From the Guidelines
VVI pacing at 40 beats per minute refers to a specific pacemaker mode where V stands for Ventricle, the second V stands for Ventricle, and I stands for Inhibited, as defined by the American College of Cardiology/American Heart Association task force on assessment of diagnostic and therapeutic cardiovascular procedures 1. This means the pacemaker paces the ventricle (first V), senses electrical activity in the ventricle (second V), and is inhibited from delivering a pacing stimulus when it detects intrinsic ventricular activity (I). The rate of 40 beats per minute indicates that the pacemaker will deliver electrical impulses to stimulate the ventricle 40 times per minute if the patient's natural heart rate falls below this threshold. Some key points to consider about VVI pacing include:
- It is a single-chamber pacing mode that doesn't coordinate with atrial activity, making it suitable for patients with chronic atrial fibrillation or other conditions where atrial pacing isn't necessary or beneficial.
- This mode doesn't maintain AV synchrony, which may reduce cardiac output in some patients compared to dual-chamber pacing modes.
- According to the 2012 HRS/ACCF expert consensus statement on pacemaker device and mode selection, single-chamber VVI pacing may be considered in instances where frequent pacing is not expected or the patient has significant comorbidities that are likely to influence survival and clinical outcomes 1.
- The European Heart Journal's 2001 guidelines on management of syncope suggest that physiological pacing (atrial or dual-chamber) has been definitely shown to be superior to VVI pacing in patients with sinus node dysfunction, as it lowers the risk of developing atrial fibrillation and may improve quality of life 1.
- The 2016 ESC guidelines for the management of atrial fibrillation note that ablation of the atrioventricular node/His bundle and implantation of a VVI pacemaker can control ventricular rate when medications fail to control rate and symptoms, but this procedure renders patients pacemaker-dependent for the rest of their lives 1.
- The American College of Cardiology/American Heart Association task force on assessment of diagnostic and therapeutic cardiovascular procedures also provides guidelines for implantation of cardiac pacemakers and antiarrhythmia devices, including recommendations for rates less than 40 beats/min 1.
From the Research
VVI Pacing Definition
- VVI pacing stands for Ventricular Paced, Ventricular Sensed, Inhibited, which is a type of pacemaker mode used to regulate heart rhythm 2, 3, 4.
- In VVI pacing, the pacemaker paces the ventricle when it senses a slow heart rate, and inhibits pacing when it senses a normal heart rate 3, 4.
- The "40" in VVI pacing at 40 beats per minute refers to the minimum heart rate at which the pacemaker will pace the ventricle 2.
Clinical Applications
- VVI pacing is used in patients with bradycardia, or slow heart rate, to prevent symptoms such as dizziness and syncope 3, 5.
- It is also used in patients with cardioinhibitory syncope, where the heart rate slows down in response to certain stimuli 3, 5.
- However, VVI pacing may not be effective in preventing syncope in all patients, and other treatments such as drug therapy may be more effective in some cases 6.
Pacemaker Settings
- The pacemaker settings for VVI pacing can be adjusted to optimize heart rate and prevent unnecessary pacing 3.
- Hysteresis, or a delay in pacing after a sensed beat, can be used to avoid unnecessary ventricular stimulation and preserve cardiac output 3.
- The choice of pacemaker mode and settings depends on the individual patient's needs and medical history 2, 3, 4.