LBBB Incorrect Statement Analysis

A Left Bundle Branch Block (LBBB) occurs when the electrical impulse traveling down the left bundle branch is blocked, causing delayed ventricular depolarization. This leads to characteristic ECG changes.

Evaluating LBBB Characteristics

• Prolonged QRS Complex: LBBB is defined by a QRS duration typically greater than 120 milliseconds (or 0.12 seconds). This indicates a delay in ventricular depolarization. Therefore, statement 3, "QRS complex is prolonged in LBBB," is correct.
• Aetiologies of LBBB: Various conditions can lead to LBBB. These include structural heart diseases like cardiomyopathies (affecting the heart muscle) and ischaemic heart disease (like coronary artery disease affecting the septum). Statements 1 ("Coronary artery disease can be one of the possible aetiologies of LBBB") and 4 ("Cardiomyopathy is another possible aetiology of LBBB") are both correct.
• ST Segment Changes in LBBB: LBBB causes secondary repolarization abnormalities. Typically, there are ST segment depressions and T wave inversions in the leads with a predominantly positive QRS complex (e.g., V4-V6, I, aVL). Conversely, ST segment elevation might be seen in leads with a predominantly negative QRS complex (e.g., V1-V3). However, ST segment elevation is not considered an integral part of LBBB itself; it is a primary indicator of acute myocardial infarction (STEMI). While some ST elevation can occur in specific leads due to the LBBB pattern, it's not a defining or universal characteristic in the same way a prolonged QRS is. Therefore, statement 2, "ST segment elevation is an integral part of LBBB," is incorrect.

Based on the analysis, the incorrect statement regarding LBBB is that ST segment elevation is an integral part of it.