Differentiating wide complex tachycardias.

Wide complex tachycardias are cardiac rhythm disorders with three or more consecutive beats, rates exceeding 100 beats per minute and a QRS duration of 120 msec (0.12 second) or greater. The width of the QRS complex should be verified in a number of leads, since the QRS complex often appears mistakenly narrower (i.e., a QRS duration of less than 120 msec) in one or two of the 12 leads. Most wide complex tachycardias are ventricular tachycardia, and they are managed with antiarrhythmic drugs and correction of serum potassium and magnesium levels. Electrical cardioversion/defibrillation may be used in patients with serious cardiac compromise. Supraventricular tachycardias occur with or without ventricular conduction abnormalities. The management of supraventricular tachycardia requires careful evaluation for aberrant ventricular conduction or preexcitation. The cause of a wide complex tachycardia must be identified, because certain therapies can result in potentially fatal arrhythmias. If the cause cannot be determined, a test dose of intravenous adenosine can be used. Another approach is intravenous administration of procainamide and a beta-adrenergic blocker.

Wide-complex tachycardias. The importance of identifying the mechanism.

Initial assessment of widecomplex tachycardias (WCTs) should begin with patient history and physical examination. If there is a history of remote myocardial infarction, WCT should be considered as ventricular tachycardia until proved otherwise. In most cases, WCT is subsequently shown by electrophysiologic evaluation to be ventricular tachycardia. The presenting symptoms and degree of hemodynamic compromise should not be used to distinguish ventricular tachycardia from supraventricular tachycardia. A 12-lead electrocardiogram (ECG) should be carefully reviewed by looking for signs of ventricular tachycardia (atrioventricular dissociation, captured and fusion beats, certain QRS shapes and concordance). If the surface ECG is inconclusive, changing the position of V1 or use of a transesophageal lead may allow assessment of atrial activity. When more QRS than P waves are documented, the diagnosis is ventricular tachycardia. Cardioversion-defibrillation is required in patients with WCT who are in unstable condition. Atrioventricular node blockers are the agents of choice for arrhythmias that are atrioventricular node-dependent, but they may cause hemodynamic collapse if administered to patients with ventricular tachycardia or with atrial fibrillation and preexcitation. Lidocaine hydrochloride (Xylocaine HCl IV), preferred for ventricular tachycardia, has been reported to cause ventricular fibrillation in patients with atrial fibrillation and preexcitation. When there is doubt about the diagnosis, elective electrical cardioversion may be considered. Medical therapy should consist of intravenous magnesium sulfate and procainamide hydrochloride (Pronestyl). A beta blocker may also be considered if more aggressive blockade of the atrioventricular node becomes necessary.

Torsades de pointes and long QT syndromes.

Torsades de pointes is a polymorphic form of ventricular tachycardia that is usually associated with prolongation of the QT interval. This QT prolongation may be either congenital or acquired. Etiologies for the acquired form include hypokalemia, hypomagnesemia, hypocalcemia, starvation, sick sinus syndrome, atrioventricular block and drug effects. Medications that have been implicated include most antiarrhythmic agents, some nonsedating histamine blockers, erythromycin and ketoconazole. Accurate and timely recognition of torsades de pointes is critically important because of the risk that traditional antiarrhythmic drug treatment will likely worsen the problem rather than improve it. Effective treatment requires withdrawal of any offending drugs or correction of the underlying cause of the QT prolongation. Beta blockers have been shown to be effective in preventing problems in congenitally at-risk patients. An implantable cardioverter defibrillator should be considered in some patients with recurrent episodes.

Surgical management of ventricular tachycardia in subannular left ventricular aneurysm.

Submitral left ventricular aneurysms typically affect young adults of African ancestry. These aneurysms are characterized by heart failure and mitral insufficiency, and occur in the absence of coronary disease. We report a rare case of symptomatic ventricular tachycardia in association with submitral left ventricular aneurysm (and no mitral insufficiency). Ventricular tachycardia was abolished by aneurysm resection and ventricular reconstruction. We suggest surgical management is indicated for ventricular tachycardia associated with this unusual condition, and may be curative.

Cerebral cysticercosis. A disease to suspect in recent travelers or immigrants.

The initial assessment of the young adult patient with multiple intracerebral lesions is challenging. The etiologic factors must be categorized as neoplastic, infectious, inflammatory, vascular, and hematologic, among others. Unfortunately, these lesions are not easily accessible for sampling, and all other diagnostic methods must first be exhausted. This case report describes a patient who was brought to an emergency department in New Jersey after her first seizure. The diagnosis was cerebral cysticercosis, an intracerebral parasitic infection that is extremely rare in this area but very common in other areas of the world. As more and more people immigrate to the United States, researchers believe that cerebral cysticercosis will become more common. It is imperative, therefore, for primary care physicians to understand this disease and to consider it in the appropriate setting.