What is the recommended treatment approach for patients undergoing Cardiac Resynchronization Therapy (CRT)?

Cardiac Resynchronization Therapy: Evidence-Based Treatment Approach

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

Patient Selection Criteria

Class I Recommendations (Strongest Evidence)

• LBBB with QRS duration >150 ms: CRT is recommended for chronic heart failure patients with LVEF ≤35% who remain in NYHA functional class II, III, and ambulatory IV despite adequate medical treatment 1
• LBBB with QRS duration 120-150 ms: CRT is recommended for chronic heart failure patients with LVEF ≤35% who remain in NYHA functional class II, III, and ambulatory IV despite adequate medical treatment 1

Class IIa Recommendations (Should be Considered)

• Non-LBBB with QRS duration >150 ms: CRT should be considered in chronic heart failure patients with LVEF ≤35% who remain in NYHA functional class II, III, and ambulatory IV despite adequate medical treatment 1

Class IIb Recommendations (May be Considered)

• Non-LBBB with QRS duration 120-150 ms: CRT may be considered in chronic heart failure patients with LVEF ≤35% who remain in NYHA functional class II, III, and ambulatory IV despite adequate medical treatment 1

Class III Recommendations (Not Recommended)

• QRS duration <120 ms: CRT is not recommended in patients with chronic heart failure with QRS duration <120 ms 1, 2

Device Selection

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

1. CRT-D preferred for:

   • Secondary prevention ICD indications
   • Ischemic cardiomyopathy
   • NYHA class II patients with LVEF ≤30% 2

2. CRT-P may be appropriate for:

   • Very elderly patients
   • Patients with significant comorbidities limiting survival
   • Non-ischemic cardiomyopathy with less severe LV dysfunction 2

Special Populations

Atrial Fibrillation Patients

• CRT can be useful in patients with atrial fibrillation and LVEF ≤35% if:
  • AV nodal ablation or pharmacologic rate control will allow near 100% ventricular pacing 1, 2

Patients with Conventional Pacemaker Indication

• In patients with a conventional indication for pacing, NYHA III/IV symptoms, LVEF ≤35%, and QRS ≥120 ms, a CRT-P/CRT-D is indicated 1
• Chronic right ventricular pacing in patients with LV dysfunction should be avoided 1

Timing of Implantation

Patients should generally not be implanted during admission for acute decompensated heart failure. Guidelines recommend:

• Optimizing guideline-directed medical therapy first
• Reviewing the patient as an outpatient after stabilization 1

Optimization of CRT

The standard modality of CRT pacing consists of:

• Simultaneous RV and LV pacing
• Sensed AV delay programmed between 100-120 ms
• LV lead preferably located in a lateral or posterolateral vein 1

The TARGET trial demonstrated that positioning the LV lead at the latest activated areas (as assessed with speckle tracking echocardiography) resulted in:

• Greater proportion of echocardiographic responders (70% vs. 55%)
• More clinical responders
• Lower rates of all-cause mortality and heart failure hospitalizations 1

Expected Benefits

CRT provides significant clinical benefits including:

• 36% reduction in all-cause mortality in NYHA III-IV patients 2
• 52% reduction in unplanned hospitalizations for worsening heart failure 2
• Improved functional status with increased 6-minute walk distance by approximately 20% 2
• Promotion of reverse remodeling with reduction in LV volumes and improvement in LVEF 2, 3

Common Pitfalls and Caveats

1. Patient selection errors:

   • Implanting in patients with narrow QRS (<120 ms) shows no benefit and potential harm 1, 2
   • RBBB morphology is associated with poorer outcomes than LBBB 1, 2

2. Suboptimal lead placement:

   • LV lead placement should target the latest activated areas for optimal response 1

3. Inadequate device programming:

   • Failure to achieve biventricular pacing close to 100% of the time reduces effectiveness 1

4. Atrial fibrillation management:

   • Without adequate rate control or AV nodal ablation, CRT may be ineffective in AF patients 2

5. Timing of implantation:

   • Implanting during acute decompensated heart failure may lead to suboptimal outcomes 1

By following these evidence-based guidelines for patient selection and device optimization, CRT can significantly improve morbidity, mortality, and quality of life in appropriately selected heart failure patients.