7.1.3.3.3 CRT in patients with narrow QRS

Recommendation 58: We recommend CRT for patients in sinus rhythm with NYHA class II, III or ambulatory class IV HF despite optimal medical therapy, a LVEF ≤ 35%, and QRS duration ≥ 130 msec with LBBB (Strong Recommendation, High Quality Evidence).

Recommendation 59: We suggest that CRT may be considered for patients in sinus rhythm with NYHA class II, III or ambulatory class IV HF despite optimal medical therapy, a LVEF ≤ 35%, and QRS duration ≥ 150 msec with non-LBBB (Weak Recommendation, Low Quality Evidence).

• There is no clear evidence of benefit with CRT among patients with QRS durations < 150 msec because of non-LBBB conduction.

Recommendation 60: We suggest that CRT may be considered for patients in permanent AF who can expect to achieve close to 100% pacing and are otherwise suitable for this therapy (Weak Recommendation, Low Quality Evidence).

• It is important to ensure that the amount of biventricular pacing approaches 100% where possible. AV junctional ablation might be necessary to achieve sufficient biventricular pacing.

Recommendation 61: We suggest that CRT may be considered for patients requiring chronic RV pacing in the setting of heart failure symptoms and reduced LVEF (Weak Recommendation, Moderate Quality Evidence).

Recommendation 62: We recommend CRT not be used for patients with QRS < 130 msec, irrespective of HF symptoms, LVEF, or the presence or absence of mechanical dyssynchrony demonstrated on current imaging techniques (Strong Recommendation, Moderate Quality Evidence).

Recommendation 63: We recommend the addition of implantable cardioverter-defibrillator (ICD) therapy be considered for patients referred for CRT who meet primary ICD requirements (Strong Recommendation, High-Quality Evidence).

Values and preferences: These recommendations place a value on the benefit of CRT in patient groups included in the landmark RCTs and high quality systematic reviews, and less value on post hoc subgroup analyses from clinical trials. Based on the available evidence, there is insufficient evidence to recommend CRT in patients with NYHA class I status or in hospitalized NYHA class IV patients. Patients with a QRS duration ≥ 150 msec are universally more likely to benefit from CRT than patients with less QRS prolongation. The 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.