From brain freeze to heart freeze: A case of deglutition syncope–induced asystole/tachyarrhythmia in a patient with titin cardiomyopathy

Key Teaching Points.

• ▪Deglutition syncope is a known but rare form of syncope that can manifest extreme cardioinhibitory and autonomic dysfunction resulting in asystole and tachyarrhythmias, that is, atrial fibrillation with rapid ventricular response.
• ▪Patients with deglutition syncope should be closely monitored with outpatient follow-up visits and cardiac monitoring.
• ▪Avoidance of deglutition triggers should be advised to all patients affected by deglutition syncope.

Introduction

Deglutition syncope (DS) is a rare condition in which swallowing triggers a reflex leading to loss of consciousness. DS usually causes cardiac inhibition and bradyarrhythmias, but rarely results in tachyarrhythmias. Here we present a 36-year-old man with inherited titin (TTN) mutation cardiomyopathy presenting with DS-induced asystole with subsequent atrial fibrillation (AF) with rapid ventricular response (RVR).

Case report

A 36-year-old man with a medical history significant of inherited pathogenic TTN mutation cardiomyopathy (LAMA4 variant of uncertain significance mutation, American College of Cardiology/American Heart Association heart failure stage B) and supraventricular tachycardia taking metoprolol presented to the heart failure clinic for a follow-up after 2 weeks of mobile cardiac outpatient telemetry for palpitations. The telemetry unit was ordered because he had reported experiencing a “brain freeze” after drinking a crushed ice beverage, resulting in severe dizziness and nearly fainting while driving. He also endorsed diaphoresis, nausea, lightheadedness, pounding in his chest, and throat tightness at the time. The event lasted 2–3 minutes. He noted on his smart watch after the event that he was in AF. Outpatient telemetry was unremarkable. Given the severity of his presenting complaints, we asked the patient to repeat the events he described previously. In the clinic, on continuous 12-lead telemetry, he drank a crushed ice beverage. Subsequently, he developed asystole starting approximately 5 seconds after rapidly drinking the beverage. Asystole lasted approximately 17 seconds. He then developed AF with RVR, with heart rates ranging from 120 to 130 beats per minute. His AF was very short lived and spontaneously reverted to sinus rhythm (Figure 1). His observed symptoms after drinking the crushed ice beverage resulting in subsequent AF with RVR very closely replicated his previous presenting symptom complex. He felt well shortly after this event in the clinic. After monitoring in the clinic 30 minutes after the event, he was told to avoid icy beverages indefinitely and was discharged home. Echocardiography showed stable, mildly impaired biventricular global hypokinesis with normal chamber size and wall thickness. The patient underwent a loop recorder placement, which was unremarkable for any additional asystole or tachyarrhythmia events after 1 year of monitoring.

Figure 1.

Rhythm strip 5 seconds after patient rapidly drank the frozen beverage showing approximately 17 seconds of asystole, followed by atrial fibrillation with rapid ventricular response.

Discussion

DS has been documented almost 100 times since its first reported case in 1793.¹ The exact etiology is unknown; however, there are 2 proposed mechanisms. The first is through a neural vagal reflex. The neural vagal reflex is thought to be stimulated through the vagal or glossopharyngeal nerve or stretching of the mechanoreceptors of the esophagus resulting in vasodilation, hypotension, and bradycardia.¹ This vagal reflex has been known to be triggered by ingestion of solid, acidic, or cold foods/drinks.^2,3 The second mechanism is thought to be caused by external compression of the left atrium as food boluses travel down the esophagus, obstructing left-sided cardiac blood flow.⁴ However, this obstruction mechanism is unlikely to cause cardioinhibitory and vasodepressor findings, as well as the symptoms of “brain freeze” endorsed by the patient in our case.

Certain risk factors can predispose patients to DS. Although there are strong esophageal conditions linked with food ingestion associated with DS such as hiatal hernia and esophageal strictures, cardiac risk factors are somewhat unclear. 1 review showed that 33% of those affected by DS had underlying cardiac diseases such as coronary artery disease and sick sinus node syndrome and 28% had underlying metabolic disturbances (obesity, diabetes, etc).⁵ DS tends to affect older men, likely owing to the increased burden of relevant comorbidities and progressive age-related autonomic dysfunction that reduces parasympathetic regulation.

There have been documented cases of asystole that occur during DS, but reports of associated tachyarrhythmias are rare. There have been fewer than 0.6% of reported cases of deglutition-induced AF and only 1 reported case of DS associated with paroxysmal AF.^6,7 There are reported cases of deglutition-induced AF in patients with underlying cardiomyopathies among patients with muscular dystrophy and hypertrophic cardiomyopathy.^6,8

The exact mechanism of DS in our patient is unclear, but his symptoms and subsequent telemetry reading favor a neural vagal reflex. He may have experienced a severe form of cardioinhibitory and vagal vasodepressor syncope with referred pain from his glossopharyngeal nerve, clinically manifesting as a “brain freeze” after drinking an icy beverage. This postulation is supported by both cardioinhibitory and vasodepressor responses in DS observed in 1 small-scale study, noting drops in both heart rate and blood pressure (with patients drinking cold liquid).⁹ Although this patient is young and has no typical risks for DS as previously described, he does have nonischemic cardiomyopathy secondary to an inherited TTN mutation. Whether TTN cardiomyopathy is a risk factor for severe cardioinhibitory response is difficult to determine, given that no cases of DS in patients with TTN cardiomyopathy have been reported. If the mechanism was vagally mediated, the heightened vagal tone may have been relatively short lived, because he was tachycardiac while in AF after asystole. Alternatively, he may have had a reflexive sympathetic surge leading to his RVR in AF. Increased vagal activity shortens atrial refractoriness and, when combined with a sympathetic catecholamine surge, creates a favorable substrate for both triggered activity and reentry.¹⁰ We did not recommend an endoscopy workup because he had no odynophagia or dysphagia other than what had been described. Nor was a pacemaker recommended, because he had a clear trigger for his syncope. No additional events have been captured on 1-year loop recorder monitoring. Behavioral changes (avoidance of DS triggers) remain the preferred treatment in this particular patient.

Conclusion

This is the first reported case of DS in a patient with underlying TTN cardiomyopathy. DS remains a rare condition with known gastrointestinal and possible cardiac risk factors. Whether TTN cardiomyopathy is a risk factor is unclear. This case demonstrates the extremes of cardioinhibitory and autonomic dysfunction where, likely, a severe vagal response resulted in syncope and a subsequent surge of sympathetic activity led to AF with RVR. These patients should be closely monitored with follow-up visits and long-term outpatient cardiac monitoring. If no additional events or arrhythmias are observed or reported, discontinuation of cardiac monitoring can be considered. Additional studies are needed to understand the mechanisms of DS and potential risk factors that may predispose patients to DS. Until further elucidation, avoidance of deglutition triggers should be advised to all patients affected by DS.

Disclosures

The authors have no conflicts of interest to disclose.