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Cannata et al. Mini-invasive Surg 2020;4:53 I http://dx.doi.org/10.20517/2574-1225.2020.41 Page 7 of 17

outflow tract and the position of other intracardiac devices. Indeed, an ambitious combined percutaneous
procedure of MitraClip plus occluder would be contraindicated in the presence of active endocarditis, and
an accurate preoperative planning should take into account the risk of iatrogenic obstruction of ventricular
[13]
outflow or interference with proximally-located prostheses .
Leaflet flails and prolapse are categorised as Carpentier type II mechanism and occur through sudden
[11]
rupture of chordae tendineae or papillary muscles due to many possible causes . Myxoid degeneration or
Barlow’s disease is a major cause of chordal rupture and remains extremely challenging for percutaneous
repair due to altered anatomy, including extensive leaflet thickening, multi-segmental prolapse, elongated
[14]
or fused chordae tendineae, diffuse calcifications and annular dilatation . Beyond procedural challenges,
the main issue is the balance between a relevant residual MR due to the highly mobile and redundant
leaflets and a resultant iatrogenic mitral stenosis owing to extensive grasping with multiple clips.
However, the introduction of MitraClip XTR device, with a wider reach and longer clip arms than NTR,
has broadened the “graspable” MV anatomies, including Barlow’s disease, as documented by a few case
series [15-17] . Nonetheless, myxoid degeneration appears early in life and patients are usually referred for
surgery due to young age and low risk, on the contrary fibroelastic deficiency affects elderly people with
significantly different operative risk. In fibroelastic deficiency MV is characterized by impaired production
of connective tissue and shows thin leaflets, prolapse of single segments, and rupture of thin chordae with
[14]
limited flail width . MitraClip has been shown to be feasible and safe in this type of MV anatomy, even in
octogenarians, but care should be taken in cases of fragile leaflet tissue due to the risk of grasping-related
[18]
leaflet tears or lacerations .

Papillary muscle rupture is a severe, albeit rare, mechanical complication of acute myocardial infarction.
This anatomic lesion is challenging given the large flail width and flail gap with frequent commissural
[19]
localization requiring an extensive grasping with a concomitant high risk of chordal entanglement . As
a papillary muscle head may mimic an endocarditic mass, clinical context should guide the differential
[20]
diagnosis . Moreover, infective endocarditis itself may be causative of chordal rupture and papillary
[21]
muscle laceration, in the presence of typical echocardiographic criteria such as vegetations and abscesses .

Among functional alterations of MV, the main cause of acute MR is myocardial ischemia. Indeed, in the
very acute phase of myocardial infarction, even modest valve tenting due to regional and/or global left
[22]
ventricular dysfunction may result in hemodynamically-significant MR . Echocardiography should be
performed to assess the presence of wall motion abnormalities and myocardial scarring, and the “symmetry”
of mitral leaflets with respect to their point of coaptation. In cases of asymmetric tenting, it is generally
the posterior leaflet that tethers while the anterior leaflet shows a ‘‘pseudoprolapse’’ motion. The MR jet
is eccentric and oriented against the posterior wall of left atrium. In cases of symmetric tethering, both
leaflets are tented but the coaptation point is displaced apically at the leaflets’ tips, and the jet is typically
[23]
central .
An infrequent cause of acute MR is SAM of mitral leaflet, which represents a life-threatening condition
and may result also in critical left ventricular outflow tract obstruction. Hypertrophic obstructive
cardiomyopathy is the main pathology associated with SAM and is characterized by abnormalities
of MV and subvalvular apparatus, such as malpositioned papillary muscles, elongated chordae and
thickened leaflets . These anatomic features may impact on transmitral gradients and residual MV area
[24]
[25]
after MitraClip procedure . SAM with left ventricular outflow obstruction may occur in several other
conditions such as Takotsubo cardiomyopathy, hypertensive hypertrophic cardiopathy, hypovolemia,
severe bleeding, sepsis, vasodilatation, sympathetic activation, pericardial tamponade, after aortic valve
[25]
replacement, and after surgical mitral valve repair . In these acute conditions a transcatheter edge-to-edge
technique certainly sounds appealing to target both MR and hypotension.