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At a glance

Ventricular Preexcitation Syndrome. It is considered a Preexcitation Syndrome that leads to ventricular dysrhythmias that can be life-threatening. It is grouped with the Wolf-Parkinson-White, which is an atrioventricular reentrant tachycardia condition. Patients affected present a short PR interval with normal QRS complexes and paroxysms of clinically significant tachycardia.

Synonyms

Accelerated Atrioventricular Nodal Conduction; Enhanced Atrioventricular Nodal Conduction Syndrome; Short PR/Normal QRS Syndrome; Short PR/Narrow QRS Syndrome.

History

Occurrence of frequent paroxysms of tachycardia in patients with short PR interval was first described by A. Clerc in 1938. Subsequently, Bernard Lown, William F. Ganong, and Samuel A. Levine gave it their eponym in 1952.

Nature

Ventricular Preexcitation Syndrome (other types include Wolff-Parkinson-White Syndrome via Kent fibers and preexcitation via Mahaim fibers).

Incidence

0.5% of the overall adult population. Retrospective analysis has suggested that paroxysmal supraventricular tachycardia occurs in approximately 9.5% of patients with short PR and normal QRS duration.

Genetic inheritance

Unknown. A familial occurrence has been suggested.

Pathophysiology

Atriofascicular tracts (called James fibers) completely or partially bypass the atrioventricular node, resulting in a short PR interval (<0.12 seconds). These tracts insert into the bundle of His or its branches; thus, the ventricles are depolarized in a normal sequence and the QRS complex appears normal on ECG (no delta wave as in Wolff-Parkinson-White Syndrome). Paroxysmal tachycardias classically arise from reentry through the bypass tract. Direct atrioventricular connections have been suggested to be part of the syndrome; such connections could allow tachycardias to develop as a result of antegrade, rather than retrograde conduction.

Diagnosis

History; ECG; short PR interval with normal QRS complex; electrophysiologic studies.

Clinical aspects

Patients may remain asymptomatic. Episodes of paroxysmal palpitation (atrial flutter, supraventricular tachycardia) may be associated with shortness of breath, signs of ventricular failure, and syncope. Investigations include ECG and electrophysiologic studies to define the site of accessory conducting tissue and the individual mechanism for tachycardia generation. The tachycardia is usually a narrow complex, but functional right bundle or left bundle branch block may cause a wide complex tachycardia. Several drugs may be used in the management of the condition, including adenosine (acutely), verapamil, beta-blocker, procainamide amiodarone, or digitalis. However, verapamil and digoxin are contraindicated for treatment of atrial fibrillation or flutter in these patients because they might accelerate conduction through the bypass tract and induce ventricular fibrillation. Surgical or catheter pathway ablation or pacemakers (overdrive pacing) may be used.

Precautions before anesthesia

Obtain a history of the frequency of dysrhythmias and the current treatment regimen. Continue antidysrhythmic drugs perioperatively. In case of chronic amiodarone therapy, check thyroid function and exclude pulmonary fibrosis. Review the results of electrophysiologic studies if available. A preoperative ECG is mandatory. It is recommended to consult a cardiologist in presence of a pacemaker in case of overdrive pacing is being used to control supraventricular tachycardias. Correct any electrolyte disturbance (sodium, potassium, and magnesium).

Anesthetic considerations

Minimize perioperative catecholamine surges. Premedication may be beneficial. Atropine is relatively contraindicated. Hypoxia, hypercarbia, or acidosis must be prevented ...

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