Isthmic spondylolisthesis is caused by a defect in a part of the vertebra called the pars interarticularis. This defect can cause the vertebra to slip forward.
What's a normal heart rate? Most adults have a resting heart rate of 60-100 beats per minute (bpm). The fitter you are, the lower your resting heart rate is likely to be. For example, athletes may have a resting heart rate of 40-60 bpm or lower. You should contact your GP if you think your heart rate is continuously above 120 bpm or below 40 bpm, although this could just be normal for you.
For most adults, normal heart rate is 60 to 80 BPM. Well-trained athletes can have a normal heart rate of 40 to 60 BPM.