Alternation of QRS width and cycle length during a long RP' tachycardia: what is the mechanism?

@article{Intini2004AlternationOQ,
  title={Alternation of QRS width and cycle length during a long RP' tachycardia: what is the mechanism?},
  author={Anselma Intini and Bartolomeo Giannattasio and N. Somasekhar Varma},
  journal={Heart rhythm},
  year={2004},
  volume={1 3},
  pages={364-7}
}