Normal stroke volume
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Normal Stroke Volume: Key Insights from Recent Research
Normal Stroke Volume Values by Age, Sex, and Ethnicity
Stroke volume (SV), a critical measure of cardiac function, varies significantly based on age, sex, and ethnicity. A comprehensive study by the World Alliance of Societies of Echocardiography (WASE) examined 1,450 healthy adults across different age groups and ethnicities using three echocardiographic techniques: Doppler, 2D, and 3D. The study found that SV was generally lower in females compared to males across all methods. Additionally, SV decreased with age, and significant differences were observed among ethnic groups, with Asians having the smallest SV and whites the largest, even after adjusting for body surface area (BSA).
Stroke Volume in Children
In children aged 6 to 16 years, stroke volume is less variable than cardiac output or oxygen pulse, making it a reliable measure of cardiac function. A study involving catheterization data from 21 children established that a stroke index of 42 ml/beat/m² is valid within a BSA range of 0.7 to 1.5 m². This highlights the importance of considering BSA when evaluating SV in pediatric populations.
Stroke Volume and Heart Rate Relationship
The relationship between stroke volume and heart rate is crucial in both healthy individuals and patients with cardiovascular diseases. Research indicates that in normal individuals, ejection time varies inversely with heart rate and directly with stroke volume. In patients with cardiovascular conditions, such as aortic valvular disease, ejection time prolongation correlates with the severity of the disease. This relationship underscores the importance of monitoring both SV and heart rate in clinical assessments.
Fetal Stroke Volume Development
In fetuses, stroke volume increases exponentially with gestational age. A study using Doppler echocardiography on 80 normal human fetuses found that right ventricular stroke volume increased from 0.7 ml at 20 weeks to 7.6 ml at 40 weeks, while left ventricular stroke volume increased from 0.7 ml to 5.2 ml over the same period. This exponential growth highlights the dynamic changes in cardiac function during fetal development.
Gender Differences in Stroke Volume During Exercise
Gender differences in stroke volume control during exercise have been observed. A study involving 34 men and 27 women during staged bicycle ergometry found that while men had higher absolute stroke volumes, there were no significant differences in stroke volume index between genders when adjusted for body size. Both groups showed similar mechanisms of stroke volume increase during exercise, primarily through increased left ventricular filling pressure and end-diastolic volume at low exercise levels.
Stroke Volume Regulation During Exercise
During submaximal and maximal exercise, stroke volume regulation is influenced by heart rate, left ventricular filling, and contractility. In a study of 24 male volunteers, stroke volume index increased significantly during low levels of exercise due to increased left ventricular filling pressure and end-diastolic volume. However, at higher exercise levels, further increases in cardiac output were driven entirely by heart rate increases, with stroke volume maintained by a decrease in end-systolic volume.
Stroke Volume Variation and Fluid Responsiveness
Stroke volume variation (SVV) is a useful predictor of fluid responsiveness, especially in patients with reduced cardiac function. A study on mechanically ventilated patients post-cardiac surgery found that SVV correlated significantly with changes in stroke volume index following volume loading. This suggests that continuous monitoring of SVV can effectively assess hemodynamic changes and guide fluid management in critical care settings.
Non-Invasive Stroke Volume Monitoring
Non-invasive methods for monitoring stroke volume, such as finger arterial pressure wave analysis, have shown promise. A study involving blood withdrawal in patients with normal cardiac function demonstrated that stroke volume estimates derived from finger pressure closely mirrored the actual blood volume withdrawn, indicating the potential for non-invasive monitoring in clinical practice.
Clinical Significance of Stroke Volume Changes in Pulmonary Hypertension
In patients with pulmonary hypertension, a change in stroke volume of approximately 10 mL is considered clinically significant. This threshold was determined using both anchor-based and distribution-based methods, providing a valuable benchmark for assessing treatment efficacy and disease progression in these patients.
Stroke Volume Decline During Prolonged Exercise
During prolonged exercise, the decline in stroke volume is primarily related to an increase in heart rate rather than changes in cutaneous blood flow. A study found that preventing the increase in heart rate with a beta-blocker also prevented the decline in stroke volume, highlighting the interplay between heart rate and stroke volume during sustained physical activity.
Conclusion
Understanding the normal values and variations of stroke volume across different populations and conditions is essential for accurate cardiac function assessment. These insights from recent research provide valuable reference points for clinicians and highlight the importance of considering factors such as age, sex, ethnicity, and exercise in evaluating stroke volume.
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