Assessment of Speckle-Tracking Echocardiography-Derived Global Deformation Parameters During Supine Exercise in Children.

Exercise echocardiography is an underutilized tool in pediatrics with current applications including detecting segmental wall abnormalities, assessing the utility of global ventricular function, and measuring pulmonary hemodynamics. No prior study has applied speckle-tracking echocardiography (STE) during exercise echocardiography in children. The aim of this study was to determine the feasibility of measuring speckle-tracking-derived peak systolic velocities, global longitudinal and circumferential strain, and global strain rates at various phases of exercise. Ninety-seven healthy children underwent cardiopulmonary exercise testing using supine cycle ergometry. The exercise stress test consisted of baseline pulmonary function testing, monitoring of blood pressure and heart rate responses, electrocardiographic recordings, and oxygen saturations while subjects pedaled against a ramp protocol based on body weight. Echocardiographic measurements and specifically speckle-tracking analysis were performed during exercise at baseline, at a heart rate of 160 beats per minute and at 10 min after exercise. Peak systolic velocity, peak systolic strain, and peak systolic strain rate at these three phases were compared in the subjects in which all measurements were accurately obtained. We were able to complete peak velocity, strain, and strain rate measurements in all three exercise phases for 36 out of the 97 subjects tested. There was no significant difference between the feasibility of measuring circumferential versus longitudinal strain (p = 0.25, B-corrected = 0.75). In the 36 subjects studied, the magnitude of circumferential strain values decreased from -18.3 ± 4.8 to -13.7 ± 4.0 % from baseline to HR 160 (p < 0.0001, B-corrected < 0.0001), before returning to -19.6 ± 4.4 % at recovery (p = 0.19 when compared to baseline). Longitudinal strain did not vary significantly from baseline to HR 160 (from -17.7 ± 4.4 to -16.6 ± 4.4 %, p = 0.16); likewise the average recovery strain was no different from those values (-18.4 ± 3.6 %; p = 0.34). Peak circumferential and longitudinal strain rates increased from baseline to HR 160, but neither decreased to baseline levels after 10 min of recovery, which correlated with heart rate variations with exercise. We studied the effects of frame rate on deformation measurements and we observed no difference between measurements taken at lower (<60 frames per second, fps) and higher (≥60 fps) frame rates. This study shows that it is technically difficult to retrospectively measure peak velocities, strain, and strain rate in exercising pediatric subjects with STE. The majority of subjects that were excluded from the study had inadequate echocardiographic images when tachycardic from increased respiratory effort and body movements near peak exercise. Improvements in technique and higher image frame rates could make application of STE to pediatric cardiopulmonary testing more successful in the future.

Supine exercise echocardiographic measures of systolic and diastolic function in children.

BACKGROUND: Echocardiography has been used to determine ventricular function, segmental wall motion abnormality, and pulmonary artery pressure before and after peak exercise. No prior study has investigated systolic and diastolic function using echocardiography at various phases of exercise in children. The aim of this study was to determine the fractional shortening (FS), systolic-to-diastolic (S/D) ratio, heart rate-corrected velocity of circumferential fiber shortening (VCFc), circumferential wall stress (WS), ratio of mitral passive inflow to active inflow (E/A), ratio of passive inflow by pulsed-wave to tissue Doppler (E/E'), and right ventricular-to-right atrial pressure gradient from tricuspid valve regurgitation jet velocity (RVP) and time duration at various phases of exercise in children. METHODS: In an 8-month period (December 2007 to July 2008), 100 healthy children were evaluated, and 97 participants aged 8 to 17 years who performed complete cardiopulmonary exercise stress tests using supine cycle ergometry were prospectively enrolled. The participants consisted of 48 female and 49 male subjects with various body sizes, levels of exercise experience, and physical capacities. The cardiopulmonary exercise stress test consisted of baseline pulmonary function testing, continuous gas analysis and monitoring of blood pressure and heart rate responses, electrocardiographic recordings, and oxygen saturation measurement among participants who pedaled against a ramp protocol based on body weight. All participants exercised to exhaustion. Echocardiography was performed during exercise at baseline, at a heart rate of 130 beats/min, at a heart rate of 160 beats/min, at 5 min after exercise, and at 10 min after exercise. FS, S/D ratio, VCFc, WS, E/A, E', E/E', and RVP at these five phases were compared in all subjects. RESULTS: All echocardiographic parameters differed at baseline from 160 beats/min (P < .0001) except E/E', which remained at 5.4 to 5.8. Specifically, FS (from 37% to 46%), S/D ratio, VCFc (from 1.1 to 1.6), WS (from 200 to 258 g/cm(2)), E' (from 0.2 to 0.3), and RVP (from 18 to 35 mm Hg) increased from baseline to 160 beats/min and then subsequently decreased to at or near baseline, while tricuspid valve regurgitation duration decreased (from 370 to 178 msec). CONCLUSIONS: Normal values for systolic and diastolic echocardiographic measurements of function are now available. FS, VCFc, WS, and RVP increase with exercise and then return to near baseline levels. The E/E' ratio is unaltered with exercise in normal subjects.