Sick sinus syndrome is caused by an abnormality in the automaticity of the sinus node itself or a conduction defect from the sinus node to the atria, resulting in bradycardia and associated symptoms [2]. Clinical symptoms include shortness of breath, fatigue on exertion, lightheadedness, dizziness, and syncope, and the diagnosis is made by electrocardiography and electrophysiological examination. Based on the characteristics of the electrocardiographic waveform, this disease is classified into three types using the Rubenstein classification: type I is sinus bradycardia, type II is sinus arrest and sinus atrial block, and type III is bradycardia-tachycardia syndrome [6]. In this case of bradycardia-tachycardia syndrome, bradyarrhythmia (sinus bradycardia, sinus atrial block, sinus arrest) and paroxysmal tachycardia (atrial fibrillation, supraventricular tachycardia, ventricular tachycardia) coexist, causing syncope and heart failure, about 80% of which are idiopathic [7], and treatment methods include drug therapy and pacemaker therapy, although asymptomatic patients are not usually treated with such therapy. In some cases, patients may be followed up. The frequency of sudden death with pacemaker therapy is 0.06%, while the frequency of sudden death without therapy is estimated to be 2% [3]. In the present case, there were no abnormalities on history taking, 12-lead electrocardiogram, blood test, head CT, and EEG. Echocardiography showed valvular disease, but no abnormality that would cause syncope. On the other hand, Holter electrocardiography showed sinus arrest after atrial fibrillation. Since the patient was taking beta-blockers and digitalis preparations that suppress sinus node function, the cause of syncope was diagnosed as drug-induced sinus arrest, and surgery was performed after drug administration was discontinued.
It is often the case that latent sick sinus syndrome that could not be diagnosed before surgery is diagnosed after surgery and anesthesia, as in the present case, and there have been reports of bradycardia and sinus node arrest during anesthesia induction and intraoperative pacing [7, 8]. During the perioperative period, the use of anesthetics tends to cause cardiac instability, and bradycardia or sinus arrest can result in compensatory changes such as increased preload and increased cardiac output per cycle. But, there are cases in which compensatory changes are not feasible, and failure to maintain sufficient cardiac output may result in lethal arrhythmias. Factors that induce intraoperative arrhythmias include hypoxemia, hypercarbia, shallow anesthesia, vagal reflex, air embolization, acidosis, alkalosis, and drug use (beta-blockers, digoxin, anesthetics). In this case, there were no abnormalities in vital signs, ventilatory status, or electroencephalographic monitoring during anesthesia induction, endotracheal intubation, and general anesthesia. Beta-blockers and digoxin were withdrawn preoperatively and were not used intraoperatively. Therefore, factors such as hypoxemia, hypercarbia, shallow anesthesia, and drug use were ruled out. On the other hand, no arrhythmia was observed before sinus arrest, and sinus arrest occurred immediately after the repair of the zygomatic fracture, and the patient became in sinus rhythm when the surgery was terminated, so the possibility that the trigeminal vagal reflex was activated by stimulation from the bone fragment cannot be denied [9–11]. The trigeminal reflex during oral surgery is thought to be caused by stimulation of the second and third branches of the trigeminal nerve, and there have been reports of the trigeminal vagus reflex during contemplative fixation of zygomatic fractures, but the incidence is low at 1–2% [10–13]. Cha et al. [14] reported that the presence of preexisting cardiac disease predisposes to the trigeminal vagus reflex. Therefore, the present patient had an underlying sick sinus syndrome, which may have been related to the intraoperative trigeminal vagus nerve reflex induction. After the surgery, tachycardic atrial fibrillation was observed during extubation, and although sinus arrest was not observed, atrial tachyarrhythmia with dizziness, palpitations, and other symptoms, and subsequent sinus arrest were observed. Although the diagnosis of drug-induced arrhythmia was made during the preoperative examination, similar symptoms and electrocardiographic findings were repeatedly observed even after discontinuation of drug therapy. Based on these findings, the intraoperative sinus arrest was diagnosed as trigeminal vagal reflex, and the postoperative sinus arrest was diagnosed as sinus arrest due to sick sinus syndrome (bradycardia-tachycardia syndrome), not drug-induced arrhythmia, and a pacemaker was inserted.
In the treatment of traumatic injuries in the maxillofacial region, it is necessary to consider the timing of surgery when the underlying disease is present. In the present case, an opening disturbance was observed at the time of initial examination, and surgery was performed on the 5th day after the injury. However, there was no persistent bleeding or significant pain, and if surgery is indicated when the patient is repaired within 2 weeks, which is the time of fresh fracture, it was considered necessary to stop drug administration and follow-up, and to consider giving priority to identifying the cause of the dizziness and palpitations. In Japan, where the elderly population is rapidly increasing, the number of elderly patients with multiple systemic diseases and taking multiple medications is increasing, and in the case of facial fracture after syncope, the cause of syncope should be identified as much as possible before surgery. For differential diagnosis of syncope, history taking, blood tests, electrocardiography, echocardiography, echocardiography, and central nervous system examination should be performed to consider sudden changes due to drug interactions, potential diseases [15]. In the case of sinus arrest during emergency surgery, intraoperative transvenous cardiac pacing was inserted, or transcutaneous pacing was prepared after resuming heartbeat by chest compression and dopamine administration, and the importance of consultation with cardiology and anesthesiology was reaffirmed.
The patient occured sinus arrest during treatment of zygomatic fracture and was diagnosed as sick sinus syndrome. In cases of maxillofacial injuries due to cardiogenic syncope, the cause of syncope should be thoroughly investigated to avoid complications due to abnormalities of the circulatory system.