Circadian variation of left ventricular diastolic function in healthy people
S Voutilainen1, M Kupari, M Hippelainen
1Department of Medicine, Päijät-Häme Central Hospital, Lahti, Finland.
Insights
Healthy individuals exhibit a circadian rhythm in left ventricular relaxation, indicated by Doppler indices of left ventricular filling. This daily variation is likely influenced by the day-night cycle of sympathoadrenal activity.
Area of Science:
- Cardiology
- Physiology
- Chronobiology
Background:
- Circadian rhythms influence numerous physiological processes.
- Understanding diurnal variations in cardiac function is crucial for cardiovascular health.
- Previous research has not fully elucidated left ventricular function's daily patterns in healthy individuals.
Purpose of the Study:
- To investigate the presence and extent of circadian variation in left ventricular function.
- To assess diurnal changes in left ventricular diastolic function parameters in healthy adults.
Main Methods:
- 10 healthy participants (7 men, 3 women, aged 35-50) underwent 24-hour monitoring.
- M-mode echocardiography and Doppler velocimetry of transmitral flow were performed at 4-hour intervals.
- Standardized conditions for diet, meal times, and sleep were maintained.
Main Results:
- Heart rate and blood pressure showed significant circadian rhythms.
- Left ventricular diameters and systolic function did not exhibit significant diurnal trends.
- Key left ventricular diastolic function indices, including relaxation time and isovolumic relaxation period, demonstrated significant diurnal variations (p < 0.05).
Conclusions:
- Doppler-derived indices of left ventricular filling display diurnal changes in healthy individuals.
- These findings suggest a circadian rhythm in the rate of left ventricular relaxation.
- The day-night cycle in sympathoadrenal activity is proposed as the primary underlying mechanism.
Aim:
To assess whether left ventricular function shows circadian variation in healthy people.
Subjects And Methods:
10 healthy men (7) and women (3) aged 35-50 underwent M mode echocardiography of the left ventricle and Doppler velocimetry of transmitral flow at 4 h intervals over 24 h. The participants were in hospital over the study period and their diet, meal times, and sleeping hours were standardised as far as possible.
Measurements:
Heart rate, blood pressure, left ventricular and atrial diameters, fractional shortening, peak early and late transmitral velocities, time from the second heart sound to the early diastolic velocity peak (relaxation time), isovolumic relaxation period, acceleration and deceleration of the early transmitral flow, atrial filling fraction.
Results:
A circadian rhythm was observed in heart rate and blood pressure, but neither the left ventricular diameters and systolic function nor the left atrial size showed statistically significant diurnal trends. The relaxation time (mean (SD)) measured 144 (16) ms at 2 pm, 144 (21) ms at 6 pm, 149 (22) ms at 10 pm, 168 (23) ms at 2 am, 174 (28) ms at 6 am, and 151 (21) ms at 10 am (P = 0.009). Diurnal rhythms were seen also in the isovolumic relaxation period (P = 0.003) and in the acceleration of the early diastolic transmitral flow (P = 0.037); the lowest and highest values of flow acceleration were observed during the nocturnal and daytime hours, respectively.
Conclusions:
The Doppler indices of left ventricular filling in healthy people show diurnal changes suggestive of a circadian rhythm in the rate of left ventricular relaxation. The most likely underlying mechanism is the day-night cycle in sympathoadrenal activity.
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