Class IIa indication for cardiac resynchronization therapy for reducing the risk of HF worsening:

- CHF requiring conventional pacing + NYHA Class III- IV persisting despite optimal pharmacotherapy + LVEF < 35% + patients in whom expected survival time with good functional status is > 1 year.

Class IIb indication for cardiac resynchronization therapy for reducing the risk of HF worsening:

- CHF requiring conventional pacing + NYHA Class II persisting despite optimal pharmacotherapy + LVEF < 35% + patients in whom expected survival time with good functional status is > 1 year.