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Doppler echocardiographic studies in sequential atrioventricular pacing
Insights
Sequential atrioventricular pacing using Doppler echocardiography revealed significant changes in cardiac output. Switching from DVI to VVI mode reduced peak aortic blood flow velocity by an average of 18.4% in most patients.
Area of Science:
- Cardiology
- Medical Imaging
- Biomedical Engineering
Background:
- Sequential atrioventricular pacing is a common cardiac rhythm management strategy.
- Doppler echocardiography is a noninvasive tool for assessing hemodynamic parameters.
- Previous studies established a correlation between Doppler peak velocity and stroke volume/cardiac output.
Purpose of the Study:
- To evaluate the impact of switching pacemaker modes (DVI to VVI) on cardiac output.
- To assess the utility of Doppler echocardiography in measuring changes in stroke volume/cardiac output during sequential AV pacing.
Main Methods:
- Six patients with sequential atrioventricular pacemakers were studied.
- Transcutaneous aortovelography using continuous wave Doppler echocardiography was employed.
- Pacemaker modes were switched between DVI and VVI while maintaining constant heart rate.
- Peak aortic arch blood flow velocity was measured in each mode.
Main Results:
- Five out of six patients demonstrated a reduction in peak Doppler velocities (13-25%, mean 18.4%) when switching from DVI to VVI pacing mode.
- One patient showed no significant change in peak velocity.
- These velocity changes correlate with stroke volume/cardiac output.
Conclusions:
- Doppler echocardiography offers a simple, noninvasive method to estimate stroke volume/cardiac output.
- Sequential AV pacing mode changes can significantly affect cardiac output.
- This technique can be valuable for optimizing pacemaker settings.
Abstract:
Six patients with sequential atrioventricular pacemakers were studied by Doppler echocardiography. A commercially available continuous wave system (transcutaneous aortovelography) was used and the transducer was placed in the suprasternal notch and angled to obtain peak aortic arch blood flow velocity. Changes in Doppler peak velocity have been previously shown to correlate closely and reliably with changes in hemodynamically measured stroke volume/cardiac output in the same patients following interventions. In all patients, the pacemaker was programmed from DVI mode to VVI (heart rate was kept constant) and then back to DVI, with the Doppler transducer held in a fixed position all the time, and peak velocities measured after the patient had been in any particular mode for at least 1 minute. Five of 6 patients showed reduction in peak velocities ranging from 13-25% (mean 18.4%) when the pacing mode was switched from DVI to VVI. Doppler peak velocity remained unchanged in 1 patient. Doppler echocardiography represents a simple, noninvasive method for estimating increments in stroke volume/cardiac output obtained with sequential AV pacing.