This paper theoretically analyzes how the pulsive Lamb wave triggered by aortic‑valve closure propagates through the interventricular septum—a viscoelastic plate surrounded by blood. Starting from the Rayleigh‑Lamb dispersion relation, the authors derive an “easy‑to‑use” dispersion formula in the long‑wavelength limit that contains the universal constant 1/√3. The new closed‑form expression replaces complex, numerically optimized dispersion relations with a concise approximation.
Applied to high‑spatio‑temporal‑resolution ultrasonic phase‑tracking data from healthy subjects, the formula precisely reproduced the frequency dependence of phase velocity across a wide 10–90 Hz band. Moreover, it enabled unique estimation of the Voigt‑model elastic modulus and viscosity without resorting to nonlinear numerical optimization.
Because myocardial viscoelastic parameters are crucial for assessing diastolic dysfunction, fibrosis, and other pathologies—and because non‑invasive in vivo quantification methods are scarce—the proposed formula offers a straightforward, broadly applicable tool. Potential clinical uses include early lesion detection through elasticity mapping and mechanical analysis of rhythm disorders.
Article information & citation
Naoaki Bekki, Seine A Shintani. Simple Dispersion Equation Based on Lamb‑Wave Model for Propagating Pulsive Waves in Human Heart Wall. Journal of the Physical Society of Japan 84, 124802 (2015).