Electrocardiographic dynamic development and heart rate variability in lambs during the neonatal period

Figures & data

Figure 1. Placement of ‘alligator’-type electrodes and manual restraint in right latero-lateral decubitus for performing electrocardiography in the frontal plane.

Figure 2. Electrocardiographic tracing of lamb 20, deriving DII, frontal, and birth (24 h) at 35 days of age (25 mmseg, N).

Table 1. Mean and standard deviation of variables obtained by ECG in the frontal plane at the second moment of evaluation.

	Moments
	24 hours	7 days	14 days	21 days	28 days	35 days
HR (bpm)	211.16 ± 37.81^c	209.81 ± 50.84^c	179.87 ± 40.22^b	162.10 ± 33.70^ab	153.19 ± 36.55^ab	149.35 ± 33.51^a
P (ms)	43 ± 0.09	43 ± 0.09	41 ± 0.09	42 ± 0.08	44 ± 0.08	43 ± 0.08
P (mV)	0.112 ± 0.04^b	0.090 ± 0.037^a	0.095 ± 0.04^ab	0.086 ± 0.036^a	0.088 ± 0.033^a	0.085 ± 0.034^a
PR (ms)	79 ± 0.18^a	83 ± 0.2^ab	84 ± 0.19^abc	88 ± 0.2^bcd	92 ± 0.18^cd	93 ± 0.21^d
QRS (ms)	45 ± 0.15	48 ± 0.17	47 ± 0.14	46 ± 0.15	47 ± 0.16	47 ± 0.16
R (mV)	0.190 ± 0.098^c	0.142 ± 0.075^b	0.108 ± 0.059^ab	0.105 ± 0.075^ab	0.091 ± 0.06^a	0.087 ± 0.055^a
QT (ms)	168 ± 0.31^a	168 ± 0.31^a	179 ± 0.31^ab	197 ± 0.31^b	204 ± 0.36^bc	209 ± 0.37^c
T (ms)	620 ± 30^b	461 ± 246^a	466 ± 271^ab	513 ± 28^ab	545 ± 273^ab	593 ± 309^ab
T (mV)	0.587 ± 0.181^b	0.511 ± 0.279^ab	0.507 ± 0.278^ab	0.515 ± 0.307^ab	0.397 ± 0.285^a	0.411 ± 0.257^ab
Axis (°)*	30 (−150; 164)	30 (−150; 180)	0 (−174; 180)	−90 (−177; 169)	30 (−173; 180)	90 (−173; 172)

Notes: ABCD: numbers followed by letters indicate a significant difference between moments.

Tukey test and Wilcoxon test. Bonferroni correction. A significance level of 5%.

*Median (minimum; maximum).

Table 2. Mean and standard error* of variables obtained by 24-h ECG using a Holter system for the second moment of evaluation.

	Moments
	24 hours	7 days	14 days	21 days	28 days	35 days
Artefacts (%)	1.72 ± 0.80	2.38 ± 0.86	2.91 ± 1.44	1.03 ± 0.40	3.34 ± 1.66	5.00 ± 3.48
HR (bpm)**	192.13 ± 7.74^a (79; 249)	175.88 ± 5.54^ab (74; 250)	148.63 ± 4.12^b (76; 250)	132.75 ± 4.84^b (71; 250)	129.75 ± 4.7^b (76; 250)	119.63 ± 4.2^b (69; 248)
QRSt	251,215.38 ± 16,720.05^a	234,434.56 ± 9,225.02^ab	194,258.63 ± 8,110.58^b	171,426.44 ± 9,612.74^b	238,481.88 ± 66,598.40^ab	150,725.94 ± 9,814.76^b
NNmed (ms)	372.13 ± 38.65^a	381.94 ± 10.74^b	423.50 ± 12.63^b	474.75 ± 17.75^b	483.50 ± 19.75^b	527.33 ± 23.15^b
rMSSD (ms)	68.25 ± 36.46^a	58.44 ± 11.10^ab	57.00 ± 9.39^ab	59.38 ± 9.76^b	53.38 ± 7.81^ab	67.00 ± 9.31^b
pNN50 (%)	6.58 ± 4.41^a	7.53 ± 2.08^ab	9.60 ± 2.21^b	14.96 ± 2.95^b	14.74 ± 3.27^b	20.03 ± 3.94^b

Notes: AB: numbers followed by letters indicate a significant difference between moments.

Tukey test and Wilcoxon test. Bonferroni correction. The significance level was set to 5%.

*Artefacts (%), percentage of interference during 24 h of examination; FC (bpm), average HR during 24 h of examination; QRSt, number of QRS complexes during the 24 h of examination; NNmed (ms), the average value of all normal cycles measured during the evaluation; rMSSD (ms), square root of successive differences of the duration of normal cycles measured high squared; PNN > 50 NNs (%), percentages of successive cycles that differ in duration up to 50 ms.

**Mean ± standard error.