Sara Boccalini MD, PhD1,2, Salim Si-Mohamed MD, PhD1,2, Philippe Douek MD, PhD1,2Patient
50 years, female
A 50 years-old woman presented a cardiopulmonary arrest. ECG revealed negative waves in V3-V6, AVF, echography was normal. Her medical record was uneventful besides an episode of ventricular extrasystole and mitral prolapsus. Coronarography was negative but a torsade de pointe was recorded during the procedure. The patient was transferred to a tertiary centre and referred for cardiac CT, with a dual-energy dual-layer CT scanner, and cardiac MRI for further investigation. In particular, the presence of myocardial necrosis/fibrosis had to be excluded and, since MRI was not immediately available, cardiac CT with arterial and late enhancement acquisitions was performed at first.
Cardiac CT consisted of two acquisitions with retrospective ECG-gating, one performed in arterial phase and the other, for late enhancement assessment, after ten minutes. The arterial phase did not show any plaque, stenosis and coronary occlusion. The myocardium of the left ventricle had homogeneous thickness with the exception of the mid-ventricular lateral wall (that measured 4 mm vs the 7 mm of the adjacent wall) (Figure 1 and 2 respectively). In the same area, on the late acquisition, the myocardium was more enhanced than the rest (Figure 3). The two leaflets of the mitral valve showed an aspect of billowing/prolapsus (Figure 1 and 2). In addition, there was some abnormal space between the annulus of the mitral valve and the myocardium of the left ventricle.
The cardiac MRI confirmed all findings including the area of enhancement of the mid-lateral wall (Figure 4), which was also hypokinetic on cine-SSFP images (Video 1).
Malignant arrhythmias can derive from myocardial fibrosis that can originate from different pathologies including valvular anomalies. Among the latter, one poorly known entity is mitral-annulus disjunction (MAD) which is defined as the atrial displacement of the posterior mitral valve leaflet hinge point[1, 2].
Although mitral valve prolapse is often associated with mitral-annulus disjunction, this can also be an independent anomaly in up to 22% of cases. Some have even advocated that MAD might be a precursor of mitral valve prolapse and the exact relationship between the two entities remains scarcely understood.
MAD can be associated to ventricular arrhythmias, ranging from frequent premature ventricular contractions to cardiac arrest. The underlying mechanism is not yet completely clarified. One of the most likely hypotheses is that the anatomic anomaly determines a mechanical stretch of the inferobasal wall and papillary muscle fibres, eventually leading to myocardial hypertrophy and scarring, ultimately acting as arrhythmogenic focus.
It is important to know and recognise MAD since it can be associated with malignant ventricular arrhythmias. In patients with mitral prolapsus, MAD should always be searched for.
CT with retrospective ECG-gating and cine sequences on cardiac MRI can help diagnose and quantify MAD. Both can easily highlight the presence of an abnormal space between the left myocardial base and the annulus of the mitral valve along with the posterior leaflet. This space is more evident in ventricular systole.
Greater longitudinal MAD distance located in the posterolateral wall assessed by CMR is an independent risk marker for all ventricular arrhythmias. Therefore, this parameter should always be calculated and written in reports. In addition, the circumferential extension of MAD (expressed in degrees) has been regarded as a negative prognostic factor by some authors and should be indicated as well.
Although MRI yields all relevant information without radiations, CT is an interesting imaging modality in this context as it allows assessing the mitral valve and valvular apparatus in any desired plane and in 3D. Nevertheless, to dispose of images of each phase of the cardiac cycle, a retrospectively ECG gated acquisition with contrast administration is needed. Therefore, risks and advantages have to be weighed carefully for each patient.
Late enhancement acquisition/sequences should always be integrated into these exams since they are necessary to assess the presence of fibrosis of the papillary muscles and lateral wall, which represents the second factor showing strong association with arrhythmias. Fibrosis in MAD is believed to be the consequence of the stretching of the myocardium secondary to the changes in morphology and dynamics of the annulus of the mitral valve . This specific physiopathology explains also why the myocardium at this level is thinner than in the rest of left ventricle.
Dual-energy CT reconstructions (especially mono-energetic reconstructions at low energies and iodine-maps) can help highlight these often small areas of late enhancement. For this reason, cardiac CT with this type of scanner can be a valid alternative to MRI, especially where this is not available in short delay.
The outcome of MAD depends on the association with ventricular arrhythmias as well as on mitral valve regurgitation if also prolapsus is present.
MAD is an often unknown and overlooked anomaly that is, on the contrary, detectable on cardiac CT and MRI and important to diagnose since it can be associated to malignant arrhythmias and sudden cardiac death.
 Bennett S, Thamman R, Griffiths T, Oxley C, Khan JN, Phan T, Patwala A, Heatlie G, Kwok CS (2019) Mitral annular disjunction: A systematic review of the literature. Echocardiography 36:1549–1558
 Lee APW, Jin CN, Fan Y, Wong RHL, Underwood MJ, Wan S (2017) Functional Implication of Mitral Annular Disjunction in Mitral Valve Prolapse: A Quantitative Dynamic 3D Echocardiographic Study. JACC Cardiovasc Imaging 10:1424–1433
 Dejgaard LA, Skjølsvik ET, Lie ØH, et al (2018) The Mitral Annulus Disjunction Arrhythmic Syndrome. J Am Coll Cardiol 72:1600–1609
 Marra MP, Basso C, De Lazzari M, et al (2016) Morphofunctional abnormalities of mitral annulus and arrhythmic mitral valve prolapse. Circ Cardiovasc Imaging 9:1–10
 Naoum C, Blanke P, Cavalcante JL, Leipsic J (2017) Cardiac Computed Tomography and Magnetic Resonance Imaging in the Evaluation of Mitral and Tricuspid Valve Disease: Implications for Transcatheter Interventions. Circ Cardiovasc Imaging 10:1–17
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