April 2015: Sighting the Subtlety Down Below

CASE: 

A 63 y/o gentleman calls 911 for "chest pressure" and indigestion. The patient is nauseated but denies LOC, SOB, or dizzinesss. The pressure started approximately 1 hour prior to 911 arrival. The patient has a history of hypertension and takes an aspirin daily. He is hemodynamically stable. BP is 110/70, P: 82, R: 16. Sp02: 95% on RA.

12 LEAD ECG:

12 LEAD ECG DISCUSSION:

There is a sinus rhythm. PR depression is present in lead II. There is slight ST segment elevation present in II, III, and aVF. Elevation measures about 1 mm. There is no evidence of recriprocal change. A biphasic T wave is present in lead III and terminal T wave inversion is present in the lateral precordial leads. The QRS axis appears physiologic.

12 LEAD INTERPRETATION: 

Inferior wall STEMI

TREATMENT

The patient was transported to a hospital capable of percutasneous coronary intervention. A right sided ECG was not performed, and NTG was withheld due to the patient's marginal blood pressure or relative hypotension. 325 mg of ASA was administered. The patient's RCA was 75% occluded.

Thanks always to the Baltimore City Fire Department for its endless supply of pathologic 12 lead tracings.

Deadly 12 Lead ECG Diagnosis: Pulmonary Embolism

Its well known that there are things other than STEMI that stand ready to confound, perturb, and otherwise confuse your clinical impression. Pulmonary embolism (PE)  is one of those things. Massive PE has been linked to all sorts of ECG changes. A recent article printed in the American Journal of Emergency Medicine highlighted some of the ECG features associated with cardiogenic shock:

• The S1 Q3 T3 sign
• qR in lead V1
• T wave inversions in V2-V4
• STE in lead V1
• STE in lead aVR

These problematic ECG signs come as no surprise to fellow ECG enthusiasts. The incomplete right bundle branch pattern + T wave inversion indicate "heart strain" that accompanies large pulmonary emboli, 

Here's a recent prehospital 12 lead concerning for pulmonary embolism: 

Bottom line:

The ECG represents a valuable screening tool. Though its not particularly sensitive or specific for pulmonary embolism, there are definitely patterns that should alert the clinician to an adverse outcomes. In the setting of suspected pulmonary embolism, for example, watch out for:

• Right bundle branch block
• Anterior T wave inversions
• STE in aVR or V1

Anterior Wall Changes and Abnormal ECG, UNCONFIRMED!

A 60 yo male with a history of CAD, MI, and HTN presents with retrosternal chest discomfort. He is hemodynamically stable. The prehospital provider obtains a 12 lead ECG.

12 lead ECG interpretation: 

A sinus tachycardia is present, and there are plenty of abnormal ST segment changes to point out. First, there is minimal ST segment elevation in V1, V2, and V3 .The ST approaches 2 mm in V2. In addition, the ST segments have a non-concave, or worrisome, appearance in V4. There is T wave inversion in aVL and downsloping ST segments in lead I. Those ST segments resemble the pattern of "ventricular strain."

Sinus tachycardia, ST segment elevation in the anterior precordial leads, anterior and lateral T wave inversion consistent with ischemia.

12 lead ECG case discussion: 

The paramedic scrutinized the anterior ECG changes and declared a, "STEMI." Though the receiving facility determined that the initial prehospital ECG changes did not meet strict STEMI criteria, the paramedic was clearly advocating for the patient's best interest by electing to transport directly to a cardiac interventional center. Previous ECGs from the same patient reflected prior ST segment abnormalities, and the patient wasd admitted to the cardiology service for further testing. Minor, baseline ST segment elevations in precordial leads in addition to high left ventricular voltage can confound the diagnosis of STEMI. The presence of at least 2 mm of elevation plus the identification of reciprocal change (in the form of ST segment depression) makes the diagnosis of STEMI much more likely. Always remember that serial ECGs are extremely important when dealing with concerning or "borderline" presentations.

LVH, Strain, Ischemia, or What?

A patient calls 911 for chest pain. The discomfort is desribed as a retrosternal pressure. It is worse with coughing and slightly improved with rest. The patient reports a productive cough and subjective fevers.  The patient is awake and alert. Past medical history is significant for COPD, asthma, and tobacco abuse.

BP: 180/100
P: 140
R: 16

Sp02: 92% on room air.

Prehospital 12 lead:

12 lead ECG interpretation:

Sinus tachycardia, left ventricular hypertrophy, diffuse ST segment depression and T wave inversion (inferior, anterior, lateral leads) consistent with strain, possible anterior-lateral ischemia

A baseline sinus tachycardia is present. There are diffuse and prominent ST segment changes. The ECG meets voltage criteria for the diagnosis of LVH. The S wave in V1 plus the R wave in V5/V6 is greater than 35 mm. ST segment depression and T wave inversion is most pronounced in the anterior precordial and lateral leads (V3-V6). This ECG illustrates an ischemic "mimic." Changes associated with high left ventricular voltage, by definition, include ST segment abnormalities. Repolarization abnormalities include ST segment depression, ST segment elevation, and T wave inversion.  The downsloping and depressed ST segment is also consistent with a condition called, "strain." Increases in heart rate can also cause "demand" related ischemia. As the heart rate accelerates, the myocardium's demand for oxygen increases. Tachycardia can therefore induce (and accentuate) ST segment changes such as T wave inversion and ST segment depression.

Left ventricular hypertrophy refers to an increase in heart muscle mass. This change is usually secondary to advanced and uncontrolled hypertension. Simply put, the ventricular muscle increases in order to pump against the increased (hypertension-mediated) afterload. Left ventricular hypertrophy manifests on the ECG as increased R wave amplitude (height). There are several scoring systems for LVH and some have rather poor sensitivity. The definitive diagnosis of LVH is by echocardiogram. The echocardiogram actually measures the thickness of the left ventricle.

General ECG features of LVH:

• Left axis deviation
• Repolarization changes (ST depression)
• Increased QRS amplitude (tall R waves, deep S waves)

Electrocardiographic voltage criteria for LVH:

• http://en.wikipedia.org/wiki/Left_ventricular_hypertrophy#ECG_criteria_for_LVH
• http://lifeinthefastlane.com/ecg-library/basics/left-ventricular-hypertrophy/

The STRAIN of hypertension:

Ventricular strain is usually associated with hypertensive heart disease and coronary artery disease. It is a type of ECG pattern seen in ECGs consistent with ventricular hypertrophy. It usually indicates a compensatory response to uncontrolled hypertension and may indicate underlying ischemia. Electrocardiographic criteria for ventricular strain includes:

• ST depression greater than or equal to 1mm in lateral leads I, aVL and V4-V6
• Direction of the T wave usually opposite an upright QRS complex
• Downsloping ST-T segment, rapid upslope

"Strain" of the ST segment:
http://www.medscape.com/viewarticle/504439_3

Case Resolution:

The patient was transported to a local emergency department. The tachycardia resolved following administration of intravenous fluids. Repeat ECGs showed some improvement of the ST segment abnormalities. Given the patient's hypertension and ECG changes, blood was also sent to the lab for cardiac enzyme analysis. Cardiac enzymes remained negative throughout the patient's hospital stay. The patient was diagnosed with bronchitis. The patient was admitted to the hospital for symptom management, blood pressure control, and cardiac stress testing.

EMS Pearls:

• Fix the rate first! Tachycardia, by itself, increases myocardial oxygen demand and produces ST segment changes
• Left ventricular hypertrophy causes ST segment changes that resemble ischemic patterns
• The "strain" pattern, characterized by ST sepression and T wave inverison, is associated with underlying coronary artery disease
• LVH is a common response to long standing and uncontrolled hypertension