Wednesday, February 20, 2013

Challenging Tradition: Better Precordial Lead Placement

This post is part of a series presenting challenges to the traditions of EMS.

Challenging Tradition: Better Precordial Lead Placement

Application of the precordial electrodes for a 12-Lead ECG is a process steeped in over 75 years of tradition. Drs. Wolferth and Wood first described the usages of additional chest leads for the diagnosis of myocardial infarction using the leads IV, V, and VI in 1932[1] and by 1938 the standard nomenclature and position of the V-leads was described in a joint paper from the American Heart Association and the Cardiac Society of Great Britain and Ireland[2].

Since 1938, there has been little focus in validating the classical precordial lead placement. Instead, efforts to improve the sensitivity and specificity of the 12-Lead ECG focused on adding new electrodes[3,4,5] or improving existing morphological and ST-segmental criteria[6].

In 1971, the concept of body surface potential mapping (BSPM) was introduced as an alternative to the standard 12-Lead ECG [7], and by the 1980's it was recognized as providing larger gains in sensitivity in acute myocardial infarction detection over the usage of the classical precordial leads[8]. However, BSPM relies on expensive recording and post-processing techniques, and is cumbersome in its requirement for a large electrode vest which envelops the chest of the patient.
Figure 1: 80-Lead body surface potential mapping locations.
In 1985 the first paper on improving the positions of the precordial leads using BSPM was introduced by Drs. Kornreich et al[9]. They explored electrode locations which provided higher degrees of sensitivity and specificity than the traditional precordial lead placement and continued their research into 2008 with a paper describing 4 additional leads which could be added to the traditional 10 electrodes to provide information similar to that of a BSPM[10].

Research in 2002 by Drs Kors and Herpen found that moving only two precordial electrodes (V4 and V6) was required to transform the 6 precordial electrodes into a viable interpolated BSPM[11]. Their paper was notable in it sought to find the minimal derangement of the classical positioning in order to obtain diagnostic results.

In 2007 and 2008, Drs. Finlay et al explored alternative precordial lead placement using a data driven approach which sought to improve the sensitivity and specificity of MI, LVH, and other ECG abnormalities[12,13]. As with prior research, they proved again that the classical precordial lead positions perform poorly when compared to interpolated BSPMs, however, they acknowledged their improved lead positions were not practical in clinical application. Also of note, Drs. Finlay et al commented that any change to the precordial lead placement would be, "unlikely to succeed because the familiar format of the 12-lead ECG coupled with the considerable amount of diagnostic criteria accumulated in the literature mean that it is a tool with which most clinicians are extremely comfortable and which they are therefore unlikely to relinquish."[14]

However, in 2011, Drs. Peter Scott et al demonstrated a simple repositioning of the precordial electrodes which not only improved sensitivity and specificity of acute myocardial infarction identification, but also could be performed in a practical manner[15]. Using data derived from 80-lead BSPM tracings, they performed analysis which found the most appropriate positions of the precordial leads to be located along a horizontal line beginning from V1 and V2 and extending along to the midaxillary.

Figure 2: Optimal location of the precordial leads V1-V6 for the detection of acute myocardial infarction.
This paper has a high potential to challenge the status quo in not only pre-hospital acquisition of 12-Lead electrocardiograms but also in-hospital. The electrode positions given are simple to apply, and could provide for a lesser degree of inter-operator variability in positioning. More importantly, this optimized placement provided for a higher sensitivity and specificity across all types of myocardial infarction.

In personal correspondence with Dr. Scott, I inquired as to the changes this presented to other common uses of the 12-Lead ECG--such as bundle branch block definitions or VT vs SVT algorithms--and he related that this research served to open the door to further research into the practical clinical benefits.
  • Does the evidence support challenging traditional precordial lead placement?
  • What possible limitations does this lead placement present?
  • What barriers exist to the adoption of this lead placement today?
References
  1. Wolferth CC, Wood FC. The electrocardiographic diagnosis of coronary occlusion by the use of chest leads. Am J Med Sci 1932;183:30-35.
  2. Barnes AR, Pardee HEB, White PD, et al. Standardization of precordial leads. Am Heart J 1938;15:235-239.
  3. Perloff JK. The Recognition of Strictly Posterior Myocardial Infarction by Conventional Scalar Electrocardiography. Circ 1964;30:706-718. [FullText]
  4. Erhardt LR, Sjogrn A, Wahlberg I. Single right-sided precordial lead in the diagnosis of right ventricular involvement in inferior myocardial infarction. Am Heart J 1976;91:571-6. [PubMed]
  5. Zalenski RJ, Cook D, Rydman R. Assessing the diagnostic value of an ECG containing leads V4R, V8, and V9: The 15-lead ECG. Ann Emerg Med 1993;22:786-793. [PubMed]
  6. O'Gara PT, Kushner FG, Ascheim DD, et al. 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction: A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circ 2013;127:e362-e425. [FullText]
  7. Barr RC. Selection of the Number and Positions of Measuring Locations for Electrocardiography. IEEE Trans Biomed Eng 1971;18(2):125-138.
  8. Kornreich F, Rautaharju PM. The missing waveform and diagnostic information in the standard 12 lead electrocardiogram. J Electrocardiol 1981;14(4):341-50. [PubMed]
  9. Kornreich F, Rautaharju PM, Warren J, et al. Identification of best electrocardiographic leads for diagnosing myocardial infarction by statistical analysis of body surface potential maps. Am J Cardiol 1985;56(13):852-6. [PubMed]
  10. Kornreich F, MacLeod RS, Lux RL. Supplemented standard 12-lead electrocardiogram for optimal diagnosis and reconstruction of significant body surface map patterns. J Electrocordiol 2008;41(3):251-6. [PubMed]
  11. Kors JA, van Herpen G. How many electrodes and where? A "poldermodel" for electrocardiography. J Electrocardiol 2002;35 Suppl:7-12. [PubMed]
  12. Finlay DD, Nugent CD, Kors JA, et al. Optimizing the 12-lead electrocardiogram: a data driven approarch to locating alternative recording sites. J Electrocardiol 2007;40(3):292-9. [PubMed]
  13. Finlay DD, Nugent CD, Donnelly MP, Black ND. Selection of optimal recording sites for limited lead body surface potential mapping in myocardial infarction and left ventricular hypertrophy. J Electrocardiol 2008;41(3):264-71. [PubMed]
  14. Ibid. 12.
  15. Scott PJ, Navarro C, Stevenson M, et al. Optimization of the precordial leads of the 12-lead electrocardiogram may improve detection of ST-segment elevation myocardial infarction. J Electrocardiol 2011;44(4):425-431. [PubMed]

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