Yes, the low heart rate for 14 hours needs a look unless you're a world class athlete.
Generally speaking, normal heart rate is about 65 (60-90) beats per minute (BPM). Bradycardia is slow heart rate (less than 60), Tachycardia is fast heart rate ( greater than 90). Your heart has four chambers, one each in and out, and upper and lower. Upper is atrial, lower is ventrical. Ectopic refers to beats occuring when not expected, couplets refers to double beat. PACs refers to Premature Atrial Contraction. Your doctor ordering cardiology follow up means they have some concerns and need more information to make a determination. Could be something as simple as diet/excercise, or drug/medication, or could be more.
DISCLAIMER: I am NOT a doctor. You should only accept medical advise from a licensed professional.