Swallowing-induced Atrial Tachycardia with a Thymic Cyst

Abstract

Introduction

Cardiac arrhythmias accompanying swallowing are rare disorders; swallowing-induced atrial tachycardia (SIAT) was first reported as “schlucktachykardie” by Sakai and Mori (1) in 1926. While the pathophysiology of SIAT remains unclear at present, several pathophysiological mechanisms have been suggested (2-4).

We herein report a case of a patient with a mediastinal nodule, who presented with paroxysms of atrial tachycardia (AT) induced by swallowing. The AT was diagnosed as SIAT, and it disappeared after surgical enucleation of the nodule.

Case Report

A 34-year-old man presented to our outpatient clinic with a 2-week history of palpitations and presyncope that occurred almost every day while he was eating without any other symptoms, such as chest or abdominal pain. An initial electrocardiograph showed a normal sinus rhythm without abnormalities in other parameters (Fig. 1). Twenty-four-hour Holter monitoring revealed AT-related palpitation and presyncope during eating and swallowing at 2 pm and 6 pm (Fig. 2). These findings raised suspicion of SIAT. Esophagogastroduodenoscopy and echocardiography demonstrated no abnormalities, while chest CT showed a 1.5-cm nodule in the front of the ascending aorta (Fig. 3).

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Figure 1.

Initial electrocardiograph findings. A 12-lead electrocardiograph recording shows a normal sinus rhythm and a heart rate of 73 beats per minute (bpm) without any abnormality.

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Figure 2.

Findings of 24-hour Holter monitoring. Twenty-four-hour Holter monitoring shows an increase in atrial tachycardia occurrence during lunch (2 pm) and dinner (6 pm), with each episode lasting a few seconds. HR: heart rate

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Figure 3.

Computed tomography (CT) findings. Computed tomography shows a flat nodule in the anterior mediastinum (arrows).

The small nodule showed no imaging signs of malignancy, and there was no apparent relationship between the arrhythmia and the nodule; however, the patient was concerned about the possibility of the nodule being a malignant tumor. He requested a consultation with a thoracic surgeon who decided to remove the nodule via thoracoscopic surgery. Thoracoscopic nodulectomy was performed, and a pathological analysis revealed that the nodule was a thymic cyst. One month after the diagnosis, the procedure was completed without any complications. Notably, the patient's SIAT and palpitations unexpectedly disappeared after the procedure. At the one-year follow-up visit, the patient showed no symptoms of AT; furthermore, he was able to eat without any concern.

Written informed consent was obtained from the patient for the publication of this case report.

Discussion

The main highlight of this case is the complete resolution of SIAT after thoracoscopic anterior mediastinal nodulectomy. The patient presented with palpitations almost every day while eating before the surgical procedure. However, the symptoms disappeared after surgery. There exists little evidence of a correlation between SIAT and surgical intervention. A Holter monitor was used for 24 hours after the procedure in the present patient, and changes in the esophageal pressure were measured. The drastic change in symptom frequency underscores the role of surgical intervention in SIAT disappearance.

SIAT is a rare clinical condition that is not usually associated with cardiac or gastrointestinal comorbidities (5), although cardiac diseases such as hypertrophic cardiomyopathy (6) and Wolff-Parkinson-White syndrome (7) have been reported in some patients. Our patient had no cardiac or gastrointestinal disorders but had a small thymic cyst in front of the ascending aorta.

The mechanism underlying the development of SIAT remains controversial; however, some studies have suggested possible mechanisms of SIAT development without any cardiac or gastrointestinal structural disorders (2,3). Direct mechanical interaction between the esophagus and atrium or the occurrence of a vagal nerve-mediated neural reflex during swallowing are suspected causes of AT. Swallowing can stimulate the efferent cardiac branches of the vagal nerve, thereby shortening the relative atrial refractory period and inducing abnormal atrial excitement (4). Anatomically, given that the left cardiopulmonary nerves run on the anterior surface of the aorta, they may have been attached to the thymic cyst in this case. The left cardiopulmonary nerves join to form the dorsal plexus, from which many small nerves arise to innervate the aorta, pulmonary artery, pulmonary veins, atrium, and trachea (8). Since the surgical documentation of this case did not include descriptions of neural findings, it is possible that the surgical procedure may have indirectly affected some activities of the autonomic system. In addition, although we did not see a significant translocation of the esophagus or atrium after the procedure, we hypothesized that the degree of alteration in the position of the esophagus or atrium, or the anatomical relationship between the esophagus and nearby structures that would be necessary to reduce or eliminate the stimulation causing the arrhythmia, might have been too small to notice.

Some cases of successful catheter ablation for SIAT have been reported (3,6,7,9-12), wherein AT and atrial fibrillation were found to be the major prevalent tachycardias; furthermore, ATs originating from the pulmonary veins or superior vena cava were reported to trigger SIAT in these cases. The ganglionated plexus related to the vagal nerve reflex is also reportedly the origin of SIAT (11). The surgical procedure or general anesthesia, including endotracheal intubation, may have affected the distribution of the epicardial fat in which the ganglionated plexus were embedded, and a perioperative inflammatory response may have occurred in the epicardial fat. Interestingly, the abovementioned origins of SIAT are not directly adjacent to the esophagus. The origin of SIAT was not detected in our patient, as we did not perform electrophysiological studies, and the surgical findings did not confirm direct denervation; however, inflammation related to the surgery may have been associated with the denervation that occurred. Histological studies of this case did not reveal the etiology of the arrythmia or the relationship between thymic cyst and SIAT. However, this case suggests that SIAT may be related to intrathoracic lesions; thus, imaging tests, such as CT, may be useful for evaluating SIAT.

Mediastinal masses are known to cause arrhythmias such as bradycardia resulting from an atrioventricular block. Previous reports have suggested that a mediastinal cyst can stimulate the atrium and pulmonary veins, thereby causing ectopic foci of arrhythmia (13,14). Thymic cysts are normally asymptomatic and are discovered as incidental findings on chest radiography or computed tomography. Although thymic cysts are benign tumors, it may be difficult to distinguish them from neoplasms. Generally, surgical cystectomy is recommended for patients with thymic cysts; nevertheless, the need for surgery in patients with small asymptomatic thymic cysts (diameter ＜3 cm) is still controversial. Efthymiou et al (15). reported a patient with tachy-brady syndrome and a large thymic cyst located in the left anterior mediastinum.

The authors state that they have no Conflict of Interest (COI).

References