What does this all mean? Underlying rhythm is sinus with a sinus arrhythmia. Slight P wavemorphology changes noted, mostly during time frames of sinus slowing. Heart rates range 41 bpm (sleep) to 166 bpm (light walking) and average 81 bpmoverall (27% Note- the 166 bpm is noted with SVT and not exercising/was only folding clothes. I am 30 yrs old, low blood pressure, no sings of blockage, 128 lbs, etc. Overall healthy but experiencing chest pains when my heart rate is low and rapid heart rate with minimal activity. This also started recently after I had a sudden fast heart rate of 202 bpm shortly after waking / little activity.