Scanning electron microscopy of the human myocardium

Area of Science:

• Cardiovascular Pathology
• Microscopy Techniques
• Human Anatomy

Background:

• Fixation of human hearts for microscopy is challenging due to in vivo perfusion impossibility and limited availability of fresh tissue.
• Post-mortem examination offers a viable alternative for studying cardiac ultrastructure if performed promptly after demise.

Purpose of the Study:

• To explore the utility of post-mortem human hearts for detailed ultrastructural analysis using scanning electron microscopy (SEM).
• To compare cardiac morphology in normal versus hypertensive hearts using SEM.
• To investigate the impulse conducting system of the heart via SEM.

Main Methods:

• Perfusion fixation of post-mortem hearts (within 2 hours of death) with 2.5% glutaraldehyde.
• Scanning electron microscopy (SEM) utilizing the osmium-thiocarbohydrazide-osmium (O-T-O) method.
• Light microscopy (LM) for correlative analysis.

Main Results:

• Good correlation observed between LM and SEM findings.
• SEM revealed step-wise myofibril transection, identifying Z and M bands, mitochondria, and myofilaments.
• SEM demonstrated differences in vascularity and para-arterial fibrosis in hypertensive myocardium.
• SEM successfully identified pacemaker cells in the sinoatrial (SA) and atrioventricular (AV) nodes.

Conclusions:

• Prompt post-mortem examination enables high-resolution SEM of human cardiac ultrastructure.
• SEM provides valuable insights into myocardial differences between normal and hypertensive states.
• SEM is effective for visualizing the detailed morphology of the cardiac impulse conducting system.