Figure 2.
Spontaneous initiation of arrhythmias in LQT2 (long QT syndrome type 2). A, Top, Schematic of the PCa ramp protocol. The ramp starts at t=5 s and ends at t=25 s. ECG traces: ECG traces from t=10 to 50 s for 6 PCa,H values (in units of µm/s) as indicated on each ECG. Heart rate was 60 beats per minute. ABAB marks T-wave alternans (TWA). * marks the premature ventricular complexes, and horizontal arrows indicate episodes of polymorphic ventricular tachyarrhythmia (PVT). In the second ECG, we also show the V1 lead (inset) for TWA. B, Numbered snapshots of voltage maps (first and second rows) and wave fronts (colored red, third row) from the time points marked by corresponding red arrows on the last ECG in A (PCa,H=2.8 µm/s). See Movie I in the Data Supplement for full episode. C, PVT induced by the pause protocol, changing the heart rate from 120 to 60 beats per minute with a constant PCa=2.8 µm/s.