OVERVIEW
Brugada syndrome, also known as right bundle branch block-polymorphic ventricular tachycardia-syncope syndrome and sudden unexpected nocturnal death syndrome, is a cardiac genetic disease.In 1992, the two Brugada brothers firstly reported four cases of right bundle branch block with ST-segment elevation in the right thoracic lead, polymorphic ventricular tachycardia and episodes of ventricular fibrillation, and there were no abnormal findings on cardiac ultrasound and cardiac angiography, which was called Brugada syndrome in clinical and electrocardiographic terms. This clinical and electrocardiographic sign is called Brugada syndrome.
Brugada syndrome is the leading cause of sudden death in young adults. It occurs most often in men aged 20-49 years, mostly in the summer months, and most sudden deaths occur during nighttime sleep.
Etiology
There is a genetic and familial predisposition to the disease, with an increased incidence in siblings with a family history. Nocturnal hypoxemia aggravated by exertion, defective membrane Na+/K+ pumps, and endocrine disorders are predisposing factors.
Symptoms.
Patients are mostly young males, often with a family history of syncope or sudden cardiac death, most often occurring in the nocturnal sleep state, with no aura before the attack. There may be no symptoms between attacks. Sometimes cardiac arrest or syncope, almost always ventricular fibrillation on electrocardiographic monitoring during the attack. Routine examination is mostly without abnormality, and pathologic examination may reveal mild left ventricular hypertrophy in most patients. Cardiac electrophysiologic examination can induce polymorphic ventricular tachycardia or ventricular fibrillation in most cases.
Examination
1. Electrocardiogram
The most characteristic clinical manifestation of Brugada syndrome is its hallmark electrocardiographic changes, i.e. J-point and ST-segment elevation in the right thoracic lead (V1-3).
2. Drug provocation test
Sodium channel blocker drug provocation test can improve the sensitivity of the diagnosis of Brugada syndrome.
Diagnosis
Detailed history and family history is the key to diagnosis. Unexplained syncope, syncope aura, history of sudden death survival and family history of sudden cardiac death are important clues for diagnosis.
Brugada syndrome can be diagnosed if the patient presents with typical type I ECG changes with one of the following clinical manifestations and other factors causing ECG abnormalities are ruled out: (i) documented ventricular fibrillation; (ii) self-terminating polymorphic ventricular tachycardia; (iii) a family history of sudden cardiac death (<45 years of age); (iv) typical type I ECG changes in family members; (v) electrophysiologically induced ventricular fibrillation; and (vi) syncope or nocturnal near-death-like breathing.
For those with type II and III ECGs, Brugada syndrome is diagnosed after a positive drug provocation test and if the above clinical signs are present. In the absence of the above clinical signs only characteristic ECG changes cannot be diagnosed as Brugada syndrome, but can only be called idiopathic Brugada sign-like ECG changes.
Treatment
Currently, drug therapy cannot effectively prevent cardiac events from occurring. When ventricular tachycardia or ventricular fibrillation occurs, appropriate rescue measures should be taken, and the only effective way to prevent sudden death is to put in an ICD at an early stage.
1.Non-pharmacological treatment
(1) Implantable cardioverter-defibrillator (ICD): ICD is the only proven effective treatment for Brugada syndrome.
(2) Radiofrequency ablation: Patients with a history of electrical storm episodes or repeated ICD discharge therapy may be considered for catheter-based radiofrequency ablation.
2.Drug therapy
(1) Acute treatment of ventricular arrhythmia: after ventricular tachycardia or ventricular fibrillation electrical resuscitation, isoprenaline can be used to prevent ventricular fibrillation electrical storm. Isoproterenol can increase calcium inward flow by agonizing β-receptor and reduce the imbalance of inward and outward ion flow during repolarization, which can normalize the elevated ST segment and prevent ventricular arrhythmia attack.
(2) Prevention of ventricular arrhythmia episodes treatment: quinidine is a class IA antiarrhythmic drug, which also has the effect of blocking sodium current and Ito.