Pulmonary Embolism ECG

ECG fingdings can be very helpful in diagnosing Pulmonary Embolism. A pulmonary embolism happens with a blood clot closes off one of the main arteries that sends blood back and forth between the heart and the lungs. When CT scans cannot effectively diagnose a pulmonary embolism, ECG can be very helpful if there are changes.

A pulmonary embolism is caused by a blood clot blocking one of the arteries in the lungs. This most often starts in one of the deep veins way down in the legs, which travels up into the smaller arteries in the lungs. Less commonly, clots can start out in the pelvic area or even the arms. Tiny blood clots that start within a surface vein rarely cause blood clots. Other causes of blood clots and pulmonary embolism include infections, fat embolism, air bubbles in the blood, or tumors caused by cancer.

Pulmonary Embolism Symptoms

The symptoms of pulmonary embolism are often non-specific, which include:

  • Shortness of breath that is very severe and sudden
  • Chest pains that are sharp and get worse when breathing or coughing
  • Pink or foamy sputum
  • Anxiety
  • Dizziness
  • Sweating
  • Increased heart rate
  • Heart palpitations

Quick and expedient diagnosis can help doctor’s begin immediate treatment and one of the ways is by looking at pulmonary embolism ECG changes. Let’s take a look at some of those changes and what they look like on a tracing.

Pulmonary Embolism ECG Changes

It is important to be cautious when using ECG tracings for diagnosing an Acute Pulmonary Embolism, because the changes can be seen with other conditions. The changes are usually due to pulmonary hypertension, low oxygen, and constricted blood vessels in the lungs due to hypoxia (low oxygen). Differential diagnosis for these changes include cardiomyopathy, hypothyroidism, portal hypertension, mixed connective tissue disease, scleroderma, mitral stenosis, and obstructive sleep apnea.

The findings on the ECG tracing need to be weighed quickly but carefully to promote an accurate diagnosis. Findings that may point to pulmonary embolism may include:

  • Sinus Tachycardia – This shows up in about 44% of people that have PE. Sinus tachycardia is a heartbeat of more than 100 beats per minute.
  • Complete or Incomplete Right Bundle Branch Block – This issue occurs when the right ventricle of the heart cannot be activated by the electrical impulses from the right bundle branch. The left ventricle continues to work properly. One of the causes is PE, but it can also be caused by congenital heart defects, hypertension, and heart disease.
  • Right Ventricular Strain Pattern – This is an acute right heart syndrome that happens to around 34% of patients that have PE. It usually does not occur with long-standing heart disease so when it does happen it is usually indicative of PE.
  • Right Axis Deviation – This test shows that the right side of the heart has to work harder to push the blood through. This may be caused by things likeCOPD, myocardial infarction, or pulmonary arterial hypertension. It is also a sign of pulmonary embolism in about 16% of people.
  • Dominant R Wave in V1 – The QRS complex is the actual de-polarization and re-polarization of the heart. If the R wave in V1 is very tall, it could be a sign that the right ventricle is dilated.
  • Right Atrial Enlargement – In about 9% of people with PE, the P wave may peak over 2.5mm and be a sign of right atrial enlargement.
  • SI, QIII, and TIII – This pattern has a specific T wave inversion that is indicative of pulmonary embolism in about 20% of patients. It is almost always a “classic” sign of PE, but not specific. It is commonly used for diagnosis when all other cardiac testing is negative.
  • Clockwise Rotation – When the right ventricle becomes enlarged and dilated, the heart tends to shift and rotate over to the right. This can happen with pulmonary disease and PE.
  • Atrial Tachyarrhythmia – In a small number of patients, around 8% of PE patients, certain tachyarrhythmia’s are seen such asatrial tachycardia, atrial fibrillation, and atrial flutter.
  • Non-specific ST Segment and T Wave Changes – The ST segment may be either elevated or depressed. This is a classic sign in up to 50% of PE patients.

Now let’s take a look at some examples of pulmonary embolism ECG changes.

Figure 1: Sinus Tachycardia

The normal heart rate is 60 to 100 beats per minute. In sinus tachycardia, the rate goes over 100 beats per minute.

(Photo Courtesy of: en.wikipedia.org)

Figure 2: Complete or Incomplete RBBB (Right Bundle Branch Block)

This shows the failure of the right side of the heart to beat properly.


(Photo Courtesy of: en.wikepedia.org)

Figure 3:   Right Ventricular Strain Pattern

The ST pattern and T wave are usually negative. When this is seen, the PE is usually large.

(Photo Courtesy of: Lifeinthefastlane.com)

Figure 4: Right Axis Deviation

The down stroke of the heart is larger than the upstroke.

(Photo Courtesy of: Lifeinthefastlane.com)

Figure 5: Dominant R wave in V1

In lead 1, you can see the R wave is taller than usual.

(Photo Courtesy of: lifeinthefastlane.com)

Figure 6: Right Atrial Enlargement (P Pulmonale)

In right atrial enlargement, the P waves tend to peak higher than usual and is a sign of PE.

(Photo Courtesy of: lifeinthefastlane.com)

Figure 7: SI QIII TIII Pattern

Note the T wave inversion in lead 3.

(Photo Courtesy of: lifeinthefastlane.com)

Figure 8: Clockwise rotation

The waves begin to transition and get larger after V4. If they did this around or before V2 the heart is “counterclockwise rotation.” Clockwise rotation can happen is the right atrium is enlarged and weighs the heart over to the right side.

(Photo Courtesy of: emedu.org)

Figure 9: Atrial Tachyarrhythmia’s

In these rhythm’s the right atrium has a “short-circuit.” The atria are beating faster than the ventricles.

(Photo Courtesy of: emedu.org)

Figure 10: Non-specific ST segment and T wave changes

These can happen to anyone at any time such as after eating, if your electrolytes are off, or for no reason at all. In PE, the ST segment and T waves may either be elevated or depressed.

(Photo Courtesy of: Clevelandclinicmeded.com)

Treatment Based on Pulmonary Embolism ECG Pattern

The most common treatments for PE include blood thinning medications to thin the clots and prevent new ones, supplemental oxygen, anti-thrombolytic medications to dissolve the clot very quickly, and possible embolectomy. It is also helpful to insert a vena cava filter that prevents clots from traveling from the legs to the lungs. 

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