Sabrina is a 67-year-old woman with a history of cardiac abnormalities. You perform a resting ECG test to evaluate her heart’s electrical activity. You notice that her PR interval is 0.25 s. Considering that this measure is often between 0.12 s and 0.20 s, what does this indicate about the anatomical locale as the source of the electrical disturbance in Sabrina’s heart?
