Left ventricular global strains by linear measurements in three dimensions: interrelations and relations to age, gender and body size in the HUNT Study

BACKGROUND: Strain is a relative deformation and has three dimensions, in the left ventricle (LV) usually longitudinal (ε(L)), transmural (ε(T)) and circumferential (ε(C)) strain. All three components can be measured generically by the basic systolic and diastolic dimension measures of LV wall length, wall thickness and diameter. In this observational study we aimed to study the relations of normal generic strains to age, body size and gender, as well as the interrelations between the three strain components. METHODS: Generic strains derived from dimension measures by longitudinal and cross-sectional M-mode in all three dimensions were measured in 1266 individuals without heart disease from the Nord-Trøndelag Health Study. RESULTS: The mean ε(L) was −16.3%, ε(C) was −22.7% and ε(T) was 56.5%. Normal values by age and gender are provided. There was a gradient of ε(C) from the endocardial, via the midwall to the external level, lowest at the external. All strains decreased in absolute values by increasing body surface area (BSA) and age, relations were strongest for ε(L). Gender differences were mainly a function of BSA differences. The three strain components were strongly interrelated through myocardial incompressibility. CONCLUSIONS: Global systolic strain is the total deformation of the myocardium; the three strain components are the spatial coordinates of this deformation, irrespective of the technology used for measurement. Normal values are method-dependent and not normative across methods. Interrelation of strains indicates a high degree of myocardial incompressibility and that longitudinal strain carries most of the total information.