Anupraiwan, Orawan

Introduction: Hypertrophic cardiomyopathy (HCM) is associated with excessive left ventricular (LV) hypertrophy (LVH), myocyte disarray and expansion of interstitial collagen. These factors alter mechanical properties of the myocardial tissue. Intrinsic velocity propagation (iVP) of myocardial stretch is a new validated measure of myocardial elasticity. Hypothesis: iVP in left ventricular (LV) myocardium of patients with HCM will be increased compared to normal subjects. Methods: We studied prospectively 100 subjects: 42 with HCM (age 57 ± 14 years; 79% with asymmetric septal LVH) and 58 normal controls without cardiovascular disease (age 48 ± 13 years). Patients had comprehensive transthoracic echocardiography and cardiac magnetic resonance imaging (MRI; n=29). iVP was measured throughout the LV myocardium during late diastole using ultra-high frame rate tissue Doppler imaging (350-460 fps) (6 LV walls, 3 standard apical views). Chamber stiffness (CS) was evaluated from end-diastolic pressure-volume relationship (EDPVR) estimated noninvasively by the single-beat method (EDP=αV β ). End-diastolic pressure (EDP) was estimated from E/e’. Results: LV ejection fraction was normal in both groups (HCM: 68 ± 7%; Controls: 65 ± 5%). Myocardial stiffness by iVP was markedly higher in HCM vs. controls (Fig.A, left panel). This was confirmed by EDPVRs, which were steeper and shifted leftward (Fig. B, left). The slope (β, load-independent) of EDPVR and CS (dP/dV) were higher and LV capacitance (V 30 , estimated volume at 30 mmHg EDP) was lower in HCM (Fig. B, right) and correlated significantly, though weakly, with iVP (β: r = 0.41; CS dP/dV: r = 0.48; EDP: r = 0.61; p<0.002 for all). Patients with apical variant had lower levels of global iVP compared to patients with predominant septal LVH and diffuse concentric LVH (Fig. A, right). Conclusions: Myocardial stiffness measured noninvasively by the intrinsic wave method is highly abnormal in HCM. This novel approach allows mapping of myocardial elasticity of the entire left ventricle and shows promise to become a clinical tool for evaluation of patients with diastolic tissue abnormalities.

Introduction: Intrinsic wave propagation is a novel approach to measure myocardial stiffness (MS) as validated in animal studies. Aims and Hypothesis: 1) To compare MS measured by the wave method with chamber stiffness (CS) derived from noninvasively estimated end-diastolic pressure-volume relationship (EDPVR) in patients; 2) To test the hypothesis that MS is superior to CS for predicting outcomes in patients with cardiac amyloidosis (CA). Methods: Prospective study in 56 patients with amyloidosis (CA: 38, noncardiac amyloidosis, NCA: 18; 90% AL-type; age 63 ± 10 yrs; ejection fraction 57 ± 11%) and 36 normal subjects (age 49 ± 13 years). Intrinsic velocity propagation of myocardial stretch (iVP), a measure of MS, was measured by ultra-high frame rate (250-465Hz) tissue Doppler imaging. Left ventricular (LV) EDPVR were reconstructed using the noninvasive single-beat method (Fig.A). Stiffness coefficients (α, β, load-independent) and CS (dP/dV) were calculated. End-diastolic pressure (EDP) was estimated from E/e’. Adverse events at follow-up (death, heart failure, stroke, significant arrhythmia) were recorded. Results: iVP was higher in CA compared to NCA and controls, indicating higher MS (Fig. B). This was confirmed by EDPVR, which were steeper and shifted leftward (Fig. A). The slope (β) of EDPVR and CS (dP/dV) were higher and LV capacitance (V 30 , volume at 30 mmHg) was lower in CA (Fig. A) and correlated with iVP (β: r = 0.59; CS dP/dV, r = 0.43; EDP, r = 0.61; all p<0.0001). Patients with higher LV thickness (r = 0.66), lower LV longitudinal strain (r = -0.57) and elevated NT-proBNP (r = 0.69) had higher iVP. At follow-up (median 2.5 years), after adjusting for relevant confounders, an iVP >2.7 m/s was strongly associated with excess events (p<0.0001; Fig. C) and was superior to measures of CS (dP/dV: p = 0.28; β >6.5: p = 0.03; Fig. D). Conclusions: Myocardial stiffness by intrinsic wave method shows similar findings to chamber stiffness by EDVPR, but is more strongly related to outcomes in patients with amyloidosis.