P764Which is the best combination of pacing sites on left ventricular torsional parameters after an acute experimental myocardial infarction?

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Purpose: Left ventricular (LV) torsional parameters are known to play an important role in systolic and diastolic LV performance. The purpose of this study is to examine the effect of various combinations of pacing (P) sites on LV function including rotational and torsional parameters after an acute myocardial infarction (AMI).Methods: AMI was produced by occlusion of the left anterior descending coronary artery in 5 healthy pigs. Atrio-ventricular epicardial pacing (P) was performed with various combinations of right ventricular (RV) and/or LV P sites 30 min after AMI. The combinations tested were:1) RVapex+LVapex lateral, 2) RVapex+ LVbasal posterior, 3) RVapex+ LVbasal anterior, 4) RVapex+LVbasal anterior +LV basal posterior, 5) LVbasal posterior+LVapex lateral, 6) LVbasal posterior + LVbasal anterior and 7) LVbasal anterior + LVapex lateral in a random order. LV torsion was calculated by measuring LV basal and apical rotation from basal and apical short-axis epicardial planes with speckle-tracking technique using EchoPac software. LV torsion, ejection fraction (EF), fractional shortening of long (fsl) and short (fss)axes, cardiac output (CO), QRS duration, apical rotation (rotap), basal rotation (rotbas), circumferential strain apical (circapex) and basal (circbasal) in sinus rhythm were compared to every P combination.Results: TableConclusions: The combination of P in LV basal posterior and LV apex lateral sites increased significantly the LV torsion and torsion rate in comparison to sinus rhythm after AMI. More data are needed to confirm the beneficial effect of this combination.

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