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.
References
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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.