- the AAI-DDD (Vp-suppression) mode has been designed to allow pacing in ADI mode with permanent monitoring of atrioventricular conduction and switching to DDD mode when the device detects an alteration in atrioventricular conduction
- there are 4 switching criteria from AAI to DDD corresponding to the different degrees of atrioventricular block
- first-degree AV block: the device switches to DDD mode when 2 consecutive atrial events are conducted with an AS-VS or AP-VS delay exceeding 450 ms
- second-degree AV block: the device switches to DDD mode when X (programmable) out of 8 atrial events are blocked
- third-degree AV block: the device switches to DDD mode when 2 consecutive spontaneous or paced atrial activities are blocked
- ventricular pause: the device switches to DDD mode when the interval between 2 sensed ventricular activations exceeds 2 seconds
- when the device is operating in DDD mode, it searches for the presence of a spontaneous atrioventricular conduction every 30 seconds and subsequently spaces the latter (1, 2, 4, 8, 16 … 128 minutes, up to 20 hours) if the search is inconclusive
- the device prolongs its AV delay to 450 ms for 8 cycles
- the search is successful and the device switches to ADI mode if the set number of ventricular cycles (nominal value 6) has been sensed consecutively within 8 cycles
- during the search, no P wave can be blocked but there is an increased risk of pacemaker mediated tachycardia
10 things you need to know about Vp suppression
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