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Hemodynamics and exercise capacity during pacemaker stimulation
1Division of Cardiology, Karolinska Hospital, Stockholm, Sweden.
Insights
Restoring heart rate variability is key for pacemaker patients, improving cardiac output and exercise tolerance. Atrioventricular synchronization offers additional benefits, particularly at rest, enhancing overall cardiac function.
Area of Science:
- Cardiology
- Biomedical Engineering
- Physiology
Background:
- Pacemaker technology significantly impacts cardiovascular function.
- Understanding hemodynamic and myocardial effects of pacing is crucial for patient outcomes.
- Heart rate variability and atrioventricular synchronization are key considerations in pacing.
Purpose of the Study:
- To review the hemodynamic and myocardial effects of different pacing modalities.
- To assess the roles of heart rate variability and atrioventricular synchronization.
- To evaluate the impact of pacing on cardiac output and exercise tolerance.
Main Methods:
- Literature review of studies on pacing modalities.
- Analysis of hemodynamic parameters (cardiac output, heart rate).
- Assessment of myocardial oxygen consumption and sympathetic activity.
Main Results:
- Adequate heart rate increase is critical for cardiac output and exercise tolerance, regardless of atrioventricular synchronization.
- Atrioventricular synchronization provides hemodynamic benefits, especially at rest.
- Rate-adaptive pacing demonstrates more "economic" cardiac work and may mitigate negative long-term effects compared to fixed-rate pacing.
Conclusions:
- Restored rate variability benefits most pacemaker-dependent patients.
- Atrial electrograms are optimal triggers for rate-adaptive pacing.
- Alternative rate-triggering signals can yield comparable hemodynamic and exercise tolerance results when atrial signals are unreliable.
Abstract:
This review summarizes the present knowledge concerning the hemodynamic and myocardial effects of various pacing modalities with special reference to the importance of heart rate variability and atrioventricular synchronization. An adequate increase in heart rate, irrespective of atrioventricular synchronization, seems to be the most important denominator for cardiac output and exercise tolerance. Atrioventricular synchronization will add some hemodynamic benefit, which is most pronounced at rest. The importance of a rate-adaptive atrioventricular delay and a normalized ventricular activation sequence remains, however, to be fully established. Myocardial oxygen consumption does not differ during fixed rate ventricular pacing, atrial synchronous or non-synchronous rate-adaptive ventricular pacing, neither at rest nor during exercise, despite a higher cardiac output during the rate-adaptive modes. This indicates a more "economic" cardiac work with rate-adaptive pacing. Fixed rate ventricular pacing, on the other hand, may have negative long-term effects on myocardial function due to an increased cardiac sympathetic activity compared with rate-adaptive ventricular pacing, in particular during exercise. It is concluded that the majority of pacemaker-dependent patients will benefit from restored rate variability, with the atrial electrogram still being the most appropriate trigger for rate-adaptive ventricular pacing. When the atrial signal cannot be used or when it is unreliable, however, other rate-triggering signals can be used with comparable results regarding hemodynamics and exercise tolerance.