# Unroofed Coronary Sinus in a Dog: Diagnostic Utility of ECG-Gated Computed Tomography

## TL;DR

A rare heart condition in a dog was successfully diagnosed using ECG-gated CT when echocardiography failed to provide a clear diagnosis.

## Contribution

This is the first reported case of unroofed coronary sinus syndrome diagnosed using ECG-gated CT in veterinary medicine.

## Key findings

- ECG-gated CT revealed a communication between the coronary sinus and the left atrium.
- Transthoracic echocardiography failed to identify the defect in the atrial septum.
- The dog was diagnosed with unroofed coronary sinus syndrome.

## Abstract

Due to technological improvements in echocardiography, most cardiac problems can be diagnosed using transthoracic echocardiography. However, when there is a substantial change in the cardiac morphology, it may be insufficient for diagnosis. Electrocardiogram (ECG)-gated computed tomography (CT) is a type of exam that synchronizes with the patient’s ECG to capture a detailed image of the diastolic and systolic cardiac morphology, with less cardiac-motion-induced artifacts, allowing for a better insight and a more definitive diagnosis. This case report describes a rare instance of an unroofed coronary sinus syndrome, which was challenging to diagnose by conventional echocardiography but was successfully diagnosed using ECG-gated CT scans.

A Labrador Retriever (4-year-old, castrated male) with signs of fatigue was diagnosed with an atrial septal defect at his primary veterinary clinic. Due to the uncertainty of this diagnosis, he was referred to the Tokyo University of Agriculture and Technology Animal Medical Center for further investigation. Transthoracic echocardiography performed on arrival showed an irregular blood flow from the left atrium (LA) to the right atrium (RA), yet no opening was found in the septum. An electrocardiogram (ECG)-gated computed tomography (CT) exam revealed a communication between the coronary sinus (CS) and the LA, causing a shunt between the LA and the RA. A diagnosis of unroofed coronary sinus syndrome (UCSS) was made. The dog’s condition was stable and plans to keep observations were made. This is the first case of UCSS diagnosed with an ECG-gated CT exam.