Episode of high variability

Episodes of high variability include those parts of the heartbeat recording in which at least 5 out of every 6 consecutive minutes have long-term variability (LTV) above a certain level. The presence of episodes of high variability in the CTG recording is a fairly good indicator of a satisfactory fetal condition. Long-term variability (LTV) is calculated as the average of the difference between the minimum and maximum heart rate intervals per minute or, in the case of a long acceleration, between the maximum and the basal level.