The Effects of Exercise Intensity vs. Metabolic State on the Variability and Magnitude of Left Ventricular Twist Mechanics during Exercise

Impaired cardiac mechanical synchrony revealed with increased myocardial work in women with advanced age

BACKGROUND

Whether the synchronous nature of the myocardium is sex-dependent or affected by the aging process remains unknown. This study aimed to determine the influence of sex and age on cardiac mechanical synchrony during controlled hemodynamic stress.

METHODS

Transthoracic speckle-tracking echocardiography analyses and central hemodynamics were assessed at rest and during moderate- to high-intensity exercise in healthy young (<45 yr) and older (≥45 yr) women (n = 32) and men (n = 34) matched by age, physical activity and exercise capacity. Left ventricular mechanical dyssynchrony (LVMD) was determined as the time to peak standard deviation (TPSD) of longitudinal and transverse strain and strain rates (LSR, TSR).

RESULTS

Physical activity, aerobic capacity, heart rate, blood pressure and LVMD at rest were similar between women and men in each age group (P > 0.05). The rate pressure product, an index of myocardial work, did not differ between sex and age groups at rest and during exercise at a given percentage of peak heart rate (P > 0.05). A consistent age effect was observed for transverse LVMD (P-for-age ≤ 0.011). Specifically, older women presented with marked increments (≥42 %) in TSR TPSD at all exercise levels compared with younger women (P ≤ 0.005). Sex per se did not generally affect LVMD.

CONCLUSION

A prevailing impairment of cardiac mechanical synchrony in the transverse axis of the left ventricle is revealed during conditions of elevated hemodynamic stress in women with advanced age.

Key role of left ventricular untwisting in endurance cyclists at onset of exercise

The rise in oxygen consumption during the transition from rest to exercise is faster in those who are endurance-trained than those who have sedentary lifestyles, partly due to a more efficient cardiac response. However, data regarding this acute cardiac response in trained individuals are limited to heart rate (HR), stroke volume, and cardiac output. Considering this, we compared cardiac kinetics, including left ventricular (LV) strains and twist/untwist mechanics, between endurance-trained cyclists and their sedentary counterparts. Twenty young, male, trained cyclists and 23 untrained participants aged 18-25 yr performed five similar constant workload exercises on a cyclo-ergometer (target HR: 130 beats/min). During each session, LV myocardial diastolic and systolic linear strains, as well as torsional mechanics, were assessed using speckle-tracking echocardiography. Cardiac function was evaluated every 15 s during the first minute and every 30 s thereafter, until 240 s. Stroke volume increased during the first 30-45 s in both groups but to a significantly greater extent in trained cyclists (31% vs. 24%). Systolic parameters were similar in both groups. Transmitral peak filling velocity and peak filling rate responded faster to exercise and with greater amplitude in trained cyclists. Left ventricular filling pressure was lower in the former, whereas LV relaxation was greater but only at the base of the left ventricle. Basal rotation and peak untwisting rate responded faster and to a greater extent in the cyclists. This study provides new mechanical insights into the key role of LV untwisting in the more efficient acute cardiac response of endurance-trained athletes at onset of exercise.NEW & NOTEWORTHY Our study assessed for the first time, to our knowledge, the kinetics of left ventricular function during the transition from rest to constant-load exercise in endurance-trained subjects. We observed a faster cardiac response in cyclists characterized by a faster response of cardiac output, left ventricular transmitral filling, basal rotation, and untwisting. This study highlighted the key role of left ventricular twisting mechanics in the more efficient acute cardiac response of endurance-trained athletes at onset of exercise.

Characterisation of LV myocardial exercise function by 2-D strain deformation imaging in elite adolescent footballers

Purpose

Few data exist on the descriptions of LV myocardial mechanics and reserve during dynamic exercise of adolescent athletes. The aim of this study was to describe the LV myocardial and cardiopulmonary changes during exercise using 2-D strain deformation imaging.

Methods

Elite adolescent male football players (n = 42) completed simultaneous cardiopulmonary exercise testing (CPET) and exercise echocardiography measurement of LV myocardial deformation by 2-D strain imaging. LV longitudinal and circumferential 2-D strain and strain rates were analyzed at each stage during incremental exercise to a work rate of 150 W. Additionally, exercise LV myocardial deformation and its relation to metabolic exercise parameters were evaluated at each exercise stage and in recovery using repeated measures ANOVA, linear regression and paired t tests.

Results

LV peak systolic baseline 2-D strain (longitudinal: − 15.4 ± 2.5%, circumferential: − 22.5 ± 3.1%) increased with each exercise stage, but longitudinal strain plateaued at 50 W (mean strain reserve − 7.8 ± 3.0) and did not significantly increase compared to subsequent exercise stages (P > 0.05), whilst circumferential strain (mean strain reserve − 11.6 ± 3.3) significantly increased (P < 0.05) throughout exercise up to 150 W as the dominant mechanism of exercise LV contractility increase. Regression analyses showed LV myocardial strain increased linearly relative to HR, VO₂ and O₂ pulse (P < 0.05) for circumferential deformation, but showed attenuation for longitudinal deformation.

Conclusion

This study describes LV myocardial deformation dynamics by 2-D strain and provides reference values for LV myocardial strain and strain rate during exercise in adolescent footballers. It found important differences between LV longitudinal and circumferential myocardial mechanics during exercise and introduces a methodology that can be used to quantify LV function and cardiac reserve during exercise in adolescent athletes.

Cardiovascular responses during submaximal cycling with and without left-lateral tilting: insights for practical applications of stress echocardiography

We investigated the cardiorespiratory responses to semi-supine exercise with (SS+45°) and without (SS-0°) a left-lateral tilt in 15 adults at fixed power output (70 W) and matched heart rates. At 70 W, oxygen uptake and heart rate reduced from upright to SS-0° then increased to SS+45° (p < 0.05). At matched heart rates, oxygen uptake and efficiency were lowest in SS+45° (p < 0.05). Left-lateral tilting should not be performed under the assumption that each position replicates the same cardiorespiratory responses. Novelty: Cardiorespiratory responses to exercise are influenced by left-lateral tilting, which should not be performed under the assumption that physiological responses are replicated between left-lateral positions.