Transcatheter Mitral Valve Repair as Bridge Therapy to Heart Transplantation

Background: Heart transplantation (HTx) is the most effective therapeutic option for patients with advanced or end-stage chronic heart failure (HF). However, the increasing number of patients with refractory chronic HF and the declining willingness for organ donation, have resulted in expanded waiting lists and prolonged waiting times for patients listed for HTx. Furthermore, more than 60% of patients are transplanted in high-urgency status, leaving little chance for patients listed for less urgent transplantation. In order to improve the general conditions of these latter patients during the waiting period, several pharmacological and mechanical bridging therapies have been developed. Anyway, limited data are now available regarding the use of MitraClip treatment as bridge strategy in patients with severe mitral regurgitation (MR) and end-stage HF waiting for HTx.

Methods: The MitraBridge registry is an observational, multicenter, international registry including all consecutive patients with chronic end-stage HF [New York Heart Association (NYHA) III or IV and/or left ventricular ejection fraction (LVEF) ≤35%] and concomitant moderate-severe or severe MR who were potential candidates for HTx, that were treated with MitraClip in the contest of a pre-specified bridge strategy.

According to the clinical conditions present at the time of the MitraClip procedure, patients are classified in:

1. patients on active HTx list (In list group, "pure bridge") with a rapidly progressive disease and a low likelihood to receive a donation shortly;
2. patients waiting for clinical decision (Bridge to decision "BTD" group), also including unstable patients during the screening for HTx;
3. patients who could not be listed for HTx (Not in list group, MitraClip as "bridge to candidacy") because of concomitant, potentially reversible, contraindications (e.g. severe pulmonary hypertension, elevated pulmonary-vascular-resistance).

The registry was initiated in June 2018 without the support of any external funding and was designed to involve centers across the world that have experience with transcatheter MitraClip device (Abbott Vascular, Santa Clara, California).

Study endpoints. The primary endpoint: 1-year composite adverse events rate of all-cause of death, urgent/unplanned HTx or LVAD implantation and first re-hospitalization for HF.

As exploratory outcomes: individual components of the primary endpoint.

Moreover, the investigators described the clinical status of patients at the time of last available follow-up, in order to report the rates of patients going for elective HTx, entering (or remaining) in the waiting list and having no more indication to HTx (delisting) because of significant echocardiographic and/or clinical improvements during the entire observational period.

Mitral Valve Academic Research Consortium (MVARC) criteria are used to define procedural success and composite events 12.

Follow-up data will be collected for patients at 1 month and 1-year and then according to the time frame elapsed from the index procedure to data lock for present analysis.

Patients that did not implant any clip during the index procedure were not included in the follow-up. For patients who underwent HTx or LVAD implantation, the follow-up time was stopped at the date of transplant or mechanical device placement.