Artefacts in continuous ECG recordings – Provoking and preventing manoeuvres

Figures & data

Table I.  Perfect ECG for QRS interpretation.

	No modification	Tape	Cup	Tape + cup
No provocation	79	81.3 (ns)	83.7 (ns)	83.3 (ns)
Shaking cables	54.7**	60.7**(ns)	59.3**(ns)	67.7*(*)
Rotating shoulders	60.3*	67.3 ns(ns)	63.3**(ns)	66.3*(ns)
Touching electrodes	46.0***	56.3***(*)	77.7 ns(***)	75.0*(***)
Washing	56.3**	57.7**(ns)	60.0**(ns)	64.0**(*)
Teeth-brushing	62.0*	73.3 ns(*)	75.0**(*)	76.7 ns(*)

Mean percentage of perfect ECG for QRS complex interpretation in ECG strips during various provocations of artefacts and modifications of technical equipment. Levels of significance are indicated by *** if p<0.001, ** if p<0.01, and * if p<0.05. Ns represents not significant. Signs outside the brackets indicate the difference between the peculiar type of provocation and no provocation. Signs within the brackets indicate the difference between the peculiar type of artefact-preventing modification and no such modification.

Figure 1. Examples of ECG recordings distorted by artefact provocations. Lines below the tracings indicate artefactual ECG. A and B: slight touching of the skin electrodes. C and D: teeth-brushing. E: rotation of the arms. In recording A, for example, some parts of the ECG are valueless for interpretation because of the concealment of ordinary P waves and QRS complexes. In recording B, QRS complexes but not P waves can be discerned.

Figure 2. Mean percentage of categories of quality during different types of artefact provocation. QRS complexes without artefact prevention.

Figure 3. Mean percentage of categories of quality during different types of artefact provocation. P waves without artefact prevention.

Table II.  Valueless ECG for QRS interpretation.

	No modification	Tape	Cup	Tape + cup
No provocation	4.0	2.0 (ns)	1.3 (ns)	1.3 (ns)
Shaking cables	16.0*	9.0** (ns)	4.3 ns (ns)	7.3* (ns)
Rotating shoulders	13.3 ns	6.7 ns (*)	3.3 ns (*)	4.7 ns (ns)
Touching electrodes	3.7 ns	7.0 ns (ns)	1.0 ns (ns)	0.7 ns (ns)
Washing	11.3*	4.7 ns(*)	7.0* (ns)	5.3 ns (*)
Teeth-brushing	10.3*	3.3 ns (**)	1.7 ns (*)	2.3 ns (**)

Mean percentage of valueless ECG for QRS complex interpretation in ECG strips during various provocations of artefacts and modifications of technical equipment. Design of the table and levels of significance as in Table I.

Table III.  Perfect ECG for P wave interpretation.

	No modification	Tape	Cup	Tape + cup
No provocation	59.7	50.7 (ns)	61.7 (ns)	54.0 (ns)
Shaking cables	41.0***	43.7 ns (ns)	36.3*** (ns)	47.3 ns (ns)
Rotating shoulders	28.7***	37.7* (ns)	38.0** (ns)	47.0 ns (*)
Touching electrodes	18.3***	24.0** (ns)	46.0* (***)	33.0** (*)
Washing	23.7***	25.3** (ns)	23.0*** (ns)	30.0*** (ns)
Teeth-brushing	27.3***	37.3 ns (ns)	41.7** (ns)	33.3** (ns)

Mean percentage of perfect ECG for P wave interpretation in ECG strips during various provocations of artefacts and modifications of technical equipment. All patients were in sinus rhythm. Design of the table and levels of significance as in Table I.

Table IV.  Valueless ECG for P wave interpretation.

	No modification	Tape	Cup	Tape + cup
No provocation	18.3	17.7 (ns)	19.7 (ns)	18.7 (ns)
Shaking cables	38.7**	37.7* (ns)	42.0** (ns)	41.0* (ns)
Rotating shoulders	44.7**	37.0* (ns)	35.7* (ns)	33.0* (ns)
Touching electrodes	36.7*	30.0* (ns)	13.7 ns (**)	22.7 ns (ns)
Washing	48.0***	37.0** (ns)	42.0** (ns)	42.3** (ns)
Teeth-brushing	38.3**	28.3* (ns)	22.3 ns (ns)	28.3 ns (ns)

Mean percentage of valueless ECG for P wave interpretation in ECG strips during various provocations of artefacts and modifications of technical equipment. All patients were in sinus rhythm. Design of the table and levels of significance as in Table I.