PMC3021246_01
12-Lead surface electrocardiogram during normal ventricular conduction and during left bundle branch block. a Narrow QRS (90 ms), heart rate 67 bpm. b Wide QRS (160 ms) with complete LBBB, heart rate 73 bpm
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Fig1
A 24-h electrocardiogram registration showed complete LBBB that disappeared at slower heart rates between 70 and 80 bpm (Fig. 1).
Acute haemodynamic response to cardiac resynchronisation therapy (CRT) during left bundle branch block (LBBB) and normal ventricular activation. a Absolute LV dP/dtmax values at baseline (no CRT) and during CRT with four different AV delays. b Relative increase in LV dP/dtmax during CRT compared with baseline without CRT. Mean +- standard error are shown. Squares narrow QRS, diamond LBBB, AVI intrinsic atrioventricular interval, AV delay atrioventricular delay
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PMC3021246_01_12471_2010_48_Fig2_HTML.jpg
Fig2
LBBB (QRS 90 ms, interventricular delay 60 ms). LBBB caused a sudden decline in average baseline dP/dtmax from 820 +- 75 to 662 +- 52 mmHg/s (p < 0.001, paired t test; Fig. 2a). CRT during LBBB increased dP/dtmax by 19.9% (Fig. 2b). In the absence of LBBB, optimised CRT did not change dP/dtmax compared with baseline; CRT with short AV delay worsened dP/dtmax (Fig. 2b).