The Power of the 12th Lead

EMS responds to the home of a 70 yo female patient. She reports severe, left-sided chest pain and mild shortness of breath.  Her skin is warm and dry.  Her abdomen is soft and non-tender.  She denies any medical history.

Vital signs:
BP: 142/76
P: 75
R: 18

Sp02: 98%

12 Lead ECG:

12 Lead ECG Interpretation and Discussion:

There is a baseline sinus rhythm. The rate is approximately 75 beats per minute.

The ECG also reveals left anterior fascicle block as noted by the rS pattern in leads II, III, aVF, and Rs pattern in leads I and aVL.

There is left axis deviation as demonstrated by the predominantly positive QRS complex in lead I, and predominantly negative QRS complex in lead aVF.

There is ST segment elevation in leads aVR and V1. In addition, ST segment changes (flat, depressed, or T wave inversion) are present in essentially every other lead (reciprocal changes).  Simultaneous ST segment elevation in leads aVR and V1 may predict left main coronary artery, or left anterior descending artery occlusion, and is considered to be a STEMI equivalent.  Patients who present with ST segment elevation in leads aVR and V1 should be transported to a facility capable of performing cardiac angioplasty.

Take-Home Points
Simultaneous ST segment elevation in leads aVR and V1 predicts LMCA or LAD occlusion
Patients should be transported to a cardiac intervention center and treated the same as STEMI

The Eclectic Equivalent

A 64 yo female calls 911 for chest discomfort. The patient reported chest pressure that waxed and waned in intensity. The discomfort was retrosternal and did not radiate. The patient compared the pressure to previous bouts of "indigestion." The patient experienced associated nausea. No LOC, no diaphoresis. Providers obtain a 12 lead ECG. Vital signs remained stable.

12 Lead ECG

12 Lead ECG Interpretation 

The rhythm is sinus and the rate is regular. ST depressions are present in leads II, III, and aVF. There are also ST depressions noted in the precordial leads V3-V6. R wave progression is preserved, and it appears that R waves reach their maximum amplitude in lead V4. There is no obvious ectopy.

ST elevation of > 1 mm is noted in aVR and V1.

Sinus rhythm, diffuse ST segment depression, ST segment elevation in aVR and V1.

Case Discussion

Providers correctly identify the ECG tracing as a potential STEMI equivalent. The STE in aVR and V1 is concerning for its association with acute left main occlusion. The patient was transported to the cardiac cath lab. Cardiologists discovered a near total occlusion of the left main coronary artery.

aVR has long been cast as the "forgotten lead" in electrocardiography. Studies link ST elevation in aVR to left main disease and cardiogenic shock. There is also data to suggest that patients with changes in aVR are more likely to require surgical intervention and progress into cardiogenic shock. Indeed, ST elevation in aVR is often considered a, "STEMI equivalent" due to its association with a poorer prognosis. Always scrutinize all leads of the electrocardiogram for abnormal ST segment morphology. In some studies, STE in aVR that is greater than the STE in V1 distinguishes left main disease from left anterior descending artery disease.

Findings such as STE in aVR are often labeled, "STEMI equivalents." Though not widely recognized as automatic triggers for cath lab activation, these concerning electrocardiographic findings represent time sensitive conditions that benefit from an early interventional approach. Other equivalents include:

• Posterior wall MI (ST depression anteriorly)
• New left bundle in association with chest pain/ACS history 
• Hyperacute T waves
• The deWinter ST/T complex
• Positive Sgarbossa criteria

References
1. Yamaji H, Iwasaki K, Kusachi S, et al. Prediction of acute left main coronary artery obstruction by 12 lead electrocardiography. ST segment elevation in lead aVR with less ST segment elevation in lead V1. J Am Coll Cardiol. 2001;38(5):1348-54

2. Nough H, Jorat MV, Varasteravan HR, et al. The value of ST segment elevation in lead aVR for predicting left main coronary artery lesion in patients suspected of acute coronary syndrome. Rom J Intern Med. 2012;50(2):159-64

3. Nikus KC, Eskola MJ. Electrocardiogram patterns in acute left main coronary artery occlusion. J Electrocardiol. 2008;41(6):626-9

aVR Rears its Ugly Elevation

A cardiologist's office calls 911 for an elderly patient who suffered a syncopal episode. The patient presented to the physician's office for a few weeks of bilateral arm pain and fatigue. The patient experienced mild dyspnea on exertion and was undergoing a chemical stress test when he experienced a brief syncopal episode. The patient was pain free at the time of EMS arrival. The patient was awake and alert. Vital signs:
BP: 104/70
P: 100
R: 22/non labored
Sp02: 96%

The cardiologist suggested transport to a facility capable of percutaneous coronary intervention. Why was the cardiologist so concerned (aside from the presence of an elderly patient with syncope in his office)? What's going on with this ECG?

12 lead ECG

12 Lead Interpretation and Discussion

The patient's rhythm is a borderline sinus tachycardia. ST segment elevation is present in leads aVR and V1. Diffuse ST segment elevation is present in the inferior and lateral leads. Though ST segment elevation in lead aVR isn't typically considered a "STEMI," there is sufficient evidence in the emergency cardiology literature that it should be considered as a "STEMI equivalent." ST segment elevation of > 1 mm (or > 0.5 mm in some studies) is associated with obstruction of the left main coronary artery. Furthermore, these patients are more likely to require surgical revascularization (CABG) or experience congestive heart failure. The skilled paramedic will easily recognize the widespread and diffuse ST segment abnormalities. This patient requires evaluation at a facility capable of percutaneous coronary intervention.

Final 12 lead ECG Interpretation

Sinus rhythm, ST segment elevation in leads aVR and V1. Probable acute obstruction of the left main coronary artery. Diffuse ST segment depression in the inferior (II, III, aVF), anterior (V4-V6), and lateral (I, aVL) leads.

Suggested Readings

• Rokos IC, French WJ, Mattu A et al. Appropriate cath lab activation: optimizing electrocardiogram interpretation and clinical decision making for acute ST elevation myocardial infarction. Am Heart Journ. Dec 2010;160(6):995-1003

• Barrabes JA, Figueras J, Moure C, et al. Prognostic value of lead aVR in patients with a first non ST segment elevation acute myocardial infarction. Circulation. 2003;108(81):814-819

• Williamson K, Mattu A, Plautz CU. Electrocardiographic applications of lead aVR. Am J Emerg Med. 2006;24:864-874

"Abnormal ECG" and Bypass of the Closest Facility

So.. would you call this one and activate the cath lab from the prehospital ECG? The patient is a 72 year old female with severe uncontrolled hypertension. She called 911 for mild shortness of breath. Her blood pressure is over 200 mm Hg systolic. The patient is awake, alert, and oriented. The paramedic is bypassing a local facility in favor of the closest cardiac interventional center.

What's your analysis?

12 Lead ECG

 

12 Lead ECG Interpretation and Discussion

A baseline sinus rhythm is present. There is a significant amount of artifact that interferes with interpretation in the limb leads. A fusion beat is seen in the limb lead tracings. However, there is > 1mm of ST segment elevation in lead III. Lead aVF also has minimal ST segment elevation. Pathologic Q waves are present in contiguous leads (III and aVF). Though an isolated Q wave is common in limb lead III, the presence of Q waves in contiguous inferior leads (III and aVF) suggests ischemia. In addition, ST segment depression is present in the reciprocal leads of I and aVL. This finding further supports the presence of acute injury. ST segment elevations are also seen in leads aVR and V1. As discussed in a previous case, the presence of STE in leads aVR and V1 may predict obstruction of the left main coronary artery. Poor R wave progression is present across the precordial leads V2-V6. This finding  (the loss of R wave amplitude) is consistent with the machine generated diagnosis of "anterior infarct, age undetermined." These findings, when put together, reveal an inferior wall STEMI. This patient is best cared for at a facility capable of percutaneous cardiac intervention.

Final interpretation

Sinus rhythm, inferior wall STEMI. Anterior wall ischemia. Reciprocal changes in the form of ST depression present in the anterior-lateral limb leads.

The Forgotten 12th Lead

A 70 yo patient presented to the ED with chest discomfort, diaphoresis, and nausea. The patient had a history of coronary artery disease and was hemodynamically stable. The patient stated that his retrosternal discomfort was similar his previous "heart attacks." The patient was pain free by the time he was moved into a monitored bed. An initial troponin level sent from triage was negative. Here's the triage EKG:

12 lead EKG interpretation
Sinus rhythm, diffuse ST segment depression, ST segment elevation in lead aVR

Discussion
The ECG, coupled with the patients presentation, is concerning for ischemia. At first glance, this ECG does not meet criteria for activation of the cath lab. A closer look at this ECG reveals cause for concern. There is ST segment elevation present in lead aVR. Often forgotten, overlooked, and otherwise thrown away, lead aVR provides important cluses to underlying cardiovascular disease. ST segment elevation in lead aVR may actually predict acute occlusion of the left main coronary artery. Specifically, STE in aVR that is LESS than STE present in lead V1 is associated with left main occlusion.

References
Gorgels APM, Engelen DJM, Wellens HJJ. Lead aVR a mostly ignored but very valuable lead in clinical electrocardiography. J Am Coll Cardiol. 2001;38:1355-1356
http://content.onlinejacc.org/cgi/content/full/38/5/1355
Mattu A. Lead aVR: importance of the "forgotten 12th lead" in patients with ACS. Medscape Emergency Medicine. 2009. Available at: http://www.medscape.com/viewarticle/589781. Accessed February 2012