Table 6.

Loss of Cardiac Resynchronization During DDD or DDDR Pacing in the Presence of Preserved LV Pacing

A. Intrinsic

Atrial undersensing from low amplitude atrial potentials

T wave oversensing and other types of ventricular oversensing such as diaphragmatic potentials

Long PR interval

Circumstances that push the P wave into the PVARP such as a junctional rhythm

New arrhythmia such as atrial fibrillation with a fast ventricular rate

First‐generation devices with a common sensing channel: ventricular double counting and sensing of far‐field atrial activity

B. Extrinsic

Inappropriate programming of the AV delay or any function that prolongs the AV delay such as rate smoothing, AV search hysteresis, etc.

Low maximum tracking rate

Functional atrial undersensing precipitated by an atrial premature beat or ventricular premature beat. Long PVARP including post VPC automatic PVARP extension

Intra‐atrial conduction delay where sensing of AS is delayed in the right atrial appendage. A short AS–VP interval may not be able to achieve biventricular pacing