Complexities of Atrial Fibrosis Imaging: Exploring Relationships Between Endocardial Voltage, Extracellular Volume,...

Area of Science:

• Cardiology
• Medical Imaging
• Pathology

Background:

• Atrial fibrillation (AF) is linked to electrical abnormalities in the left atrium (LA).
• AF significantly elevates risks for myocardial infarction, stroke, and heart failure.

Purpose of the Study:

• To explore the relationship between left atrial sympathetic innervation, extracellular volume, and endocardial voltage in a canine model of atrial fibrosis.
• To correlate in vivo imaging findings with post-mortem histological assessment of LA tissue fibrosis.

Main Methods:

• Hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) was used in 9 canines.
• Atrial pacing induced fibrosis in 6 animals; imaging and voltage mapping were performed before and after pacing.
• Left atrial fibrosis was quantified post-mortem using Masson's trichrome staining.

Main Results:

• Pacing increased left ventricular and left atrial sympathetic innervation and extracellular volume.
• Interstitial fibrosis increased in the left atrium.
• No significant correlation was found between fibrosis extent and bipolar voltage or MRI measures; a weak negative correlation existed with unipolar voltage.

Conclusions:

• Mild to moderate left atrial interstitial fibrosis may exist before impacting LA voltage maps.
• Positron emission tomography (PET) shows potential for early detection of atrial fibrillation.