label: Incomplete right bundle branch block
label_lc: incomplete right bundle branch block
description: "Right bundle branch block (RBBB) represents an abnormality in the intraventricular electrical conduction system of the human heart, generating enlarged QRS and modified vectors on the electrocardiogram (ECG). Incomplete RBBB (IRBBB) is defined by (i) QRS duration between 110 and 120 ms in adults; (ii) rsr, rsR, or rSR in leads V1 or V2. The R or r deflection is usually wider than the initial R wave. In a minority of patients, a wide and often notched R wave pattern may be seen in leads V1 and/or V2; (iii) S wave of greater duration than R wave or greater than 40 ms in leads I and V6 in adults; and (iv) Normal R peak time in leads V5 and V6 but greater than 50 ms in lead V1. The first 3 criteria should be present to make the diagnosis. When a pure dominant R wave with or without a notch is present in V1, criterion 4 should be satisfied."