This 61-year-old hypertensive man is followed in the nephrology clinic because of severe progressive renal failure:

• Sinus tachycardia, 104/min
• Left anterior fascicular block
• Intermittent (2:1) right bundle branch block (RBBB)

Notice that in leads I, II and III the first 80 msec. of the QRS complexes with RBBB show the pattern of left anterior fascicular block (bifascicular block).