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Original Articles

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

Robert W. Mills, PhD; Richard N. Cornelussen, PhD; Lawrence J. Mulligan, PhD; Marc Strik, MD; Leonard M. Rademakers, MD; Nicholas D. Skadsberg, PhD; Arne van Hunnik, MSc; Marion Kuiper, MSc; Anniek Lampert, MSc; Tammo Delhaas, MD, PhD and Frits W. Prinzen, PhD

From the Departments of Physiology, Pediatrics, and Cardiothoracic Surgery (R.W.M., R.N.C., M.S., L.M.R., A.v.H., M.K., A.L., T.D., F.W.P.), Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands; Bakken Research Center (R.N.C.), Medtronic, BV, Maastricht, The Netherlands; and Medtronic, Inc (L.J.M., N.D.S.), Minneapolis, Minn.

Correspondence to Frits W. Prinzen, PhD, Department of Physiology, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands. E-mail Frits.Prinzen{at}fys.unimaas.nl

Received May 28, 2009; accepted August 24, 2009.

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.

Key Words: pacing • hemodynamics • mapping • mechanics • oxygen

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CLINICAL PERSPECTIVE

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