<P> In electrocardiography, the PR interval is the period, measured in milliseconds, that extends from the beginning of the P wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization); it is normally between 120 and 200ms in duration . The PR interval is sometimes termed the PQ interval . </P> <P> Variations in the PR interval can be associated with certain medical conditions: </P>

What is the significance of the pq interval