Assessment of LV function response to incremental dynamic exercise in healthy children and adolescents using 2-D speckle tracking echocardiography

Background: Exercise performance has prognostic value in patients with congenital heart disease (CHD). Cardio-pulmonary exercise testing (CPET) cannot directly assess myocardial response and this limits its predictive value in children with CHD. 2-D speckle-tracking-echocardiography (2-D STE) is validated at rest but not during exercise. This is the first study using 2-D STE, gas analysis and near-infrared spectroscopy (NIRS) to simultaneously assess cardio-vascular and pulmonary exercise response.
Methods: 17 healthy volunteers, 11 boys and 6 girls (mean age 12.4±2.4y; stature 155.9±13.4cm; body mass 47.7±17kg; BSA 1.42±0.32m2) completed an incremental CPET on a recumbent cycle ergometer to volitional exhaustion (25W∙3min increments). 2-D trans-thoracic echocardiographic images were obtained at rest and during each exercise stage using a 4-6Mhz transducer echocardiography system from an apical 4-chamber view. LV longitudinal peak systolic strain was measured by 2-D STE and analysed using offline analysis software. Strain parameters in 6 segments of the LV were acquired at rest and at baseline (unloaded pedalling), at 50W, 75W, 100W and in recovery 2 (Rec2) and 10 (Rec10) minutes from end exercise. Simultaneous gas exchange analysis and NIRS were performed to determine oxygen consumption and muscle oxygen uptake.
Results: Participants achieved a peak oxygen uptake (VO2peak) of 40.4±9.2mL∙kg-1∙min-1 and a maximal work rate of 135±36W with linear increase in muscle oxygen extraction. Longitudinal peak systolic strain at rest, baseline, 50, 75, 100W, Rec2 and Rec10 were as follows for septal LV wall: -19±3,-23±3,-22±3,-22±6,-23±3,-19±5 and -14±5% respectively and for lateral LV wall: -18±3,-19±4,-20±4,-22±5,-21±5,-17±5 and -14±5% respectively. LV global longitudinal peak systolic strain increased significantly from rest to maximal exercise (p=0.001) but did not increase in a linear fashion with increments in work rate (p>0.05) There was moderate positive correlation between LV peak systolic longitudinal strain of the lateral wall and the work rate at 100W (r=0.65, p<0.05). There was no correlation between resting and exercise LV strain parameters.
Conclusion: This study provides novel normative data on LV contractile response during staged maximal aerobic exercise in children. LV longitudinal peak systolic strain in healthy volunteers increases during exercise. This methodology can help comprehensively investigate contractile exercise response and contractility reserve in CHD patients, correlate exercise LV function to other CPET parameters and early detect subclinical ventricular dysfunction.