A Serial Case

An elderly male patient is transported to the emergency department following a syncopal episode. The patient reported feeling lightheaded, and experienced two witnessed syncopal episodes lasting for several minutes. Symptoms were made worse when standing up. The patient denied chest pain and reported some mild dyspnea. The patient had been in his usual state of health. The patient's medical history is significant for a tibial fracture several months prior.

Vitals:

Afebrile

BP: 72/P

P: 100

R: 24

Sp02: 92%, poor waveform, on NRB

Physical exam:

Pt is diaphoretic and alert.

Lungs are clear bilaterally.

The patient's abdomen is soft and non tender.
No evidence of lower extremity edema.

(Prehospital) 12 lead ECG:

Upon arrival at the hospital, large bore IV access was secured. A FAST (Focused Assessment with Sonography for Trauma) exam revealed no obvious free fluid and no obvious pericardial effusion. The abdominal aorta appeared grossly normal. The patient remained alert and responded to a bolus of IV crystalloid. A repeat ECG was obtained following another pre-syncopal event in the emergency department.

12 Lead ECG Interpretation and Discussion

On the repeat ECG, a sinus rhythm is present. The electrical axis is physiologic. Artifact interferes with the tracing in the inferior limb leads. ST segment elevation is present in aVR, V1, and V2. The ST segments appear horizontal in shape. That particular morphology is concerning for ischemia. While some mild ST segment depression is present in lead I, there are no clear cut reciprocal changes. The evolving changes suggest a septal wall myocardial infarction.

Final Interpretation

Sinus tachycardia, septal ST segment elevation myocardial infarction

(WRONG!)

Case Conclusion

The patient was transported emergently to the cardiac catheterization lab. The patient's coronary arteries were CLEAN and without evidence of disease. An emergent echocardiogram showed a severely dilated right ventricle with concurrent diastolic dysfunction. The clean coronary arteries and echocardiograpghic findings combined point to a massive pulmonary embolism as the cause of the patient's symptoms. Another subtle clue to this diagnosis was the hypoxia that persisted with high flow oxygen administration.

Though not all that elevates is a STEMI, field providers should nevertheless focus on identifying worrisome ST segment changes. The patient's initial ECG was somewhat non-specific. Though close inspection can reveal some slight ST segment elevation of less than 1mm in aVR and V1, it certainly did not meet standardized criteria for STEMI. The second ECG, however, represents a clear-cut evolution. ST segments have become more pronounced (elevated) in the septal leads. The increase in elevation combined with the horizontal plateau of the ST segments in leads V1-V2 suggest an evolving myocardial infarction- or an alternative diagnosis.

The patient presented with a syncopal episode and profound hypotension. Any number of emergent medical conditions can present with those complaints. Pulmonary embolism, internal bleeding, and aortic dissection must be considered in the initial assessment of the hypotensive patient. Unfortunately, there are no "classic" electrocardiographic findings associated with a large PE. That said, the following features can be seen in the setting of a pulmonary embolism.

PULMONARY EMBOLISM ECG FINDINGS

• Sinus tachycardia
• Right bundle branch block or incomplete right bundle branch block
• Deep S wave in lead I, Q wave in lead III, and an interveted T wave in lead III (S1, Q3, T3)
• T wave inversions
• Right axis deviation
• ST segment deviation (depression and elevation)

Sinus tachycardia and right bundle branch block may suggest "heart strain." These are electrical manifestations caused by the right ventricle that is pumping against a greatly increased pulmonary resistance.

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 Deceptive Ears of a Rabbit

This particular ECG resulted in a great deal of discussion. Though I don't have the actual details of the patient encounter, its clear that the ECG machine, the paramedic student, the preceptor, and the emergency physician all contest the actual interpretation of the following tracing. ECGs like this one represent fantastic learning opportunities. When confronted with a bunch of squiggly lines and conflicting information, it is imperative to stay focused and proceed through the ECG interpretation in a stepwise fashion. Judging from all of the hashmarks, pen marks, and circles, there wasn't any resolution by the time the paramedics had cleaned their stretcher and left for their station!

1) What's the rate?
2) What's the rhythm?
3) Are concerning ST/T segment changes present?
4) Where are my defibrillator / pacer pads?

12 lead ECG

12 lead ECG interpretation and discussion

The ECG tracing reveals a regular rhythm. Before getting distracted by rabbit ears or conduction delays, it is important to discern whether or not a sinus rhythm is present. P waves are occasionally visualized, but there is simply no fixed PR ratio. The absence of a fixed PR suggests that a high grade block is present. Considering the widened QRS, it is likely that the tracing represents a third degree heart block. Further corroborating that interpretation is the relatively fixed R to R interval. Putting this together: wide QRS + fixed R to R + varied PR interval  = third degree heart block. By definition, a right bundle branch block or left bundle branch block CANNOT be diagnosed in the absence of a sinus rhythm.

The ST/T segments are grossly abnormal. The large QS wave present in leads III and aVF suggest a prior inferior wall myocardial infarction. In addition, there is poor R wave progression across the precordial leads. The R wave is still of decreased amplitude in lead V4. Recall that the R wave should transition to a mostly positive deflection by lead V4. There is minimal ST segment elevation in the inferior leads as well. Though this patient may be suffering from acute ischemia, the presence of a third degree block is requires aggressive management and expeditious transport. This rhythm, in the presence of anginal symptoms, warrants chemical or electrical therapy. Transport to an interventional facility, patient stability permitting, is a good strategy.

Fix the rate first!

Final interpretation

Probable third degree heart block, probable inferior wall myocardial infarction, old anterior wall myocardial infarction  

All that elevates isn't STEMI

Further confounding the already difficult job done by EMTs and paramedics is the idea of falsely positive ST segment elevation. Even when the EMS provider's eyes are focused on the STE prize, there are lots of distractors out there. This ECG was transmitted as a "priority one" STEMI patient. The cath lab was NOT activated from the field.

Of course, providers should ALWAYS err on the side of caution and transport patients with concerning ECG findings to the closest appropriate hospital. That said, this ECG is a bit more reassuring when placed under a bit more intensive scrutiny.

The patient as an otherwise healthy 30 year old male. The patient had no previous medical history and reported constant chest discomfort over the past week. The patient denies nausea, vomiting, shortness of breath, syncope, or other associated symptoms.  Vitals were unremarkable except for a blood pressure of 140/76. The patient appeared non toxic and in no acute distress.

12 lead ECG:

12 Lead ECG and Discussion

There is a baseline sinus bradycardia. Tall R waves are present in the limb leads and in the precordial leads V4 and V5. These tall R waves are most appropriately called, "high left ventricular voltage." Left ventricular hypertrophy is not technically correct since this patient is (1) young and (2) we don't have a formal echocardiogram. High left ventricular voltage may be a physiologic finding in young and otherwise healthy patients. Slight ST segment elevation is present in leads V2 and V3. There is J point elevation in lead II as well. Slight ST segment elevation may also be a physiologic finding- in the ABSENCE of a concerning patient presentation. This particular patient had no concerning medical history and appeared well. Also reassuring is the ABSENCE of reciprocal change.

The shape of the ST segment can also help guide your medical decision making. Pathologic ST segments are typically more horizontal in shape. Convex ST segments are also associated with worsent outcomes. Test for convexity by drawing a line from the J point to the peak of the T wave. If the line superimposes the ST segment or if the T wave appears above the drawn line, the ST segment is classified as convex. Convex shape= NOT reassuring. Broad based and wide ST segments also favor ischemia.

Here is an "ugly" appearing ST segment. No offence intended to the poor ST segment depicted:

Another NOT reassuring ST segment :

Subtlety and STEMI ?

Providers respond to an elderly male reporting 2 syncopal episodes earlier in the day. Upon arrival, the patient is hypotensive to 80/40. The patient is somnolent but arousable. His speech is intact. The patient responds to an infusion of isotonic crystalloid. The patient denies chest pain, abdominal pain, or vomiting.

The patient denies any medical history except orthopedic surgery several months prior. The patient takes daily aspirin and has no known allergies.

Vitals at the time of initial prehospital 12 lead:
BP: 70/P
P: 82
R: 16
Sp02: 88% on room air

Medics establish a large bore external jugular intravenous line. The patient's mental status improves as does his vital signs following a bolus of isotonic crystalloid.

BP: 110/70

P: 90
R: 16

Sp02: 95% on non re-breather

A 12 lead ECG is obtained:

12 lead ECG interpretation and discussion:A baseline sinus rhythm is present. There is minimal ST segment elevation in V1 and V2. Recall that ST segment elevation of greater than 1-2 millimeters is consistent with the diagnosis of STEMI. There is some ST depression present in the inferior leads II, III, and aVF. There are also ST segment depressions in the anterior and lateral precordial leads. The medics are concerned about acute myocardial infarction and transport to the closest cardiac interventional center. A close inspection of lead aVR reveals minimal < 0.5 mV elevation. Recall that ST elevation in lead aVR may be associated with obstructive disease of the left main coronary artery.

The presentation of syncope and hypotension is particularly ominous. Patients could be suffering from an acute myocardial infarction, aortic dissection, pulmonary embolism, or sepsis, just to name a few potentially concerning conditions. This patient's vitals warrant rapid assessment and transport. The field determination of STEMI is challenging with respect to this case but transport to a cardiac interventional center is an excellent option. Patients who are acutely hypotensive from a myocardial infarction (STEMI) are usually suffering from massive anterior wall ischemia. This ECG shows acute ischemic changes in the septal leads. Changes that occur in conjunction with a massive anterior wall MI include ST elevations in precordial leads V1-V6.

The patient's hypoxia is also alarming. This patient didn't have any known medical conditions. The acute onset of hypoxia and hypotension suggests alternative diagnoses. The hypoxia could be due to poor peripheral perfusion. However, the patient's hypoxia persisted despite adequate fluid boluses. Most patients should saturate close to 100% when on high flow oxygen.  

The patient is diagnoses with a large saddle type pulmonary embolism upon arrival at the receiving facility. Recall that risk factors for pulmonary embolism include:

-Orthopedic surgery
-Immobility
-Recent injury or venous stasis
-Birth control use
-Active cancer

As always, remember that your 12 lead ECG is a valuable tool! Have a low threshold to obtain a 12 lead ECG in patients who report syncope. The initial 12 lead findings can relay valuable information to both paramedics and emergency physicians.

Looking Beyond STEMI

Providers respond to the report of a young patient with syncope. The patient is a young female, well conditioned, with no obvious medical history. The patient states that her resting heart rate is "usually in the 40s-50s." The patient reports mild shortness of breath which has been within the past week. The patient takes no medicines and has no known drug allergies.

Physical examination is remarkable for orthostatic hypotension.

Providers obtain a 12 lead ECG:



12 Lead ECG interpretation and discussion:
The rhythm is baseline sinus at a rate of 90 beats per minute. A first degree atrioventricular block is present. There is evidence of an incomplete (less than 0.12 seconds) right bundle branch block. Lead V1 reveals a slightly prolonged QRS duration. Close inspection of the p wave reveals increased amplitude. There are no clear cut ST-T segment changes suggestive of acute infarction.

Diagnosis is very difficult to achieve in the prehospital setting. However, astute paramedics can spot the "normal" ECG tracings from the abnormal ones. This patient's ECG and physical examination findings are extremely concerning. Hypotension in the setting of:

• Incomplete right bundle branch block
• First degree AV block
• Borderline (relative)  tachycardia

is very concerning. This ECG suggests right heart strain. Right heart strain points to the diagnosis of pulmonary embolism. Though there aren't "classic" ECG findings, the diagnosis of pulmonary embolism is supported by the relative tachycardia and shortness of breath.

The patient is transported to the receiving facility where the diagnosis of a large, saddle-type pulmonary embolism is confirmed.