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[Noninvasive evaluation of changes in stroke volume and left ventricular filling dynamics. Produced by
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Atrioventricular pacing interval adjustments did not significantly alter stroke volume in most patients. However, left ventricular filling dynamics compensated, with short intervals favoring rapid filling and long intervals favoring atrial filling.
Area of Science:
- Cardiology
- Biomedical Engineering
- Echocardiography
Context:
- Atrioventricular (AV) pacing is crucial for managing bradyarrhythmias.
- Optimizing the AV pacing interval is essential for hemodynamic efficiency.
- Previous studies have explored AV interval effects, but detailed filling dynamics require further investigation.
Purpose:
- To assess the impact of varying AV pacing intervals on stroke volume and left ventricular (LV) filling dynamics.
- To investigate the compensatory mechanisms of LV filling in response to AV interval changes.
- To determine the utility of Doppler echocardiography in evaluating AV pacing hemodynamics.
Summary:
- Stroke volume remained consistent across different AV intervals in most patients studied.
- Short AV intervals increased the time-velocity integral of rapid filling (TVI-R).
- Long AV intervals increased the time-velocity integral of atrial filling (TVI-A), indicating compensatory LV filling.
- Patients with a high atrial to rapid filling ratio (A/R) showed stroke volume variability, suggesting insufficient compensation.
Impact:
- Doppler echocardiography is a valuable noninvasive tool for assessing hemodynamic responses to AV pacing.
- Understanding LV filling dynamics aids in optimizing pacemaker settings for individual patients.
- Identifies patient subgroups (high A/R ratio) who may require tailored AV interval programming.
Abstract:
To evaluate the effects of atrioventricular pacing interval on hemodynamics, we studied the changes in stroke volume and left ventricular filling dynamics in fourteen consecutive patients with implanted atrioventricular pacemakers using a Doppler echocardiographic technique. Twelve patients had sick sinus syndrome and 2 had complete atrioventricular block. Stroke volume was determined as the time-velocity integral of the pulsed Doppler recordings at the aortic annulus multiplied by the area of the aortic annulus obtained by 2-dimensional echocardiography. Left ventricular filling velocity was measured at the mitral annulus by the pulsed Doppler technique to provide the time-velocity integral of rapid filling (TVI-R) and that of atrial filling (TVI-A). No significant change in stroke volume was noted during the atrioventricular interval manipulation. TVI-R was greater with short atrioventricular intervals than that with the long atrioventricular intervals. On the contrary, TVI-A was greater with long atrioventricular intervals than that with short atrioventricular intervals. These results suggested that there is a compensatory mechanism in the left ventricular filling dynamics to keep the stroke volume constant despite the change in the atrioventricular interval. However, in patients with high atrial filling to rapid filling ratio (A/R), the stroke volume varied with change of atrioventricular interval, suggesting that the compensatory mechanism was not sufficient in such patients. We conclude that Doppler echocardiography is a useful, noninvasive technique to assess the changes in the hemodynamics produced by atrioventricular interval manipulation in patients with implanted atrioventricular pacemakers.