Heterogeneous Myocardial Adaptation to Pressure Overload Reveals a Spared, Vulnerable Segment Identified by...

Area of Science:

• Cardiovascular Research
• Medical Imaging
• Physiology

Background:

• Cardiac adaptation to chronic pressure overload is typically viewed as uniform concentric hypertrophy.
• Emerging evidence indicates spatially heterogeneous myocardial responses.
• Understanding these regional differences is crucial for comprehending ventricular dysfunction.

Purpose of the Study:

• To systematically map regional and temporal adaptation patterns of the left ventricle (LV) under experimental pressure overload.
• To test the hypothesis that distinct regional adaptation phenotypes contribute to local functional differences and global ventricular dysfunction.
• To utilize high-resolution multiparametric cardiac MRI for detailed LV analysis.

Main Methods:

• Thirty-seven mice underwent transverse aortic constriction (TAC) surgery and were monitored for 7 weeks.
• High-resolution multiparametric cardiac MRI (cine, T1-mapping, T2-mapping) was performed longitudinally.
• A 200-sector LV segmentation allowed quantitative regional analysis of wall thickness, fractional shortening (FS), and relaxation times.

Main Results:

• All TAC animals developed global LV hypertrophy, with increased LV mass.
• A significant proportion (49%) exhibited spared hypertrophy (SH) in a discrete basolateral LV segment, failing to hypertrophy despite pressure elevation.
• SH regions showed markedly reduced regional FS and were associated with lower global ejection fraction and LV dilatation; distinct T1-mapping signatures were observed in hypertrophied versus SH sectors.

Conclusions:

• Pressure overload induces diverse regional myocardial adaptations, not uniform hypertrophy.
• Failure to hypertrophy in specific myocardial regions identifies territories prone to early dysfunction and subsequent global decline.
• Multiparametric MRI is a valuable translational tool for detecting regional vulnerability in pressure-overload cardiac remodeling and guiding early interventions.