Figure 1.

Transoesophageal atrial pacing protocol. (A) Schematic of the transoesophageal atrial pacing protocol from a typical resting HR (∼470 b.p.m.), accelerated to the maximum HR obtainable while maintaining 1:1 AV and VV synchrony (∼710 b.p.m.), sustained for 45 min, then gradually restored to baseline. (B) Representative baseline NSR (top) and an AP rate at 600 b.p.m. (100 ms cycle length, bottom). Note: 1:1 AV synchrony and a normal VV activation pattern, identical to that during NSR, are preserved during atrial pacing. Horizontal scale bar represents 100 ms. AP, atrial-paced; AV, atrioventricular; HR, heart rate; NSR, normal sinus rhythm; p, atrial waveform; qrst, ventricular waveform; VV, interventricular.