Electrocardiographic Features and Prevalence of Bilateral Bundle Branch Delay
Background—Definitive diagnosis of bilateral bundle branch delay/block (BBBD) may be made when catheter induced right bundle branch block (RBBB) develops in patients with baseline left bundle branch block (LBBB). We hypothesized that a RBBB pattern with absent S waves in leads I and aVL will identify BBBD.
Methods and Results—Fifty patients developing transient RBBB pattern in lead V1 during right heart catheterization were studied. Patients were grouped according to whether the baseline ECG demonstrated a normal QRS, left fascicular blocks or LBBB pattern. The RBBB morphologies in each group were compared. The prevalence of BBBD pattern was examined in our hospital ECG database. All patients with baseline normal QRS complexes (n=30) or left fascicular blocks (4 anterior, 5 posterior) developed a typical RBBB pattern. Among the 11 patients with a baseline LBBB pattern, 7 developed an atypical RBBB pattern with absent S waves in leads I and aVL and the remaining 4 demonstrated a typical RBBB. The absence of S waves in leads I and aVL during RBBB was 100% specific and 64% sensitive for the presence of pre-existing LBBB. Among the consecutive 2253 hospitalized patients with RBBB, 34 (1.5%) had the BBBD pattern.
Conclusions—An ECG pattern of RBBB in lead V1 with absent S wave in leads I and aVL indicates concomitant LBB delay. 'Pure RBBB' and bifascicular blocks are associated with S waves in leads I and aVL.
- Received August 24, 2013.
- Revision received June 8, 2014.
- Accepted June 16, 2014.