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.