'Time of the year' was used as the most important criterion in 8% of the herds and 'presence of two preceding heats with a normal interval' was used in 3% of the herds.
It is often the practice in industry to apply one or two years as the normal recertification interval of PSV.
However, in the large study by Laurent et al, 13 including 51 MD patients with a normal HV interval of less than 70 ms followed up during 57±36 months, only one patient developed a complete AVB, 52 months after the initial electrophysiological testing, whereas 19 of 49 patients with HV interval of 70 ms or greater developed 3° AVB.
We further divided euthyroid type 2 diabetic patients into two subgroups (TSH: 2.0 to <4.0 vs. 0.4 to <2.0 μIU/ml) and compared the two based on a more stringent "normal" reference interval of TSH suggested by the National Health and Nutrition Examination Survey NHANESS) III (7).
In a subset of the MSC group, HRV measures of standard deviation of normal intervals was 75 ± 30 msec at baseline and increased to 87 ± 32 msec (p =.02) at 12 months, and root mean square of intervals between successive complexes was 36 ± 30 msec and increased to 58.2 ± 50 msec (p = .01) at 12 months.
The time-domain measures include rMSSD, the square root of the mean squared difference of successive normal to normal intervals, and SDNN, the SD of the normal to normal intervals.
The ECG records were analyzed to quantify HRV in the time and frequency domains including the square root of the mean of the sum of the squared differences between adjacent normal to normal intervals (rMSSD), the standard deviation of all NN intervals over the entire period (SDNN), the low-frequency power (LF) and the high-frequency power (HF).
*p < 0.05; SDNN, standard deviation of the normal-normal interval; RMSSD, root-mean-square of the successive normal sinus RR interval difference; pNN50, percentage of absolute differences between successive normal RR intervals that exceed 50 ms; HF, high frequency power; LF, low frequency power; LF HF, ratio of low frequency to high frequency power; HR, heart rate.
Other popular Time Domain Analysis include SDNN Standarddeviationof of RR of normal-to-normal intervals), rMSSD Square root of the mean squared difference of successive RR intervals), NNx (Number of valid adjacent NN values not separated by data breaks), pNNx (Proportion of valid adjacent RR values not separated by data breaks) and Cycles (Number of available NN values).
