Systolic and Diastolic Myocardial Response to Exercise in a Healthy Pediatric Cohort

Background: The aims of the present study were to evaluate the feasibility and reproducibility of color Doppler tissue imaging (DTI) and two-dimensional speckle-tracking echocardiography during semisupine cycle ergometric stress echocardiography and to establish normal myocardial systolic and diastolic left ventricular (LV) and right ventricular (RV) response to exercise in children.

Methods: This was a single-center prospective study of 62 healthy children (35 girls). The median age was 14 years (range, 8-19 years). A stepwise semisupine cycle ergometric protocol was used. Color DTI peak systolic (s') and peak diastolic (e') velocities and myocardial acceleration during isovolumic contraction were measured in the LV lateral wall, RV free wall, and septum. Early mitral inflow Doppler (E) was measured from the apical four-chamber view, and the ratio of diastolic filling to tissue early diastolic velocity (E/e') was calculated. LV and RV longitudinal strain were measured from four-chamber apical views. LV circumferential strain was derived from the parasternal short-axis view at the midventricular level. The relationship of each parameter with increasing heart rate was evaluated at each stage of exercise.

Results: During exercise color DTI, velocities were obtained in 96% of subjects, with isovolumic contraction having the lowest feasibility among DTI measurements (89%). Strain analysis was measurable in 87% of subjects, with LV longitudinal strain measured in 98% of the subjects compared with 93% for circumferential strain. RV longitudinal strain had the lowest feasibility (70%). A linear relationship was observed between heart rate and color DTI velocities, E, E/e', and myocardial longitudinal and circumferential strain. The relationship between isovolumic contraction and heart rate was exponential.

Conclusions: This study provides reference values for systolic and diastolic reserve during exercise in healthy children as measured by color DTI and two-dimensional speckle-tracking echocardiography. These data allow the evaluation of myocardial response in pediatric cardiac disease.