Cardiac Resynchronization Therapy

Introduction to Cardiac Resynchronization Therapy

Cardiac Resynchronization Therapy (CRT) is recommended for heart failure patients with reduced ejection fraction and electrical dyssynchrony, as it significantly improves cardiac output through enhanced left ventricular function and reverse remodeling, according to the American College of Cardiology 1
The goal of CRT is to restore electromechanical synchrony by coordinating ventricular contraction, improving the efficiency of cardiac pumping, as noted by the American College of Cardiology 1

The American College of Cardiology recommends CRT for patients with NYHA class III or ambulatory class IV heart failure, LVEF ≤35%, and QRS ≥120 ms, with strong evidence (Class I) 1, 2, 3
Patients with LVEF ≤35%, LBBB, and QRS duration ≥150 ms with NYHA class II-IV symptoms despite optimal medical therapy are recommended for CRT, with strong evidence (Class I) 1, 2, 3
The American Heart Association suggests that patients with LVEF ≤35%, non-LBBB pattern, and QRS ≥150 ms with NYHA class III/ambulatory IV symptoms may benefit from CRT, with moderate evidence (Class IIa) 1, 3
Predictors of response to CRT include LBBB morphology and QRS duration ≥150 ms, with strong evidence (Class I) 1, 3
Non-ischemic cardiomyopathy may result in better structural remodeling than ischemic cardiomyopathy, although this is not directly related to CRT response 3

CRT provides a 22-36% reduction in all-cause mortality, with strong evidence (Class I) 2, 3, 4
CRT reduces heart failure hospitalizations by 37-52%, with strong evidence (Class I) 2, 3, 4
CRT improves cardiac function by increasing LVEF by approximately 3-6.9% in responders, with strong evidence (Class I) 2, 3, 4
CRT enhances quality of life by improving functional status and NYHA class, with strong evidence (Class I) 1, 2, 3, 4

CRT-D is preferred for patients meeting criteria for both CRT and ICD, with strong evidence (Class I) 4, 5
CRT-P is appropriate for patients with significant comorbidities limiting survival, with moderate evidence (Class IIa) 4, 6
Ensuring high percentage (≥95%) of biventricular pacing is crucial for optimal CRT effectiveness, with strong evidence (Class I) 2, 3, 4
Targeting LV lead placement to the latest activated areas (typically lateral or posterolateral vein) is recommended, with strong evidence (Class I) 2, 6, 7

Patients with mild heart failure (NYHA I-II) may benefit from CRT, with moderate evidence (Class IIa) 2, 4
Patients with narrow QRS complex (<120 ms) are generally not recommended for CRT, with strong evidence (Class I) 1, 3
Patients with atrial fibrillation may benefit from CRT if adequate biventricular pacing can be achieved, with moderate evidence (Class IIa) 2, 3
Class IV patients should be ambulatory, not have recent HF hospitalizations, and have a reasonable survival expectation (>6 months) 4

Patients with comorbidities and/or frailty limiting survival with good functional capacity to less than 1 year should not receive CRT 3
Patients with QRS duration <120 ms without evidence of electrical dyssynchrony are not candidates for CRT, despite echocardiographic evidence of dyssynchrony 3
Patients with significant comorbidities limiting survival to <1 year should not receive CRT 3