Rick Schreurs

67 Effective mechanical atrioventricular delay A-P for all ventricular pacing sites. During the A-P protocol LV dP/dt max was significantly higher during BiV pacing compared to LV and RV pacing. RAP max was significantly higher during LV pacing compared to BiV and RV pacing in A-P mode. Table 1. Hemodynamic baseline characteristics (AV-delay 300ms) for atrial pacing and atrial sensing during BiV, LV and RV pacing. Atrial pacing (N=7) Atrial sensing (N=6) BiV LV RV BiV LV RV HR (bpm) 100±2 100±2 100±2 84±3* 84±3* 84±3* CO (L/min) 3.1±0.1 3±0.1 3.1±0.1 2.8±0.1* 2.8±0.1* 2.8±0.1* SW (mL·mmHg) 3828±478 3505±433 3616±517 3413±414 3332±428 3439±506 MAP (mmHg) 84±9 81±9^ 82±9 69±7* 69±7 71±7 LVP max­ (mmHg) 99±8 96±8^ 96±8 87±6 87±6 88±6 LVEDP (mmHg) 6.9±1.1 6.6±1 6.6±1 8.4±1.5* 8.1±1.5* 8.4±1.4* LVEDV (mL) 80±15 78±14 80±16 87±18 89±17* 88±17 LV dP/dt max (mmHg/s) 1265±118 1188±119^ 1182±110^ § 1087±127 1035±115 1061±119 RVESP (mmHg) 25±2 26±1 26±2 25±2 26±2 26±2 RVEDP (mmHg) 6.1±1.2 6.2±1.2 6.4±0.8 8.1±1.6* 7.8±1.6* 8.1±1.4 RV dP/dt max (mmHg/s) 368±12 354±22 396±27 318±20* 306±23* 342±26* LAP max (mmHg) 11±2 12±2 12±2 10±2 10±2 12±2 RAP max (mmHg) 10±1 12±1^ 11±1 § 9±1 10±1 9±1 Forward flow (mL/beat) 51±3 48±2 51±4 53±4 51±3 55±4 Diastolic MR (mL/beat) -6.1±1.5 -5.7±1.4 -8±2.2 -6.9±2.1 -6.7±1.8 -9.1±2.9 Presented are mean±SEM. BiV: biventricular, LV: left ventricle, RV: right ventricle, HR: heart rate, CO: cardiac output, SW: stroke work, MAP: mean arterial pressure, LVP max : maximal left ventricular pressure, EDP: end diastolic pressure, EDV: end diastolic volume, LAP max : maximal left atrial pressure, RAP max : maximal right atrial pressure, MR: mitral regurgitation. * indicates P<0.05 compared to atrial pacing for same pace site, ^ indicates P<0.05 compared to BiV pacing for same atrial mode, § indicates P<0.05 compared to LV pacing for the same atrial mode. Changes in passive and active ventricular filling during AV-delay optimization Figure 3 represents an example of the changes in passive (E-wave) and active (A-wave) LV filling during BiV pacing at different AV-delays. During A-P mode (upper row) at an AV-delay of 50ms the A-wave was absent, because LA contraction began after the start of ventricular contraction. This led to atrial contraction against a closed mitral valve leading to high LA pressure (up to 20mmHg). At an AV-delay of 100ms a clear distinction appeared between the E-wave and the A-wave. With increasing AV-delay the time between passive and active filling shortened, causing E and A-wave fusion at AV-delays of 150ms and 200ms. At 200ms filling was finished well before the start of ventricular contraction, leading to late diastolic MR. At the longest AV-delay of 250ms no distinction between the passive and active filling could be made due to complete fusion of the E and A-wave, resulting in a more premature stop of LV filing and larger diastolic MR. 4