What arrhythmia is associated with a "pseudo R" wave in lead V1?

The presence of a "pseudo R" wave in lead V1 is characteristically associated with a right bundle branch block (RBBB). In RBBB, the electrical conduction through the right bundle branch is delayed, leading to abnormal ventricular depolarization. This results in a characteristic ECG pattern, including an initial downward deflection and a secondary upward deflection in lead V1, which is interpreted as a "pseudo R" wave.

This feature is significant in recognizing right bundle branch block because it aids in distinguishing it from other conditions. In contrast, left bundle branch block typically shows a completely different morphology in the V1 lead, primarily demonstrating a broad, monomorphic R wave or a deep S wave instead of a "pseudo R." Atrial fibrillation does not produce distinct features in lead V1 associated with "pseudo R" waves, as it is characterized by unpredictable atrial contractions rather than a specific conduction delay. Ventricular tachycardia also presents with different morphology and can produce wide QRS complexes, but it does not usually feature a "pseudo R" wave pattern in lead V1.

Thus, recognizing the "pseudo R" wave is critical for identifying the presence of right bundle branch block on an ECG.