Abstract
Aim. To assess the effect on left ventricular (LV) function of atrioventricular (AV) and ventricular pacing at the LV apical or lateral wall and to compare the normal torsional and deformation pattern of the intact LV myocardium with those created by the aforementioned LV pacing modes and sites. Methods. Experiments were conducted in pigs (n = 21) with normal LV function to investigate the acute hemodynamic effects of epicardial AV and ventricular LV pacing at the LV apical or lateral wall. Torsional and deformation indices of LV function were assessed using speckle tracking echocardiography. Results. AV pacing at the apex revealed a significant reduction in the radial strain of the base (P < 0.03), without affecting significantly the ejection fraction and the LV torsion or twist. In contrast, AV pacing at the lateral wall produced, in addition to the reduction of the radial strain of the base (P < 0.01), significant reduction of the circumferential and the radial strain of the apex (both P < 0.01) as well as of the ejection fraction (P < 0.002) and twist (P < 0.05). Conclusions. In pig hearts with intact myocardium, LV function is maintained at sinus rhythm level when AV pacing is performed at the LV apex.
Highlights
Temporary epicardial pacing is commonly indicated in cardiac surgical patients, when right ventricular (RV) and/or right atrial (RA) pacing wires are used to prevent postoperative bradyarrhythmia and atrioventricular (AV) block
The role of speckle tracking echocardiography (STE) in the assessment of the effects of RV apical pacing on left ventricular (LV) function and the upgrade from RV to biventricular pacing have been evaluated in few studies [4, 5]
The present study, performed in pig hearts with normal ventricular conduction, demonstrates that LV function was maintained at the same level as in sinus rhythm when AV pacing was implemented at the LV apex
Summary
Temporary epicardial pacing is commonly indicated in cardiac surgical patients, when right ventricular (RV) and/or right atrial (RA) pacing wires are used to prevent postoperative bradyarrhythmia and atrioventricular (AV) block. There is growing interest in seeking methods that use different pacing modes and/or pacing sites to maximize the benefits and minimize the harmful effects of artificial cardiac stimulation on LV function [1]. In these patients, frequent echocardiographic investigation is needed to follow up the LV function, even if patients remain asymptomatic. Novel two-dimensional speckle tracking echocardiography (STE) allows detailed evaluation of LV mechanics, including LV mechanical dyssynchrony, LV strain, and LV torsion [2, 3] This technique provides important additional information for the selection of the optimal pacing site. Data based on STE comparing the effects of different LV pacing modes (dual chamber versus single chamber pacing) and sites on the LV mechanics, LV strain, and LV torsion are still lacking
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