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Figure 2 Atrial Fibrillation With Slow Ventricular Rate (36 to 40 beats/min) in an 83-Year-Old Woman Presenting With Effort Intolerance

The patient’s only medication, verapamil, was stopped 48 h before this electrocardiogram. The potassium level was 4 meq/l. Note the LQT2-like morphology (T1-T2) in the inferior and anterior leads (with T2>>T1 in V₄ to V₆). (Lower panel) Shortly thereafter, this patient had torsade de pointes. Note that the irregularity of ventricular rate during atrial fibrillation creates short and long cycles (time duration between 2 consecutive R waves of the ECG [RR intervals] shown in seconds). The longest cycle (RR interval of 1.5 s) antecedes the complex that is followed by the first extrasystole (arrowhead), which probably represents triggered activity. A series of short-long sequences ensues and culminates in torsade de pointes. As expected, the torsade de pointes complexes originate from T2 (arrows).