Review Question - QID 203689

The patient suffers from Wolff-Parkinson-White (WPW) syndrome, in which the accessory bundle of Kent causes ventricular pre-excitation and can predispose to paroxysmal tachycardia.

The bundle of Kent is an accessory conduction pathway found in 0.1%-0.3% of the general population. Problems arise when this pathway creates an electrical circuit that bypasses the AV node. Characteristic EKG changes in WPW include a ‘delta wave’ that demonstrates ventricular pre-excitation. The delta wave makes the PR interval appear short and the QRS interval appear long. The arrow in Image A points to this patient’s delta wave.

Collucci et al. reviews the diagnosis and management of supraventricular tachycardias. Short-term treatment consists of calcium channel or beta blocks when the vagal maneuver no longer works. For long-term therapy, patient can be given atrioventricular nodal blocking agents or class IC or III antiarrhythmics. Also, catheter ablation can be used in patients who cannot tolerate the medications and experience persistent or recurrent supraventricular tachycardias, and for WPW patients this can be curative.

Durham and Worthley also review the management of tachycardias. Adenosine is helpful for immediate resolution of tachycardias but it contraindicated in PSVT with WPW syndrome. Although treatment aimed at resolving the arrhythmias is useful, resolving the underlying precipitant or abnormality ("e.g. hypokalemia, hypomagnesaemia, anti-arrhythmic proarrhythmia, myocardial ischemia, etc") is necessary to reduce future episodes.

Figure A shows an EKG tracing in lead V2 with the arrow pointing to the delta wave. Illustration A demonstrates abnormal electrical conduction in WPW syndrome. Illustration B is a flow chart from the New England Journal of Medicine detailing the differential diagnosis and treatment of tachycardias.

Incorrect Answers:
Answer 2: The bundle of His allows conduction from the AV node to the left and right bundle branches. Pathology at the bundle of His may result in third degree heart block.
Answer 3: In Lown-Ganong-Levine (LGL) syndrome, an extension of the anterior intermodal tract termed the bundle of James bypasses the AV node and may cause supraventricular tachycardia. Delta waves are not present on EKG.
Answer 4: Pathology to the sinoatrial node would not cause delta waves to appear on EKG.
Answer 5: Ectopic foci around the pulmonary veins are theorized to initiate atrial fibrillation. The patient’s EKG is not suggestive of atrial fibrillation.