Available online 28 March 2024

A 69-year-old woman had three syncopal events while flying on an airplane. She was found to be profoundly bradycardic. Two 12‑lead electrocardiograms (ECGs) showed ventricular rates in the thirties. In one, the QRS complexes were narrow. In the second ECG, there were wide negative deflections following the QRS complexes. Analysis of telemetry recordings revealed the underlying mechanism and helped establish appropriate programing of an implanted pacemaker.

A 69-year-old woman from the Philippines had three syncopal events on her flight to the United States. Except for air travel, during which syncope is the most common medical emergency [1], there were no obvious triggering factors. She did not have seizure-like activity or bowel-bladder incontinence. Each time she came to spontaneously within a few minutes and except for being “washed out” and dizzy, she had no other complaints. Approximately 30 min after the last syncopal spell, paramedics

Unidirectional AV block is characterized by block in the anterograde direction, but preserved retrograde conduction [5]. Unidirectional block signifies dual AV nodal physiology or an accessory pathway that conducts in the retrograde direction only. Unidirectional block is present in 15%–35% of patients with complete anterograde heart block [6].

A unique feature of this case was the intermittent nature of retrograde conduction. The explanation was found in telemetry strips. Fig. 3 illustrates two

The single author is responsible for the content of the manuscript. No part of the manuscript has been previously published or is under consideration elsewhere. There are no conflicts of interest in relationship with the manuscript.

Laszlo Littmann: Writing – original draft, Supervision, Data curation, Conceptualization.

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