Spatial relationship of blood vessels within the mitral isthmus line

Area of Science:

• Cardiac Anatomy
• Vascular Relationships
• Histology

Background:

• The mitral isthmus is a critical area in cardiac anatomy, particularly for understanding atrial electrophysiology and potential arrhythmogenic substrates.
• Detailed knowledge of the spatial relationship between cardiac vessels and atrial wall thickness in this region is essential for interventional procedures.

Purpose of the Study:

• To precisely map the spatial relationship of blood vessels within the mitral isthmus line.
• To determine the thickness of the left atrial wall in relation to these vessels.

Main Methods:

• Examination of 200 autopsied Caucasian adult human hearts.
• Longitudinal sectioning of the mitral isthmus line to measure myocardial thickness.
• Identification and spatial assessment of blood vessels (great cardiac vein, left circumflex artery, Marshall vein) relative to the endocardial surface, mitral annulus, and left inferior pulmonary vein ostium.

Main Results:

• Mean myocardial thickness varied across the mitral isthmus: 1.9±1.0 mm (upper), 3.0±1.5 mm (middle), and 2.7±1.3 mm (lower).
• The great cardiac vein (GCV) was present in 98.0%, left circumflex artery (LCx) in 57.0%, and Marshall vein in 35.0%.
• The LCx was frequently close to the endocardial surface (49.1% < 3 mm) and often positioned between the GCV and the left atrial endocardial surface (55.3%).

Conclusions:

• The mitral isthmus myocardium is thinnest in the upper third, with major vessels predominantly located in the middle and lower thirds.
• The close proximity of the LCx to the endocardial surface highlights its potential relevance in catheter-based interventions.
• Understanding these anatomical variations is crucial for safe and effective cardiac procedures in the mitral isthmus region.