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Is Congenital Muscular Mitral-Aortic Discontinuity Another Feature of Obstructive Hypertrophic Cardiomyopathy? A

Monica De Gaspari1, Mariachiara Mazzucato1, Maria Bueno Marinas1

  • 1Department of Cardiac, Thoracic, Vascular Sciences and Public Health, University of Padua, Padua, Italy; Cardiovascular Pathology Unit, Azienda Ospedaliera, Padua, Italy.

Laboratory Investigation; a Journal of Technical Methods and Pathology
|June 11, 2023
PubMed

Insights

Pathologic analysis of hypertrophic cardiomyopathy (HCM) hearts did not confirm a "muscular mitral-aortic discontinuity." Instead, an extension of left atrial myocardium was observed, decreasing with age.

Area of Science:

  • Cardiovascular Pathology
  • Cardiac Anatomy
  • Inherited Cardiac Diseases

Background:

  • Hypertrophic cardiomyopathy (HCM) is a genetic heart muscle disease associated with sudden cardiac death and heart failure.
  • Surgical observations in obstructive HCM have suggested a
  • muscular mitral-aortic discontinuity
  • .

Purpose of the Study:

  • To pathologically validate the existence of a
  • muscular mitral-aortic discontinuity
  • in hypertrophic cardiomyopathy (HCM).
  • To characterize the mitral-aortic continuity in HCM hearts through gross and histologic examination.

Main Methods:

  • Analysis of 30 HCM hearts and 30 age- and sex-matched controls from a cardiovascular pathology registry.
  • Gross and histologic examination of the mitral valve apparatus and mitral-aortic continuity.
  • Comparison of findings between HCM and control groups.

Main Results:

  • A myocardial layer overlapping the mitral-aortic fibrous continuity was present in 97% of HCM hearts, identified as left atrial myocardium.
  • Features such as septal bulging, endocardial fibrous plaque, and anterior mitral leaflet thickening were noted in HCM.
  • The length of the overlapping myocardial layer showed a negative correlation with age and anterior mitral leaflet length, but did not differ between HCM and controls.

Conclusions:

  • Pathologic findings do not support the existence of a
  • muscular mitral-aortic discontinuity
  • in obstructive HCM.
  • An extension of left atrial myocardium overlapping the intervalvular fibrosa is consistently observed.
  • The length of this myocardial extension decreases with age, potentially due to left atrial remodeling, emphasizing the importance of detailed gross examination.

Keywords:
hypertrophic cardiomyopathyleft ventricular outflow tractmitral valvemitral-aortic continuity

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