Abstract 10954: Magnetocardiography Can Disclose Left Intraventricular Conduction Delay in Patients with Left Ventricular Dysfunction and Complete Right Bundle Branch Block
Background: Left ventricular (LV) intraventricular conduction delay (i.e., dyssynchrony), generally seen with left bundle branch block, further deteriorates hemodynamics and status of patients with heart failure (HF) due to LV dysfunction. In the presence of complete right bundle branch block (CRBBB), which is occasionally observed in HF and a possible negative predictor for cardiac resynchronization therapy outcomes, we can hardly estimate intra-LV conduction delay by ECG. Our newly developed magnetocardiographic (MCG) approach with 3 directional measurements capable of delineating the whole heart activation in a 3-D fashion (AHA 2010) may be useful for this purpose.
Methods: Using a 64-Ch MCG system (Hitachi), we repeated 3 measurements (1ms sample) with sensors placed close to anterior, posterior, and left lateral chest (in supine, prone, and lateral positions, respectively) in CRBBB patients with normal (N-CRBBB, n=11), and those with depressed LV function (D-CRBBB, n=13, LVEF 31±11%) and in healthy subjects (Cont, n=25). We averaged MCG signals (>20 beats) with simultaneously digitized ECG, which was used to synchronize 2-D current arrow maps for each recording. The ratio (LV/QRSd) of LV conduction time to QRS duration (QRSd) was calculated.
Results: QRSd was 89±6ms in Cont, 141±19ms in N-CRBBB, and 162±34ms in D-CRBBB (N-CRBBB vs. D-CRBBB N.S.). LV conduction time in N-CRBBB (54±6ms) was almost identical to that in Cont (51±5ms, N.S.). In contrast, LV conduction time in D-CRBBB was significantly prolonged (88±26 ms, p<0.001) compared with N-CRBBB (Figure A for N-CRBBB, and B for D-CRBBB representative cases). LV/QRSd was greater in D-CRBBB than in N-CRBBB (55±16 vs 39±5%, p<0.01). Of note, there was a strong correlation between echocardiographic LV diastolic dimension and LV conduction time (r= 0.91, p<0.01).
Conclusions: Our developed MCG approach can disclose intra-LV conduction delay in patients with LV dysfunction even when representing CRBBB.
- © 2011 by American Heart Association, Inc.