Septal perfusion defects in LBBB (left bundle branch block)

Isolated reversible perfusion defects can occur in the inter ventricular septum with nuclear cardiology imaging in left bundle branch block (LBBB). It is partly due to the heterogeneity in blood flow between left anterior descending and left circumflex coronary arteries due to the delayed septal relaxation. It may be noted that myocardial blood flow is better in diastole when the myocardium relaxes as the systolic contraction reduces blood flow in systole into the intramyocardial vessels. There may be a reduced oxygen demand due to the late septal contraction which occurs when the wall stress is less.