▁others ▁are ▁ar ising ▁elsewhere . ▁ ▁This ▁is ▁taken ▁as ▁evidence ▁of ▁multiple ▁( i . e . ▁at ▁least ▁two ) ▁e ct op ic ▁fo ci , ▁and ▁is ▁called ▁mult if ocal ▁( or ▁more ▁correctly , ▁mult iform ) ▁at rial ▁rh ythm ▁if ▁the ▁rate ▁is ▁ ≤ 1 0 0 ) ▁or ▁mult if ocal ▁at rial ▁t ach y card ia ▁if ▁the ▁rate ▁is ▁over ▁ 1 0 0 . ▁ ▁This ▁appears ▁particularly ▁commonly ▁in ▁ex ac erb ations ▁of ▁chron ic ▁ob struct ive ▁lung ▁disease . ▁ ▁If ▁the ▁bas eline ▁has ▁a ▁totally ▁irregular ▁form , ▁this ▁suggests ▁f ibr ill atory ▁waves ▁of ▁at rial ▁f ibr ill ation ▁or ▁possibly ▁arte fact ; ▁a ▁saw ▁to oth ▁sh aped ▁bas eline ▁suggests ▁the ▁flutter ▁waves ▁of ▁at rial ▁flutter . ▁ ▁With ▁either ▁of ▁these ▁rh yth ms , ▁if ▁the ▁vent ric ular ▁rate ▁is ▁fast , ▁the ▁f ibr ill atory ▁or ▁flutter ▁waves ▁can ▁easily ▁be ▁mis inter pre ted ▁as ▁P ▁waves . ▁ ▁Abs ence ▁of ▁the ▁P ▁wave ▁with ▁a ▁flat ▁bas eline ▁may ▁indicate : ▁ ▁Fine ▁at rial ▁f ibr ill ation ▁ ▁S ino at rial ▁arrest ▁( with ▁a ▁secondary ▁escape ▁rh ythm ) ▁If ▁P ▁waves ▁are ▁not ▁clearly ▁del ine ated ▁in ▁the ▁surface ▁E CG , ▁a ▁Lewis ▁lead ▁may ▁be ▁used ▁to ▁better ▁visual ize ▁P ▁waves . ▁ ▁At rial ▁rep olar ization