A case of vasovagal syncope associated with carotid sinus hypersensitivity: Effectiveness of tilt training and subsequent squatting

Abstract

A 43-year-old man fainted on a train and was transported to our hospital by an ambulance. No structural heart diseases or neurological abnormalities were observed. Electrocardiogram on admission demonstrated a junctional escape rhythm with bradycardia at 39 bpm. Sick sinus syndrome was excluded from electrophysiological studies. He had lifelong episodes of recurrent syncope that occurred due to emotional stress in daily life and pain associated with medical procedures. Since both the head-up tilt and carotid sinus massage tests showed a positive response, he was diagnosed with vasovagal syncope (VVS) and carotid sinus hypersensitivity. He was encouraged to continue the modified tilt training at home, which included leaning on the wall and squatting if leaning was intolerant. Thereafter, syncope was not observed in his daily life. This case highlights the importance of an accurate diagnosis, full education, and home training for recurrent syncope. This case also suggests that the carotid sinus may be involved in the neural network that causes VVS.

Learning objective

Reflex syncope includes both vasovagal syncope (VVS) and carotid sinus syndrome (CSS); however, VVS is discriminated from CSS according to current guidelines. We encountered a case of VVS associated with carotid sinus hypersensitivity. Recurrent syncope disappeared with modified tilt training characterized by conventional tilting and subsequent squatting when tilting was intolerant. This case indicates that the carotid sinus may be involved in the neural network responsible for VVS.

Introduction

Syncope is defined as a transient loss of consciousness caused by global cerebral hypoperfusion, and vasovagal syncope (VVS) is the most common type of reflex syncope. Although VVS is generally a benign type of syncope, it lowers the quality of life and self-confidence of affected patients. The head-up tilt (HUT) test is widely performed to obtain an accurate diagnosis of VVS, and it induces the gravitational shift of blood to the lower body. This orthostatic stress physiologically causes a compensatory response to increased heart rate, cardiac contractility, and vascular tonus, mediated by sympathetic activation. However, cardioinhibitory VVS is characterized by a paradoxical autonomic response associated with vagal overdrive and sympathetic withdrawal in the context of HUT. Tilt training is a cost-effective nonpharmacological therapy for VVS, and repeated tilt training increases vasoconstrictor reserve that leads to hemodynamic tolerance against prolonged orthostatic stress [1]. Carotid sinus syndrome (CSS) is characterized by bradycardia and hypotension associated with syncope triggered by carotid sinus manipulations, such as shaving and fitting a tie. Carotid sinus massage (CSM) test is the primary diagnostic test for suspected patients to evaluate the carotid sinus hypersensitivity. However, the relationship of VVS and CSS is controversial. Here, we report a case of VVS associated with carotid sinus hypersensitivity that was managed successfully by home-tilt training and subsequent squatting.

Case report

A 43-year-old man had a history of repeated fainting since childhood. Syncope occurred at the time of painful medical procedures, such as subcutaneous or intramuscular vaccination, venipuncture for blood sampling, and intravenous injection. In his daily life, he sometimes experienced fainting after drinking alcohol. Prodromal symptoms such as sweating, pallor, and unpleasant feelings were always preceded by fainting. Therefore, such prodromal symptoms did not lead to fainting while sitting, and fainting usually occurred after prolonged standing. One morning, he fainted while standing on a crowded commuter train and was transported to our hospital by an ambulance. He had been tired for several days, moreover, had skipped breakfast that day. On arrival at our hospital, he was slightly vague (JCS I-1), and electrocardiogram on admission showed bradycardia (heart rate, 39 bpm) caused by junctional escape rhythm (Fig. 1). He was 185 cm in height and 80.1 kg in weight (body mass index of 23.4, and body surface area 2.0 m²). His blood pressure was 117/68 mmHg. He fainted when the peripheral venous route was accessed for intravenous drip infusion in the emergency room. His consciousness recovered after intravenous atropine and junctional bradycardia was converted to normal sinus rhythm 3 min after starting atropine. The patient was hospitalized for an accurate diagnosis and optimal treatment. Physical examination revealed no abnormalities. No abnormalities were found in the head computed tomography scan and diffusion magnetic resonance imaging. Echocardiography showed no structural abnormalities and a normal left ventricular ejection fraction of 62 %. Cardiac catheterization was performed, and no organic stenosis was observed on the coronary angiography. There were no abnormalities in the sinoatrial node function or atrioventricular conduction in the electrophysiology study. However, sinus arrest (maximum 5.2 s) was reproducibly observed when the CSM test was applied (Fig. 2). The patient underwent an HUT test for diagnostics of VVS. Five minutes after starting the tilting, a junctional escape rhythm of 40 bpm was confirmed, and the patient complained of feeling sick. Immediately after the complaint, sinus arrest appeared for 7 s, and fainting occurred. His consciousness recovered immediately after the intravenous injection of 0.5 mg atropine. Based on these findings, we diagnosed the patient with coexisting VVS and carotid sinus hypersensitivity. After diagnosis, HUT training was started in the rehabilitation room. We set the angle of the tilt table at 80°, and the patient was encouraged to keep standing for 5 min on the tilt table. However, he was intolerant to the conventional HUT training. He practiced squatting after tilting to activate the sympathetic nervous system and prevent venous blood from pooling in the lower extremities. In the two years after discharge, the fainting was no longer observed. He was discharged home and encouraged to continue modified tilt training at home. We instructed the patient to lean against the wall for 20–30 min every day and perform squatting when leaning became intolerable. Subsequently, the fainting did not recur in his daily life, including during immunization or blood collection. Two years after discharge, he visited the hospital and underwent a HUT test again. Unfortunately, 7 min after the start of the examination, he fainted transiently. However, unlike in the past, sinus arrest did not occur, and only bradycardia (40 bpm), escaped rhythm, and hypotension were observed. Surprisingly, sinus arrest did not occur even when a carotid massage was administered. These results suggest that the tilt training at home was effective.

Fig. 1.

Electrocardiogram recorded in the emergency room.

Fig. 2.

Electrocardiogram (II, V₅) monitoring and aortic pressure; 5.2 s of sinus arrest appeared under the maneuver of carotid sinus massage.

Discussion

A 43-year-old male patient presented with VVS associated with carotid sinus hypersensitivity. This case was managed successfully by tilt training combined with squatting at home. Although pacemaker implantation is required in patients with severe cardioinhibitory VVS, characterized by repetitive and prolonged sinus arrest, orthostatic tilt training is listed as a class IIb recommendation in the current guidelines [1]. This patient complained of recurrent syncope and showed positive HUT and CSM test. In this case, the patient was intolerant to tilt training alone. Therefore, sequential training consisting of passive tilting and active squatting was designed to prevent venous pooling into the lower extremities and activate the sympathetic nervous system, counteracting the preceding parasympathetic nervous system augmented by tilting. This unique training was easy to continue at home and remarkably effective for the prevention of cardioinhibitory response to orthostatic stress. CSS is prevalent in middle-aged or elderly patients with hypertension or atherosclerosis, while VVS is prevalent in younger patients. Current guidelines describe the diagnosis and treatment of reflex syncope, including VVS and CSS, respectively. However, they do not address the relationship between the two disorders [1]. This case presented lifelong recurrent episodes of syncope caused by VVS, while clinical episodes compatible with CSS were scanty. Carotid hypersensitivity has been reported to predict the cardioinhibitory response to VVS. Maggi et al. compared VVS patients with a positive CSM test with those showing a negative massage test and observed that sinus arrest (more than 3 s) occurred more frequently in VVS patients with positive test than in those with negative test. They speculated that the carotid sinus is involved in the neural reflex loop of VVS, at least in the cardioinhibitory type [2].

The reports on the therapeutic effects of tilt training in patients with VVS are conflicting. This training has been reported to be effective in VVS patients in case-control studies [3], [4] and uncontrolled trials [5], [6], but not in prospective randomized controlled trials (RCTs) [7], [8], [9], [10]. Although the reason for this is not clear, the age of the participants may have affected the outcome of such trials investigating the effectiveness of conventional tilt training. The mean age of participants in the trials supporting its effectiveness ranged from 16 ± 2 to 37 ± 12 years [3], [6], whereas that of RCTs showing no benefits ranged from 40 ± 19 to 45 ± 17 years [7], [10]. This case indicates that the effectiveness of tilt training-on in middle-aged patients with VVS is increased by squatting. Furthermore, the effectiveness of tilt training depends on the motivation of the patients to continue home-tilt training. Long-term compliance with tilt training has been shown to influence the outcome of RCTs [7]. Home tilt training to prevent recurrent syncope was remarkably effective in the present case of VVS associated with carotid hypersensitivity. The effectiveness of tilt training is explained by the fact that the first accurate diagnosis of lifelong episodes of syncope and in-hospital education motivated this patient toward long-term self-directed training of tilting and squatting. This education includes a full explanation of diagnosis and its benign nature, provision of assurance, skills to avoid recurrence, and daily life management to prevent sleeplessness and fatigue. The issue in this case was confirming that the patient was performing the home training correctly. Therefore, we instructed the patient to continue the correct training at each outpatient visit.

Conclusions

VVS and CSS are categorized as reflex syncope in the current guidelines [1], and we report a case of VVS associated with carotid sinus hypersensitivity. The modified training consisting of tilting and subsequent squatting at home was remarkably effective in preventing recurrent syncope. Although transient syncope was induced by the tilt test at the 2-year follow-up, a marked cardioinhibitory response was not evoked by HUT and CSM 2 years after starting the follow-up.

This line of evidence suggests that active squatting prevents venous blood from pooling in the lower extremities during tilting and activates the sympathetic nervous system counteracting parasympathetic predominance, and the carotid sinus plays an important role in the cardioinhibitory response in VVS.

Declaration of competing interest

All authors declare no conflict of interest with this case presentation.