Conference Coverage

MitraClip learning curve may top 200 cases



– It took about 50 MitraClip cases for operator outcomes to start improving, and outcomes were still improving at 200 cases, in a study reviewing 14,923 MitraClip procedures in the Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapy Registry from November 2013 to March 2018.

Dr. Adnan Chhatriwalla

Dr. Adnan Chhatriwalla

“These findings demonstrate the key role of operator experience in optimizing outcomes” of transcatheter mitral valve repair (TMVr) with MitraClip (Abbott Structural), said investigators, led by Adnan Chhatriwalla, MD, an interventional cardiologist at Saint Luke’s Mid America Heart Institute in Kansas City, Mo.

“New operators may experience a ‘learning curve’ irrespective of the overall site experience or experience of other members of the Heart Team,” they wrote in the study (JACC Cardiovasc Interv. 2019 Sep 27. doi: 10.1016/j.jacc.2019.09.014).

“As TMVr becomes more prevalent in the U.S., it may be prudent for less experienced operators to be cognizant of where they sit on the ‘learning curve’ and to pay particular attention to case selection in their early experience, considering that more complex patients may be referred to more experienced centers for treatment when prudent,” they noted.

“The overall duration of the learning curve may exceed 200 cases,” Dr. Chhatriwalla said at the Transcatheter Cardiovascular Therapeutics annual meeting in a presentation that coincided with the study’s publication.

“This is a more complex procedure than [transcatheter aortic valve replacement], and the volume/outcome relationship is stronger. We are seeing issues that are related to early experience in low-volume programs. Public reporting so consumers can determine how many cases a center does is going to be critical,” said cardiothoracic surgeon Michael Mack, MD, director of the cardiovascular service line at a health system in Dallas, after the talk. He was one of the authors of the study.

The investigators compared outcomes among 549 operators who had done 1-25 MitraClip cases, 230 who had performed 26-50 cases, and 116 who had performed 50 or more.

Optimal procedural success – defined as less than or equal to 1+ residual mitral regurgitation (MR) without death or cardiac surgery – was 63.9%, 68.4%, and 75.1%, respectively, across the three groups (P less than .001). The “acceptable” procedural success rate – less than or equal to 2+ residual MR without death or cardiac surgery – was 91.4%, 92.4%, and 93.8% (P less than .001). No interaction was observed between the mechanism of mitral valve regurgitation and procedural outcomes.

Procedure time decreased as operators gained experience (145, 118, and 99 minutes), and atrial septal defect closure rates increased (0.9%, 1.4%, and 2.2%, respectively).

Composite complications rates also fell (9.7%, 8.1%, and 7.3%), driven mostly by less frequent cardiac perforation (1.0%, 1.1%, and 0.4%) and less frequent blood transfusion (9.6%, 8.6%, and 6.5%). The results were statistically significant.

“Adjusted learning curves for procedural success were visually evident after approximately 50 cases, and continued improvement in clinical outcomes was observed for the entire case sequence up to 200 cases,” the investigators wrote. The improvements could not be attributed to patient selection alone, they said.

More experienced operators were more likely to use more than one clip per case, and more frequently treated central and medial, as opposed to lateral, pathology. Operators with more than 50 cases were less likely to treat patients who had preexisting mitral stenosis or required home oxygen, and experienced operators were more likely to perform the procedure in unstable patients, when appropriate. The proportion of patients with functional MR – as opposed to degenerative disease – increased with increasing experience.

There were no statistically significant differences across the groups in stroke rates (P = .26), single-leaflet device attachments (P = .11), trans-septal complications (P = .25), urgent cardiac surgery (P = .42), or in-hospital mortality (P = .55).

Patients were a median of 81 years old, and most were white; 93% had 3+ or 4+ MR at baseline, and 86.3% had degenerative mitral disease. Two-thirds had atrial fibrillation/flutter.

The work was supported by the ACC/STS TVT Registry. Dr. Chhatriwalla is a proctor for Edwards Lifesciences and Medtronic, and is a speaker for Abbott, Edwards Lifesciences, and Medtronic. Dr. Mack has served as an investigator for Edwards Lifesciences and Abbott, and as a study chair for Medtronic. Other investigators reported similar industry disclosures.

The meeting is sponsored by the Cardiovascular Research Foundation.

SOURCE: Chhatriwalla A et. al. JACC Cardiovasc Interv. 2019 Sep 27. doi: 10.1016/j.jacc.2019.09.014.

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