Original Article
Twisted Leads: The Footprints of Malpositioned Electrocardiographic Leads

https://doi.org/10.1016/j.hlc.2015.05.010Get rights and content

Background

Malposition of electrocardiograph (ECG) leads is poorly recognised even by cardiologists who report tracings. When ECG tracings are regularly performed by doctors, nurses or technicians, lead malposition is very uncommon particularly if the operator can also interpret the findings. However, a significant proportion of 12-lead ECG tracings are today performed in a doctor's surgery or by private pathology services, often in haste without sufficient attention to correct lead positioning. As a result, a variety of malposition combinations occur, which in turn may confuse the interpreter of the ECG tracing, leading to incorrect diagnoses.

Objectives

To investigate various combinations of ECG lead malposition and determine if characteristic findings can be summarised into identifiable footprints.

Methods

In 10 normal subjects, 12-lead ECGs were performed with normal lead positioning as well as six limb lead malpositions and reversal of chest leads.

Results

In all subjects, there was consistency in the ECGs performed allowing the creation of five characteristic and easily identifiable footprints.

Conclusions

A summary of the footprints of ECG lead malposition should be readily available for those who perform ECGs, those who interpret the tracings and those responsible for clinical care.

Introduction

An electrocardiogram is a surface record of the electrical activity of the heart plotted against time, with the actual recording of the non-invasive test being an electrocardiograph. Both are commonly referred to as ECGs or EKGs and for diagnostic purposes, a 12-lead tracing is generally performed at rest and documented electronically in a standardised manner. The correct placement of the limb and chest leads is vital to the correct interpretation of the tracings. Incorrect placement or malposition of the leads is believed to only rarely occur and consequently very little emphasis has been given to the understanding and interpretation of the consequent abnormal tracings.

Electrocardiograms are performed by doctors, nurses or technicians who are trained in the placement of the electrodes and leads. In the hospital setting, few errors occur particularly if the operator is also trained in the interpretation of the tracing. Today, however a significant proportion of 12-lead ECG tracings are performed in the doctor's surgery or by private pathology services, often in haste without sufficient attention to correct lead positioning. As a result, particularly with the limb leads, a variety of malposition combinations can occur, which in turn may confuse the interpreter of the ECG tracing leading to incorrect diagnoses. Some of these are common and easily identified, whereas others may fool even the most experienced interpreter.

It is not possible to accurately determine the incidence of ECG lead malposition. However, from experience reporting large numbers of ECGs from small hospitals and pathology services and carefully searching for these obscure ECG appearances, about 1/200 ECGs (0.5%) have an appearance consistent with lead malposition. It is the purpose of this review to present the most commonly recognised appearances of lead malposition. This is to assist those who perform the test, those who interpret the tracings and finally those who order ECGs and are required to couple the results to the clinical scenario.

The ECG's with malpositioned leads will be presented as simple footprints which can be immediately recognised. However, in order to understand the recognised ECG abnormalities of malpositioned leads, it is necessary to understand the basic ECG appearances.

Section snippets

The Normal 12-lead ECG

The ECG recording depends on the creation of electrical circuits between three limb and six precordial chest surface electrodes. There are three conventional lead arrangements: limb leads; augmented limb leads; and precordial chest leads. The limb lead electrodes should be positioned equidistant from each other, one electrode on each arm and a third electrode on the left leg. The electrical geometric figure so created is called Einthoven's triangle (Figure 1). A fourth electrode placed by

Methods and Materials

A series of eight 12-lead ECGs were performed on 10 volunteer normal subjects with all ECGs from the same subject taken at the same time. The order was:

  • Normal lead positioning

  • Reversed arm leads

  • Reversed limb leads (arm leads on legs)

  • Reversed arm and leg leads on the right

  • Reversed arm and leg leads on the left

  • Reversed left arm and right leg leads

  • Reversed right arm and left leg leads

  • Reversed chest leads.

The appearances of reversed arm leads and reversed chest leads are well known and thus the main

Results

The ECG findings of all the lead malpositions were consistent across the 10 volunteers. An eleventh study was discarded because of probable mislabelling. The illustrations were taken from one volunteer performed on a second occasion to create tracings suitable for illustrative purposes. Figure 2 is the normal ECG used as the control. The Table 1 summarises the major and minor footprints of limb lead malposition.

Discussion, Limitation and Conclusion

Apart from reversed arm leads, limb lead malposition is very poorly recognised even by those physicians who regularly report ECGs. The objective of this study was to review the changes that occur with lead malposition and to provide an easy method of recognising these abnormalities through characteristic footprints. The major finding was the appearance of isoelectric voltages in leads I, II and III with the offending lead malposition recognised as lying between the two lower limb positions.

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