How Harmful is Conventional Right Ventricular Apical Pacing? Iatrogenic Left Bundle Branch Block: Need for Alternate Site Pacing

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 specific sites 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. I N T R O D U C T I O N Since the first report of the use of the transvenous route for pacemaker implantation in 1959 by Furman, the right ventricular (RV) apical region has represented the preferred pacing site [1]. The main reason has been the ease of implantation and the stability of passive-fixation leads in the apical trabeculae. However, apart from some specific diseases like hypertrophic cardiomyopathy, RV apical pacing often results in substantial functional, hemodynamic, electrical, and structural changes as already demonstrated in many studies. It is interesting to note that the roentgenogram from the early report of Furman shows the pacing lead position in the RV outflow tract (RVOT) [1]. As early as 1925, Carl Wiggers showed that RV apical pacing was associated with a diminished dP/dt and an asynchronous contraction pattern [2]. It is only in recent years that interest in the use of alternate pacing sites has developed. Tse et al [3] have shown that RV apical pacing produces significant myocardial perfusion defects, apical wall-motion abnormalities (incidence increases with the duration of pacing), and worsening of global left ventricular function during long-term pacing. Several other studies confirmed the hypothesis that RV apical pacing negatively CARDIOLOGY UPDATE 2006 1st Department of Cardiology, “Evagelismos” General Hospital of Athens, Athens, Greece HOSPITAL CHRONICLES 2006, SUPPLEMENT: 160–175 Address for correspondence: Kostas G. Kappos, MD Ass. Director of Cardiology