What are the criteria for considering a patient for Cardiac Resynchronization Therapy (CRT)?

Criteria for Cardiac Resynchronization Therapy (CRT)

CRT is indicated for patients with LVEF ≤35%, sinus rhythm, LBBB with QRS duration ≥150 ms, and NYHA class II, III, or ambulatory IV symptoms on guideline-directed medical therapy (GDMT). 1

Primary Indications (Class I)

Strong Evidence for CRT Benefit:

• LVEF ≤35%
• QRS duration ≥150 ms with LBBB morphology
• NYHA class II, III, or ambulatory IV symptoms
• On optimal GDMT for at least 3 months
• Sinus rhythm

Secondary Indications (Class IIa)

CRT can be useful for patients with:

• LVEF ≤35%, sinus rhythm, LBBB with QRS 120-149 ms, and NYHA class II-IV symptoms on GDMT 1
• LVEF ≤35%, sinus rhythm, non-LBBB pattern with QRS ≥150 ms, and NYHA class III/ambulatory IV symptoms on GDMT 1
• Atrial fibrillation with LVEF ≤35% if:
  • Patient requires ventricular pacing or meets other CRT criteria
  • AV nodal ablation or pharmacologic rate control will allow near 100% ventricular pacing 1
• LVEF ≤35% with anticipated requirement for significant (>40%) ventricular pacing 1

Possible Benefit (Class IIb)

CRT may be considered for:

• LVEF ≤30%, ischemic heart failure, sinus rhythm, LBBB with QRS ≥150 ms, and NYHA class I symptoms 1
• LVEF ≤35%, sinus rhythm, non-LBBB pattern with QRS 120-149 ms, and NYHA class III/ambulatory IV 1
• LVEF ≤35%, sinus rhythm, non-LBBB pattern with QRS ≥150 ms, and NYHA class II symptoms 1

Not Recommended (Class III: No Benefit)

• NYHA class I or II with non-LBBB pattern and QRS <150 ms 1
• Patients whose comorbidities and/or frailty limit survival with good functional capacity to <1 year 1

CRT-D vs. CRT-P Selection

• NYHA class I and II patients: Evidence supports CRT-D (with defibrillator) as these patients may not experience immediate symptomatic benefit but may avoid long-term heart failure consequences 1
• NYHA class III and ambulatory IV: Either CRT-D or CRT-P (pacing only) may be appropriate based on clinical factors and patient preferences 1

Important Clinical Considerations

QRS Morphology and Duration

• LBBB morphology with QRS ≥150 ms shows the strongest evidence of benefit 1, 2
• Mechanical dyssynchrony is present in up to 70% of patients with QRS ≥150 ms 1
• Non-LBBB patterns show less consistent benefit, particularly with QRS <150 ms 1

Patient Selection Pitfalls

1. Inadequate medical therapy: Ensure patients have been on optimal GDMT for at least 3 months before considering CRT 1
2. Ignoring QRS morphology: LBBB pattern shows greater benefit than non-LBBB patterns 1, 2
3. Overemphasis on LVEF cutoffs: While guidelines specify LVEF ≤35%, some patients with LVEF >35% might benefit from CRT 3
4. Inadequate rate control in AF: Patients with AF require near 100% biventricular capture, often requiring AV nodal ablation 4
5. Failing to consider life expectancy: CRT is not indicated when comorbidities limit survival to <1 year 1

Special Populations

Atrial Fibrillation

• CRT can be beneficial in AF patients if:
  • LVEF ≤35%
  • Rate control or AV nodal ablation ensures near 100% ventricular pacing 1, 4

Patients Requiring Significant Ventricular Pacing

• CRT should be considered for patients with LVEF ≤35% who require >40% ventricular pacing 1

By following these evidence-based criteria, clinicians can appropriately select patients who will derive mortality, morbidity, and quality of life benefits from CRT.