Heart rate down to 48 beats/per minute, issue?

A resting HR even as low as the 30s is of no concern if there are no symptoms from it (lightheaded, passing out) and the rate increases appropriately with exercise. A lot depends on the individual's age, with HRs being lower as one gets older. A rate of 140 with moderate exercise would be unusually low (but not alarming) for a teenager, but typical for, say, a 30yo. (Resting and exercise rates trend lower in people who are physically fit.)

"Missed beats" are usually due to an extra heart beat that occurs early after the previous (normal) beat. Since the heart has not had time to fill when the extra beat occurs, no blood is ejected and there is no pulse. This is perceived as a pause between beats, since only the normal beats are felt. Almost everyone has such premature beats at times (although not everyone is aware of them), and they are of no concern.

Heart Rate 48 Beats Per Minute

Normal heart rate varies between 60-100 bpm, while heart rates of under 40 bpm can be seen with athletes. Tachycardic heart rates (during physical/psychological stress) vary between 100-180 bpm, depending on your age. Your heart rate sounds a bit, but not abnormally, high for your age. What was your average heart rate a couple of months ago? Has it changed much? If not, you're perfectly fine. If it has, you should probably think of could your surrounding conditions/diet/any other factor possibly affecting your average heart rate have changed.