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

Sep 28, 2026

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Case report of a 55-year-old man with recurrent syncope and vertigo linked to high-grade atrioventricular (AV) block despite initially negative evaluations. Multiple diagnostic steps—including echocardiography, myocardial perfusion imaging, Holter monitoring, and electrocardiography—showed no conduction abnormalities. Persistent symptoms led to implantable loop recorder placement, documenting transient 6:1 high-grade AV block and bradycardia. Because the documented conduction abnormality persisted alongside ongoing symptoms, permanent pacemaker implantation followed. The report underscores the need for detailed electrophysiologic assessment and close monitoring.

LanguageEnglish

CategoryHealthcare

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Abstract

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Received 10/22/2025 Review began 11/02/2025 Review ended 11/29/2025 Published 12/03/2025 © Copyright 2025 Witte et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 4.0. , which permits unrestricted use , distribution , and reproduction in any medium , provided the original author and source are credited. DOI: 10.7759/cureus.98384 Open Access Case Report Published via VCOM Clinical, Biomedical, and Educational Research An Elusive Case of Transient 6 : 1 High-Grade Atrioventricular Block Despite Normal Initial Testing Colten L. Witte 1 , David J. Dillard 1, Thomas D. Mesaris 1 , Alexis N. Hall 1, Darren Beck 2, Ghassan Dalati 3 1. College of Osteopathic Medicine, Edward Via College of Osteopathic Medicine, Auburn, USA 2. Cell Biology and Physiology, Edward Via College of Osteopathic Medicine, Auburn, USA 3. Cardiology, Medical Center Enterprise, Enterprise, USA Corresponding author: Colten L. Witte, [cwitte@auburn.vcom.edu](cwitte@auburn.vcom.edu) 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. Categories: Cardiology Keywords: atrioventricular block, high-grade, holter monitoring, presyncope, sleep apnea and hypertension Introduction High-grade atrioventricular (AV) block is a serious cardiac conduction disturbance that can cause syncope and presyncope, necessitating permanent pacemaker implantation [1] . Causes vary from structural heart disease, including idiopathic conduction system fibrosis and myocardial infarctions, to cardiotoxic compounds, such as digoxin and carbon monoxide. Essentially, any interruption in the electrical impulses of the AV conduction system can cause AV block [2] . A thorough evaluation, including resting electrocardiogram, ambulatory monitoring, stress testing, and electrophysiologic studies, is essential for diagnosis [3] . Here, we report a unique case with recurrent syncope and transient high-grade AV block, with comprehensive negative evaluations prior to pacemaker placement, highlighting the importance of ongoing assessment in symptomatic patients. Case Presentation A 55-year-old man presented with recurrent episodes of syncope and presyncope with a history of arthritis, hyperlipidemia, hypothyroidism, obesity (BMI 36 .4 kg/m2), and obstructive sleep apnea (OSA) treated with a continuous positive airway pressure (CPAP) machine for years. He had no allergies and did not take any medications. His family history included a cerebrovascular accident in his brother, heart disease in his maternal grandmother, and cancer in his father, who was exposed to Agent Orange. Surgical history included a right hip replacement. Event monitoring followed by Holter monitoring was performed, and both returned negative for any conduction abnormalities, despite correct placement. Five months later, the patient returned with the same symptoms as before. An echocardiogram, implantable loop recorder (Confirm Rx™; Abbott, Sylmar, USA), and myocardial perfusion imaging test were performed, all of which were negative, despite the patient continuing to suffer episodes of dizziness and bra

FAQs

Why was an implantable loop recorder inserted despite normal initial tests?

The patient continued to experience recurrent dizziness, bradycardia, and presyncope after multiple earlier evaluations were negative. Implantable monitoring was used to capture intermittent conduction abnormalities.

What did the loop recorder reveal?

It documented a transient 6:1 high-grade AV block with associated bradycardia and presyncope, despite previously normal monitoring results.

What treatment was ultimately chosen and what was the outcome?

Because of the documented high-grade AV block and persistent bradycardia, a permanent pacemaker was placed. Follow-up reported no further episodes of bradycardia, presyncope, or syncope.

Sep 28, 2026

Uploaded by dawugda