What are the indications for Cardiac Resynchronization Therapy with defibrillator (CRT-d)?

Indications for Cardiac Resynchronization Therapy with Defibrillator (CRT-D)

CRT-D is strongly recommended for heart failure patients with LVEF ≤35%, QRS duration ≥120 ms (especially with LBBB pattern), and NYHA class II-IV symptoms despite optimal medical therapy. 1, 2

Primary Indications by NYHA Class

NYHA Class III/IV Patients

• Class I recommendation (strongest evidence):
  • LVEF ≤35%
  • QRS ≥120 ms (especially ≥150 ms)
  • Sinus rhythm
  • On guideline-directed medical therapy (GDMT) for ≥3 months
  • Ambulatory for class IV patients 1

NYHA Class II Patients

• Class I recommendation:
  • LVEF ≤35%
  • QRS ≥150 ms
  • LBBB pattern
  • Sinus rhythm
  • On GDMT for ≥3 months 1

NYHA Class I Patients

• Class IIb recommendation (may be considered):
  • LVEF ≤30%
  • Ischemic cardiomyopathy
  • QRS ≥150 ms
  • LBBB pattern
  • On GDMT for ≥3 months 1

Special Clinical Scenarios

Atrial Fibrillation

• Class IIa recommendation:
  • NYHA class III/IV symptoms
  • LVEF ≤35%
  • QRS ≥130 ms
  • AV nodal ablation or pharmacological rate control that ensures ≥95% biventricular pacing 1, 2

Conventional Pacemaker Indication

• Class I recommendation:
  • NYHA class III/IV symptoms
  • LVEF ≤35%
  • QRS ≥120 ms
  • Anticipated frequent (>40%) ventricular pacing 1

Non-LBBB QRS Morphology

• Class IIa recommendation:

  • NYHA class III/IV symptoms
  • LVEF ≤35%
  • QRS ≥150 ms 1

• Class IIb recommendation:

  • NYHA class III/IV symptoms
  • LVEF ≤35%
  • QRS 120-149 ms 1

When to Choose CRT-D vs. CRT-P

CRT-D (with defibrillator) is preferred over CRT-P (pacemaker only) in the following scenarios:

1. Secondary prevention ICD indications (prior cardiac arrest or sustained VT)
2. Ischemic cardiomyopathy
3. NYHA class II patients with LVEF ≤30% 2, 3

CRT-P may be more appropriate in:

1. Very elderly patients
2. Significant comorbidities limiting survival
3. Non-ischemic cardiomyopathy with less severe LV dysfunction 2, 3

Contraindications and Inappropriate Candidates

CRT-D is not recommended for:

• QRS duration <120 ms (regardless of mechanical dyssynchrony) 1, 2
• NYHA class I or II with non-LBBB pattern and QRS <150 ms 1
• Patients with comorbidities limiting survival with good functional capacity to <1 year 1
• NYHA class IV patients who are not ambulatory or dependent on intravenous inotropes 1

Clinical Outcomes and Benefits

CRT-D therapy provides:

• Reduction in all-cause mortality
• Decreased heart failure hospitalizations
• Improved functional capacity
• Reverse cardiac remodeling with increased LVEF 2

Important Considerations

• LBBB morphology predicts better response than RBBB or nonspecific intraventricular conduction delay 1, 2
• QRS duration ≥150 ms is associated with greater benefit 1
• Patients should generally not receive CRT-D during acute decompensated heart failure 2
• Even patients who improve beyond guideline criteria for ICD after CRT implantation may still have substantial risk of ventricular arrhythmias, supporting the continued need for defibrillator capability 4
• Optimal LV lead placement targeting the latest activated areas improves outcomes 2

CRT-D therapy should be considered as part of a comprehensive heart failure management strategy, with careful patient selection based on these established criteria to maximize benefits and minimize risks.