Rick Schreurs

68 Chapter 4 The diastolic filling pattern during A-S differed from A-P especially at the shortest AV-delay where LA contraction started prior to ventricular activation, which resulted in a visible A-wave and significantly lower RAP max and LAP max (see lower row figure 3 ). E- and A-wave fusion seemed to happen at a shorter AV-delay and diastolic MR was present also at the shortest AV-delays. No major differences between the various ventricular pacing sites could be observed. Atrial pacing Atrial sensing Flow (mL/s) 0 10 20 E 100 200 300 400 500 -500 0 500 0 10 20 E A 100 200 300 400 500 -500 0 500 0 10 20 E A 100 200 300 400 500 -500 0 500 Pressure (mmHg) Flow (mL/s) Time (ms) 0 10 20 E A 100 200 300 400 500 -500 0 500 0 10 20 E 100 200 300 400 500 -500 0 500 FF MR SV LV RV LA RA 0 10 2 E 250 500 -500 0 500 0 10 20 E A 250 500 -500 0 500 0 10 20 E A 250 500 -500 0 500 0 10 20 E A 250 500 -500 0 500 0 10 20 E A 250 500 -500 0 500 AV-delay 50ms Pressure (mmHg) 250ms 100ms 150ms 200ms Figure 3. Typical example of changes in left ventricular filling during BiV pacing at various AV-delays in atrial pacing (upper row) and atrial sensing (lower row) mode. Left (LA) and right atrial (RA) and left (LV) and right ventricular (RV) pressures are shown. Ventricular filling (FF: forward flow) is de - picted in grey and diastolic mitral regurgitation (MR) in yellow. The vertical light grey zone indicates diastole. Note the progression in diastolic MR with increasing AV-delays, the fusion of E and A-wave at long AV-delays and truncation of the A-wave at short AV-delays, especially during atrial pacing at AV-delay 50ms. Values of all animals for absolute changes in forward flow and diastolic MR, compared to BL, are presented in figure 4 . In A-P mode forward flow showed an increase at intermediate AV-delays and decreased at AV-delay 50ms compared to BL values. Also, shortening AV-delay decreased diastolic MR, which was largest at the shortest AV-delays and less pronounced when AV-delays were longer than 100ms. No significant differences were found between the various ventricular pacing sites. Also, the patterns during A-S were comparable to A-P mode.