Page 699 - Read Online

Page 2 of 10 Rodinò et al. Mini-invasive Surg 2020;4:70 I http://dx.doi.org/10.20517/2574-1225.2020.55

over 75 years of age), which in the last decades has led a to a sharp rise in the number of patients requiring
[1]
hospitalization or intervention . It is acknowledged that an organic (or primary) and a functional (or
secondary) etiology of MR can be distinguished, and these two entities carry different prognosis and
[2]
management . The purpose of the current review is to outline the percutaneous treatment of primary MR,
from available evidence to technical practice, with a focus on transcatheter “edge-to-edge” leaflet repair.

ETIOLOGY AND TREATMENT OF PRIMARY MR
Organic MR is defined as a primary structural abnormality of the mitral valve (MV) apparatus. Its etiology
is largely dominated by myxomatous degeneration of the leaflets (which ranges from fibroelastic deficiency
to Barlow’s disease), followed by rheumatic disease, infective endocarditis, connective tissue and ischemic
[3,4]
disease, congenital malformations, and iatrogenic (radiation therapy or drugs) and traumatic lesions .
Fibroelastic deficiency usually presents with thin transparent leaflets with focal prolapse or flail due to
chordal rupture, while Barlow’s disease hallmarks are multi-segment prolapse involving one or both leaflets
in a valve with significant myxomatous changes, excess leaflet tissue and dilated annulus. Between these
[5]
two phenotypes, a broad spectrum of degenerative disease is found in clinical practice . Regardless of
the anatomical background, MV prolapse is the most common cardiac valvular anomaly in developed
countries affecting approximately 2% of the general population. It is associated with a variable degree of
MR, with most patient having trivial or mild regurgitation; previous studies have found a 6% prevalence of
[6,7]
a severe degree of the disease in the outpatient population with valve prolapse . However, very little data
[8,9]
are available in these patients regarding the progression of MR severity and the associated risk factors .
Left untreated, chronic severe MR may lead to left ventricular (LV) remodeling because of volume
overload, myocardial dysfunction, heart failure, left atrial dilatation, atrial fibrillation and pulmonary
hypertension. Surgical correction, by means of valve repair or replacement, is the gold standard for the
[2]
treatment of symptomatic patients with severe primary MR . The optimal timing for intervention has to be
according to symptom onset, worsening of LV function, significant LV dilatation, or development of atrial
fibrillation or pulmonary hypertension. Despite the lack of randomized clinical trials comparing the results
of valve replacement and repair, it is widely accepted that valve repair is the preferred treatment, when it is
[2]
feasible when and a durable repair is likely . However, symptomatic patients are frequently denied surgical
treatment mainly because of impaired LV ejection fraction, older age and comorbidities [3,10] . Therefore, in
recent years, great effort was made to develop less invasive, percutaneous therapeutic alternatives suitable
for high or prohibitive surgical risk patients. Possible catheter-based approaches for the treatment of MR
include transapical or transseptal valve repair or replacement, placement of annular tightening devices,
and insertion of artificial chordae. The “edge-to-edge” surgical repair technique, making a “double-orifice”
MV, was the first to be adapted for the percutaneous approach with the MitraClip System (Abbott Vascular,
Santa Clara, CA, USA), reaching over time more than 70,000 implants worldwide, since its first use in
[11]
humans in 2003 . Later in 2019, the new PASCAL repair system (Edwards Lifesciences, Irvine, CA, USA)
received CE mark for the percutaneous “edge-to-edge” repair treatment of MR, further expanding the
therapeutic options available to the interventional cardiologist and the population eligible for treatment.
As a matter of fact, current guidelines recommend a percutaneous edge-to-edge repair for the treatment of
patients with symptomatic moderate-to-severe or severe primary MR who fulfill echocardiographic criteria
of eligibility and are judged inoperable or at high surgical risk by the Heart Team evaluation (Class IIb,
[2]
LOE C) .

TECHNICAL ASPECTS OF TRANSCATHETER MV “EDGE-TO-EDGE” LEAFLET REPAIR
Proper patient selection with preoperative echocardiography using both 2D and 3D transesophageal
echocardiography (TEE) is mandatory to confirm MR severity and define its mechanism while evaluating
anatomic eligibility for an “edge-to-edge” transcatheter repair and, ultimately, achieve satisfactory
results [2,12] . In the early years of MitraClip usage, eligibility was evaluated according to the preliminary