What are the EKG findings in pulmonary embolism (PE) with shock?

EKG Findings in Pulmonary Embolism with Shock

In pulmonary embolism with shock, the most significant EKG findings include sinus tachycardia, S1Q3T3 pattern, right bundle branch block (complete or incomplete), T wave inversions in leads V1-V4, and signs of right ventricular strain. 1

Key EKG Findings in PE with Shock

Most Common Findings

• Sinus tachycardia - The most frequent ECG sign in PE 1, 2
• S1Q3T3 pattern (S wave in lead I, Q wave in lead III, and inverted T wave in lead III) 1, 3
• Right bundle branch block (complete or incomplete) - strongly associated with cardiogenic shock in PE 3
• T wave inversions in leads V1-V4 - indicates right ventricular overload 1
• QR pattern in V1 - associated with more severe cases 1, 3

Additional Significant Findings in Shock

• Low QRS voltage - independent predictor of cardiogenic shock in PE 3
• ST-segment elevation in lead V1 - strongly associated with hemodynamic instability 4, 3
• ST-segment elevation in lead aVR with concomitant ST depression in leads I and V4-V6 4
• ST-segment depression in leads V4-V6 - indicates severe strain 3
• ST-segment elevation in lead III - more common in PE with shock 3
• QRS fragmentation in lead V1 3

Pathophysiologic Correlation

The ECG findings in PE with shock reflect acute right ventricular pressure overload and strain:

1. Right Ventricular Dysfunction Signs:

   • The European Society of Cardiology guidelines note that ECG signs of right ventricular overload are usually seen in more severe cases of PE 1
   • These include T wave inversions in leads V1-V4, QR pattern in V1, and right bundle branch block

2. Hemodynamic Compromise Markers:

   • In patients with shock due to PE, ECG patterns often show signs of both myocardial ischemia and right ventricular strain 4
   • The 60/60 sign (acceleration time of pulmonary ejection <60 ms with midsystolic "notch" and peak systolic gradient <60 mmHg) may be present 1

3. McConnell Sign:

   • While not an ECG finding, this echocardiographic finding (hypokinesia of the mid-RV free wall with normal contraction of the RV apex) often correlates with severe ECG abnormalities 1

Clinical Significance

The presence of these ECG findings in a patient with shock should raise immediate suspicion of PE:

• In patients with suspected high-risk PE presenting with shock, ECG findings of right ventricular overload support the diagnosis 1
• The absence of ECG signs of RV overload practically excludes massive PE as the cause of hemodynamic instability 1
• The severity of ECG abnormalities often correlates with the extent of vascular obstruction 5

Important Caveats

1. Limited Sensitivity: Recent research indicates that classical ECG findings have modest sensitivity for PE diagnosis 2. Therefore, absence of these findings doesn't rule out PE.

2. Dynamic Changes: ECG abnormalities in PE are often transient and changing, so serial ECG recordings are recommended 5

3. Diagnostic Accuracy: While specific ECG patterns can increase suspicion for PE with shock, definitive diagnosis requires imaging studies like CT pulmonary angiography 1

4. Differential Diagnosis: Similar ECG patterns can be seen in other conditions causing right heart strain, such as COPD exacerbation or right ventricular infarction 1

In the setting of shock with ECG findings suggestive of PE, immediate echocardiography should be performed to assess for right ventricular dysfunction while arranging for definitive imaging or considering empiric treatment if the patient is too unstable for transport 1.