iRBBB stands for Incomplete Right Bundle Branch Block, which is an ECG finding and not a disease itself. It is defined by QRS width 100–120 ms (slightly prolonged, but not as wide as full RBBB), rSR’ pattern in V1–V2 (that small extra R’ wave shows delayed right ventricle activation), and wide S waves in leads I and V6. It indicates delayed conduction in the right bundle of His/Tawara system, but not complete blockage.

This systematic review, published in the journal Cardiology and Therapy, explores the intricacies of the iRBBB in different types of populations. In healthy individuals, it is often benign; sometimes it may signal Right ventricular overload, Congenital heart disease, Cardiomyopathies, Ischemia, or infarction (RV involvement). The decision about its severity depends upon the clinical context. It has several causative factors such as Pulmonary embolism, Pulmonary hypertension/COPD (chronic RV strain), Congenital defects, etc. 

iRBBB’s pathophysiology is characterized by delayed conduction of impulses in the right bundle, which leads to slower right ventricular depolarization. Furthermore, iRBBB can share a similar diagnosis with other complications like complete RBBB, Brugada syndrome, or ARVC, making the diagnosis even more challenging. iRBBB is completely asymptomatic and benign in healthy individuals, but in compromised patients, it may lead to complete RBBB, RV dysfunction, HF risk, or arrhythmias (e.g., AFib).

In summary, a clinical examination is essential to establish the severity of iRBBB. ECG (QRS width 100–120 ms, rSR’ in V1, broad S in I/V6) is the most essential technique of iRBBB diagnosis. Based on the symptoms and supplementary information, Clinicians can decide upon the heart condition in the patient.