What is the role of Cardiac Resynchronization Therapy (CRT) in the management of Congestive Heart Failure (CHF) with reduced ejection fraction?

Cardiac Resynchronization Therapy in Congestive Heart Failure with Reduced Ejection Fraction

Cardiac resynchronization therapy (CRT) is strongly recommended for patients with heart failure with reduced ejection fraction (HFrEF) who have LVEF ≤35%, QRS duration ≥120 ms (especially with LBBB morphology), and remain symptomatic (NYHA class II-IV) despite optimal medical therapy. 1

Patient Selection Criteria for CRT

Strong Indications (Class I)

• NYHA Class III-IV (ambulatory):

  • LVEF ≤35%
  • QRS ≥120 ms
  • Sinus rhythm
  • Especially with LBBB morphology (QRS ≥150 ms)
  • Expected survival >1 year with good functional status 1

• NYHA Class II:

  • LVEF ≤35%
  • QRS ≥150 ms
  • Sinus rhythm
  • LBBB morphology
  • Expected survival >1 year 1

Reasonable Indications (Class IIa)

• NYHA Class III-IV:

  • LVEF ≤35%
  • QRS ≥150 ms
  • Non-LBBB morphology 1

• NYHA Class II-IV:

  • LVEF ≤35%
  • QRS 120-149 ms
  • Sinus rhythm 1

• Atrial fibrillation patients:

  • When AV nodal ablation or pharmacological rate control allows near 100% ventricular pacing 1

Benefits of CRT in HFrEF

CRT provides significant benefits in properly selected patients:

1. Mortality reduction:

   • 36% reduction in all-cause mortality in NYHA III-IV patients 1
   • Most pronounced when combined with ICD (CRT-D) 2

2. Morbidity reduction:

   • 52% reduction in unplanned hospitalizations for worsening HF 1
   • 39% reduction in hospitalizations for major cardiovascular events 1

3. Functional improvements:

   • Improvement in NYHA class by 0.5-0.8 points
   • Increase in 6-minute walk distance by approximately 20%
   • Increase in peak oxygen consumption by 10-15% 1

4. Reverse remodeling:

   • Reduction in LV volumes
   • Improvement in LVEF
   • Reduction in mitral regurgitation 1

CRT Device Selection: CRT-P vs. CRT-D

The choice between CRT with pacemaker (CRT-P) or CRT with defibrillator (CRT-D) should be based on:

• CRT-D is preferred for:

  • Patients with secondary prevention ICD indications
  • Patients with ischemic cardiomyopathy (higher risk of ventricular arrhythmias) 3
  • NYHA class II patients with LVEF ≤30% 1

• CRT-P may be appropriate for:

  • Very elderly patients
  • Patients with significant comorbidities limiting survival
  • Patients with non-ischemic cardiomyopathy and less severe LV dysfunction 3

Important Caveats and Considerations

1. QRS duration and morphology matter:

   • Benefit increases with QRS duration (greatest at ≥150 ms)
   • LBBB morphology predicts better response than RBBB or nonspecific IVCD 1
   • RBBB is associated with poorer outcomes 1

2. CRT is contraindicated in patients with narrow QRS (<120 ms):

   • Multiple trials (RethinQ, ESTEEM-CRT, LESSER-EARTH) showed no benefit or potential harm 1
   • Even with mechanical dyssynchrony on imaging, patients with narrow QRS do not benefit 1

3. Atrial fibrillation patients:

   • Require adequate rate control or AV nodal ablation to ensure high percentage of biventricular pacing 1
   • May have less pronounced benefit compared to patients in sinus rhythm

4. Response prediction:

   • Non-ischemic etiology typically shows better reverse remodeling than ischemic etiology 3
   • Women tend to have better response rates than men
   • Patients with more severe LV dilation may have diminished response

5. Ambulatory status for NYHA IV patients:

   • Class IV patients should be ambulatory and not have recent HF hospitalizations (within 1 month) 1
   • Reasonable survival expectation (>6 months) is needed

Optimization After CRT Implantation

• AV and VV delay optimization may improve response in some patients
• Continue guideline-directed medical therapy for HFrEF
• Regular follow-up to assess response and adjust device settings as needed
• Consider lead repositioning if no response and suboptimal LV lead position

CRT represents a significant advancement in HF management, offering substantial improvements in mortality, morbidity, and quality of life when applied to appropriate patients according to established guidelines.