From the Guidelines
Asynchronous pacing mode refers to a cardiac pacing setting where the pacemaker delivers electrical impulses at a fixed rate regardless of the heart's intrinsic activity, and is primarily used in temporary situations due to its risks, including competitive pacing and arrhythmias 1.
Definition and Usage
Asynchronous pacing mode is typically designated as VOO, AOO, or DOO, where the first letter indicates the chamber being paced (ventricle, atrium, or dual), and the double "O" indicates that the pacemaker neither senses cardiac activity nor responds to it. This mode is used in specific situations such as during surgical procedures where electromagnetic interference might cause inappropriate sensing, in patients with complete heart block who are pacemaker-dependent, or during emergencies when rapid implementation of pacing is needed 1.
Risks and Limitations
Asynchronous pacing carries the risk of competitive pacing, where the pacemaker stimulus may fall on a vulnerable period of the cardiac cycle, potentially triggering arrhythmias. For this reason, asynchronous modes are rarely used for permanent pacing in modern practice. Instead, synchronous modes (VVI, AAI, DDD) that sense intrinsic cardiac activity and pace only when needed are preferred for long-term management as they provide more physiological heart function and reduce the risk of pacemaker syndrome and arrhythmias 1.
Clinical Considerations
In choosing between pacemakers with or without adaptive rate functions, factors such as the cardiac conduction abnormality, comorbidities, coronary heart disease, and left ventricular dysfunction should be considered. Virtually all modern pacemakers are multiprogrammable, rendering them adaptable to changing clinical situations 1.
Recommendations
The use of asynchronous pacing mode should be limited to temporary situations, and synchronous modes should be preferred for long-term management to minimize risks and optimize patient outcomes 1.
From the Research
Asynchronous Pacing Mode
Asynchronous pacing mode refers to a type of cardiac pacing where the pacemaker delivers electrical impulses to the heart without being synchronized to the heart's natural rhythm.
- The asynchronous ventricular pacing has been shown to increase the risk of development of atrial fibrillation (AF) due to various mechanisms such as retrograde atrioventricular conduction and increased atrial pressure 2.
- Dual-chamber pacing preserves atrioventricular synchrony, but may not completely avoid unnecessary ventricular pacing, which can lead to other problems 2.
- Dedicated algorithms that enhance spontaneous AV conduction in the dual-chamber mode are desirable for a large proportion of pacemaker patients 2.
Types of Pacing Modes
Different types of pacing modes are available, including:
- VVI(R) pacing mode, which is a single-chamber pacing mode that can provide ventricular pacing but may not preserve atrioventricular synchrony 3.
- DDD(R) pacing mode, which is a dual-chamber pacing mode that can provide both atrial and ventricular pacing and preserve atrioventricular synchrony 2.
- AAI(R) pacing mode, which is a single-chamber pacing mode that can provide atrial pacing and is superior to the dual-chamber mode but cannot be used if AV conduction is impaired 2.
Clinical Applications
Asynchronous pacing mode may be used in various clinical applications, including:
- Treatment of bradyarrhythmias, where an external cardiac pacemaker can be used to generate a pulse in patients with asystole or bradycardia 4.
- Management of atrioventricular blocks, where pacemaker programming can be optimized to preserve atrioventricular synchrony and minimize unnecessary ventricular pacing 5.
- Treatment of congenital heart disease, where pacing may be indicated to improve quality of life and prevent sudden death 6.