Thus, current guidelines of LBBB require absence of q waves in lead I and V5/V6.

Initial left-to-right septal forces should be absent in complete LBBB (cLBBB) ( Figure 1). 15–18Īn ECG showing LV conduction delay may be due to: true proximal LBBB delay in the distal conduction system or LV conduction delay. The 12-lead electrocardiogram (ECG) remains one of the strongest predictors of response to CRT: a QRS duration of ≥150 ms pre-implant 3, 12, 13 a reduced QRS duration (delta-QRS) with LV pacing 6, 14 and a left bundle branch block (LBBB) morphology on the pre-implant ECG-patients with right bundle branch block (RBBB) or non-specific intraventricular conduction delay (IVCD) showing little or no benefit.

8 Conversely, CRT without objective LV improvement may be proarrhythmic. 7, 8 Generally speaking, the magnitude of improvement in LV ejection fraction (LVEF) and reduction in LV dimensions in patients with heart failure is proportional to survival 9, 10 specifically, reduction in LV dimension but not clinical response to CRT is associated with reduced mortality.

3, 4 Still, ∼30% of patients derive no clinical benefit with CRT 5, 6 and a smaller percentage display reverse LV remodelling, or improved LV function. Cardiac resynchronization therapy, Electrocardiogram, Electrophysiology, Left bundle branch, Cardiac failureĬardiac resynchronization therapy (CRT) reduces heart failure symptoms, 1–3 improves left ventricular (LV) function, and decreases mortality in New York Heart Association (NYHA) II–NYHA IV (ambulatory) heart failure with a wide QRS complex.

Ivcd ecg definition