This 59-year-old man was brought to the Emergency Department after an episode of sudden syncope lasting three minutes while at work. On arrival, he had no complaints. His vitals and neurological examination were normal. He reports two occasions during the past three months where he felt weak and lightheaded for a few minutes:

• Sinus bradycardia, 56/min with first degree AV block (PR = 230 msec)
• Bifascicular block: right bundle branch block plus left posterior fascicular block

Comment: The patient was admitted and monitored. Two brief periods of transient complete heart block were demonstrated, and so an AV sequential pacemaker was implanted.  Occasionally, the term “trifascicular block” is used to describe the presence of first degree AV block with bifascicular block but this term is a misnomer and its used is avoided on our website.