Discussion
PMR is a rare but life-threatening emergency, generally associated with
coronary artery disease, specifically acute myocardial ischemia. There
have been other non-ischemic etiologies related to PMR. Gouda et al
published a review of all non-ischemic spontaneous PMR case reports up
to 2015 (2), differential etiologies noted in the summary include
myocarditis (5,6), endocarditis and fungal infections (7,8), Ehler
Danlos type IV, Takotsubo cardiomyopathy and mitral annular
calcification are other described entities (3,4, 9, 10). From the 12
cases published thus far, 4 of them had an unknown etiology (2,
11,12,13).
In our case, the angiography showed some coronary artery disease, but
nothing supported an acute coronary syndrome. Furthermore, there was no
previous clinical evidence of stable angina, abnormal wall motion,
recent infarct, hypertension, vasculitis, trauma, hypercoagulable state,
infection and no clinical and/or surgical evidence of ventricular
hypertrophy that could justify the rupture.
We believe three things could explain the spontaneous PMR in our
patient, one is related with the pathology findings of fibrosis and
myxoid degeneration in the mitral valve, Seve and Shim (9,10) published
connective tissue disorders (Ehler Danlos) as a cause for rupture. The
second important factor in our patient is the history of sudden onset of
dyspnea shortly after strenuous physical activity. The papillary muscle
works as an independent mechanism to absorb and compensate sudden
geometric changes of the left ventricular wall and to maintain the basic
mitral valve geometry (14). Blunt trauma itself explains how an extreme
and critical change of the intrathoracic pressure can cause rupture of
the papillary muscle (2), through probable failure of the mitral
subvalvular apparatus in maintaining the ventricular geometry. The
Valsalva respiratory phenomenon associated with extreme exercise (as
lifting a heavy weight) could be analogous to the blunt chest trauma
with a closed glottis.
And finally, even when this patient did not have an acute coronary
syndrome or previous myocardial infarction, we believe that there may
have been possible hypoperfusion from microvascular disease or existing
coronary artery disease, which could have been an added factor to this
complication (2). Mitral surgery is mandatory and urgent once a PMR
diagnosis is made, the standard treatment is valve replacement,
although, Fiore et al., reported a case of a successful mitral valve
repair with papillary muscle reimplantation (14).
The presence or combination of a tissue myxoid degeneration in the
mitral valve, with an extreme force applied suddenly in the chordae
tendinea and papillary muscle, and some possible tissue hypoperfusion of
the subvalvular apparatus, should be considered etiologies in
spontaneous PMR.
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Figure 1 Legend
Figure A: Transesophageal echocardiogram demonstrating a mid-esophageal
4-chamber view with the anterior leaflet of the mitral valve prolapsing
into the left atrium on diastole.
Figure B: Transesophageal echocardiogram image with torrential eccentric
posterior regurgitant jet of the mitral valve creating a “Coanda
effect”.
Figure C: Transesophageal echocardiogram with an echo dense structure at
the end of the anterior leaflet representative of ruptured papillary
muscle.
Figure D: Excised anterior leaflet of mitral valve, showing the rupture
in the head of the papillary muscle.