Patients, follow-up, and endpoints:
We prospectively included consecutive patients with symptomatic moderate-to-severe or severe refractory MR undergoing the MitraClip procedure (NTR/XTR Clip Delivery System, Abbot Vascular, Inc., Santa Clara, California) at the Heart Center of the University Hospital Bonn between February 2017 and January 2019.
All patients underwent standardised echocardiographic examinations for non-invasive MG assessments at baseline, intraprocedurally, at discharge, and six months after MitraClip. Multiple measurements were done to minimise angulation- and acquisition-related errors and exclude any relevant mitral valve stenosis (>5 mmHg) during each examination, or directly after clip deployment and before clip release. All echocardiograms were performed after a relaxing time of 5 minutes to occasion a resting condition to avoid misinterpretations due to hemodynamic undulations. Clinical examinations comprised an assessment of NYHA functional class, a six-minute walk test (6MWT), and a comprehensive blood test, which included serum levels of NT-proBNP. The six-month FU was performed in our outpatient clinic and included transthoracic echocardiography, a routine physical examination, an electrocardiogram, and a blood test. Survival status was reassessed by either a FU visit in the outpatient clinic or a phone call 12 months after the procedure.
We defined all-cause mortality at 12-month FU as the primary endpoint in line with MVARC (Mitral Valve Academic Research Consortium) definitions (11). Secondary endpoints were defined as follows: NYHA functional class at FU < III, amelioration in the walk distance of 25%, intraprocedural MG ≥ 4.5 mmHg, residual MR> II at discharge, and MR at FU > II.
The study was authorised by the local ethics committee (Medical Faculty of University Bonn, Bonn, Germany) and in accordance with the Declaration of Helsinki. All patients signed their written informed consent before inclusion in the study. All patients’ data were anonymised before use in the study. Echocardiographers and clinicians from the in- and outpatient clinics were blinded to the study parameters. Trained study nurses carried out clinical FU evaluation, unattended by the interventionalists or the procedural echocardiographer.