Can pulmonary embolism cause bradycardia and atrioventricular (AV) block?

Pulmonary Embolism Can Cause Bradycardia and AV Block

Yes, pulmonary embolism (PE) can cause bradycardia and atrioventricular (AV) block, though these are atypical presentations compared to the more common tachycardia seen in PE. 1, 2

Pathophysiological Mechanisms

• Acute PE interferes with both circulation and gas exchange, with right ventricular (RV) failure due to acute pressure overload being the primary cause of death in severe cases 3
• The desynchronization of the ventricles may be exacerbated by the development of right bundle branch block, which can affect the cardiac conduction system 3
• In some cases, PE can lead to profound bradycardia, which is considered a marker of high-risk PE 1
• The excessive neurohumoral activation in PE can result from both abnormal RV wall tension and circulatory shock, potentially affecting heart rate and rhythm 3
• Bradycardia in PE may be related to several mechanisms:
  • Vagal reflex triggered by sudden RV distension 2
  • Myocardial ischemia affecting the conduction system due to imbalance between oxygen supply and demand 3
  • Inflammatory response in the RV myocardium that can affect electrical conduction 3

Clinical Evidence

• High-risk PE is defined by hemodynamic instability that can include persistent profound bradycardia 1
• Case reports have documented bradycardia as a rare presenting sign of PE 2
• There have been documented cases of transient disappearance of left bundle branch block pattern in acute PE, demonstrating how PE can significantly affect the cardiac conduction system 4
• The European Society of Cardiology notes that PE can lead to right bundle branch block, which may be part of a broader effect on the cardiac conduction system 3

Diagnostic Considerations

• Traditional ECG manifestations of acute cor pulmonale (S1Q3T3, right bundle branch block, P pulmonale, or right axis deviation) occur in only 26% of PE patients, making it unreliable to depend solely on these findings 5
• Recent research (2025) confirms that classical ECG findings in PE have minimal diagnostic accuracy, with most findings being non-informative 6
• The most common ECG abnormalities in PE are nonspecific T wave changes (42%) and nonspecific abnormalities of the RST segment (41%) 5
• Bradycardia and AV block should raise suspicion for PE, especially when:
  • They occur suddenly in a patient with risk factors for venous thromboembolism 3
  • They are accompanied by signs of right heart strain 3, 7
  • Other more common causes have been ruled out 1

Clinical Implications

• Recognition of bradycardia and AV block as potential manifestations of PE is important as these findings may be overlooked, potentially delaying diagnosis 2
• PE and atrial fibrillation (AF) may coexist with a bidirectional association, further complicating the cardiac rhythm picture 8
• Patients presenting with new-onset bradycardia or AV block of unclear etiology should be evaluated for possible PE, especially if they have risk factors for venous thromboembolism 3, 2
• Hemodynamic monitoring is crucial in PE patients as bradycardia can be a critical marker of severity and poor prognosis 1

Common Pitfalls

• Focusing only on tachycardia as the expected heart rate abnormality in PE, potentially missing the diagnosis in patients presenting with bradycardia 1, 2
• Attributing new bradycardia or AV block to other causes without considering PE in the differential diagnosis 2
• Relying solely on ECG findings to rule in or rule out PE, as they lack sufficient standalone accuracy 6
• Overlooking that PE can affect the cardiac conduction system in various ways, including causing transient changes in bundle branch blocks 4