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).
Dr. Michael A. Acker
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.