Mechanical discoordination rather than dyssynchrony predicts reverse remodeling upon cardiac resynchronization

Area of Science:

• Cardiology
• Biomedical Engineering
• Medical Imaging

Background:

• Many patients do not respond to cardiac resynchronization therapy (CRT) despite current selection criteria.
• Mechanical discoordination, defined as opposing strain within the left ventricular (LV) wall, may be a better predictor of CRT response than mechanical dyssynchrony.

Purpose of the Study:

• To investigate whether mechanical discoordination predicts reverse LV remodeling after CRT more accurately than mechanical dyssynchrony.
• To compare the predictive value of internal stretch fraction (ISF) against traditional dyssynchrony indices for CRT outcomes.

Main Methods:

• MRI tagging was used to assess circumferential strain in CRT candidates and healthy controls.
• Mechanical discoordination (ISF) and dyssynchrony indices were derived from strain data.
• Left ventricular volumes and ejection fraction were measured before and after CRT to assess remodeling.

Main Results:

• Patients with higher ISF (>0.4) showed significantly greater reduction in LV end-systolic volume (LVESV) after CRT compared to those with lower ISF.
• Internal stretch fraction (ISF) was significantly different between CRT responders and non-responders, unlike traditional dyssynchrony measures.
• CRT significantly improved LV remodeling in responders, characterized by decreased LVEDV and LVESV and increased LVEF.

Conclusions:

• Mechanical discoordination, quantified by ISF, is a superior predictor of reverse LV remodeling following CRT compared to mechanical dyssynchrony.
• Discoordination, rather than dyssynchrony, may better reflect the recruitable contractile reserve targeted by CRT.
• These findings suggest ISF could refine patient selection for CRT to improve treatment efficacy.