Elsevier

Journal of Electrocardiology

Volume 44, Issue 2, March–April 2011, Pages 115-118
Journal of Electrocardiology

Standardization of electrode placement for continuous patient monitoring: introduction of an assessment tool to compare proposed electrocardiogram lead configurations

https://doi.org/10.1016/j.jelectrocard.2010.10.031Get rights and content

Abstract

Numerous modified electrocardiogram (ECG) lead configurations are used for continuous patient monitoring, and they often produce waveforms substantially different from the standard 12-lead ECG. Serial comparisons between modified and standard lead configurations can lead to misdiagnosis and inappropriate therapy. To address this problem, an international Lead Summit was convened in June 2010 to discuss standardizing lead configurations for patient monitoring. The present article summarizes an invited presentation at the Lead Summit where the author proposed an assessment tool to compare the clinical utility of various lead configurations to provide a framework for ongoing and future discussions. The tool (0-20 points, with 20 being the perfect score) weighs 5 factors that are clinically important including equivalency to the standard ECG (6 points), patient comfort (4 points), noise immunity (4 points), noninterference with clinical interventions (3 points), and identifiable anatomical landmarks for accurate electrode placement (3 points). Because research is lacking for some of these factors (eg, patient comfort and noise immunity), studies conducted in patients in actual clinical environments are needed to reach consensus about ideal lead configurations for patient monitoring.

Introduction

Widely endorsed practice standards for electrocardiogram (ECG) monitoring in hospital settings were published in 2004 that provided classes I, II, and III indications for monitoring patients in various diagnostic categories.1 This consensus document recommended that patients should be assessed for 3 potential goals of ECG monitoring: arrhythmia, ischemia (ST segment), and QT/QTC interval monitoring for patients at risk of torsade de pointes. Because monitoring goals often differ between patients, the cardiac monitoring equipment and lead configuration need to be able to support all 3 goals of monitoring. A more recent consensus document in 2010 focused solely on QT/QTC interval monitoring recommendations to prevent cardiac arrest due to torsade de pointes in hospital settings.2

During a hospitalization episode, patients often move between various units providing continuous ECG monitoring. For example, patients who present to an emergency department with chest pain are typically monitored in the emergency department, the cardiac catheterization laboratory, an intensive care unit and/or a “step-down” progressive care unit with wireless telemetry monitoring. In addition, “diagnostic” 12-lead ECGs are usually acquired daily, interpreted by cardiology, and stored in the hospital computer ECG database system. Today, the diagnostic 12-lead ECGs can be acquired using a standard electrocardiograph machine or from a bedside cardiac monitor with 12-lead capability.

Because various brands of cardiac monitors often exist within a hospital, a plethora of standard, Mason-Likar, and reduced lead sets may be used in a single patient during the same hospitalization and documented in the patient's medical record. Recently, case studies have been reported that involve misdiagnosis due to serial comparisons of nonequivalent lead configurations.3, 4, 5 When diagnosis depends on the equivalency of 2 ECGs; for example, comparing ST-segment elevation before and after early reperfusion therapy to determine whether myocardial injury is resolving or worsening, different lead configurations can result in misdiagnosis and inappropriate treatment.

Two professional societies are collaborating to standardize ECG lead configurations for patient monitoring. The International Society for Computerized Electrocardiology sponsored an initial Lead Summit in 2007 in Durham, NC, and more recently, the International Society of Electrocardiology held a second Lead Summit in 2010 in Lund, Sweden. Two recommendations from the initial Lead Summit were to (1) keep the standard 12-lead ECG as it is currently acquired with limb electrodes on the distal extremities and provide more education regarding accurate precordial electrode placement and (2) standardize a lead configuration for continuous patient monitoring that would be both practical and more equivalent to the standard 12-lead ECG.

Standardization is targeted for hospital, prehospital, and outpatient ambulatory (Holter) monitoring applications but not necessarily for ECG monitoring during exercise stress testing. The rationale for not including exercise testing is that serial ECG comparisons are made over the brief time period of the test and acquired in a single laboratory with consistent electrode placement during the baseline, exercise, and recovery periods. As a result, there is no risk of making serial comparisons with nonequivalent lead configurations.

Several lead configurations have been proposed to standardize hospital, prehospital, and ambulatory monitoring. Currently, a subset of the Mason-Likar6 lead configuration using 1 chest (“V”) lead is the most commonly used lead configuration for patient monitoring in the United States. The remaining 5 precordial leads can be attached periodically to acquire a full 12-lead ECG. Less commonly used lead configurations include 12-lead ECGs that are derived from 5 or 6 electrodes (reduced lead sets).7, 8, 9 Limb electrodes that are placed on the torso as in the Mason-Likar lead configuration have been shown to result in smaller amplitude or missing Q waves of prior inferior infarction as well as differences in QRS morphology and frontal plane QRS axis.10, 11 For this reason, the Lund lead configuration with limb electrodes placed more distally has also been proposed for patient monitoring.12, 13, 14

The purpose of the present report is to introduce an assessment tool to compare the clinical utility of various lead configurations for the purpose of providing a framework for ongoing and future discussions with a goal of reaching a universally accepted standard.

Section snippets

Methods/Results

A scoring system was developed to compare the value of proposed ECG lead configurations. Five factors were considered important when selecting an ideal electrode configuration for patient monitoring (Table 1). Each factor was assigned a weight to represent its relative clinical importance. The ideal lead configuration would have a perfect score of 20 points.

Discussion

This is the first attempt to introduce an assessment tool to compare various ECG lead configurations for patient monitoring. Ongoing and future discussions may reveal additional factors that need to be considered and/or different weight scores for individual factors. Once consensus is reached on a tool to compare lead configurations, then the next step is to review the published research on each of the proposed ECG lead configurations to determine their scores for each of the factors. In some

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    An assessment tool to compare various ECG lead configurations for long-term patient monitoring has been suggested by Drew et al. [37], however needs more study to reach standardization of electrode placement. The tool is based on scoring (0–20 points, with 20 as perfect score) and considers 5 factors that are clinically important: equivalency to the standard ECG (6 points), patient comfort (4 points), giving less noise (4 points), non-interference with clinical interventions (clinical interventions should not interfere with ECG electrode sites) (3 points), and identifiable anatomical landmarks for accurate electrode placement (3 points) [37]. For 12-Lead ECG Monitoring, different lead systems can be used such as EASI™ Lead System using 5 electrodes, Mason-Likar Placement using 10 or 5 electrodes, or conventional electrocardiograph 10-electrode [38].

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