Does atrioventricular dissociation precede heart block?

AV dissociation: Atrioventricular dissociation can occur with or without heart block. For example, during ventricular tachycardia, the ventricular impulses are usually not going retrogradely to the atrium, so there is av dissociation without any heart block. The important thing is whether av dissociation is resulting in a ventricular rate slow enough to be symptomatic with dizziness or syncope.