Constant work-load exercise increased stroke volume from 104 mL at rest to 126 mL at 60 seconds (P<0.001), driven by early filling, left ventricular relaxation, and untwisting.
Observational (n=28)
How do left ventricular mechanics and stroke volume adapt during the transition from rest to exercise in young men?
Early filling, driven by increased venous return, LV relaxation, and untwisting, is the main determinant of stroke volume adaptation during the first minute of exercise.
Tasa de eventos absoluta: 126% vs 104%
valor p: p=<0.001
PURPOSE: At the onset of physical exercise, oxygen (O2) transport adapts to meet the working muscle O2 demands. Cardiac output abruptly increases through the concomitant changes of HR and stroke volume (SV), which is conditioned by the left ventricular (LV) function. The purpose of this study was to investigate the contribution of many LV diastolic and systolic function parameters, including twist-untwist mechanics, to SV adaptation during the first minutes after exercise onset. METHODS: Diastolic and systolic myocardial strains and twist were monitored by two-dimensional speckle-tracking echocardiography with high temporal resolution in 28 young men (mean age, 23 ± 4 yr) who performed five similar constant work-load exercises on a cycloergometer (target HR: 125 bpm). Two-dimensional cine-loops were recorded every 15 s during the first minute of exercise, and then every 30 s for the next 3 min. RESULTS: During the first 60 s of exercise, SV (from 104 ± 15 mL to 126 ± 21 mL, P < 0.001) increased concomitantly with LV strain and strain rates. Early filling was the main SV determinant during this phase, probably linked to the increase of venous return (at the very beginning of exercise), LV relaxation (from 1.5 ± 0.3 s to 2.5 ± 0.4 s, P < 0.001) and untwisting (from -78 ± 34°·s to -165 ± 61°·s, P < 0.001). After the first minute, SV remained constant, whereas LV untwisting continued to increase (from -165 ± 61°·s to -187 ± 60°·s, P < 0.001) and the other systolic and diastolic parameters reached a plateau. CONCLUSIONS: This study gives new mechanical insights into LV kinetics to address the challenge of SV response at the onset of exercise.
Izem et al. (Thu,) reported a observational. Constant work-load exercise vs. Rest was evaluated on Stroke volume (SV) adaptation during the first 60 seconds of exercise (p=<0.001). Constant work-load exercise increased stroke volume from 104 mL at rest to 126 mL at 60 seconds (P<0.001), driven by early filling, left ventricular relaxation, and untwisting.