Focus on right ventricular outflow tract septal pacing

Abstract

Experimental and clinical studies have shown that right ventricular apical pacing may result in long-term deleterious effects on account of its negative impact on left ventricular remodeling through desynchronization. This risk appears more pronounced in patients with even moderate left ventricular dysfunction and generally occurs after at least 1 year of pacing. As right ventricular apical pacing may be associated with the development of organic mitral insufficiency, other sites that allow for more physiological stimulation, such as right ventricular outflow tract septal pacing, have been developed, with good feasibility and reproducibility. However, the prospective randomized studies and meta-analyses to date have only demonstrated a modest effect on ejection fraction in the medium term, without any significant effect on quality of life and morbimortality. However, the absence of a favorable effect for right ventricular outflow tract septal pacing compared with right ventricular apical pacing in terms of clinical manifestations and patient prognosis appears to be more associated with the designs of these studies, which were not homogeneous with regard to methodology used, judgment criteria, follow-up and, especially, statistical power. Two randomized prospective multicentre studies are currently ongoing in order to evaluate the favorable effect of infundibular septal pacing, when considering the indirect negative effects of right ventricular apical pacing as reported in the literature.

Right Ventricular Outflow Tract Septal Pacing Is Superior to Right Ventricular Apical Pacing

“…3–4 These pathophysiological consequences are now attributed to the violation of several electrophysiological properties of the myocardium. 5 Electrical conduction in the myocardium is at least 4 times slower than that in the Purkinje system; conduction along muscle fibers is 2 times faster than that with perpendicular activation. 6 In addition, the conduction characteristics between the endocardial and epicardial layers are different.…”

“…1,5 For these reasons, alternative pacing sites with a more synchronous ventricular activation pattern have been explored. 1,5 …”

“…16 These conflicting studies appear to be associated with study designs that were not homogeneous regarding the methodology; judgment criteria; follow‐up; and, particularly, statistical power used. 5 In addition, limited studies have focused on the effect of pacing sites on structure and function of the left atrium, findings that may be important for the development of atrial arrhythmias. 15,17 P‐wave dispersion (PWD) is a novel prediction index of atrial arrhythmia.…”

“…7,8 In the setting of RVAP, the activation front becomes ellipsoidal, and slowed conduction results, particularly in the intermediate and epicardial layers. 1,5 For these reasons, alternative pacing sites with a more synchronous ventricular activation pattern have been explored. 1,5 The region and pacing alternatives to RVAP are numerous, including His-bundle pacing and para-His pacing, medial septum, lower septum, right ventricular outflow tract (RVOT) in the septal region, and pulmonary infundibulum.…”

“…1,5 For these reasons, alternative pacing sites with a more synchronous ventricular activation pattern have been explored. 1,5 The region and pacing alternatives to RVAP are numerous, including His-bundle pacing and para-His pacing, medial septum, lower septum, right ventricular outflow tract (RVOT) in the septal region, and pulmonary infundibulum. 9,10 Although these strategies are not well defined and standardized because of the ease of catheter implantation and catheter stability in this region, the most preferred area of pacing is the RVOT in the septal region.…”