The complement system is activated in a biphasic pattern after coronary artery bypass grafting.

Area of Science:

• Immunology
• Cardiovascular Surgery
• Inflammation

Background:

• The complement system plays a crucial role in the inflammatory response post-coronary artery bypass grafting (CABG).
• Understanding the precise pathways of complement activation and deactivation after cardiac surgery remains unclear.
• This study aimed to elucidate the routes of complement activation following uncomplicated CABG.

Purpose of the Study:

• To analyze the specific pathways involved in complement activation after uncomplicated coronary artery bypass grafting.
• To investigate the temporal dynamics of complement activation and deactivation post-cardiac surgery.

Main Methods:

• Measurement of complement components and activation products in 20 adult patients undergoing elective CABG.
• Serial sampling from intensive care unit admission through postoperative recovery.

Main Results:

• Complement activation exhibited a biphasic pattern post-CABG.
• Initially (0-8 hours), activation involved classical/lectin and alternative pathways, leading to terminal complement complex formation.
• Later (post-8 hours), activation was primarily via the classical/lectin pathway without alternative pathway augmentation or terminal complex formation, suggesting engagement of inhibitory mechanisms.

Conclusions:

• Complement activation following cardiac surgery is a complex, biphasic process.
• Inhibitory mechanisms appear to be engaged approximately 8 hours postoperatively, modulating the complement response.