Background: Echocardiographic estimation of global left ventricular (LV) function is subjective and time consuming. Our aim was to develop a novel approach for assessment of global LV function from 2-dimensional echocardiographic images
Methods: Novel computer software for tissue tracking was developed and applied as follows: digital loops were acquired from apical 2-, 3-, and 4-chamber views and a line was loosely traced along the LV endocardium at the frame wherein it was best defined. Around this line, the software selected natural acoustic markers moving with the tissue. Automatic frame-by-frame tracking of these markers during the heart cycle yielded a measure of contractility along the selected region of interest. Global longitudinal strain (GLS) and GLS rate (GLSR) were calculated for the entire U-shaped length of LV myocardium (basal, mid, and apical segments of 2 opposite walls in each view). To test this software, computer-derived GLS and GLSR were analyzed by a nonechocardiographer, blinded to the echocardiographic interpretation, in 27 consecutive patients after myocardial infarction (MI) (age 64.4 +/- 12.9 years; 19 men; mean wall-motion score index of 1.79 +/- 0.44) and compared with those obtained in 12 consecutive control patients (age 59.0 +/- 9.7 years; 8 women), with a normal echocardiographic study.
Results: GLS and GLSR, averaged from the 3 apical views, differed significantly in patients post-MI compared with control patients (GLS -14.7 +/- 5.1% vs -24.1 +/- 2.9% and GLSR -0.57 +/- 0.21/s vs -1.02 +/- 0.09/s for patients post-MI vs control patients, respectively; both P <.0001). There was a good linear correlation between the wall-motion score index and the GLS and GLSR (R = 0.68 and R = 0.67, respectively; both P <.0001). A cut-off value for GLS of -21% had 92% sensitivity and 89% specificity and a cut-off value for GLSR -0.9/s had 92% sensitivity and 96% specificity for the detection of patients post-MI.
Conclusions: GLS and GLSR are novel indices for assessment of global LV function from 2-dimensional echocardiographic images. Early validation studies with the method are suggestive of high sensitivity and specificity in the detection of LV systolic dysfunction in patients post-MI.