Although mitral valve operation is the fastest-growing category of heart surgery, it is often performed too late to completely reverse the damage caused by mitral valve disease, researchers found.

Isolated primary mitral valve (MV) operations increased by 24% per year between 2011 and 2016, and surgery for degenerative mitral valve disease increased by 44% during the 5-year study period, James S. Gammie et al. reported online in Annals of Thoracic Surgery.

The team analyzed trends in data from the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database (ACSD), which includes more than 90% of all adult cardiac surgery hospitals across the United States and Canada.

Primary isolated mitral valve surgery — i.e., surgery without concomitant coronary artery bypass graft surgery or aortic valve (AV) procedures — was performed on 87,214 patients (average age of 64, 50% of whom were female) at 1,125 centers, most frequently for degenerative leaflet prolapse (DLP) (60.7%). About 4% of the patients had functional mitral regurgitation.

Mitral valve repair rate

Preoperative data showed that 47% of patients had an ejection fraction <60%, and 34% had atrial fibrillation. Mitral valve repair rate for the cohort overall was about 66% (n=57,244) — a decline from 67% to 63% (P<0.0001) between 2011 and 2016. Most of the repairs were etiology-related (DLP, 82.5%; rheumatic, 17.5%).

Of the almost 30,000 mitral valve replacements included in the analysis, 16% were preceded by an attempted repair. While surgery for mitral valve disease is the fastest-growing type of heart operation and has low risks of complications and death, with an operative mortality rate of 2.0%, "a significant number of patients are still referred for mitral valve surgery later than they should be," Gammie noted in a news release. 

Reflecting the emerging trends in mitral valve surgery, less-invasive operations were performed in 23% of the patients and concomitant tricuspid valve repair in 15.7%. Unadjusted operative mortality was 3.7% for replacements and 1.1% for repairs.

'Important Wake-Up Call'

"On the cardiology side, patients with severe primary MR should be considered for surgery earlier, as once they develop left ventricular dysfunction, atrial fibrillation or pulmonary hypertension, these conditions may not be reversible and will impact long-term postoperative outcomes," Bonow continued.

"And patients need to be referred to surgical centers that are expert in mitral valve repair. On the surgery side, that only 86% of patients with MVP undergo mitral valve repair falls well short of the target for repair, and that 16% of mitral valve replacements happen after failed attempts at repair identifies another point of concern."

"Surgical centers need to audit their results, and referring cardiologists need to be aware of them," Bonow said. "What is also needed is more emphasis on the indications for surgery patients with severe MR, as well as attempts by the cardiology and cardiac surgery communities to further define criteria for centers of excellence for mitral valve surgery."

Gammie et al. said that study limitations for the analysis included the use of incomplete data — for example, etiology was reported for only 69% of the patients — or potentially incorrect data, echocardiographic data that was not laboratory adjudicated, and a risk model for MV operations that did not include the performance of tricuspid valve repair or AF ablation.