二尖瓣修复术并不优于置换术

美国心脏协会(AHA)年会上公布并同步发表在《新英格兰医学杂志》上的一项随机临床研究显示，二尖瓣修复术治疗功能性缺血性二尖瓣反流的效果并不优于保留腱索的二尖瓣置换术(N. Engl. J. Med. 2013 [doi:10.1056/NEJMoa1312808])。

现行治疗指南建议，对于药物治疗无效的重度反流患者，可进行二尖瓣修复或保留腱索的二尖瓣置换术，但指南未指明应首选哪种手术，因为目前尚无表明何者更优的确凿证据。近期该领域倾向于首选二尖瓣修复术而非置换术，但这并无依据。


Michael A. Acker医生

因此，心胸外科试验网络(CTSN)的Michael A. Acker医生及其同事在22个医学中心进行这项多中心研究，旨在251例重度功能性缺血性二尖瓣反流患者中评价两种手术的相对获益。126例患者随机接受二尖瓣修复术，125例接受完全保留瓣下结构的置换术。主要终点是1年时通过经胸壁超声心动图左室收缩末期容积指数(LVESVI)测定的左室(LV)逆重构程度。修复组和置换组的平均LVESVI无显著差异，分别为54.6 mL/m²和60.7 mL/m²，反映的降幅分别为6.6 mL/m2和6.8 mL/m2。两组术后LVESVI评分变化的差异的中位数也无临床意义。

然而，修复组有32.6%的患者在1年内出现反流复发，而置换组该比例仅为2.3%。修复组3例患者需再次手术，而置换组无患者需再次手术。两组在累积死亡率、30天术后死亡率和1年死亡率方面均无显著差异，在主要不良心脏事件或脑血管事件这一复合终点方面也无显著差异。两组的严重不良事件发生率、住院时间和再入院率相似。两种不同评估量表测定的所有生活质量指标和功能状态也相似。

研究者表示，该研究结果与既往发表的有关这一课题的研究结果不一致。既往研究显示，与二尖瓣置换术相比，二尖瓣修复术具有一些优势，包括手术死亡率较低、左室功能改善和长期生存率较高。该研究观察到的置换术结果与修复术相当，这可归因于瓣膜置换术的发展，左室内部结构的保留使收缩效率得以维持，并可减少左室扩张和功能障碍。

该研究获美国国立心肺血液研究所、国立神经疾病与卒中研究所及加拿大卫生研究院资助。Acker医生及其同事声明无经济利益冲突。

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By: MARY ANN MOON, Cardiology News Digital Network

Mitral valve repair was no better than chordal-sparing mitral valve replacement in the first randomized clinical trial attempting to settle the controversy over which procedure is superior for treating functional ischemic mitral regurgitation, which was simultaneously reported at the annual scientific sessions of the American Heart Association and online Nov. 18 in the New England Journal of Medicine.

In the past few years, the use of mitral valve repair has far exceeded that of mitral valve replacement for this indication, largely on the basis of reports that the repair procedure yields lower operative mortality, improved left ventricular function, and higher long-term survival rates. In particular, a 2011 meta-analysis found a 35% lower relative risk of death in the long term with mitral valve repair, compared with replacement, said Dr. Michael A. Acker and his associates in the Cardiothoracic Surgical Trials Network (CTSN).
 
But in their multicenter study directly comparing the two procedures in 251 patients with severe functional ischemic mitral regurgitation, there was no significant difference between the surgeries in left ventricular end-systolic volume index at 1 year, nor in mortality at either 1 month or 1 year.

Moreover, study participants who underwent mitral valve repair showed a disturbing excess in the rate of recurrence of mitral regurgitation at 1 year, with a rate that was 30 percentage points higher than that among patients who underwent mitral valve replacement. "This lack of durability in correction of mitral regurgitation is disconcerting, given its reported association with further progression and long-term negative outcomes," said Dr. Acker of the division of cardiovascular surgery, University of Pennsylvania, Philadelphia, and his associates.

Functional ischemic mitral regurgitation, a "high-prevalence" condition affecting an estimated 2-3 million Americans, differs from primary degenerative mitral regurgitation in that the valve leaflets themselves remain normal while the defect occurs in the myocardium. "Ischemic mitral regurgitation is a consequence of adverse left ventricular remodeling after myocardial injury, with enlargement of the left ventricular chamber and mitral annulus, apical and lateral migration of the papillary muscles, leaflet retethering, and reduced closing forces.

"These processes lead to malcoaptation of the leaflets and variable degrees of mitral regurgitation that can fluctuate dynamically as a function of volume status, afterload, heart rhythm, and residual ischemia," the researchers said.

Current practice guidelines recommend mitral valve repair or chordal-sparing mitral valve replacement for severe regurgitation unresponsive to medical therapy, but do not specify which procedure is preferred because there is no conclusive evidence demonstrating the superiority of one over the other. "Recently, the field has embraced mitral valve repair over replacement," even without such evidence, Dr. Acker and his colleagues said.

The CTSN performed this study at 22 medical centers to assess the relative benefits of the two surgeries, with 126 patients randomized to undergo mitral valve repair and 125 to undergo replacement that included complete preservation of the subvalvular apparatus.

The primary endpoint was the degree of LV reverse remodeling, as measured by the left ventricular end-systolic volume index (LVESVI) on transthoracic echocardiography, at 1 year. The mean LVESVI was not significantly different between the repair group (54.6 mL per square meter) and the replacement group (60.7 mL per square meter), reflecting decreases of 6.6 mL per square meter and 6.8 mL per square meter, respectively, the investigators said (N. Engl. J. Med. 2013 [doi:10.1056/NEJMoa1312808]).

The median between group difference in the change in LVESVI score after surgery also was not clinically significant.

However, 32.6% of patients who underwent mitral valve repair had a recurrence of regurgitation within 1 year, compared with only 2.3% of those who had mitral valve replacement. Three patients in the repair group required reoperation, compared with none in the replacement group.

There were no significant differences in cumulative mortality, 30-day postoperative mortality, or 1-year mortality between the two study groups, and no significant difference in a composite endpoint of major adverse cardiac or cerebrovascular events.

Rates of serious adverse events were similar, and the durations of hospitalization were similar between the two study groups, as were rates of readmission. All measures of quality of life and functional status on two different assessment tools also were similar.

"Our findings contradict much of the published literature on this topic, which reports several advantages to mitral valve repair over replacement, including lower operative mortality, improved left ventricular function, and higher rates of long-term survival," Dr. Acker and his associates noted.

The evolution of the valve replacement procedure, which now includes chordal sparing, "may account for the improved results we observed, as compared with previous studies, since the retention of the internal architectural support of the left ventricle may preserve contractile efficiency and reduce left ventricular dilatation and dysfunction," they said.

This study was funded by the National Heart, Lung, and Blood Institute, the National Institute of Neurological Diseases and Stroke, and the Canadian Institutes of Health Research. Dr. Acker and his associates reported no financial conflicts of interest.