8 - Mitral Annular Disjunction as an Anatomical Variant of Mitral Valve Anatomy in Autopsied Material

Poster Board Number: 8
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Abstract Body : Introduction and Objective
Mitral annular disjunction (MAD) consists of a perceptible separation between the left atrial wall-mitral valve junction and the top of the left ventricular wall. Research related to MAD has focused on the association between MAD and mitral valve prolapse, arrhythmias and sudden cardiac death. Only few studies noted MAD in healthy patients.
In our study, we would like to present three anatomic variants of mitral valve leaflets attachment assessed in autopsied healthy human hearts.
Materials and Methods
This study was approved by the Bioethical Committee of the Jagiellonian University, Cracow, Poland. The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki.
This study was performed in the Department of Anatomy of the Jagiellonian University Medical College in Cracow. A total of 224 autopsied human hearts (21.9% female) with a mean age of 47.9 ± 17.6 years were analyzed. We defined the type of hinge line of the mitral valve leaflet: no-MAD, atrial MAD, ventricular MAD. We have described the morphological features of MAD and the mitral valve.
Results
No-MAD was found in 153 (68,3%) hearts. Atrial MAD was found in 26 (11.6%) cases and ventricular MAD in 45 (20.1%) cases. Atrial and ventricular MAD were observed in similar frequency in men and women. The mean height of the atrial MAD was 2.9 (2.5 - 3.3) mm behind P1, 3.3 (2.6 - 4.0) mm behind P2 and 2.7 (2.5 - 3.0) mm behind P3. The mean height of ventricular MAD was 4.1 (3.5 - 5.3) mm above P1, 4.4 (3.8 - 5.4) mm above P2, 3.0 (2.9 - 4.0) above P3, 4.1 (4.0 - 4.2) mm above P1/P2 and 4.3 (4.3 - 4.3) above P2/P3. In both MAD’s types, the greatest height was in P2 scallop compared to P1 and P3, but it was statistically insignificant. In 16 (61.5%) cases, atrial MAD was present behind one scallops of posterior mitral valve leaflet. As well as ventricular MAD was frequently found in one scallop: in 36 hearts (80.0%). Atrial MAD was most frequently located only in the P1 part of the mitral annulus (10 hearts) 35.7%. Most ventricular MADs were located only in the P2 part of the mitral annulus: (35 hearts) 77.8%. It is interesting to note the simultaneous presence of atrial and ventricular MAD, which we found in one case. The aorto-mural diameter and intracommisural diameter of the mitral valve were significantly smaller in hearts with ventricular MAD than in the general population.
Conclusion
The most common type of mitral valve leaflets insertion is normal mitral leaflets pattern (no-MAD), almost in 70% of heart specimens. The prevalence of atrial MAD is 11.6% and ventricular MAD is 20.1%. Both types of MAD were most commonly observed in the region of one scallop: atrial MAD behind P1, and ventricular MAD above P2.
Significance
In our study, we defined and presented the prevalence and morphologic description of three types of mitral valve leaflets insertion in examined autopsy healthy human hearts. The strength of our anatomic analysis is the exclusion of a potential mistake from overdiagnosed MAD, so called „pseudo-MAD”. Furthermore, our detailed study has shown that we can find pronounced variations of mitral insertion along the annular circumference not only from heart to heart but also within the same heart. If we do not evaluate the possibility of MAD along the entire annulus, we cannot notice the MAD. We hope that our observations may encourage novel investigations to further analysis and to confirm our results. We point out the need for definitions of clinically significant MAD.