Out-of-hospital cardiac arrest in a mitral valve prolapse young male patient with acute mitral regurgitation due to cordal rupture. A case with a literature review

Till now, the presence of ventricular arrhythmias among patients with MVP has been underappreciated. Some previous studies described an increased incidence of serious ventricular arrhythmias in this kind of patients. On the contrary, other studies demonstrated that occurrence of MVP, among sudden cardiac arrest causes in the community, may not be significantly increased from what is expected in the general population (2, 6). This rare case regards a young male with asymptomatic MVP who was resuscitated from out-of-hospital sudden cardiac arrest. The exact mechanism linking MVP to sudden cardiac arrest is still not known. An autoptic study in patients with MVP had shown that mitral valve leaflet length and posterior leaflet thickness were greater in hearts of patients who died suddenly compared to patients with MVP who died from other causes (7).
Until now the debate continues as to whether MVP is the cause of SCD or merely an association. However, several possibilities have been advanced. Previous studies supposed the hypothesis of an abnormal autonomic and hyperadrenergic state (8). Boudoulas et al (9) demonstrated that patients with MVP had frequent, transient and inappropriate increases of catecholamines during the day or stressful activities. The above condition may produce transient QT prolongation relative to the QS2 interval (electromechanical systole). To further support this hypothesis another study showed that 24-hour catecholamines excretion and frequency of premature ventricular beats were parallel (10). Wilde and colleagues (11) performed detailed mapping studies on a patient with MVP and ventricular tachycardia and concluded that delayed afterdepolarization-induced triggered activity was the mechanism, with stretch and fibrosis of the papillary muscles, contributing to the origin of the arrhythmia.
Furthermore, some studies have suggested that ventricular arrhythmias may be more frequent in MVP when mitral regurgitation is present (12,13,14). This could reflect hemodynamic consequences of volume overload; however it is noteworthy that the mean left ventricular ejection fraction was normal and left ventricular diameter not significantly increased in the MVP patients compared to the cases without MVP in our population. Additionally, it has been proposed that a subset of young patients with isolated MVP and SCD could actually have less mitral regurgitation (15,16). Certain studies have found women to be at higher risk (4, 14) that not regards our patient. An other study, using signal-averaged ECG, identified an increased frequency of late potentials in MVP patients (17); however the utility of this tool in risk prediction is unclear.
The arrhythmic substrate in this setting of patients was also recently investigated by Basso and colleagues (18), who found that in patients who experienced sudden cardiac death with MVP was present fibrosis in the papillary muscles of adjacent free wall and infero-basal wall, as demonstrated by late gadolinium-enhancement on magnetic resonance study. The above features closely overlapping with the histopathological findings which described that kind of fibrosis pattern different in terms of type (i.e. scarring) and location (i.e. papillary muscles and basal potero-lateral wall). Moreover, the degree of MVP and leaflets thickness was found to be related with QT dispersion, providing also a mechanical correlation for electrical disturbances in this subset of patients (19). In a similar way, Sriram et al studying patients with out-of-hospital cardiac arrest in bileaflet mitral valve prolapsed syndrome, found on the electrophysiological study that the earliest site of origin of premature ventricular complexes was mapped to the tips, body or bases of either the anterior or posterior papillary muscles (20). Additionally, it is worth to underline that human mitral valve has distinct patterns of innervation. Mechanical stimuli produced by irregular coaptation of prolapsed mitral cups may cause an abnormal autonomic nerve feedback between the central nervous system and the mitral valve (21).
In our case we did not have the possibility of MRI investigation due to the emergency situation and the electrocardiographic evaluation after resuscitation was in sinus rhythm without significant repolarization changes. Moreover, the explanation of the genesis of ventricular fibrillation in our patient is not clear. We hypothesed that a mechanical stimulation, with an important papillary stretch and the sudden rupture of cordae tendinee, could cause an abnormal nerve feedback between central nervous system and mitral cusps. This is of relevance in most of the previous studies demonstrating the importance of papillary muscle-annular continuity in the maintenance of normal ventricular function after surgical valve correction (12). Consequently, an urgent surgical correction of the above described mechanism as first line therapeutic option, may treat also the arrhythmogenic substrate.