Table 5.

Minimal Detectable Difference (MDD) for PR interval and P wave indices

	PR interval (ms)		P-axis (°)		Maximum P wave area (μV*ms)		Maximum P duration (ms)
N	MDD	% of mean	MDD	% of mean	MDD	% of mean	MDD	% of mean
5	73.31	43.46	43.91	84.54	5,788.27	83.75	30.39	27.72
10	47.72	28.29	28.58	55.03	3,768.12	54.52	19.79	18.05
50	20.28	12.02	12.15	23.39	1,601.68	23.17	8.41	7.67
100	14.26	8.46	8.54	16.45	1,126.22	16.29	5.91	5.39
500	6.35	3.76	3.80	7.32	501.45	7.26	2.63	2.40
1,000	4.49	2.66	2.69	5.18	354.42	5.13	1.86	1.70
5,000	2.00	1.19	1.20	2.31	158.42	2.29	0.83	0.76
10,000	1.42	0.84	0.85	1.64	112.01	1.62	0.59	0.54
50,000	0.63	0.38	0.38	0.73	50.09	0.72	0.26	0.24
100,000	0.45	0.27	0.27	0.52	35.42	0.51	0.19	0.17

Grand means are as follows: 168.69 ms for PR interval, 51.94° for P axis, 6,911.74 μV*ms for maximum P wave area, and 109.64 ms for maximum P wave duration.