Programmed versus effective VV delay during CRT optimization: when what you see is not what you get

Area of Science:

• Cardiology
• Biomedical Engineering

Background:

• Cardiac resynchronization therapy (CRT) utilizes interventricular (VV) delay, the interval between left (LV) and right ventricular (RV) pacing.
• Standard VV delay optimization procedures may not always reflect the actual delay between ventricular depolarizations.

Purpose of the Study:

• To determine the proportion of CRT patients where the effective VV delay (VVeff) differs from the programmed VV delay.
• To assess the impact of programmed VV delay on VVeff during optimization.

Main Methods:

• Prospective study of 33 heart failure patients with left bundle branch block undergoing CRT.
• VVeff calculated using intrinsic AV intervals and programmed optimal AV/VV delays.
• Optimization based on maximizing LV pressure rise (dP/dtmax) with tested VV delays.

Main Results:

• Up to 46% of patients had a VVeff shorter than 80 ms LV preactivation.
• 3% of patients had VVeff shorter than 40 ms LV preactivation.
• RV preactivation showed smaller discrepancies (6% and 0% for 80 and 40 ms, respectively).

Conclusions:

• Effective VV delay is frequently shorter than programmed in CRT patients with LBBB.
• This discrepancy is most common with significant LV preactivation.
• Pre-calculation of individual VVeff may streamline the optimization process.