# An Elusive Case of Transient 6:1 High-Grade Atrioventricular Block Despite Normal Initial Testing

## TL;DR

A man with unexplained fainting and dizziness was found to have a rare heart rhythm issue only detected through long-term monitoring.

## Contribution

Demonstrates the clinical value of implantable loop recorders in diagnosing transient high-grade AV block despite normal initial tests.

## Key findings

- Transient 6:1 high-grade AV block was detected using an implantable loop recorder despite normal initial tests.
- Persistent symptoms and documented conduction abnormality led to pacemaker placement.
- Highlights the need for detailed electrophysiologic assessment in patients with unexplained syncope.

## Abstract

We present a case of a 55-year-old man with a prior history of syncope and vertigo due to high-grade atrioventricular (AV) block despite initial negative tests. The patient underwent multiple diagnostic evaluations, including a normal echocardiogram, myocardial perfusion imaging, Holter monitoring, and electrocardiography. As his symptoms continued to persist, an implantable loop recorder (Confirm Rx™; Abbott, Sylmar, USA) was inserted subcutaneously, which revealed transient 6:1 high-grade AV block and bradycardia. Despite normal initial investigations, his persistent symptoms and documented conduction abnormality prompted pacemaker (Abbott, Sylmar, USA) placement. This case highlights the importance of detailed electrophysiologic assessment and close monitoring in patients with recurrent unexplained syncope and high-grade AV block, even with prior normal testing.