This is a strain carpet map — the same transmural (depth) vs. time representation cardiologists use to read tagged/feature-tracked cine MRI strain curves, rebuilt here as a native 2D field instead of a 3D deforming ring.
Depth f ∈ [0,1]: 0 = endocardium, 1 = epicardium
Reference radius: r0(f) = R_endo0 + f·(R_epi0 − R_endo0)
Deformed radius: r(f,p) = r_endo(p) + f·(r_epi(p) − r_endo(p))
Local circumferential stretch: λcc(f,p) = r(f,p) / r0(f)
Local strain: Ecc(f,p) = (λcc − 1) · 100%
Local twist: θ(f,p) = θ_peak(p) · (1 − f)
The top panel is a heatmap over the full (depth, phase) plane: every column is one instant of the cycle, every row a transmural depth, and colour is the local circumferential strain at that depth and instant — computed independently for all 64×64 samples, not read off any 3D mesh. The horizontal cursor marks the live phase. The bottom panel is a 1D radial cross-section at that instant: the deformed vs. reference wall radius as a function of depth, with tag-line markers coloured by their own local strain and a twist-angle trace.
- Peak contractility — endocardial inward displacement at peak systole; sets the depth-dependent strain gradient seen in the carpet (endocardium always strains more than epicardium here, since kEndo > kEpi).
- Peak transmural twist — endocardial rotation relative to epicardium at peak systole; visualised as the twist trace in the profile panel, always zero at the epicardial edge.
- Phase slider / Play — scrub or auto-play one cardiac cycle; the cursor sweeps the carpet left to right.
Clinical relevance: a transmural strain gradient (endocardium contracting more than epicardium) and reduced twist are early markers of regional or subclinical myocardial dysfunction, often visible before ejection fraction changes.