A quantitative HCG done in early pregnancy is very helpful. If it doubles in 2 to 3 days, the pregnancy is normal. If it goes down instead of up, the pregnancy is not a good one. If it goes up or...
Any thing other then a "normal sinus rhythm" would be considered abnormal. The only "borderline" case I can think of would be beating to fast or to slow. So it seems you are near one of these limits....