What is an indication for CRT/His bundle pacing instead of RV apical pacing?

Choosing conduction system pacing over traditional right ventricular (RV) apical pacing is particularly important in cases where there is a combination of atrioventricular (AV) block and reduced ejection fraction (EF). In patients with an ejection fraction between 36-50%, CRT (Cardiac Resynchronization Therapy) or His bundle pacing can improve cardiac mechanics and help to restore synchronized contraction of the heart's ventricles.

The rationale for this choice lies in the goal of optimizing heart function and reducing the risk of heart failure progression. In patients with AV block and intermediate EF, pacing the His bundle or utilizing CRT techniques can lead to better outcomes by improving ventricular synchrony, which in turn can enhance cardiac output and reduce symptoms associated with heart failure.

While individuals with an EF above 50% may not benefit significantly from CRT, and severe heart failure cases generally call for different therapeutic strategies, the specific population represented by an EF of 36-50% with AV block stands to gain from the resynchronization effects provided by conduction system pacing methods. Thus, this indication is well-supported by the existing literature on pacing strategies and heart failure management.