Mitral Annular Disjunction And Arrhythmic Syndrome
Mitral annular disjunction (MAD) is a less recognised disease related to structural abnormality of heart in mitral annulus ring. In this disease, there become a separation between mitral valve and atrial valve. Therefore ventricular attachment allows hypermobility of the MV apparatus. While considering echocardiography, Mitral annular disjunction is less recognised. Mitral annular disjunction may also lead to Paradoxical annular unsaddling. There are also chances to getting arrhythmic syndrome if there will be tension in Mitral valvular apparatus (1). Mitral valve hinge place get displace from ventricular myocardium. The addition of disconnection arc extent and the highest disconnection length is being evaluated to determine a somewhat stronger summary of the detachment recognised in Mitral annular disjunction measurement in which a disjunction index is also being use. Another technique for Mitral annular disjunction detection is cardiac magnetic resonance imaging, which can also disclose arrhythmogenic foci of myocardial fibrosis/scarring.
Liza (Pseudo name) is a 24 year old woman who is suffering from “Marfan syndrome”. Patient also has a history of aortic valve replacement as well as of root repair which presented after syncopal episode. In last year she faced prodromal symptoms of tachycardia and palpitations. However, in her medical history it is also found that she do not have any past history of arrhythmia. Sinus rhythm as primary atrioventricular block as well as biatrial enlargement while focusing on previous electrocardiogram. In the first clinical diagnosis after being admit, it is found that her ECG is constant and regular with atrial fibrillation. For evaluating further arrhythmia monitoring, a loop recorder was placed in her body. There is no ventricular arrhythmia being noted by loop recorder. Mitral Annular Disjunction And Arrhythmic Syndrome
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The occurrence of MAD in Marfan syndrome is not highly evaluated and researched yet however, association of MAD with MPV unfortunately enhance the situation (2). The Marfan syndrome association with MVP is variable from the range of 27% to 80%. These factors surge with age. Marfan syndrome is also linked with mutations in fibrillin-1 on chromosome however, it may also cause because of inactivation mutations in transforming critical factor beta (TGF- β). Mitral valve prolapse is usually measured as sporadic however it is the most used approach for numbers of acquired and genetic disorders. It further reduces the joining valve tissue which causes to leaflet elongation, degeneration and thickening (3). As same as MVP, mitral annular disjunction is also linked with arrhythmic syndrome by higher occurrence of ventricular arrhythmia independent of Mitral valve prolapse. Major affecting factor of ventricular arrhythmia are low age, papillary muscle fibrosis, earlier syncope, less developed ventricular contraction in the posterolateral wall measured by cardiovascular magnetic resonance imaging. A 2-hit model or Knudson hypothesis is a hypothesis in which the fundamental arrhythmogenic genetic substrate make myocyte coupling weak. It is further exacerbated by higher stress from MVP and mitral annular disjunction (4).
Throughout the cardiac cycle, the mitral annulus’ normal saddle-shaped form undergoes complex structural modifications to produce a uniform dispersion of mechanical forces. In Mitral annular disjunction, there has been evidence of annular flatness and dilatation during systole, which increases the strain on the leaflets and chordae. In our client with MVP and MAD, strain tracing over the papillary muscle illustrates the paradoxical stress on the valve apparatus throughout systole (5). Papillary muscle strain measurements have been utilised in the past to investigate its significance in relation to various MR etiologies, frequently with significantly varied protocols. The first asymmetric stress is thought to be imposed by the respective prolapsing leaflet, according to the researchers.
Discussion
We apply a strain tracing which involves the lateral wall of the left ventricle to show that the lateral wall segments decrease, the papillary muscle lengthens when stress is raised. The paradoxical annular “unsaddling” of these altered conformational changes is described by a physiological dissociation of the annular and ventricular motions. Scarring/fibrosis in the papillary muscles and basal lateral left ventricular myocardium, which works as a nidus for arrhythmia, is likely due to higher mechanical stress on the leaflets and chordae. Mitral Annular Disjunction And Arrhythmic Syndrome
For MAD, there are no formal diagnostic or therapy criteria. Without providing specifics, ambulatory ECG observing and sequential echocardiographic monitoring is recommended. At this moment, the role of pharmaceutical and device therapy in these depressive patients is unknown, but it should be a focus of future research (6). However, focused ablation has been successfully employed to lessen the burden of premature ventricular contractions in a patient with arrhythmogenic bileaflet MVP syndrome. Surgical correction could have a role in preventing subsequent arrhythmic risk, according to the current postulated mechanism of the arrhythmic syndrome. Annular-ventricular decoupling may remain if MAD is not addressed, affecting long-term surgical outcomes. In light of this, several institutions have utilised a modified mitral valve repair procedure. Similarly, MitraClip is a trans catheter mitral valve repair system that targets leaflet disease.
Transthoracic echocardiography may detect various mitral annular discontinuities on the parasternal long-axis image. This area of discontinuity allows the mitral apparatus’s atrium-valve leaflet connection to migrate externally in reference to the atrial component of the ventricular wall throughout ventricular systole and inwards during ventricular diastole during the ventricular contraction (7). In the parasternal long-axis perspective, the MAD length was usually assessed at the endsystolic phase. Mitral annular disjunction can also be identified with cardiac magnetic resonance imaging (CMR). In midventricular systole, mitral annular disjunction can be seen on the apical 4 chamber. Mitral annular disjunction is related with curving of the mitral annulus. The extent of the MAD and the intensity of twisting have a linear relationship.
Also with anterior leaflet of the MV and the right and left fibrous trigones, the aortic valve develops fibrously. The annulus in this area is fibrous and less vulnerable to dilation. In people with mitral regurgitation, the left over two-thirds of the annulus are made up of muscles and expand easily (MR). As a result, mitral annular displacement can be detected mostly in the posterior leaflet. This portion of the mitral annulus could be compromised due to mechanical strain. Starting with Mitral annular disjunction diagnosis, transthoracic echocardiography (TTE) demonstrating the usual curling of the left ventricle lateral wall, which is a visual sign linked with the existence of annulus discontinuity, is the simplest and most widely accessible approach (8). In initial systole, the annular function ensures that the mitral valve is “waterproofed.” The usual annulus is active throughout this stage, including anteroposterior contraction and enhanced annular length, resulting in an enhanced annular saddle form.
Mitral valve prolapse can cause to mitral valve regurgitation, which is when blood leaks backward through the valve. Whenever the flaps (leaflets) of the heart’s mitral valve bulge (prolapse) like a glider into the hearts left upper chamber (left atrium) as the ventricular contraction, this is also considered as mitral valve prolapse. Mild mitral valve regurgitation does not normally create any issues. The heart has to work complexly to pump blood in the body when mitral valve regurgitation worsens (9). The left lower chamber of the heart can enlarge as a result of the strain on the heart. It’s possible that the heart muscle will weaken. Mitral annular disjunction, found in floppy valve, is an anatomical deviation of the usual morphologic properties of the mitral annulus.
If range of motion of the mitral apparatus is a factor in collapse, it is most likely caused by factors other than the so-called discontinuity. MAD has been linked to ventricular arrhythmia and abrupt heart mortality in the past. If a person’s mitral annular disjunction is discovered by chance during an echocardiogram, we must look for symptoms and a background of arrhythmia (10)Mitral Annular Disjunction And Arrhythmic Syndrome.
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Conclusion
Mitral annular disjunction, which may be observed on cardiac imaging and is linked with ventricular arrhythmias and sudden cardiac death, seems to be prevalent in myxomatous mitral valve disease and mitral valve collapse. During presurgical imaging, the occurrence of mitral annular disjunction must be verified on a regular basis. Otherwise, regardless of the existence of MVP, mitral annular disjunction may constitute an arrhythmogenic entity in and of itself. As a result, we should do an echocardiogram while having mitral annular disjunction in mind. To determine whether there is a causal mechanistic relationship between mitral annular disjunction and arrhythmic MVP or severe MR, more prospective researches are required.
References
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Konda T, Tani T, Suganuma N, Nakamura H, Sumida T, Fujii Y, et al. The analysis of mitral annular disjunction detected by echocardiography and comparison with previously reported pathological data. Journal of Echocardiography. 2017 Aug 10;15(4):176–85.
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Dejgaard LA, Skjølsvik ET, Lie ØH, Ribe M, Stokke MK, Hegbom F, et al. The Mitral Annulus Disjunction Arrhythmic Syndrome. Journal of the American College of Cardiology. 2018 Oct;72(14):1600–9.
Putnam AJ, Kebed K, Mor-Avi V, Rashedi N, Sun D, Patel B, et al. Prevalence of mitral annular disjunction in patients with mitral valve prolapse and severe regurgitation. The International Journal of Cardiovascular Imaging. 2020 Mar 27;36(7):1363–70.
Mantegazza V, Tamborini G, Muratori M, Gripari P, Fusini L, Italiano G, et al. Mitral Annular Disjunction in a Large Cohort of Patients With Mitral Valve Prolapse and Significant Regurgitation. JACC: Cardiovascular Imaging. 2019 Nov;12(11):2278–80. Mitral Annular Disjunction And Arrhythmic Syndrome