Myocardial rotation but not circumferential strain is transducer angle dependent: a speckle tracking echocardiography study.

Background: Doppler derived strain analysis has been shown to be angle dependent. Speckle tracking analysis using 2D echocardiographic images is thought to provide angle independent parameters of regional and global myocardial function. This study sought to evaluate whether myocardial circumferential strain and rotation derived from automatic frame-by-frame tracking of natural acoustic markers is dependent on angulation of the transducer.

Methods: In 48 healthy volunteers (mean age 36 ± 3 years, 20 male) parasternal short-axis views at apical level were obtained as follows: at the standard parasternal position (5th intercostal space) with a most possible circular short-axis image of the left ventricle (angulation 1), at an angulation of the transducer by 20° from this standard position to the apex (angulation 2) and at an angulation of the transducer by 20° to the base of the left ventricle (angulation 3). Using an automatic frame-by-frame tracking system of natural acoustic echocardiographic markers (EchoPAC, GE Ultrasound, Horton, Norway) circumferential strain and rotation were calculated for six segments within a short-axis circumference.

Results: Image quality was sufficient for acquisition and analysis of images at all three-transducer angulation in 90% of the analyzed segments. Rotation was measured to be 7.7 ± 1.2° at angulation 1, 2.7 ± 0.9° at angulation 2 and 4.3 ± 1.1° at angulation 3 (p < 0.05). Average circumferential strain data was found to be -27.2 ± 5.1% at angulation 1, -26.5 ± 3.8% at angulation 2 and 28.9 ± 4.4% at angulation 3 (p = 0.287).

Conclusion: Circumferential strain analysis is not dependent on transducer angulation. In contrast, determination of myocardial rotation is dependent on transducer angulation. Therefore, accurate transducer angulation has to be taken care of if rotation measurements are performed.