results.
Methods and Results: In a series of OMC performed from 1988 to 1991, involving 100 mitral valves with an echocardiographic score £ 10, we were able to achieve mean valve areas of 2.88 ± 0.49cm2, from a mean of 0.99 ± 0.23cm2 preoperatively. In a recent follow-up, conducted after a mean of 8 ½ years (7-11 years), the valve areas measured by echo-Doppler in this group of patients were 2.37 ± 0.42cm2 (range 1.6 – 3.6 cm2) and 81% had a valve area >2.0 cm2. Reoperation was required in only two patients. Late mortality was 4%, (0.5% pt.yr) in no case valve-related. Two-thirds of the patients had no or only mild mitral insufficiency. Ninety three percent were in NYHA class I or II. The 9-year actuarial survival was 96%, freedom from reoperation was 98% and freedom from all valve-related complications was 92%. Complementary to this experience, in the past 10 years we were able to perform modified OMC in 919 (79%) of all 1,151 patients with mitral stenosis submitted to surgery, including 257 with mixed disease. The mean post-commissurotomy valve area (2.9cm2) was identical to that of the study group. Moderate to severe valve calcification was not an absolute contra-indication to valve conservation.
Conclusion: OMC remains the best alternative for the treatment of all cases of mitral stenosis, independently of the degree of pliability. In our experience, the medium and long-term results are significantly better than those usually reported in PMBC series.

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Introduction: Before open-heart surgery became a reality, closed mitral commissurotomy (CMC) was the only method available and was used in many tens of thousands of patients and is still performed in less developed countries where rheumatic fever is still endemic and the low cost of the procedure is an important advantage. When it became available, open commissurotomy (OMC) gradually displaced the closed procedure, essentially because it is not blind, thus permitting the surgeon to work on all diseased components with direct visualisation of the anatomical results and, to a lesser extent, confirmation of the valvular function. Besides, open commissurotomy is applicable where non-open methods are not, including moderately fibrosed and/or calcified valves, presence of intra-atrial clots and co-existence of other valve pathologies, which can be treated concomitantly. More recently, catheter-based percutaneous balloon mitral commissurotomy (PBC) was introduced. The supporters of this method claim results similar or superior to those of surgery, based on a few randomized studies. However, its long-term results are yet to be confirmed, but it is already evident that a larger proportion of patients requires re-intervention in the medium-term. In this work, we report the 10-year results in a group of patients with pliable mitral valve stenosis subjected to OMC.

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Patients and Methods: Background. In a previously published work, we have described a group of 100 patients with pure pliable mitral valve stenosis (echocardiographic score £ 10), subjected to OMC from 1998 trough 1991. The demographic and clinical characteristics of the patients are summarised in table I and the perioperative procedures and results are detailed in table II. Mitral valve areas obtained, measured by pressure half-time on average 5 days after the procedure, were a mean of 2.88 ± 0.49 cm2 and 37% of the patients had an area ³ 3 cm2. This is far in excess of those described after PBC. It was then concluded OMC was a better alternative in the treatment of mitral valve stenosis.

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Follow-up. This same group of patients was recently reassessed. The objective of the current study was to evaluate the clinical and echocardiographic evolution of the patients and their mitral valves, up to 10 years after the procedure, and to compare the results with those observed at the time of discharge. All survivors were observed in our hospital by a single cardiologist. Clinical evaluation aimed at the diagnosis of any cardiac pathology and assessment of the current functional status. Two-dimensional echocardiographic and Doppler evaluation was performed in all patients. Mitral valve areas were calculated by both planimetric and pressure half-time methods and mitral and tricuspid valve insufficiency were carefully looked for. Patients found to have symptomatic pathology were referred to the Department of Cardiology for further investigation and/or adjustment of their current medical therapy. All survivors were accounted for and the follow-up extended for 7 to 11 years (mean 8.5 + 1.1 years).

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Results:  Four patients (0.5% pt.year) had died since the operation, all for non-valve-related causes. One patient died of intractable CCF, two of malignant tumours and the fourth of renal failure that predated surgery. Two patients (0.3% pt.year) required reoperation, one for residual/recurrent mitral valve disease and the other for aortic disease but with adequate mitral valve function. Eleven patients (11.7%) had been admitted to hospital at least once for cardiac-related causes, usually for supraventricular arrhythmias or cardiac failure, but only 2 (2.1%; 0.3% pt.yr) had major embolic events. One patient, who was anticoagulated, had an intracranial haemorrhage. Ninety three percent of the patients were in NYHA class 1 or 2 (mean 1.5± 0.6; preoperatively 2.9± 0.4).

Mitral valve areas ranged from 1.6 cm2 - 3.6 cm2, with a mean of 2.37 + 0.42 cm2 (1.0 ± 0.23 cm2 before operation and 2.9 ± 0.49 cm2 immediately after; Fig 1) and 76 patients (80.9%) had areas between 2 and 3 cm2. Fourteen patients (14.9%) had an area lower than 2.0 cm2 and 4 (4.3%) above 3 cm2. Only 14 patients (14.9%) had a mitral valve area of less than two-fold the pre-operative values. The mean grade of mitral insufficiency was 2.05 ± 0.63 (preoperatively, 1.12 ± 0.46). Two-thirds (67%) of the patients had no or mild mitral valve insufficiency and 18% had mild to moderate insufficiency. In 14 cases there was moderate to severe valve dysfunction, but most were symptomatically controlled. Twenty five patients (26%) had moderate to severe tricuspid valve regurgitation. At nine years, actuarial survival was 96%, freedom from reoperation was 98% and freedom from all valve-related events was 92% (Fig 2).

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Discussion: Mitral valve stenosis of rheumatic aetiology is often amenable to conservative surgery, which carries an operative risk below 2%. In the early days of cardiac surgery, CMC was the only available method for treatment of mitral valve stenosis, but OMC has since emerged as a safer and more practical alternative. This procedure is easier to teach, hence is more reproducible, and permits a precise assessment of the characteristics of the valve, especially of the commissures and subvalvular structures. PBC was recently introduced, allegedly with the advantages of a less invasive procedure, claiming identical, if not better results than those of the surgical methods. Although the similarity of the mechanism of commissural separation, as compared with CMC, cannot be denied, the balloon is necessarily softer that the metallic transventricular valvotome, thus permitting a greater degree of stretching, rather than splitting of the valve. Tacit acknowledgement of this fact was the very recent introduction of a metallic valvotome for percutaneous use.

All these inconvenients are clearly obviated by open commissurotomy. Thus, the indications for this procedure are much wider and largely depend on the experience and interest of the surgeons in valve conservation. In our case, it was possible to conserve 919 (79%) of the 1,151 stenotic valves operated on during a 9-year period from 1988, including 257 valves with significant regurgitation, clearly not amenable to a closed procedure, whether surgical or catheter-based. In this work, we describe the 10-year follow-up of a selected group of 100 patients with fairly pliable mitral valve stenosis subjected to OMC between 1988 and 1991. This group of patients had favourable clinical and valve characteristics, comparable to those usually described in series of PBC, because that was the criteria for inclusion. Nonetheless, 46% were in atrial fibrillation and 10% had a previous surgical (closed) commissurotomy. Besides, additional technical manoeuvres, were performed during the procedure. In 56% of the patients the papillary muscles were incised to enhance leaflet separation, fused/thickened chordae tendineae were excised or fenestrated in 44% and calcium debridement was carried out in 17%. Furthermore, 14% had concomitant cardiac pathology corrected during the procedure, obviously not possible if they were to be subjected to PBC.

Our medium to long-term results, however, appear to be superior. The 10-year survival was 96% and the freedom from valve-related complications was 92%. By contrast, Orrange et al. (1998) reported a 7-year survival of 83% and event-free survival of 65% after PBC. Similarly, Vahanian et al. (1997) referred a 7-year survival of 80%, reintervention-free survival of 63% and complication-free survival of 54%, in a series of 1,514 patients of whom only 89% had good immediate results. Finally, Palacios et al. (1995) reported an 8-year survival of 85% and event-free survival, of 45% in 497 patients with echocardiographic score <8 subjected PBC. These values were 55% and 20%, respectively, for patients with scores >8. These differences are, undoubtedly, related to the larger valve areas obtained in our patients. A mean valve area of 2.88 cm2 is far better than in any series of PBC in which, to our knowledge, nobody has reported mean areas superior to 2.3 cm2 and the majority refer to values between 2.0 and 2.2 cm2. Hence, OMC achieved, in our experience, mitral valve areas much closer to normal. Furthermore, up to 11 years after surgery, the mean valve area was 2.37 cm2 and only 15% of the patients had areas below 2.0 cm2, still with values that would have been considered an excellent immediate result in patients subjected to PBC. By contrast, PBC appears to lead to a faster rate of recurrence of valve stenosis, judging by the higher reintervention rates, as no long-term follow-ups have been reported with measurement of valve areas. Logic, which together with good sense remains an important quality, dictates that any experienced surgeon should be able to open, under vision, a mitral valve better than a relatively soft rubber balloon can do blindly.

Comparison of different surgical and PBC series is difficult in view of differences in patient clinical and valve morphology characteristics, but patients subjected to open procedures usually have significantly worse pathology. However, we would never consider acceptable valve areas of 1.3 or 1.5 cm2 which were reported as mean values in some surgical series and would immediately replace such valves, if better opening could not be achieved. Open commissurotomy is a true mitral valvuloplasty because additional surgical manoeuvres can be performed, to help improving the valve area, such as incision of the papillary muscles, fenestration or resection of thickened chordae, debridement of fibrous areas, removal of calcium and annuloplasty, and, most importantly, immediate correction of pre-existing or iatrogenic regurgitation. By contrast to PBC, OMC is extremely operator-dependent. This must be the main reason for the wide variation of outcomes reported by different groups, but should not be a justification for substandard results.

Conclusion: Open mitral comissurotomy is a direct-vision procedure, with specific manoeuvres used according to the pathology. In our experience, it achieves better final valve areas, resulting in slower evolution to restenosis in the long-term. Finally, it may be used where the balloon may not, such as in cases of intra-atrial clot and of significant calcium deposition. It thus remains the golden standard in the treatment of rheumatic mitral valve stenosis and should be preferentially used, even in patients with favourable valve characteristics.

 

Questions, contributions and commentaries to the Authors: send an e-mail message (up to 15 lines, without attachments) to surgery-pcvc@pcvc.sminter.com.ar , written either in English, Spanish, or Portuguese.

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Update
Nov/05/99