Ventricular Conduction Defects in Women

Synopsis

Ventricular conduction defects considered include left bundle branch block (LBBB), isolated right bundle branch block (RBBB), bifascicular block (RBBB with left anterior or left posterior fascicular block (LAFB and LPFB, respectively) and indetermined type ventricular conduction defect (IVCD).

In the Women’s Health Initiative (WHI) study CHD mortality was increased for LBBB over threefold in CHD-free women and nearly threefold in women with CVD. The CHD mortality risk for isolated RBBB was increased significantly (1.62-fold) only in women with CVD as was the risk for IVCD (1.62-fold increase). The risk for all-cause mortality was increased significantly in women with CVD at baseline for LBBB (1.43-fold) and for bifascicular block (2.69-fold) but not in any other subgroup by bundle branch block category and CVD status.

The risk for incident HF was evaluated in another WHI study. Compared to women with no bundle branch block, LBBB and IVCD were strong predictors of incident HF. RBBB was not a significant predictor of incident HF in multivariable-adjusted risk model but RBBB combined with LAFB was a strong predictor. QRS duration was an independent predictor of incident HF only in LBBB, with more pronounced risk for QRS ≥140 ms than for <140 ms. QRS nondipolar voltage (RNDPV) was an independent predictor in both RBBB and LBBB and in LBBB in addition, spatial QRS/T angle and ST J-point depression in aVL were independent predictors.

Repolarization abnormalities in bundle branch blocks are generally considered as strictly secondary to increased QRS duration and altered spatial sequence of depolarization and consequently clinically of little diagnostic or prognostic utility. This chapter covers more recent studies which demonstrate that repolarization abnormalities also in bundle branch blocks are important predictors of increased risk of coronary heart disease (CHD) and cardiovascular disease (CVD) mortality and adverse events such as heart failure (HF).