Left Ventricular Septal and Left Ventricular Apical Pacing Chronically Maintain Cardiac Contractile Coordination, Pump Function and Efficiency

Abstract

Background-Conventional right ventricular (RV) apex pacing can lead to adverse clinical outcome associated with asynchronous activation and reduced left ventricular (LV) pump function. We investigated to what extent alternate RV (septum) and LV (septum, apex) pacing sites improve LV electric activation, mechanics, hemodynamic performance, and efficiency over 4 months of pacing. Methods and Results-After AV nodal ablation, mongrel dogs were randomized to receive 16 weeks of VDD pacing at the RV apex, RV septum, LV apex, or LV septum (transventricular septal approach). Electric activation maps (combined epicardial contact and endocardial noncontact) showed that RV apical and RV septal pacing induced significantly greater electric desynchronization than LV apical and LV septal pacing. RV apex and RV septal pacing also significantly increased mechanical dyssynchrony, discoordination (MRI tagging) and blood flow redistribution (microspheres) and reduced LV contractility, relaxation, and myocardial efficiency (stroke work/myocardial oxygen consumption). In contrast, LV apical and LV septal pacing did not significantly alter these parameters as compared with the values during intrinsic conduction. At 16 weeks, acute intrasubject comparison showed that single-site LV apical and LV septal pacing generally resulted in similar or better contractility, relaxation, and efficiency as compared with acute biventricular pacing. Conclusions-Acute and chronic LV apical and LV septal pacing maintain regional cardiac mechanics, contractility, relaxation, and efficiency near native levels, whereas RV apical or RV septal pacing diminish these variables. Acute LV apical and LV septal pacing tend to maintain or improve contractility and efficiency compared with biventricular pacing. (Circ Arrhythmia Electrophysiol. 2009;2:571-579.)Key Words: pacing Ⅲ hemodynamics Ⅲ mapping Ⅲ mechanics Ⅲ oxygen C ompared with normal ventricular activation, conventional right ventricular (RV) apex pacing is associated with asynchronous left ventricular (LV) activation, abnormal contraction, and reduced pump function (for review, see reference 1). 1 These adverse effects have been associated with an increased risk of developing heart failure (for review, see reference 1). 1 Also contributing to this adverse outcome is a reduction in myocardial efficiency during ventricular pacing, which increases total myocardial oxygen demand. Consequently, paced hearts can be expected to be more susceptible to ischemia when coronary reserve is limited, 2 as during coronary artery disease and/or overload of the heart. Clinical Perspective on p 579Several studies have sought alternative pacing sites to improve hemodynamic performance. Because pacing leads are usually implanted transvenously, alternate sites within the RV have been studied most intensively, but results of the various studies are mixed. 3,4 Experimental and clinical studies indicate that LV pacing sites often render better hemodynamic performance than RV pacing sites. [5][6][7] In a previous acute canine stu...

Permanent Cardiac Pacing in Adults with High Grade Atriovetricular Block and Preserved Left Ventricular Function: Optimal Mode and Site of Pacing

“…In contrast, it has been shown that the RV pacing site, which leads to the best LV function, is not predicted by anatomical position or by QRS duration (Peschar et al, 2003). The hemodynamic superiority of LV apex and LV septum pacing may be explained by a relatively physiological sequence of electrical activation when pacing from these sites (Mills et al, 2009;Peschar et al, 2003). Some investigators have proposed the idea of a hemodynamic "sweet spot," where each patient has a particular optimal pacing site (Karpawich & Mital, 1997;Tse et al, 2002;Tse et al, 2009 b).…”

“…In contrast, LV apical and LV septal pacing did not significantly alter these parameters as compared with the values during intrinsic conduction. At 16 weeks, acute intrasubject comparison showed that single-site LV apical and LV septal pacing generally resulted in similar or better contractility, relaxation, and efficiency as compared with acute biventricular pacing (Mills et al, 2009). In the animal study described by Mills et al (Mills et al, 2009), the lead was implanted in the RV midseptum, based solely on position and not optimizing the QRS complex.…”

“…At 16 weeks, acute intrasubject comparison showed that single-site LV apical and LV septal pacing generally resulted in similar or better contractility, relaxation, and efficiency as compared with acute biventricular pacing (Mills et al, 2009). In the animal study described by Mills et al (Mills et al, 2009), the lead was implanted in the RV midseptum, based solely on position and not optimizing the QRS complex. Surprisingly, none of the parameters investigated in this study (electric mapping, hemodynamic, regional strains, efficiency) showed a significant difference between RV apical and RV septal pacing.…”

“…Inversely, in other animal studies (Mills et al, 2009;Peschar et al, 2003), it was demonstrated in canine hearts with normal ventricular conduction that LV function is maintained at SR level when pacing the LV apex or the LV endocardial surface of the interventricular septum (Mills et al, 2009;Peschar et al, 2003) and that electric desynchronization pacing was significantly greater in RV apical and RV septal than LV apical and LV septal pacing (Mills et al, 2009;Wyman et al, 2002). It was also demonstrated by using tagged magnetic resonance imaging that RV apex and RV septal pacing increased significantly mechanical dyssynchrony, discoordination (MRI tagging) and blood flow redistribution (microspheres) and reduced LV contractility, relaxation, and myocardial efficiency (stroke work/myocardial oxygen consumption).…”

Common sense or evidence: an optimal place for right and left ventricular leads?

“…However, experimental and clinical studies demonstrated that various RV pacing sites did not recruit the His-Purkinje system [2,4]. The majority of LV activation instead occurred via slow and dyssynchronous direct myocardial to myocardial cell conduction and that in terms of mechanical dyssynchrony, hemodynamic and electrical parameters septal pacing was not superior to RVapical pacing [2,4]. A recent cross-sectional multicenter study demonstrated that for pacing in RV, there is no better alternative to apex [5].…”