Review Question - QID 103689

This patient with sudden-onset tachycardia and a sloped QRS complex likely has 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 electrocardiogram 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 the delta wave on this patient's electrocardiogram. Patients with WPW often have episodes of paroxysmal supraventricular tachycardias, and often present for evaluation of palpitations. Definitive management is with ablation of the accessory pathway.

Chhabra et. al review the diagnosis and management of WPW syndrome. They describe the characteristic appearance of WPW on the electrocardiogram, notably the shortened PR interval and sloped QRS complex. They also discuss implications for management in patients with WPW.

Figure A shows an electrocardiogram tracing in lead V2 with the arrow pointing to the delta wave.
Illustration A demonstrates abnormal electrical conduction through the bundle of Kent 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 1: Atrioventricular node pathology typically causes atrioventricular block. Typically, atrioventricular block presents with a bradycardic rhythm, and does not cause sloping of the QRS complex.

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. It does not cause a sloped appearance of the QRS complex.

Answer 4: Ectopic foci around the pulmonary veins are typically the sites that atrial fibrillation arises from. The patient’s EKG is not suggestive of atrial fibrillation.

Answer 5: Sinoatrial node pathology may present with sick sinus syndrome. This usually presents with symptoms related to bradycardia and does not cause sloping of the QRS complex.

Bullet Summary:
Wolff-Parkinson-White syndrome is due to an accessory conduction pathway through the bundle of Kent, and presents on the electrocardiogram with shortening of the PR interval and sloping of the QRS complex.