From the Guidelines
VVI on a pacemaker stands for Ventricular paced, Ventricular sensed, Inhibited response, which is a common pacemaker mode that paces only the ventricle of the heart, senses electrical activity in the ventricle, and inhibits pacing when it detects natural heartbeats. This mode is typically used for patients with chronic atrial fibrillation who don't need atrial pacing, or for those who only need backup pacing. According to the guidelines for cardiac pacing and cardiac resynchronization therapy by the European Society of Cardiology 1, VVI is a suitable pacing mode for patients with atrioventricular block, along with DDD or single-lead VDD.
Key Characteristics of VVI Mode
- Paces only the ventricle of the heart
- Senses electrical activity in the ventricle
- Inhibits pacing when it detects natural heartbeats
- Typically used for patients with chronic atrial fibrillation or those who only need backup pacing
- Has a single lead placed in the right ventricle
Comparison with Other Pacing Modes
The CTOPP study, cited in the guidelines 1, found that the primary endpoint, the occurrence of either stroke or death from cardiovascular cause, did not differ significantly between DDD and VVI pacing modes. However, a subgroup analysis found a trend for younger patients to benefit from physiological pacing, such as DDD, in terms of the risk of stroke or death from cardiovascular causes. Another study, PASE, also found no difference in quality of life, cardiovascular events, or death between patients paced in DDD or VVI mode 1.
Clinical Implications
While VVI pacing is effective at preventing dangerous slow heart rates, it doesn't coordinate the atria and ventricles, which may lead to "pacemaker syndrome" in some patients, causing symptoms like fatigue or dizziness due to the loss of proper atrial contribution to cardiac output. More advanced pacing modes like DDD are often preferred when normal coordination between chambers is needed. However, the choice of pacing mode ultimately depends on the individual patient's needs and condition, and should be determined by a healthcare professional.
From the Research
Definition of VVI Pacemaker
- VVI stands for Ventricular Inhibited, which refers to a type of pacemaker mode that inhibits ventricular pacing when a ventricular beat is detected 2, 3, 4.
- In VVI mode, the pacemaker paces the ventricle at a fixed rate, but inhibits pacing when it detects a natural ventricular beat 2, 3.
- This mode is often used in patients with atrial fibrillation or other conditions where the atria are not functioning properly 2, 3.
Comparison with Other Pacemaker Modes
- VVI mode is compared to other pacemaker modes, such as dual-chamber pacing (DDDR) and ventricular pacing (VVIR), in terms of outcomes and complications 3, 4.
- Studies have shown that VVI pacing may be associated with a higher risk of atrial fibrillation, particularly in patients with no history of atrial fibrillation 3.
- However, VVI pacing may also be beneficial in certain patient populations, such as those with bradycardic atrial fibrillation, where it can increase cardiac output 2.
Clinical Implications
- The choice of pacemaker mode depends on the individual patient's condition and needs 3, 4, 5.
- VVI pacing may be a suitable option for patients who require ventricular pacing but do not need atrioventricular synchrony 3.
- However, the optimal pacemaker mode for bradycardia support while minimizing unnecessary and potentially harmful ventricular pacing has not been fully established 5.