Pacing mode | Indications | Function | Disadvantages | |
---|---|---|---|---|
* When DDD pacing is used in the treatment of sinus node dysfunction, the device must be programmed to minimise ventricular pacing. | ||||
AAI | Atrial pacing | Sinus node dysfunction | Senses and paces the atrium | Requires normal atrioventricular conduction |
VVI | Ventricular pacing | Slow atrial fibrillation Rarely occurring bradycardia | Senses and paces only the ventricle | Does not restore atrioventricular synchrony Pacemaker syndrome |
VDD | Single-lead physiological pacing | Atrioventricular block | Senses the atria and ventricle, paces only the ventricle | Does not pace the atria Inadequate sensing of atrial activation |
DDI | Atrioventricular sequential pacing | Atrioventricular block + atrial arrhythmia | Senses and paces the atria and, if necessary, the ventricle | Does not use atrial tracking to pace the ventricle |
DDD | Dual chamber pacing | Atrioventricular block Sinus node dysfunction* | Senses and paces the atria and the ventricle Changes the heart rate | Pacemaker-mediated tachycardia |
_ _ _ R | Rate-responsive pacings | Sinus node disease (AAIR/DDDR) Slow atrial fibrillation (VVIR) | Changes the heart rate according to sensor activity, may be connected to all modes except VDD | The kinetic sensor may erroneously react to vibration (e.g. when using a chain saw) |
Malfunction | ECG finding | Cause |
---|---|---|
* The frequency of fixed-rate pacing (asynchronous mode) triggered by interference is dependent on the device. The device will return to normal function on the disappearance of the disturbance. Should interference switch the pacemaker to the safety mode, the programming unit is needed to return normal function. | ||
Failure to output | No pacing spikes despite the underlying heart rate being slower than the programmed pacing rate. | Oversensing Faulty pacing lead or pulse generator Erroneous ECG interpretation |
Failure to capture | The pacing spike is not followed by either a QRS complex or a P wave (exit block) | Lead dislodgement or fracture Certain drugs, electrolyte imbalance, myocardial ischaemia, fibrosis Electrical cardioversion |
Undersensing | The pacemaker paces despite adequate intrinsic activity | The sensitivity of the pacemaker has been incorrectly programmed Faulty lead or pulse generator |
Oversensing | Incorrect pacing rate and/or pauses in pacing Arrhythmia initiation (R-on-T) | Myopotential interference External interference Far-field sensing |
Pacing rate faster than programmed | The pacemaker paces faster than the set lower pacing limit. Broad-complex tachycardia with pacing spikes | Pacing is guided by a sensor (R mode) Pacemaker tachycardia |
Pacing rate slower than programmed | Pacing rate is slower than programmed. Intrinsic heart rate slower than the pacing rate programmed Pacing with a fixed rate irrespective of intrinsic cardiac activity (asynchronous pacing mode)* | The battery is nearing the end of its life The hysteresis feature or night time slowing of pacing rate is activated, oversensing Interference* caused by diathermy, defibrillation, MRI or other factor |