Although most physicians are aware of S1Q3T3 Pulmonary Embolism ECG/EKG Classic Pattern. It is not every day you get to see a classic EKG finding for Pulmonary Embolism.

Pulmonary Embolism (PE) is a blockage in one of the pulmonary arteries in the lungs. In most of the cases it is caused by blood clots traveled from elsewhere in the body through the bloodstream.

The diagnosis of Pulmonary Embolism is done through ECG findings. However, it is very important to interpret the ECG/EKG image in the radiology report to identify the exact type of Pulmonary Embolism.

If a young female with shortness of breath and this EKG presents on your boards, the answer is probably pulmonary embolism. In this case, the patient had all the other signs and symptoms of right heart strain and pulmonary embolism (dyspnea on exertion, elevated d-dimer, tachycardia, enlarged right ventricle on echo, elevated pulmonary pressures, elevated troponin due to right heart strain and of course large central pulmonary emboli on CT scan).

Pulmonary Embolism ECG/EKG Findings

Following are the major ECG/EKG changes for acute pulmonary embolism can be observed in any condition causing Acute Pulmonary Hypertension. This includes Hypoxia resulting in Pulmonary Hypoxic Vasoconstriction.
  • Acute Right Heart Strain

    A large S wave in lead I, Q wave in lead III and an inverted T wave in lead III indicates Acute Right Heart Strain. This pattern only occurs in about 10% of people with Pulmonary Embolisms. It isis similar to the ECG findings in Left Posterior Fascicular Block (LPFB).

  • Atrial Tachyarrhythmias

    Atrial Tachyarrhythmias is seen in 8% of patients.

  • Clockwise Rotation

    Clockwise Rotation shift of the R/S transition point towards V6 with a persistent S wave in V6 (Pulmonary disease pattern), implying rotation of the heart due to right ventricular dilatation.

  • Complete/Incomplete RBBB

    Complete/Incomplete RBBB is associated with increased mortality; seen in 18% of patients.

  • Dominant R Wave in V1

    Dominant R Wave in V1 is the manifestation of acute right ventricular dilatation.

  • Right Atrial Enlargement

    Right Atrial Enlargement (P Pulmonale) is peaked P wave in lead II > 2.5 mm in height. Seen in 9% of patients.

  • Right Axis Deviation

    Right Axis Deviation is seen in 16% of patients. Extreme right axis deviation may occur, with axis between zero and -90 degrees, giving the appearance of left axis deviation (Pseudo Left Axis).

  • Right Ventricular Strain Pattern

    Right Ventricular Strain Patternis the T wave inversions in the right precordial leads (V1-4) ± the inferior leads (II, III, aVF). This pattern is seen in up to 34% of patients and is associated with high pulmonary artery pressures.

  • S1Q3T3 Pulmonary Embolism Classic Pattern

    S1Q3T3 Pulmonary Embolism Classic Pattern is indicated by a deep S wave in lead I, Q wave in III, inverted T wave in III. This classic finding is neither sensitive nor specific for pulmonary embolism; found in only 20% of patients with PE.

    S1Q3T3 Pulmonary Embolism ECG/EKG Classic Pattern

  • Sinus Tachycardia

    Sinus tachycardia (ST) is infact the most common abnormality and ECG finding in pulmonary embolus. It is found in 44% of cases.

  • Transient Right Bundle Branch Block

    Transient Right Bundle Branch Block is alos a common ECG finding in pulmonary embolism. It indicates acute cor pulmonale as electric conduction traverses down the right bundle. Also consider acute pulmonary embolism in patients with T-wave in versions across the anterior leads. And of course, tachycardia including both sinus tachycardia and new onset atrial fibrillation should both raise the suspicion of pulmonary embolism.

  • Non-Specific ST Segment and T Wave

    Non-Specific ST Segment and T Wave changes including ST elevation and depression. Reported in up to 50% of patients with PE.

S1Q3T3 Pulmonary Embolism ECG/EKG Classic Pattern

S1Q3T3 Pattern of Acute Cor Pulmonale is Classic Pattern, also termed as McGinn-White Sign. S1Q3T3 Pulmonary Embolism ECG/EKG Classic Pattern is the finding that indicates right sided heart strain (acute cor pulmonale).

S1Q3T3 Pattern is called classic EKG pattern. It is also the ECG pattern known to residents and hospitalists all across this country as the boards type question for evidence of a pulmonary embolism.

What does S1Q3T3 mean? It is the triad of an S wave in lead one (the first down slope after the first upslope in the QRS complex) a Q wave in lead 3 (first down slope in lead 3) and T3 (or T-wave inversion in lead 3). The S1Q3T3 was first described In a 1935 JAMA paper by McGinn and White. Some things never change despite all our great technology these days.

Interestingly, despite all these pronounced findings of large central clot burden, this patient did not have hypoxemia. Their oxygen saturation was 97% on room air. The human body has the amazing ability to counteract extreme physiological circumstances. That's what makes the diagnosis of pulmonary embolism so elusive at times. If you aren't thinking about it in your differential diagnosis, you won't be able to treat it.

S1Q3T3 EKG Findings Pulmonary Embolism

Pulmonary emboli can be deadly. Always keep PE in the back of your differential diagnosis in patients with unexplained syncope, unexplained pleural effusions. It's not every day when clinical practice presents such a classic presentation for EKG findings in pulmonary embolism. It makes all those years of medical school education worth while.

And then there is the case of syncope. Chief Complaint: I passed out. This patient was a young female on birth control pills. A V/Q scan confirmed the presence of bilateral pulmonary emboli. Her EKG also showed the classic S1Q3T3 changes one can see with pulmonary emboli.

ECG Acute/Chronic Cor Pulmonale

The ECG changes described above are not unique to PE. A similar spectrum of ECG changes may be seen with any cause of acute or chronic cor pulmonale (i.e. any disease that causes right ventricular strain / hypertrophy due to hypoxic pulmonary vasoconstriction);

Acute Cor Pulmonale

  • Severe Pneumonia
  • Exacerbation of COPD/Asthma
  • Pneumothorax
  • Recent Pneumonectomy
  • Upper Airway Obstruction

Chronic Cor Pulmonale

  • Chronic Obstructive Pulmonary Disease
  • Recurrent Small PEs
  • Cystic Fibrosis
  • Interstitial Lung Disease
  • Severe Kyphoscoliosis
  • Obstructive Sleep Apnoea

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