Is a new left bundle branch block (LBBB) an indication for acute percutaneous coronary intervention (PCI)?

New Left Bundle Branch Block (LBBB) and Acute PCI

New or presumably new LBBB alone is not an indication for acute percutaneous coronary intervention (PCI), as clinical correlation is required to determine the need for emergent reperfusion therapy. 1

Current Guidelines on LBBB and Acute Coronary Syndromes

The 2025 ACC/AHA/ACEP/NAEMSP/SCAI guideline for the management of acute coronary syndromes clearly states that "new or presumably new LBBB at presentation occurs infrequently and should not be considered diagnostic of AMI in isolation; clinical correlation is required." 1

This represents a significant evolution from earlier guidelines:

• Previous guidelines (pre-2013) considered new LBBB as a STEMI equivalent requiring immediate reperfusion
• Current guidelines have moved away from this approach based on evidence showing:
  • Only a minority of patients with new LBBB are ultimately diagnosed with AMI
  • Less than 30% of patients with new LBBB have elevated cardiac troponin-I 2
  • Only about 11.6% of patients with new LBBB require emergent revascularization 2

Decision Algorithm for Patients with New LBBB

Step 1: Assess Clinical Presentation

• High-risk features requiring immediate consideration for PCI:
  • Ongoing chest pain typical for ischemia
  • Hemodynamic instability (shock, hypotension)
  • Pulmonary edema or severe heart failure (Killip class ≥2)
  • Electrical instability (ventricular arrhythmias)

Step 2: Evaluate ECG for Specific Criteria

• Apply Sgarbossa criteria to identify true STEMI in the presence of LBBB:
  • ST elevation ≥1 mm concordant with QRS complex (highly specific)
  • ST depression ≥1 mm in leads V1-V3
  • ST elevation ≥5 mm discordant with QRS complex

Step 3: Obtain Cardiac Biomarkers

• Measure high-sensitivity cardiac troponin immediately
• Repeat measurements at 1-3 hours if initial values are normal or borderline

Step 4: Decision for PCI

• Immediate PCI indicated if:
  • Positive Sgarbossa criteria AND clinical symptoms consistent with ACS
  • Elevated cardiac biomarkers AND ongoing symptoms
  • Hemodynamic instability regardless of ECG findings
• PCI not immediately indicated if:
  • Asymptomatic patient with isolated new LBBB
  • Normal cardiac biomarkers with no ongoing symptoms
  • Alternative diagnosis more likely

Outcomes and Prognosis

Patients with STEMI and newly developed LBBB have significantly worse long-term outcomes compared to STEMI patients without LBBB, with higher rates of:

• New myocardial infarction
• Need for revascularization
• Mortality 3

The presence of LBBB in STEMI patients is an independent predictor of adverse outcomes (HR: 2.15,95% CI: 1.28-3.62) 3. This underscores the importance of proper risk stratification and management.

Common Pitfalls to Avoid

• Don't automatically activate the cath lab for all new LBBB: This leads to unnecessary procedures and risks
• Don't dismiss new LBBB in symptomatic patients: Clinical correlation is essential
• Don't delay PCI in patients with clear evidence of ongoing ischemia: Despite the change in guidelines, patients with new LBBB and strong clinical evidence of acute coronary occlusion benefit from timely reperfusion
• Don't forget to consider other causes of new LBBB: Including cardiomyopathy, valvular heart disease, and conduction system disease

Conclusion

The management of patients with new LBBB has evolved from automatic emergent reperfusion to a more nuanced approach requiring clinical correlation. While new LBBB alone is not an indication for acute PCI, patients with new LBBB and clinical evidence of acute coronary occlusion should receive prompt reperfusion therapy to improve outcomes.