Atrial mitral annular disjunction (MAD) is defined as a spatial displacement (≥2 mm) of the leaflet hinge line towards the left atrium within any part of the mitral mural leaflet or mitral commissures [1]. Similar disjunctions may be observed in the case of right atrioventricular valves – tricuspid annular disjunctions (TAD) and may occur along the whole tricuspid valve circumference [2].
We present a case of a 30-year-old, previously untreated, female admitted to the Clinical Department of Cardiology and Cardiovascular Interventions, University Hospital Krakow, Poland, after prehospital cardiac arrest in the mechanism of ventricular fibrillation, for advanced cardiac diagnostics. The patient has no known comorbidities or significant cardiac diseases in her family history. Transthoracic echocardiography showed normal left ventricular ejection fraction (60%), small mitral valve prolapse (displacement of the mitral leaflets 2–3 mm into the left atrium during systole), with mild mitral regurgitation and atrial MAD located in the posterior mitral leaflet (disjunction height of 6 mm) (Figure 1A; Supplementary material, Videos S1 and S2). Moreover, a suspicion of atrial-shifted TAD in the mural leaflet has been raised with a disjunction height of 4 mm (Figure 1B; Supplementary material, Video S3). Cardiac magnetic resonance confirmed good ejection fraction and the presence of MAD and TAD (Figure 1C–D).
Moreover, late gadolinium enhancement (LGE) was present within the tricuspid, mitral annulus, and subvalvular apparatus of both atrioventricular valves (Figure 1E). Linear subepicardial areas of LGE were found in the basal segments of the inferior and lateral walls of the left ventricle. Additionally, LGE was found in the free wall of the right ventricle. Contrast-enhanced electrocardiogram-gated computed tomography showed no changes in the coronary arteries and confirmed the presence of disjunctions (Figure 1F). In 24-hour electrocardiogram monitoring, numerous ventricular extrasystoles were found (15% of the recording) (Supplementary material, Figure S1). During the hospital stay, a cardioverter-defibrillator was implanted without complications, and the dose of the beta-blocker was gradually increased. After antiarrhythmic drug escalation, the number of ventricular ectopic beats was reduced to 6% of recordings.
Annulus disjunctions could involve both the tricuspid and the mitral annuluses. In our patient, MAD, TAD, mitral valve prolapse, and myocardial fibrosis could be potential causes of ventricular arrhythmias and cardiac arrest. Previous research related to MAD focused on the association between MAD and mitral valve prolapse, arrhythmias, and sudden cardiac death [3, 4]. The prevalence of MAD varies depending on the patient population, imaging method, and MAD’s definition [1]. Recent studies have shown that in 50% of patients with MAD, TAD is also detectable [2]. The clinical significance of TAD is still unknown; however, we can find some case reports showing that the presence of isolated TAD may be associated with ventricular arrhythmias [5]. Annular disjunctions could lead to excessive local contraction and stretching of cardiomyocytes, resulting in potential remodeling and fibrosis of the myocardium, which may predispose individuals to premature depolarization and trigger ventricular arrhythmias [4]. The presence of LGE in both the right and left ventricles in our patient suggests that the impact of both disjunctions on ventricular damage could have been a possible cause of cardiac arrest.
Supplementary material
Supplementary material is available at https://journals.viamedica.pl/polish_heart_journal.
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