Which of the following statements is true regarding Brugada syndrome?
It is characterized by ST elevation and a pseudo-RBBB pattern in the right precordial leads with persistent ST elevation. Brugada syndrome has been described worldwide but is most common in Asian countries and is the leading cause of death in young men in part of Thailand. It is characterized by ST-segment elevation and a pseudo-RBBB pattern in the right precordial leads with persistent ST elevation. These features can be induced with sodium channel blockers such as flecainide and ajmaline. (Sotalol is a potassium channel blocker.) It is related to a mutation in the sodium channel gene. Mutations in SCN5A, which encodes the α-subunit of the cardiac sodium channel gene, have been found in up to 30% of families with Brugada syndrome. It is associated with a high incidence of sudden cardiac death resulting from VF. Risk assessment and therapy remain poorly defined at this time, but the implantation of an ICD has been advocated in patient with a Brugada pattern on their ECG and additional risk factors including a history of syncope or sudden cardiac death.
In patients with long-QT syndrome:
The mechanism of torsades de pointes (TdP) is believed to be related to early afterdepolarization. The pathognomonic arrhythmia associated with long-QT syndrome is TdP. The mechanism is believed to be related to early afterdepolarization and triggered activity. Sotalol causes QT prolongation and is contraindicated in patients with long QT. Hypokalemia, not hyperkalemia, is associated with an increase of TdP in this situation. EP testing is of no value and is not indicated for the risk stratification of patients with long-QT syndrome. Cardiac arrest occurs typically with vigorous activity and infrequently during sleep in LQT1 syndrome. Acute arousal events (emotion or noise) are much more likely to trigger events in LQT1 and LQT2 than LQT3. Events in LQT3 syndrome are common during sleep.
A 75-year-old man is admitted with upper gastrointestinal (GI) bleeding. His ECG shows sinus rhythm at 90 bpm, with a PR of 220 milliseconds, RBBB, and left anterior fascicular block. He had one episode of near syncope 2 days before this admission. His current hematocrit is 20. You are consulted regarding the need for a pacemaker.
Which of the following is true?
You should perform EP testing to evaluate the AV conduction system. The patient had an episode of near-syncope, which could be related to his GI bleeding, but the possibility of intermittent heart block in the setting of bifascicular block cannot be ruled out. This is a class I indication for EP testing to evaluate AV conduction. If there is evidence of abnormally prolonged HV interval, then a permanent pacemaker should be considered.
If the syncopal episode was remote from the GI bleeding and based on the clinical history of the events there was a concern for intermittent highdegree AV block causing symptoms, then empiric placement of a PPM without an EP study prior would carry a class IIa indication. There is no indication for ICD placement in this setting. β-Blockers would blunt a reactive tachycardia resulting from the patient’s anemia.
Which of the following criteria is most helpful in differentiating supraventricular tachycardia (SVT) from VT in a patient presenting with wide complex tachycardia?
There is AV dissociation. In patients presenting with wide complex tachycardia, the presence of AV dissociation is highly specific for VT. All the other listed parameters suffer from significant overlap between SVT and VT.
A 76-year-old man walks into the emergency room reporting palpitations and dizziness. A 12-lead ECG shows wide complex tachycardia at a rate of 160 bpm. His BP is 110/50 mmHg. He reports that he recently sustained an MI. He has not had any similar symptoms before.
Which of the following should be included in further evaluation and treatment of his arrhythmia?
Procainamide, 15 mg/kg IV over 30 to 60 minutes. Wide complex tachycardia occurring after MI is most likely to be VT. Verapamil is contraindicated in this setting, as it might lead to hypotension and VF. DC cardioversion can be used if the patient does not respond to antiarrhythmic therapy or if he becomes hemodynamically unstable. Procainamide is the drug of choice because it treats ventricular as well as supraventricular arrhythmia. There is no role for digoxin and no need for urgent cardiac catheterization in this situation.