We recommend CRT in patients with NYHA III and ambulatory NYHA IV HF despite optimal medical therapy, in sinus rhythm with QRS duration ≥130 ms and left bundle branch block (LBBB) QRS morphology and EF ≤35% (Recommendation Strong, Quality High).

We recommend CRT with an ICD in NYHA II HF patients despite optimal medical therapy, in sinus rhythm with a QRS duration ≥130 ms with LBBB QRS morphology and EF ≤30% (Recommendation Strong, Quality High).

We recommend that CRT be considered in NYHA class II, NYHA class III, and ambulatory NYHA class IV HF patients, in sinus rhythm, EF ≤35%, and QRS duration ≥150 ms with non-LBBB QRS morphology (Recommendation Weak, Quality Low).

We recommend the addition of ICD therapy be considered for patients referred for CRT who meet primary ICD requirements (Recommendation Strong, Quality High).

Values and Preferences These recommendations place a significant value on the derived benefit of CRT in patient groups specifically included in the landmark Randomized Controlled Trials (RCTs), and less value on post hoc subgroup analyses and systematic analyses. Based on these trials, there is insufficient evidence to recommend CRT in patients with NYHA class I status or in hospitalized NYHA class IV patients, or those in AF. Patients with a QRS duration ≥150 ms are universally more likely to benefit from CRT than patients with less prolongation. CRT pacemaker therapy should also be considered in patients who are not candidates for ICD therapy such as those with a limited life expectancy because of significant comorbidities, and in patients who decline to receive an ICD.