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

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Pacing

Background:

• Conventional right ventricular (RV) apex pacing can cause asynchronous activation, reducing left ventricular (LV) pump function.
• Alternative pacing sites are explored to mitigate these adverse effects.

Purpose of the Study:

• To investigate if RV septum and LV septum/apex pacing sites improve LV electric activation, mechanics, hemodynamics, and efficiency over 4 months.
• To compare the effects of different pacing sites on cardiac function.

Main Methods:

• Mongrel dogs underwent AV nodal ablation and were randomized to 16 weeks of VDD pacing at RV apex, RV septum, LV apex, or LV septum.
• Electric activation, mechanical dyssynchrony (MRI tagging), blood flow redistribution (microspheres), and myocardial efficiency were assessed.

Main Results:

• RV apical and septal pacing significantly increased electric and mechanical dyssynchrony, reduced LV contractility, relaxation, and efficiency.
• LV apical and septal pacing did not significantly alter these parameters compared to intrinsic conduction.
• LV apical and septal pacing showed similar or better contractility and efficiency compared to biventricular pacing.

Conclusions:

• Acute and chronic LV apical and septal pacing maintain cardiac mechanics, contractility, relaxation, and efficiency near native levels.
• RV apical or septal pacing diminish these cardiac variables.
• LV pacing may offer advantages over biventricular pacing for cardiac function and efficiency.