Cardiology MCQ 22.4.15

 CARDIOLOGY MCQ & REVIEW

Q. All of the following statements about accessory pathways (AP) are correct except

A. Majority of APs conduct both antegradely and retrogradely

B. Around 50% of patients with preexcitation have bypass tracts that conduct only antegradely.

C. Retrograde only conduction is more common than antegrade only conduction via APs

D. In around 10% of patients spontaneous disappearance of preexcitation may be seen

Explanation:

 -The vast majority of A-V bypass tracts conduct both antegradely and retrogradely.

-Less than 5% of patients with preexcitation have bypass tracts that conduct only antegradely (1). This is much less common than the converse situation of retrogradely conducting bypass tracts in the absence of antegrade preexcitation (i.e., so-called concealed bypass tracts).
-In patients who manifest only antegrade conduction over their bypass tract, spontaneous circus movement tachycardia, either antidromic or orthodromic, is not usually observed, but when it is, it is antidromic. The primary rhythm disturbance they manifest is atrial fibrillation 

-Over time antegrade conduction over an A-V bypass tract may disappear. Chen et al. (2) noted a loss of preexcitation in one fifth of symptomatic patients with WPW. Only 7.8% lost retrograde conduction. Spontaneous loss of preexcitation has been observed in one fifth to one half of children with WPW.
References:
1. Hammill SC, Pritchett EL, Klein GJ, et al. Accessory atrioventricular pathways that conduct only in the antegrade direction. Circulation 1980;62:1335–1340.
2. Chen SA, Chiang CE, Tai CT, et al. Longitudinal clinical and electrophysiological assessment of patients with symptomatic Wolff-Parkinson-White syndrome and atrioventricular node reentrant tachycardia. Circulation 1996;93:2023–2032.
Answer: B
Keywords: Cardiology review, Cardiology, Multiple choice questions, medical students, Electrophysiology, Atrial fibrillation, WPW syndrome

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