ECG Guru - Instructor Resources

A gathering place for instructors of ECG and cardiac topics.


Subscribe to me on YouTube

Jason's Blog: ECG Challenge of the Week for July 8-15. Which lead do both of these ECGs share a “common-thread”?

jer5150's picture


Two more ECGs classified under the general heading:  “Tracing suggestive of   ____ ”.  I  like ECGs that strongly favor a very specific clinical disorder.

Recently I performed these ECGs on two different patients.  They were both recorded a little more than an hour apart and exemplified a common electrocardiographic theme I noticed during that work shift.

The primary goal of this week’s blog is not to determine the name of each ECG’s rhythm but rather what each ECG is virtually diagnostic of.

This sign is commonly referred to by one of two names:  (1.)  Either by the lead that it appears in or (2.) eponymously named after the doctor who is credited with first describing it.  

To date, the ECG machine's computer is not programmed to recognize this particular sign/pattern nor will it make the suggestion to consider this possibile clinical disorder in it's statements printed at the top of ECG.  Hopefully, in the future, manufacturers of ECG machines will add this algorithm to their computer's diagnostic statements.

Patients’ clinical data:

  • Fig. 1 (Top tracing): 61-year-old black man, underweight, active smoker (long history of tobacco abuse), and persistent cough.  The challenge for me was to obtain an artifact-free tracing in between coughing fits. When asked, this patient denied having this medical condition that his provider had diagnosed him with.
  • Fig. 2 (Bottom tracing): 70-year-old white man, active smoker (long history of tobacco abuse).  When asked, this patient also denied having this medical condition that his provider had diagnosed him with.

Personally, I think that a certain degree of denial goes hand-in-hand in this patient population when confronted with their self-destructive vices.

So, both men have similar (albeit limited) histories and a similar clue on their ECGs.  In each of the two ECGs, there is a single lead where the waveforms look nearly identical.

  • Hint # 1:  The answer to the clinical disorder is a 4-letter acronym.


  • (1.)  Which one of the 12 individual leads am I referring to and . . .
  • (2.)  What clinical disorder is that lead a highly specific marker of?
Rate this content: 
Average: 5 (1 vote)


I believe it is known as the "Lead I Sign", although I can't recall who the doc is that it is named after. It has been shown, albeit retrospectively, to be very specific for COPD. The criteria is informally given as "very low voltage Lead I", but I do believe there is a formal millimeter criteria available for each of the P, QRS, and T waves.


jer5150's picture
Submitted by jer5150 on

Thank you to Christopher for his correct observations. 

Both of these patients have “Smoker’s Lung”.  Fig. # 1 was diagnosed with chronic bronchitis which is a type of COPD.  Fig. # 2 was diagnosed with COPD.  Note the poor r-wave progression in the precordial leads of Fig. # 1.  The only real clue, suggestive of COPD, in Fig. # 2 is the disproportionately low P-QRS-T voltage in lead I. 

Whenever Lead I appears nearly isoelectric, one must consider the possibility that the arm cables have accidentally been reversed with their respective leg cables on the same side.
Despite this sign being a highly specific indicator of COPD, neither one of these ECGs prompted the computer to suggest the statement of:  “consider pulmonary disease” or “pulmonary disease pattern”.

The “Lead I sign” is largely credited as being described by the late Dr. Leo Schamroth from Johannesburg, South Africa.  It later came to be also known as “Schamroth’s sign” or “Schamroth pattern” which was an eponymous term popularized by Dr. Bill Nelson.

About 4 years ago I was performing a 12-lead ECG on a patient in the Surgical Intensive Care Unit (SICU) and I asked the assigned nurse if his patient had COPD.  The nurse confirmed my suspicions and with a very surprised expression on his face, he inquired: “You can tell that just from glancing at his ECG?!” to which I replied “Yes, it’s obvious, if you know what clue to look for”.  I went on to explain this lone clue to him.  Patient’s are also amazed when you can recognize their COPD in the waveforms of their ECG.   

Schamroth’s Sign Criteria:  Isoelectric P wave in lead I combined with a very small QRS complex of less than 1.5 mm total deflection and a T wave of less than 0.5 mm in lead I. (1)

Sources / Reference:
3.) SITE-Additional Examples-Patterns & Eponyms.ppt
4.) SITE-Patterns & Eponyms.ppt

Jason E. Roediger - Certified Cardiographic Technician (CCT)'s picture

     This interesting column by Jason brings up the important question of how to assess an ECG for the likelihood of pulmonary disease. As another Marriott disciple  I was glad to see Jason reintroduce the long forgotten (by many in the field) Schamroth sign that I've regularly looked for over decades. Jason's post reminds me that I need to add this sign to the next edition of my ECG Pocket Brain.

That said - I would add these points that I feel are important about recognizing possible pulmonary disease on ECG.
  • It is often very difficult to do. The RV has 1/3 the size, which in 3 dimensions makes up 1/10 the mass of the LV. As a result  it takes a lot for an enlarged RV to make itself evident on the insensitive ECG. By the time you see clear evidence of true RVH on an adult ECG - you have either severe longstanding disease and/or pulmonary hypertension.
  • The Schamroth Sign that Jason describes IS a helpful clue. It is rare that you see a true "null vector" in lead I (in which the P,QRS,T are all flat so as Jason emphasizes, seeing this sign should make you consider pulmonary disease that may be severe. That said  this sign is highly suggestive but not sensitive. I have not seen it often despite looking for decades.
  • The ECG Diagnosis of RVH (and of pulmonary disease) is perhaps best thought of as a "detective diagnosis". It is usually not made by any one sign - but rather by putting together the "clues" on the tracing in the context of a patient who is a longterm smoker or with other evidence of chronic pulmonary disease. One sees several of the following: i) Right or indeterminate axis; ii) RAA (Right Atrial Abnormality); iii) Low voltage; iv) Persistence of precordial S waves through V5,V6; v) S waves in leads I,II,III; vi) Tall R wave in lead V1; vii) Complete or incomplete RBBB pattern in V1; and viii) RV "strain" (usually best seen in the inferior and anterior leads).
  • The signs from the above bullet that suggest the ECG pulmonary disease is likely to be accompanied by RVH and/or pulmonary hypertension are  ii) RAA; vi) Tall R in V1; and viii) RV "strain".
  • The TOP FIGURE on this post is classic. In addition to the Schamroth sign and knowledge that this patient is a longterm smoker  there are frequent PACs (if not, almost MAT), marked axis deviation, IRBBB with persistent precordial S waves, and clear RAA  as well as ST-T wave abnormalities that may reflect RV 'strain'.
  • The LOWER FIGURE has Shamroth's sign and a history of smoking - but no other ECG signs of pulmonary disease. Jason makes the wonderful point that the low amplitude P,QRS,T wave in lead I of this LOWER TRACING should suggest the possibility of pulmonary disease  but I daresay that specificity of this type of tracing that lacks any of the other typical ECG pulmonary disease findings in the absence of a long history of smoking and in which there is not truly a "null vector" in lead I would be unproven for COPD ....
  • Both of the examples of Schamroth sign in the Nelson links that Jason provides in his Reference list had other ECG indicators of pulmonary disease in addition to the Schamroth sign.
Thanks again to Jason for reminding us of the Schamroth sign  that may be quite useful when seen.
CHRISTOPHER - The numerical criterion you are referring to is stated in Yip reference that Jason cites: Based on their small series of 15 patients, in which 5/15 had the sign - they "proposed very strict arbitrary criteria ... of a very small QRS complex of less than 1.5 mm total deflection and a T wave of less than 0.5mm in lead I." As noted in that 1998 article - Schamroth described the sign as showing "absent or very low amplitude P,QRS,T wave complexes giving the apearance of a minimally disturbed baseline" without specific cut-off values. I don't know if there have been additional studies (beyond the Yip 15 patient case series) documenting this phenomenon ...  BOTTOM LINE: You are looking for a "NULL VECTOR" in lead I.
NOTE: For those interested in more on the ECG diagnosis of Chamber Enlargement — Please check out these ECG Blog posts:

All our content is FREE & COPYRIGHT FREE for non-commercial use

Please be courteous and leave any watermark or author attribution on content you reproduce.