乌鸦传媒

Survival rates with catheter-based mitral valve repair are comparable to classic surgery and better than conservative management in high-surgical-risk patients with severe mitral valve regurgitation, researchers reported.

Results from the first study to compare transcatheter mitral valve repair with surgery and medical management in high-risk patients showed similar survival at 1 year follow-up among mitral valve (MV) repair and surgery patients (85.8% and 85.2%, respectively) and poorer survival among conservatively treated patients (67.6%).

The same trend was seen in the second and third years of follow-up, with 62.3% of MV repair patients still living after 3 years, compared with 54.2% of conservatively treated patients, researchers , of St. Antonius Hospital, Nieuwegein, the Netherlands, and colleagues wrote in the journal

Surgery Considered Too Risky for Many

Mitral valve regurgitation, also known as mitral insufficiency, is an abnormal reversal of blood flow from the left ventricle to the left atrium. It is the most common form of heart valve disease.

Without surgery, patients with symptomatic MR have a poor prognosis, even with optimal medical therapy. A found no survival benefit associated with nonsurgical medical management.

Despite the fact that guidelines call for surgical treatment of MV regurgitation, a European survey examining valve disease found that as many as 50% of patients are not referred for surgery because they are considered poor surgical candidates due to advanced age, left ventricular function, or other comorbidities, the researchers noted.

"Higher percentages of rejections have been reported recently, when MR was accompanied by heart failure," they wrote. "The reported in-hospital mortality rate in these high-surgical-risk patients is estimated to be up to 25%."

Transcatheter mitral valve repair is a new approach for treating MV regurgitation that is less invasive than surgery. MV repair using the MitraClip system (Abbott Vascular, Santa Clara, California) involves the creation of a double MV orifice by means of a clip in the mid portion of the anteromedial and posterolateral leaflets.

In earlier studies, Swaans, who is faculty member at the Abbott's Crossroads Institute, and colleagues showed the feasibility and efficacy of the clip device system in high-surgical-risk patients.

Their latest study was conducted to compare the approach with traditional surgical treatments and medical management in high-surgical-risk patients with severe MV regurgitation.

MV Repair Survival Similar to Surgery

The study included 139 consecutive patients treated with transcatheter MV repair, with outcomes compared with 53 surgically treated and 59 conservatively treated patients who were identified retrospectively. Surgical risk was based on the logistic (log EuroSCORE) or the presence of relevant risk factors, as judged by the heart team.

Participants included patients with both primary degenerative MR with reparable valves but extensive comorbid medical conditions and those with heart failure and secondary MR in whom left ventricle dysfunction increases surgical risk.

The log EuroSCORE was higher in the transcatheter MV repair group (23.9 ± 16.1%) than in both the surgically (14.2 ± 8.9%) and the conservatively (18.7 ± 13.2%; P<0.0001) treated patients.

Left ventricular ejection fraction was higher in surgical patients (43.9 ± 14.4%, P=0.003), with similar values for the transcatheter MV repair (36.8 ±15.3%) and conservatively treated (34.5 ± 16.5%) groups.

Survival rates among patients who received MV repair and surgery were better than that of conservatively treated patients at 1, 2 and 3-year follow-up.

After weighting for propensity score and controlling for risk factors, both the transcatheter MV repair (hazard ratio [HR]: 0.41, 95% CI 0.22-0.78, P=0.006) and surgical (HR: 0.52, 95% CI 0.30-0.88, P=0.014) groups showed better survival than the conservatively treated group.

"Despite higher log EuroSCORE, high-surgical-risk patients with severe symptomatic MR treated with the transcatheter MV repair show similar survival rates compared with those undergoing surgery, with both showing survival benefit compared with conservative treatment," the researchers wrote.

The 3-year mortality rate of 54.2% among conservatively treated patients was similar to that reported in other trials. Swaans and colleagues wrote that the significant survival advantage in MV repair patients suggests that it "could be the preferred treatment in high-surgical-risk patients and/or patients denied surgery."

"In an era in which up to 50% of patients are denied surgery, simply because of the high risk, transcatheter MV repair would be the only alternative therapy," the researchers wrote. "The landmark , in which patients at low and moderate risk were also included, showed that the survival rates were similar between transcatheter MV repair and surgery groups."

'Study Limitations Limit Interpretation'

In an editorial published with the study, cardiologist of Northwestern University Feinberg School of Medicine, Chicago, noted that the inclusion of patients with both primary and secondary forms of mitral regurgitation in the study, as well as earlier studies, "creates uncertainties in attempts to fully interpret the data."

Bonow, who is a past president of the American Heart Association, cited several significant study limitations, including the use of historical control patients as the conservative medically treated group instead of contemporaneously treated patients.

He added that the failure to identify the medical management of those treated conservatively makes it impossible to know how many actually received appropriate guidelines-directed medical therapy.

"The very high mortality rate of the conservative group (one-third died in the first year) does raise the question of aggressiveness of medical managment; and if there was undertreatment of these patients, the results showing better outcome with surgical or transcatheter intervention are self-fulfilling," he wrote.

Conservatively treated patients also had lower ejection fractions than those treated surgically and had undergone fewer previous revascularization procedures than the MV repair group despite a higher prevalence of coronary artery disease, and they also received fewer CRT procedures, Bonow noted.

Propensity weighting was performed to account for these baseline differences, as well as propensity matching of a smaller sample of 81 patients.

Analysis of these adjusted data continued to show significantly lower mortality in the transcatheter group compared with the control group, but Bonow wrote that "the magnitude of this effect is not clear because the survival curves (presented by the authors) show outcomes for all patients, not the matched patients."

He further noted that while eliminating or reducing MR has been shown to benefit high-risk patients with primary MR, the value of reducing MR with either surgery or minimally-invasive valve repair has not been shown.

When the analysis by Swaans and colleagues was confined to patients with functional MR, the difference in survival between transcatheter and conservative treatment groups was less significant (P=0.03) and the differences between surgically treated and conservative groups did not reach statistical significance (P=0.57).

"Importantly, it appears that this was an unadjusted analysis that did not account for the baseline risks among groups," Bonow wrote. "Thus, the current data do not define the role of mitral valve intervention in secondary MR. These data do underscore the need for prospectively designed clinical trials of mitral valve intervention (surgical or transcatheter) versus guidelines-directed medical therapy in patients with LV dysfunction and secondary MR."

Bonow noted that the NHLBI's Cardiothoracic Surgical Trials Network is conducting two trials, "that have the potential to finally clarify whether targeting the mitral valve in addition to guidelines-directed medical treatment results in improved outcomes of patients with LV dysfunction and secondary MR."

They are the Cardiovascular Outcomes Assessment of the MitraClip Therapy Percutaneous Therapy for High Surgical Risk Patients (COAPT) and the Randomized Study of the MitraClip Device in Heart Failure Patients with Clinical Significant Functional Mitral Regurgitation (RESHAPE-HF). ClinicalTrials.gov identifiers for these trials are NCT01626079 and NCT01772108, respectively.

Comment