Rick Schreurs

44 Chapter 3 AV-delay SHORTENING with BiV Pacing 0 10 20 30 AV-delay 50ms -20 0 20 40 LV outflow AV-delay 150ms Baseline 300ms 0 0.5 1 Time (s) 0 0.5 1 Time (s) 0 0.5 1 Time (s) Diastiolic MR Pressure (mmHg) Flow (L/min) Pressure (mmHg) Flow (L/min) 0 10 20 30 -20 0 20 40 Computer simulations Experimental data AV-delay shortening with BiV pacing LV inflow f(x) ECG Figure 2. Hemodynamic effect of improving atrioventricular (AV)-coupling in pig experiments and computer simulations during biventricular pacing. LV and LA pressures ( Top row ), flow ( Middle row ) and electrocardiogram ( Lower row ) from a representative porcine experiment. Pressures and flow calculated from computer simulations ( Third & Fourth row ). RESULTS Restoring AV-coupling in normal hearts: animal experimental and computational analyses Results from animal experiments and computer simulations showed good qualitative and quantitative agreement ( Figure 2 ). Under baseline conditions at long AV-delay, the delay of ventricular activation resulted in 1) suboptimal LV filling with the early filling wave (E) being fused with or prematurely interrupted by the atrial filling wave (A), and 2) diastolic MR due to atrial relaxation and related atrial pressure drop occurring before the onset of ventricular activation and, hence, papillary muscle contraction. At intermediate AV-delays (150ms) separated E- and A-waves were observed. At short AV-delays, A-wave truncation occurred as well as increases in peak and mean LA pressure, presumably caused by atrial contraction against a closed mitral valve.