Fig. 2
From: Role of strain echocardiography in patients with hypertension
Myocardial strain and strain rate. Simple diagram showing the principle of strain and strain rate. Strain is expressed as a fractional length change, where shortening is a negative value and lengthening a positive value. Strain is calculated as the difference (ΔL) of the initial (L0) and the final distance (L) between two points divided by the initial distance. Strain rate is the deformation per unit time (Δt), and derives from the ratio between the velocity variation and the initial distance between two points