The Left Ventricular Apex is the Optimal Site for Pediatric Pacing:

Abstract

Pacing at the commonly used right ventricular (RV) apex results in impaired ventricular performance. Previous animal studies indicated that the left ventricular (LV) apex is a superior pacing site. The purpose of this study was to investigate in dogs whether this good performance is associated with a more synchronous electrical activation pattern of the LV and whether the LV apex is also a good pacing site in children. In 11 healthy dogs and 8 children undergoing cardiac surgery, dual chamber pacing was performed at the RV apex, LV apex and LV lateral free wall (LVFW). In dogs, a basket electrode was inserted into the LV to assess pattern and timing of LV endocardial activation. In the children, hemodynamic measurements were performed immediately after recovery from cardiopulmonary bypass. In dogs, LV apex pacing resulted in synchronous activation around the LV circumference whereas RV apex and LVFW pacing resulted in asynchrony of activation between the septum and LVFW. In both canine and children's hearts most hemodynamic variables remained at sinus rhythm level during LV apex pacing, but LVdPdtmax, stroke work (dogs), and pulse pressure (children) were reduced as compared with sinus rhythm during RV apex and LVFW pacing. LV apex pacing results in synchronous activation of the LV and is, in adult dogs and in children, associated with superior hemodynamic performance.

Chronic Left Ventricular Pacing Preserves Left Ventricular Function in Children

“…This is consistent with other studies, in which QRS duration during pacing was not related to cardiac function [25,36,42]. It is important to bear in mind that QRS duration reflects total biventricular activation time, whereas intraventricular mechanical synchrony and sequence of electrical ventricular activation [26] probably are more important determinants of LV function [19,36]. Given the absence of a consistent correlation between cardiac function and QRS duration in acute and chronic pacing studies, we discourage the use of QRS duration as a tool for the selection of an optimal epicardial pacing site in children.…”

“…In parallel with the acute decrease in cardiac pump function during RV pacing [14,36], chronic RV pacing significantly depressed shortening fraction in the current study. Furthermore, the LV eccentricity index was significantly increased after chronic RV pacing.…”

“…During RV pacing, a left bundle branch block pattern of activation is created [16,19,26,36]. In the current study, RV-paced children showed significant intraventricular mechanical dyssynchrony, with motion of the interventricular septum toward the LV posterior wall more than 300 ms before the first peak of inward LV posterior wall movement.…”

“…Superior hemodynamic performance during LV pacing compared with RV pacing probably is caused by a more favorable balance between interventricular synchrony [13], intraventricular synchrony [36], and the sequence of electrical ventricular activation [26] during LV pacing. The idea that the sequence of activation is an important determinant of cardiac pump function is supported by other studies as well [25,26].…”

“…However, RV apex pacing causes an acute decrease in left ventricular (LV) function in animals [26], adults [6] and children [14,36]. During chronic RV pacing in children, LV function, morphology [30,31], and histology [15] are at risk for deterioration over time (for review see Karpawich [16]).…”