Effect of Different Left Ventricular Pacing Sites on Cardiac Output

Background: Epicardial wire can be placed in any epicardial position during open heart surgery. The aim of this study was to evaluate the effect of different epicardial pacing sites on cardiac output in patients who underwent cardiac surgery. Method: Patients who underwent coronary artery bypass grafting were selected for this study. Epicardial wire was implanted at 4 locations: 1-RV near apex (usual site); 2-LV near apex; 3-LV upper lateral; 4-LV upper septal anterior. External single chamber generator was used and pacing rate was 10 beat/ minute greater than patient heart rate. Cardiac output (CO) was measured by NICO system which uses Fick's method to calculate cardiac output from respiratory O2 and CO2. Result: In all patients, CO during patients' sinus rhythm was more than RV apical pacing (P< 0.001), LV apical pacing (P=0.016) and LV upper septum pacing (P=0.002). Regarding left versus right side of pacing, LV lateral wall make significantly more output than RV apex (P=0.005). When left sides are compared, LV lateral wall create more output than LV apex (P< 0.001). In comparison, LV apex produces more output than LV upper septum (P< 0.001). Also output from LV lateral wall pacing exceeds LV upper septum (P< 0.001). So the best LV site for pacing seems to be LV lateral wall. Conclusion: Pacing from left ventricular lateral wall pumps blood most efficiently than other sites of LV and RV wall. This finding suggests LV lateral wall as a best site for post cardiac surgery pacing.