Often, dissociated P waves are quite obvious, at least in one lead, making the diagnosis of ventricular tachycardia relatively easy, even when the onset of the tachycardia is not recorded.
The three simultaneously recorded leads shown here are from a 62 year old male with a prior anterior wall myocardial infarction. The dissociated P waves are quite easily seen in lead V1 (arrows), but are virtually impossible to identify in the other two leads.