Right or Left Ventricular Pacing in Young Minipigs With Chronic Atrioventricular Block

Abstract

Background-Left ventricular (LV) dyssynchrony may occur as a result of right ventricular (RV) pacing and is a known risk factor for the development of heart failure. In children with complete atrioventricular block, pacing-induced dyssynchrony lasting for decades might be especially deleterious for LV function. To determine the hemodynamic and ultrastructural remodeling after either RV free wall or LV apical pacing, we used a chronic minipig model. Methods and Results-Fourteen piglets 8 weeks of age underwent atrioventricular node ablation and were paced from either the RV free wall or the LV apex at 120 bpm for 1 year (7 age-matched minipigs served as controls with spontaneous heart rates of 104Ϯ5 bpm). Echocardiographic examinations, pressure-volume loops, patch-clamp investigations, and examinations of connexin43, calcium-handling proteins, and histomorphology were carried out. RV free wall-paced minipigs exhibited significantly more LV dyssynchrony than LV apex-paced animals, which was accompanied by worsening of LV function (maximum LV mechanical delay/LV ejection fraction: RV free wall pacing, 154Ϯ36 ms/28Ϯ3%, LV apical pacing, 52Ϯ19 ms/45Ϯ2%, control 47Ϯ14 ms/62Ϯ1%; Pϭ0.0001). At the cellular level, both pacemaker groups exhibited a significant reduction in L-type calcium and peak sodium current, shortening of action potential duration and amplitude, increased cell capacity, and alterations in the calcium-handling proteins that were similar for RV free wall-and LV apex-paced animals. Conclusions-The observed molecular remodeling seemed to be more dependent on heart rate than on dyssynchrony. LV apical pacing is associated with less dyssynchrony, a more physiological LV contraction pattern, and preserved LV function as opposed to RV free wall pacing. (Circulation. 2012;125:2578-2587.)Key Words: cardiac pacing, artificial Ⅲ myocardial contraction Ⅲ pediatrics Ⅲ ventricular remodeling T raditionally, permanent cardiac pacing has been carried out from the endocardial right ventricular (RV) apex. In smaller children, epicardial RV pacing sites were commonly used. Several larger adult [1][2][3] and smaller pediatric studies 4 -9 so far have shown that RV pacing may result in significant left ventricular (LV) dyssynchrony and impaired LV function, including the induction of progressive LV remodeling and failure. Alternative pacing sites have been looked for, including the RV septum and epicardial LV apex or free wall. Better preservation of LV synchrony and function could be shown in small observational studies in both mentioned LV pacing sites and in 1 recently published larger retrospective pediatric survey. 10 -14 Choosing an optimal pacing position may be of special importance in children subjected to cardiac pacing lasting for decades. However, until today, a prospective long-term study comparing the effects of RV or LV pacing on LV performance and ultrastructural morphology of the heart muscle has not been performed. Our aim was to examine the effects of RV free wall as opposed to LV apical pacing on LV...

Permanent Cardiac Pacing in Children: Choosing the Optimal Pacing Site

“…Our results also confirm data on preservation of LV function with LV apical or LV lateral wall pacing, [10][11][12][13][14] including a large retrospective pediatric multicenter survey 8 and a recently published experimental study. 22 Our present report does not show any superiority of RV septal over RV apical pacing. This is in agreement with another experimental work published by Mills et al 23 a few years ago.…”

“…33 The results of the present study also provide an important clinical confirmation of previously published experimental research. 22,23,34,35 Table 4.…”

Sheep can be used as animal model of regional myocardial remodeling and controllable work

“…Although the achieved conduction delay appears small compared to other animal models, it is as significant given the much faster conduction in the ovine heart [19]. Near doubling of QRS width during DDD pacing was measured, which is comparable to previously reported values in animal models of ablation or RV pacing in dogs [9] and pigs [20,21]. An overview explaining the major differences between RV pacing and ablation of left bundle branch is presented in Supplemental Table 2.…”

Electromechanical Dyssynchrony and Resynchronization of the Failing Heart

“…This was accompanied by a dislocalization of connexin 43 (Cx43) from the intercalated disk to the longitudinal plasma membrane. The latter was not observed, however, in a long-term study of dyssynchrony only in piglets 100 .…”