What are the indications for Cardiac Resynchronization Therapy (CRT) in Heart Failure (HF)?

From the Guidelines

Cardiac resynchronization therapy pacing (CRTP) is indicated for heart failure patients with left ventricular ejection fraction (LVEF) ≤35%, QRS duration ≥120 ms, and NYHA class III-IV symptoms despite optimal medical therapy, as stated in the most recent guidelines 1. The indications for CRTP in heart failure (HF) are based on the patient's symptoms, left ventricular function, and QRS duration.

• The patient should have a left ventricular ejection fraction (LVEF) ≤35%
• A QRS duration ≥120 ms
• And be in NYHA class III-IV, despite being on optimal medical therapy, including beta-blockers, ACE inhibitors/ARBs/ARNI, and mineralocorticoid receptor antagonists for at least 3 months before considering CRTP 1. The therapy is most beneficial for those with sinus rhythm, though selected patients with atrial fibrillation may benefit if adequate biventricular pacing can be achieved (>98% of beats) 1. CRTP works by correcting electrical dyssynchrony between the ventricles, which improves cardiac contractility, reduces mitral regurgitation, and promotes reverse remodeling, leading to improved exercise capacity, quality of life, and reduced heart failure hospitalizations and mortality 1. Patients should have a reasonable life expectancy (generally >1 year) to justify the procedure, as stated in the guidelines 1. CRTP differs from CRTD by not including a defibrillator component, making it appropriate for patients who need resynchronization but not defibrillation capability. Some key points to consider when evaluating patients for CRTP include:
• The presence of left bundle branch block (LBBB) morphology, which is associated with a greater benefit from CRTP 1
• The patient's ability to tolerate the procedure and the presence of any comorbidities that may affect their survival or quality of life 1. Overall, CRTP is a valuable treatment option for patients with heart failure who meet the indicated criteria, and can improve their symptoms, quality of life, and survival, as supported by the most recent and highest quality study 1.

From the Research

Indications for CRT in HF

The indications for Cardiac Resynchronization Therapy (CRT) in Heart Failure (HF) are as follows:

• Symptomatic systolic heart failure (HF) and left bundle branch block (LBBB), despite optimal medical therapy (OMT) 2
• Left ventricular ejection fraction (LVEF) ≤ 35%, sinus rhythm and typical LBBB with QRS duration ≥ 150 ms 2
• Medically intractable or recurrent after catheter ablation atrial fibrillation (AF), AV nodal ablation as an adjuvant therapy may be considered in patients qualifying for the implantation of a biventricular system 2
• Increased pacing of the right ventricle is not desirable, alternative pacing sites and strategies are available if CRT is not feasible and effective in patients 2
• New York Heart Association (NYHA) classes II-IV, LVEF of 36-45%, and left bundle branch block (LBBB) may derive significant clinical and structural benefit from CRT 3

Patient Selection

Patient selection for CRT is crucial, and the following factors should be considered:

• QRS morphology, particularly left bundle-branch block pattern 4
• Extent of QRS prolongation 4
• Etiology of cardiomyopathy 4
• Rhythm, and whether the patient requires or will eventually need antibradycardia pacing 4
• Baseline severity of functional impairment, as patients with NYHA class I may derive long-term benefit in cardiac structure and function, while certain NYHA class IV patients may be too sick to realize long-term mortality benefits from CRT 4

Limitations

CRT may not be beneficial for all patients, and the following limitations should be considered:

• Patients with QRS duration ≤ 130 ms may not benefit from CRT, and may even have higher all-cause mortality compared to implantable cardiac defibrillator (ICD) therapy 5
• Patients with systolic heart failure and QRS interval ≤ 130 ms may not have a significant reduction in morbidity and mortality with CRT 5