ECG quiz . Is it pacemaker malfunction?

@article{Kim2013ECGQ,
  title={ECG quiz . Is it pacemaker malfunction?},
  author={Edward T. Kim and Akash Makkar and Mohammad Saeed and Yochai Birnbaum},
  journal={Journal of electrocardiology},
  year={2013},
  volume={46 6},
  pages={721-3}
}