Hi andreanna,
For some perspective an EKG is a measurement of electrical impulse activty and is influence by increased wall thickness (more resistance increases voltage and longer time interval). Same with muscle damage. Will show blood flow impairment and patterns of abnormal rhythm deisturbances. The vertical axis is a metric for voltage and horizontal is time.
It appears your EKG results focus on rhythm disturbance and possible heart cell damage (interior infarct). Patterns of abnormal electrical rhythm disturbance can be related to medication, calcium and potassium can result in an EKG change. Artifacts are frequent and the EKG is only a tool for further testing.
QRS (electrode v1) indicates a ventricular constriction delay. Is it an arrythmia problem?
PR interval 140 ms. P wave is the electrical activity of the upper chamber. A prolonged
PR interval can correspond to an impaired AV node conduction. Normally the
PR interval represents the time delay to allow atrial systole to occur. It would indicate most of the delay occurs in the AV node slowing the conduction (conduction is the facility for electrical impulses to pass).
An echo is required to determine an infarct. Yes, an enlarged atrium can be an underlying cause for arrhythmia.