The Mischievous Bundle: A Case of Varying Degrees of Right Bundle Branch Block on Alternate Beats during Exercise Stress Testing


  • Financial disclosure: Author did not receive any financial support/grant for this work.

Address for correspondence: Sukhvinder Singh, M.B.B.S., M.D., D.M., Department of Noninvasive Cardiology, Ganesh PET-CT and Imaging Centre, A-109, Pocket A-1, Sector-8, Rohini, New Delhi, India. Tel: +919717205832; E-mail:


A 78-year-old male was referred for exercise stress testing. He developed incomplete right bundle branch block during first stage of exercise and later on developed incomplete and complete right bundle branch block on alternate beats (2:1). During first minute of recovery he developed complete right bundle branch block on all beats (1:1). At 3 minutes of recovery, baseline electrocardiographic pattern was resumed. Variable degree of right bundle branch block on alternate beats is a rare phenomenon. The plausible mechanisms responsible for this phenomenon are being discussed.