Left Ventricular Strain and Strain Rate during Submaximal Semisupine Bicycle Exercise Stress Echocardiography in Healthy Adolescents and Young Adults: Systematic Protocol and Reference Values

Objective: Combining stress echocardiography with strain analysis is a promising approach for early detection of subclinical cardiac dysfunction not apparent at rest. Data on normal myocardial strain and strain rate (SR) response to exercise in adolescents and young adults are contradictory and limited. The aim of this study was to propose a standardized protocol for semisupine bicycle stress echocardiography and to provide corresponding reference values of left ventricular (LV) two-dimensional speckle-tracking echocardiography (2D STE) strain and SR in adolescents and young adults. Methods: Fifty healthy adolescents and young adults (mean age, 17.8 +/- 3.2 years, 44% female) were prospectively assessed. Images were acquired at rest, low stress, submaximal stress, and during recovery. Optimal image quality for offline strain analysis was pursued, and image quality was rated. Global longitudinal strain and SR from apical four-/two-/three-chamber views and short-axis circumferential strain and SR were analyzed using vendor-independent software. Interobserver variability was assessed. Results: Strain and SR increased during progressive exercise stress. Mean LV global longitudinal strain was -20.4% +/- 1.3%, SR -1.1 +/- 0.15/sec at rest (heart rate, 79.4 +/- 12.0 beats/minute), increasing to -22.6% +/- 1.6% and -1.5 +/- 0.16/sec at low stress level (heart rate, 117.1 +/- 8.7 beats/minute) and -23.7% +/- 1.1% and -1.9 +/- 0.29/sec at submaximal stress level (heart rate, 154.2 +/- 7.0 beats/minute), respectively, returning to -20.6% +/- 1.4% and -1.2 +/- 0.16/sec postexercise (heart rate, 90.1 +/- 9.4 beats/minute). Restriction on submaximal stress level ensured adequate image quality for 2D STE strain analysis. Interobserver variability for strain was acceptable even during submaximal stress. Conclusions: This study provides a systematic, standardized protocol and corresponding reference data for 2D LV STE-derived strain and SR during semisupine bicycle exercise testing in adolescents and young adults. According to our results, global longitudinal strain and SR appear to be the most comprehensible parameters for cross-sectional studies.