Exercise Cardiovascular Magnetic Resonance Work-Volume Loop Model in Heart Failure with Preserved Ejection Fraction

Area of Science:

• Cardiology
• Medical Imaging
• Physiology

Background:

• Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome with heterogeneous causes, including overt (stage C) and exercise-induced forms.
• Impaired cardiac compliance is recognized, but contractile reserve remains less understood.
• Differentiating exercise-induced HFpEF from non-cardiac dyspnea (NCD) is challenging, especially with limited patient exercise capacity.

Purpose of the Study:

• To develop a non-invasive analytic framework using exercise cardiovascular magnetic resonance (Ex-CMR) to derive compliance and contractile reserve metrics.
• To evaluate the utility of these metrics for differentiating NCD, exercise-induced HFpEF, and stage C HFpEF.
• To establish Ex-CMR-based reserve metrics independent of fixed exercise thresholds.

Main Methods:

• A novel non-invasive work-volume (W-V) loop model was developed using Ex-CMR data (LVEDV, LVESV, workload).
• The model's base angles (θ₁ and θ₂) quantify effort-adjusted compliance and contractile reserve, respectively.
• The model was applied retrospectively to healthy controls, NCD, exercise-induced HFpEF, and stage C HFpEF groups.

Main Results:

• All HFpEF subgroups exhibited impaired effort-adjusted compliance reserve compared to controls and NCD (p<0.0001).
• Exercise-induced HFpEF showed significantly higher effort-adjusted contractile reserve than other groups (p<0.0001).
• Stage C HFpEF demonstrated depressed contractile reserve compared to all other groups (p<0.0001).

Conclusions:

• Ex-CMR-derived W-V loop geometry effectively differentiates HFpEF subgroups.
• A universal impairment of compliance reserve is observed in HFpEF.
• A novel hypercontractile profile characterizes exercise-induced HFpEF, suggesting potential therapeutic targets.