Rick Schreurs

69 Effective mechanical atrioventricular delay Atrial sensing Atrial pacing -5 0 5 10 50 100 150 200 250 mL AV-delay (ms) * -5 0 5 10 50 100 150 200 250 mL AV-delay (ms) * -5 0 5 10 50 100 150 200 250 AV-delay (ms) * -5 0 5 10 50 100 150 200 250 mL * -5 0 5 10 50 100 150 200 250 mL * -5 0 5 10 50 100 150 200 250 * Change in flow (mL) Change in flow (mL) AV-delay (ms) AV-delay (ms) AV-delay (ms) BiV pacing LV pacing RV pacing Δ Forward flow Δ Diastolic MR Figure 4. Absolute change in forward flow (red bars) and diastolic mitral regurgitation (grey bars) at various AV-delays during BiV (left), LV (middle) and RV (right) pacing in atrial pace (upper) and atrial sense (lower) mode, compared with their contribution at AV-delay 300ms. A decrease in mitral regurgitation is presented as positive bars since it leads to an increase in stroke volume. Values are presented as mean±SEM, * indicates P<0.05 using repeated measures ANOVA. Hemodynamic effect of atrioventricular optimization AV-delay optimization resulted in a parabolic curve for cardiac output and stroke work for all six pacing conditions (A-P and A-S with BiV, LV and RV pacing, see figure 5 ). During A-S the peak of the parabolic curve tended to occur at shorter AV-delays (142-150ms) than during A-P (157-171ms). In table 2 the hemodynamic parameters at the optimal AV-delay (AV opt ) are presented. All six pacing modes achieved a significant increase in cardiac output compared to BL values, ranging from +10.7% to +14.2%. Furthermore stroke work, mean arterial pressure, maximal LV pressure and RV end systolic pressure were significantly higher at AV opt compared to the BL value during all pacing modes. Ventricular filling was improved at AV opt , as evidenced by a significant increase in LV end diastolic volume in 5 out of 6 settings and in LV end diastolic pressure in 4 out of 6 settings. Interestingly, the increases in cardiac output and cardiac pressures occurred in the absence of a significant increase of LV and RV dP/dt max ( table 2 ). Diastolic MR tended to decrease in all settings, but was significantly lower compared to BL only in BiV and LV pacing in A-S mode. 4