The Dual Nature of Mitral Annular Disjunction: Normal Variation or Pathological Precursor?

The concept of mitral annular disjunction (MAD) has garnered significant attention due to its potential clinical implications. MAD refers to a spatial displacement of the hinge point of the mitral valve leaflets. Initially described over 150 years ago, MAD has evolved from being an anatomical curiosity to a potential marker of pathological processes, especially in the context of mitral valve prolapse and arrhythmic syndromes. Two distinct types of MAD can be identified: atrial (a-MAD), characterized by annular displacement toward the left atrium and ventricular (v-MAD), characterized by annular displacement toward the left ventricle. The prevalence of a-MAD varies based on the patient population studied, the imaging techniques employed, and the specific definition of a-MAD used and ranges between 7.2-8.7% to 96.0%. The prevalence of v-MAD is approximately 25%. It is critical to note that disjunction is nonuniformly distributed around the circumference of the junction supporting the mural leaflet of the valve and is also present in the commissural areas, interspersed with alternating segments of tissue that do not exhibit disjunction. Clinically, a-MAD may be associated with mitral valve prolapse, ventricular arrhythmias, and sudden cardiac death, underscoring its importance in risk stratification and management. V-MAD, while less studied, raises intriguing possibilities about its role in mitral valve dynamics and its possible contribution to pathological processes. Through a detailed review of existing literature and clinical observations, this article seeks to elucidate the spectrum of MAD's presentations, its diagnostic challenges, and its potential impact on patient outcomes.