How to manage a patient with incomplete Left Bundle Branch Block (LBBB) and ischemia?

Management of Incomplete Left Bundle Branch Block with Ischemia

Patients with incomplete Left Bundle Branch Block (LBBB) and ischemia should receive immediate reperfusion therapy if they meet Sgarbossa criteria, with primary PCI preferred if available within 90 minutes of first medical contact, or fibrinolytic therapy if PCI is not available within this timeframe. 1

Initial Assessment and Diagnosis

• A 12-lead ECG should be acquired and interpreted within 10 minutes of first medical contact to identify patients with STEMI or STEMI equivalents 2
• In patients with LBBB (including incomplete LBBB), standard ST-segment analysis is challenging, requiring application of specific criteria to identify acute myocardial infarction 2
• Sgarbossa criteria should be used to identify acute myocardial infarction in the presence of LBBB, with high specificity (>90%) for ST-segment elevation ≥1 mm concordant with the QRS complex 1, 2
• Transthoracic echocardiography should be performed to identify focal wall motion abnormalities when ECG findings are difficult to interpret 2, 3

Reperfusion Strategy

• For patients with suspected STEMI or STEMI equivalent (including those with LBBB meeting Sgarbossa criteria):
  • Immediate transport to a PCI-capable hospital for primary PCI is the recommended triage strategy, with a first medical contact-to-device time goal of ≤90 minutes 2
  • Early notification of the receiving PCI-capable hospital and activation of the cardiac catheterization team is recommended to reduce time to reperfusion 2
  • If PCI cannot be performed within 90 minutes, fibrinolytic therapy should be administered, especially for patients with symptom onset less than 3 hours 1

Important Clinical Considerations

• New or presumably new LBBB at presentation occurs infrequently and should not be considered diagnostic of acute MI in isolation; clinical correlation is required 2
• Only a minority of patients with LBBB are ultimately diagnosed with acute myocardial infarction, regardless of LBBB chronicity 4
• Patients with LBBB have historically received lower rates of reperfusion therapy despite having higher mortality rates compared to patients without BBB 1
• Serial ECGs should be performed when clinical suspicion of ACS is high, symptoms are persistent, or the clinical condition deteriorates 2

Risk Assessment and Monitoring

• LBBB is associated with increased risk of cardiovascular mortality and is often a marker of underlying cardiac disease 3
• Pharmacologic stress echocardiography has significant prognostic value in patients with LBBB, particularly in those without previous myocardial infarction 5
• Regular follow-up with serial ECGs is recommended to monitor for progression of conduction disease 3

Long-term Management

• Management of any underlying cardiac conditions identified during evaluation 3
• Control of cardiovascular risk factors, particularly hypertension, which may contribute to progression of conduction disease 3
• In patients with heart failure, mildly to moderately reduced left ventricular ejection fraction (36%-50%), and LBBB with QRS ≥150 ms, cardiac resynchronization therapy may be considered 3, 6
• Standard post-MI care including antiplatelet therapy, anticoagulation, and cardiac monitoring after initiating reperfusion therapy 1

Special Considerations

• The absence of chest pain does not rule out myocardial ischemia, as approximately 10% of patients with LBBB and acute myocardial infarction may present without typical symptoms 3
• In patients with LBB pacing, ST-segment deviation should not be ignored, and the Sgarbossa criteria should not be applied as they would for native LBBB 7
• Restoration of synchrony by biventricular pacing can improve symptoms and longevity in carefully selected patients with LBBB 8