Case presentation:

• Female.
• 65 y.o.
• No coronary risk factors.
• Typical chest pain.
• Normal rest ECG.
• Exercise test: intermittent left bundle branch block (LBBB).
• Exercise MPI (99mTc-MIBI): Frequency-dependent LBBB.

Teaching points:

• Approximately 1/3 of patients with heart failure (HF) present with conduction disturbances, most commonly (in about 25% of HF patients) as a LBBB pattern.
• This percentage is significantly higher than the estimated (1.5%) prevalence of LBBB in the general population.
• LBBB can be permanent or, more rarely, related to heart rate - that is, appearing above a frequency threshold.
• Many patients with intermittent LBBB develop a permanent conduction disturbance in the long term. Repolarization changes are common in patients with LBBB, thus interfering with interpretation of stress tests.
• Non-invasive imaging is indicated to depict ischemia in symptomatic patients with non-diagnostic ECG.
• LBBB is commonly associated with perfusion defects at the anteroseptal and apical walls.
• Frequency-dependet LBBB can cause “reversible” defects mimicking an ischemic pattern.