Is the Correct Anatomical Placement of the Electrocardiogram (ECG) Electrodes Essential to Diagnosis in the Clinical Setting A Systematic Review

Background: Anatomical misplacement of the Electrocardiogram (ECG) electrode(s) is common, with signi�cant impact on clinical diagnosis. Reasons are multi-faceted, with this review examining the consequential effects of misplacement to ECG morphology, diagnosis, prognosis, patient outcomes, and potential impact to patient care pathway. Objectives: This review examined the signi�cance of misplacement, its’ commonality and ensuing effect on patient safety, accurate ECG acquisition and diagnosis, with evaluation of reasons for such misplacement. Methodology: Review of available literature was conducted using electronic databases. In-line with the Preferred Reporting Items for Systematic reviews and Meta – analysis protocols (PRISMA) 2015 checklist, this review was conducted with search criteria, search terms, eligibility for inclusion/ exclusion criteria, extraction and data analysis predetermined by the authors. Keywords were arranged according to grouping of terms surrounding ECG, anatomical placement, and diagnosis. The search strategy was conducted during September/October 2019. Scoping searches were conducted alongside reference lists of included studies hand searched (Snowballing) for further relevant studies. The Critical Appraisal Skills Programme (CASP) was used to methodically appraise papers (CASP, 2019). Screening of titles and abstracts of identi�ed citations was performed by a single reviewer. Eligible articles then full text screened independently by two reviewers. Disagreements were discussed and resolved by a third reviewer. In instances of unclear reporting, authors were contacted to provide further information and clarity. Assessment of relevant literature and critical appraisal of primary research, pertaining to the clinical diagnosis and effects of anatomical misplacement of ECG electrodes, formulate the thematic discussion drawn by this review. Results: This review identi�ed a plethora of causes, ranging from: operator error; lack of anatomical awareness; inaccurate assessment of anatomical landmarks; obesity; differences in anatomy/gender; levels of undress and lack of appreciation of consequences of misplacement, both modi�able and non-modiable attributable to electrode misplacement. Clinical diagnosis can be altered owing to erroneous placement of electrodes. ECG morphology is altered due to incorrect anatomical misplacement, culminating substandard practice, a missed diagnosis or misdiagnosis and potential harm. Conclusion: Correct anatomical placement of ECG electrodes is essential to diagnosis in the clinical setting. Peer-led educational intervention with mandatory training is essential to improve practice.

The current recognised gold standard for assessment and identi cation of CAD is Angiography.However, there are associated risks and possible complications with this invasive modality.There is evidence that CAD and plaques are formed in childhood, yet CAD disease is preventable. [2]Typical risk factors include smoking, diabetes, high blood pressure (hypertension), family history, obesity and poor life style choices.
The standard 12 lead electrocardiogram (ECG) provides for a non-invasive, cost effective assessment that is convenient to patients. [3] Its' fundamental morphological features provide useful information in the diagnosis/prognosis of arrhythmia and cardiac disease. [7][8]Accurate electrode placement and acquisition of ECG is an essential skill required of nursing staff and health professionals alike and duly noted by The Nursing and Midwifery Council (NMC) (2010) standards for preregistration nurses. [9]incipally, acquisition of ECG traces should be reproducible and correctly identify various medical conditions such as cardiac arrhythmia, particularly acute coronary syndromes (ACS), and which aid in risk strati cation, detection and management of cardiac disease, notably ST elevation myocardial infarction. [10][6]is graphical representation of the signal potential difference between two points provides for universal standard parameters of the ECG waveform. [11]pically depicted as the P-wave (Atrial depolarization, with subsequent contraction), the QRS complex (Ventricular depolarization, with subsequent contraction), and the T-wave and U-wave which constitute the repolarisation phase of the cardiac cycle. [12]Any deviation from the perceived normal ECG baseline requires accurate and reliable detection owing to time/frequency varying morphology.
Regarded as the 'gold standard,' a non-invasive, inexpensive diagnostic tool, integral in medical investigations, the electrocardiogram remains the principal diagnostic method in the recognition of acute myocardial infarction (MI), British Cardiovascular Society (BSC) (2015) and National Institute for Health and Care Excellence (NICE) (2016). [15][16]storically, substandard levels have prevailed in the acquisition of ECG, with 50% of nurses and <20% of cardiologists correctly placing precordial electrodes V1 and V2. [17]This erroneous pervasiveness continues in Today's practice.These ndings were supported by Medani et al, (2018), [14] which revealed nurses misplaced precordial electrodes in 64% of cases.Misplacement constitutes for erroneous acquisition, diagnosis, missed diagnosis, interpretation, and treatment/mistreatment of patients. [18]Furthermore, delayed triage to early invasive strategy in the patient care pathway has resulted from erroneous placement, with consequent increased mortality and morbidity. [18]The leading cause of mortality and serious illness to date remains cardiovascular disease. [6]e prevalence of electrode misplacement is a common nding in both acute and clinical settings. [13][14]Despite the commonality of misplacement, such erroneous practice remains under reported.Of paramount importance in any attempt to acquire an ECG trace that is accurate and of good reproducible quality, is the onus placed on correct anatomical placement of the silver-silver chloride electrodes and their relative leads.The respected 'gold standard' should therefore consider the recommendations and guidelines of the Society for Cardiological Science and Technology (SCST) adherence to which remains widely neglected in clinical practice. [19]e electrocardiogram has changed little since its inception, with the overarching prerequisite for any accurate detection of signal remaining the accurate anatomical placement of electrodes and their contact interface with the skin. [20]With current information regarding electrophysiology and ECG oftentimes disjointed, contradictory and frequently misunderstood, particularly in an era of multi-authored texts, the need for a single authoritative voice is essential. [6]e SCST recommend standardization of the ECG procedure, with training and subsequent accreditation, ensuring operator skill, competency, con dence, and a gold standard of practice and promotion of excellence. [19]jectives: This systematic review investigated the signi cant importance of correct anatomical placement of the electrocardiogram (ECG) electrodes and their relative leads.Objectives were made to establish the commonality of electrode misplacement, its' subsequent potential effect on patient safety and a review of reasons for such misplacement.

Design And Methodology
Initially, the review sought to highlight the advancements in technology, which provide for signal processing of the electrocardiogram, notably, differences in Fourier Transform (FT), and Continuous Wavelet Transform (CWT).However, the caveat adopted by this review acknowledges the absence in the literature of any direct comparison between the modalities and subsequent paucity of literature to warrant expansion.
Consideration was therefore given to the common denominator governing both signal processing modalities.In short, both are reliant upon the interface between the patients' skin and the silver-silver chloride electrodes with their respective leads, for the attainment of the surface 12 -Lead ECG.

Justi cation:
A risk of bias assessment was conducted for each of the included studies using the Critical Appraisal Skills Programme (CASP) (2018). [21]The population, intervention, comparison and outcome (PICO) framework (NICE, 2012) for eligibility criteria are described as follows:

Population
Male or female adults of ≥18 years, regardless of any previous cardiac history were considered.

Intervention
Electrode placement with the sole intention to acquire a 12 -Lead electrocardiogram trace for clinical diagnosis of arrhythmia.

Comparison
Accurate anatomical placement of ECG electrodes in-line with guidelines and recommendations of the (SCST, 2017) compared with those misplaced.

Outcome
The potential effect(s) on patients' clinical diagnosis, owing to inaccurate ECG electrode placement.
In accordance with the Nursing and Midwifery Code of Conduct (NMC, 2015), [22] and guidelines/recommendations of the SCST [19] justi cation for this work is demonstration of the ongoing prevalence and relevance of ECG electrode misplacement in the clinical setting.Furthermore, the subsequent rami cations imposed on patient diagnosis and implications of erroneous ECG acquisition.

Search Strategy:
A systematic review was conducted with search criteria, search terms, eligibility for inclusion/exclusion criteria, extraction and analysis of data predetermined by the authors, in-line with the Preferred Reporting Items for Systematic reviews and Meta -analysis protocols (PRISMA) 2015 checklist. [23]Keywords and subject headings were combined according for terms surrounding, ECG, anatomical placement, and diagnosis.Table 1 highlights the systematic review synthesis and data extraction.No time/date restrictions of the literature were implemented.The inclusion criteria for this review included English language articles, international papers, and unpublished works.). [21]e search strategy was developed and conducted during September and October 2019.A total of three (3) scoping searches were conducted along with the reference lists of included studies hand searched (Snowballing) for further relevant studies.A copy of the Healthcare Databases Advanced Search (HDAS) NICE [24] search strategy is included in Table 2.An initial screening of titles and abstracts of identi ed citations was performed by a single reviewer (AH).Potentially eligible articles were then full text screened independently by two reviewers, (AH and SM) in-line with the inclusion and exclusion criteria.Disagreements regarding eligibility were discussed and resolved by a third reviewer (TU).In instances of unclear reporting, authors were contacted to provide further information and clarity.
Assessment of relevant literature and critical appraisal of primary research, pertaining to the clinical diagnosis and effects of anatomical misplacement of ECG electrodes and leads, formulate the thematic discussion drawn by this review.
The primary consideration and rationale for this review is the ongoing potential relevance of electrode misplacement, its frequency in the clinical setting, the subsequent rami cations imposed on patients and reasons leading to such error.In addition, synthesis of the literature correlate the overarching consensus for education, training and a change to practice in order to provide improved safety, and care of patients in line with the Nursing and Midwifery Code of Conduct (NMC, 2015) [22] and guidelines / recommendations of the (SCST, 2017). [19]udy Selection: Two independent reviewers (AH and SM) carried out searches of relevant and pertinent studies that met inclusion suitable to this review.Full texts were obtained, with exclusion of obviously irrelevant titles, abstracts, reviews or literature.The independent ndings were then cross-examined and assessed against the eligibility criteria.A third reviewer (TU) then made further assessment and agreement, with resolve of any doubt or disagreement prior to the submitted work.English language articles published in indexed journals have been considered along with unpublished works and 'Grey' literature considered.

Database Searches:
Medline, Embase, CINAHL, were searched, with combinations of subject headings, Boolean terms and Text words agreed from an initial scoping search ensuring a sensitive search.A supplementary search was conducted using NHS evidence and, clinical trials registries, and the international clinical trials registry platform WHO, and the U.K. clinical trials gateway NHIR.This with the view to negate publication bias, whereby published papers tend to show the positive effect of an intervention, rather than the negative effect. [25][26] hierarchy of evidence framework has been used to aid in the evaluation and reduction of bias of included papers, and in acknowledgement of evidencebased healthcare (i.e. Background information/ expert opinion, case-controlled studies, cohort studies, RCTs etc.).In support of this notion, the included papers provide for a broad range of research methods. [27]No restrictions were placed on type of ECG device (manufacturer or model), algorithm or signal processing.

Results
A total of 3186 articles were identi ed from the initial search strategy, reducing to 3131 after duplicates were removed.Full text screening was performed utilising NICE Healthcare Database Advance Search (HDAS) [24] was conducted on 78 articles, according to the eligibility criteria, which resulted in 7 included studies, Table 1 (Systematic Review Synthesis and Data Extraction) and Figure 1.PRISMA ow diagram, detailing searches strategy of systematic review.

Data Extraction and Synthesis:
Five themes were derived from the Systematic Review Synthesis and Data Extraction Table 1.The chief characteristics of included studies and themes derived are as follows: Theme 1 -Misplacement of Electrodes: It is well documented within the literature that misplacement of precordial electrodes is long-standing, to remain a common occurrence and nding that, so far, has not been effectively addressed. [13]Of concern, are the subsequent clinical and diagnostic/prognostic rami cations for the patient. [28]The ndings of this review support this notion, with V1 and V2 being consistently erroneously misplaced superiorly in the 2 nd intercostal space rather than in the 4 th intercostal space at the right sternal border and left sternal border respectively. [13][10][29][14][28] [32]tentially harmful treatment and/or therapeutic procedures may ensue. Consequently, superior misplacement of V1 and V2 spearheads to spurious ECG abnormalities that may include: poor R-wave progression; ventricular hypertrophy; anteroseptal infarct; QRS complex and T-wave alterations; incomplete right bundle branch block (IRBBB); false positive and false negative ischemic changes and Type 2 Brugada syndrome. [30][14][28]easons for such erroneous placement are multi-factoral and can include poor training, a lack of appreciation of consequences of misplacement, a failure to understand and utilise anatomical landmarks such as the sternal notch (Manubriosternal joint/Angle of Louis), and the Xiphoid process for correct identi cation of the 4 th intercostal space. [30]rthermore, levels of undress and the desire to preserve patient modesty, particularly in females, are factors that evidence signi cant impact.Fewer cardiac investigations are evidenced in women with ACS than in men.Subsequently, such inequities result in less treatment and prove potentially detrimental. [31]eme 2 -Anatomical Differences: Anatomical differences between male and female patients provide additional challenges in electrode placement and accurate ECG acquisition.SCST guidelines and recommendations state, by convention electrodes V4, V5 and V6 ought be placed beneath the breast when breast tissue overlies the correct anatomical positions. [19]study conducted by Wallen et al, (2013) [31] noted 52% of women preferred electrodes placed on the breast tissue, deeming it less intrusive, 38% were indifferent and 10% preferring under the breast. [31]Review of the wider literature and that of the included studies of this review allude to di culties, particularly on women with large breast tissue mass and, in obese patients, in accurately identifying bony landmarks as anatomical reference points to aid in the correct placement of electrodes.However, current evidence pertaining to misplacement because of women's breast tissue and obesity is inconclusive and warrants further investigation. [13][30][28] contrast, a prospective observational study by McCann et al, (2007) [10] evidenced greater lateral chest electrode discordance (V4-V6), irrespective of gender, than those of central chest electrodes (V1-V3), however, identi cation of anatomical landmarks and accurate location were impeded particularly in older, larger women and the obese. [10][30]This was further supported by the ndings of the PULSE multi-site randomised clinical trial, (2018), where < 50% of both male and female participants were found to have accurate electrode placement. [29]PULSE concluded no signi cant difference in accuracy for precordial electrode placement between men and women.
Theme 3 -Operator Error & Causes of Misplacement: even among senior clinicians, is a factor widely acknowledged for the occurrence of electrode misplacement. [10]Causes of misplacement extend to both modi able and non-modi able patient factors, such as body habitus, body position, lack of anatomical awareness, lack of con dence, competence or even over con dence. [10][13]However, con dence is no substitute for competence. [19]Cardiologists in particular fall prey to such over con dence.Assuming the position of V1 and V2 electrodes in the 2 nd intercostal space rather than that of the 4 th, which may arise from a complacency through regularly listening to auscultations of heart sounds at 2 nd intercostal level. [13] is postulated that particularly amongst paramedics, operator error is compounded by a hesitancy to expose the female breast.The connotation that the female breast is a secondary sexual organ provides ensuing embarrassment. [31]eme 4 -Clinical Impact on Diagnosis, Treatment & Management: Correlation between misplaced precordial electrodes with changes to ECG morphology dominates the theme of the majority of papers included in this review.
Such alterations have the potential to signi cantly impact clinical interpretation and diagnosis, leading to over, under or even a missed diagnosis.Conversely, superior misplacement of V1 and V2 has proven bene cial in the detection of ST-segment elevation myocardial infarction (STEMI), Non-ST-segment elevation myocardial infarction (NSTEMI) and Brugada syndrome, with no noted signi cant change to speci city. [28]However, studies have purported a shift in placement by as little as 2cm; can affect interpretation and diagnosis in as much as 17-24% of patients. [30]eme 5 -Education & Training: Overarching consensus of included papers, place education and training as tantamount, and of paramount importance to accurate ECG acquisition.Thus, optimising sound clinical diagnosis and practice.Implementation and adherence to SCST and the American Heart Association (AHA) guidelines, yields signi cant improvement. [29][14]Correct identi cation of anatomical landmarks, notably, the sternal notch (Angle of Louis), Xiphoid process and the 4 th intercostal space for the correct placement of electrodes is essential in the undertaking of ECG.This coupled with on-line education and strategies to change current erroneous practice, through raising awareness and knowledge, are fundamental to good clinical practice, quality of care and outcomes for patients, with a reduction in patient morbidity and mortality. [10][29]scussion Types of studies included randomised controlled trials (RCT), systematic reviews, literature reviews and observational studies.Studies were identi ed irrespective of design, complexity, aims and time of follow-up or hypotheses.Of note, the overriding theme and consensus of the included papers allude to the frequency, commonality and potential for erroneous recordings owing to ECG electrode misplacement.As aforementioned, V1 and V2 are most commonly misplaced anatomically superiorly, with V4 -V6 misplaced inferiorly.The majority of reviewed papers acknowledge the frequency of misplaced precordial electrodes and leads.Subsequently, this results in alteration of ECG waveform morphology, misclassi cation of ischemic changes and erroneous clinical interpretation.Consensus further points to operator error, with inability to correctly identify intercostal spaces and accurate placement of electrodes, as the overriding underpinning factor for such error.Anatomical differences prove challenging and are factors compounded by obesity and breast tissue mass particularly in women.

Limitations:
The inclusion criteria for this review included English language articles, international papers, and unpublished works.However, the authors acknowledge that the reviews ndings are limited, despite supplementary searching, and that no guarantee can be assigned that all relevant literature has been included.It is further acknowledged that there are inaccessible papers and/ or 'Grey' literature that authors did not have rights over.

Conclusion
This review has identi ed that electrode misplacement is well documented, common, ongoing and prevalent throughout healthcare.Misplacement of precordial electrodes is synonymous with erroneous acquisition and signi cantly alters ECG waveform morphology, leading to misinterpretation and the potential to alter diagnosis.Therefore, correct anatomical placement of the ECG electrodes is in fact essential to diagnosis in the clinical setting.Reasons for misplacement are as aforementioned multifaceted, however the recommendation is that peer-led educational intervention with mandatory training is essential to improve practice and thereby enhance patient safety and outcome.

Supplementary Files
This is a list of supplementary les associated with this preprint.Click to download. PRISMA2009checklistforBMCSpringerNature.doc Precordial electrodes V1 &V2 are most misplaced Operator error, anatomical differences including obesity and breast tissue mass in uence electrode misplacement Misplacement of electrodes can lead to a misdiagnosis, a missed diagnosis, under or over diagnosis Educational intervention through peer-led training is essential.

Figures
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Table 1
Systematic Review Synthesis and Data Extraction The study is reported and conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines.The systematic review protocol was prospectively registered on the PROSPERO database of systematic reviews, Registration Number: CRD42019152461, and inline with the Preferred Reporting Items for Systematic reviews and Meta-Analyses Protocols (PRISMA-P), (2015) checklist.Critical Appraisal Skills Programme (CASP) was used to methodically appraise papers(CASP, 2019

Table 2
Healthcare Databases Advanced Search (HDAS) NICE search strategy (Electronic Databases)