How Harmful is Conventional Right Ventricular Apical Pacing? Iatrogenic Left Bundle Branch Block: Need for Alternate Site Pacing
Keywords:cardiac pacing, left bundle branch block, selective site pacing, biventricular pacing, right ventricular outflow tract, cardiac dyssynchrony, heart failure
The right ventricular (RV) apex has been used as the traditional pacing site since the development of transvenous pacing in 1959. Some studies suggest that pacing the RV apex may cause an ???iatrogenic?? left bundle branch block and remodeling of the left ventricle and is therefore harmful. In the past decade, the need for alternate site pacing became imperative and there have been a multitude of studies of the hemodynamic, electrophysiological, electrocardiographic, and clinical effects of ventricular pacing at other sites.Pacing of the left ventricle singly or with biventricular pacing has emerged as an effective and safe therapy for moderate to severe congestive heart failure in patients with prolonged QRS complexes. Studies of alternate RV sites, like the RV outflow tract, have given mixed results, and further clarification of the specificsites of the RV outflow tract is needed. Direct His-bundle pacing is an attractive alternate pacing site because of the possible hemodynamic benefits that could be obtained by a normal activation sequence, but the small size and anatomic position of the His bundle have made this approach difficult. Bifocal RV resynchronization therapies have been used as an alternative to biventricular pacing.
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