Mapping the unmappable: local vector mapping.

Arrhythmias are commonly mapped using a timing reference signal. There are a number of situations where mapping may be difficult or even impossible using conventional reference-based mapping. Wobbling arrhythmias or those who do not maintain a 1:1 relationship with the reference signal are problematic. Local vector mapping may be performed in these situations to map arrhythmias without the use of a reference signal.