Left ventricular septal and left ventricular apical pacing chronically maintain cardiac contractile coordination, pump function and efficiency.
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.


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.
Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, 6200 MD Maastricht, The Netherlands.
Robert W
RW
Mills
Richard N
RN
Cornelussen
Lawrence J
LJ
Mulligan
Marc
M
Strik
Leonard M
LM
Rademakers
Nicholas D
ND
Skadsberg
Arne
A
van Hunnik
Marion
M
Kuiper
Anniek
A
Lampert
Tammo
T
Delhaas
Frits W
FW
Prinzen
D000704:Analysis of Variance; D000818:Animals; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D002306:Cardiac Volume / Q000502:physiology; D004285:Dogs; D006329:Heart Conduction System / Q000502:physiology*; D009200:Myocardial Contraction / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D011897:Random Allocation; D013318:Stroke Volume / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology*; D054088:Ventricular Septum / Q000502:physiology* / Q000601:surgery