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

Where is the Circulatory Road Block?

Case

An 81 y/o female with DM, HTN, and bilateral lower extremity amputations presents to EMS with chest pain and vomiting. VS: BP: 90/40, P: 80, R:16. Sp02: 95%. The patient is alert and oriented and in mild distress. An ECG is obtained. What is your interpretation ?

12 Lead ECG

ECG Interpretation 

A first degree AV block is present. Deep Q waves and ST elevations are present in the inferior leads III, and aVF. Additional ST segment elevations are present in the anterior precordial leads V3, V4, and V5. Reciprocal depression is present in leads I and aVL. A right bundle branch block is suggested by the positively deflected QRS and increased QRS duration seen in V1. This patient is experiencing a large STEMI given the presence of elevation in multiple territories. ST elevations suggest active injury and ischemia in the inferior and anterior leads. The relative hypotension may indciate cardiogenic shock. Cardiogenic shock complicates a significant percentage of anterior wall myocardial infarctions. Multi-territorial ST elevations indicates a poor prognosis.

Treatment Course 

Providers transmit the 12 lead ECG and alert the receiving facility of an ST elevation myocardial infarction. Aspirin is administered. The patient proceeds directly to the cath lab. The patient had severe, multi-vessel, obstructive coronary artery disease and unfortunately expired from decompensated cardiogenic shock

Key Points

• Remain vigilant for the presence of cardiogenic shock in the presence of anterior wall ischemia
• ST elevations in multiple geographic areas (inferior and anterior in this case) indicate severe disease
• Ventricular fibrillation can also accompany large anterior wall MIs
• Relative hypotension is extremely significant in patients who are accustomed to higher blood pressures. In this case, the patient's marginal blood pressure resulted from acutely decreased cardiac output.