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Effect of heart rate on Doppler indexes of systolic function in humans
M R Harrison1, G D Clifton, K L Sublett
1Division of Cardiology, College of Medicine, University of Kentucky, Lexington.
Insights
Heart rate significantly impacts Doppler echocardiography measurements of aortic blood flow in humans. Increased heart rates lead to decreased peak acceleration and velocity, crucial for assessing left ventricular systolic function.
Area of Science:
- Cardiology
- Medical Imaging
- Physiology
Background:
- Doppler echocardiography is vital for noninvasive assessment of left ventricular systolic function.
- Existing data lack information on heart rate's influence on Doppler aortic blood flow measurements in humans.
Purpose of the Study:
- To investigate the effect of varying heart rates on Doppler-derived aortic blood flow velocity and acceleration in normal human subjects.
Main Methods:
- Continuous wave Doppler ultrasound was used to record aortic blood flow from the suprasternal notch.
- Twelve healthy volunteers underwent transesophageal atrial pacing, increasing heart rate from 90 to 140 beats/min.
- Measurements were taken in both upright and supine positions to assess peak acceleration, peak modal velocity, and flow velocity integral.
Main Results:
- A significant inverse correlation was observed between heart rate and aortic blood flow parameters.
- Peak acceleration, peak modal velocity, and flow velocity integral decreased progressively with increasing heart rate.
- Linear correlations (r ≥ 0.97, p < 0.0001) were found between heart rate and all measured Doppler parameters.
Conclusions:
- Heart rate is a significant confounding factor in Doppler echocardiography assessment of aortic blood flow.
- These findings necessitate adjustments in interpreting Doppler-derived aortic flow velocities and accelerations, especially during interventions that alter heart rate.
Abstract:
Recent investigations have shown Doppler echocardiography to be useful in the noninvasive assessment of left ventricular systolic function. No data exist, however, regarding the influence of heart rate on Doppler measurements of aortic blood flow velocity and acceleration in humans. Thus, 12 normal volunteers underwent continuous wave Doppler ultrasound recording from the suprasternal notch at baseline and during progressive transesophageal atrial pacing at intervals of 10 beats/min between 90 and 140 beats/min while 100% atrial capture and 1:1 atrioventricular conduction were maintained. Subjects were studied both upright (n = 12) and supine (n = 10). With the subject upright at baseline (mean heart rate 77.8 +/- 10.6 beats/min), peak acceleration averaged to 16.8 +/- 3.4 m/s2, and peak modal velocity and flow velocity integral averaged 0.72 +/- 0.14 m/s and 8.4 +/- 2.1 cm, respectively. With pacing at 90 beats/min, peak acceleration decreased to 15.6 +/- 3.6 m/s2, a significant decline from baseline values (p less than 0.005). Similar declines were seen during pacing at 90 beats/min for peak modal velocity and flow velocity integral (0.64 +/- 0.16 m/s and 7.1 +/- 1.9 cm, respectively; both p less than 0.005 versus baseline values). At the peak pacing rate of 140 beats/min, average peak acceleration decreased to 12.8 +/- 3.1 m/s2, and peak modal velocity and flow velocity integral decreased to 0.52 +/- 0.11 m/s and 5.02 +/- 1.25 cm, respectively. A significant linear correlation (r greater than or equal to 0.97, p less than 0.0001) was obtained for the relation between heart rate and peak acceleration, peak modal velocity and flow velocity integral.(ABSTRACT TRUNCATED AT 250 WORDS)