During ventricular tachycardia, why is lead V1 preferred for diagnosis?

In the context of diagnosing ventricular tachycardia (VT), lead V1 is particularly useful because it demonstrates specific characteristics of the QRS complex during this arrhythmia. During VT, the QRS complex typically presents with a predominantly positive configuration when viewed in lead V1, especially if the VT is a monomorphic tachycardia originating from the ventricles. This positivity helps distinguish this type of tachycardia from other cardiac rhythms, such as supraventricular tachycardia (SVT), which may show different QRS patterns.

Understanding the morphology of the QRS complex is essential for identifying VT. In lead V1, the positive QRS complex is indicative of the electrical conduction pathway in the ventricles during tachycardia, where depolarization spreads through the myocardium in a way that causes the leads to capture the electrical activity as positive.

The other options, while they present characteristics of electrical activity, do not accurately describe the typical findings in lead V1 during ventricular tachycardia. Therefore, the predominant positivity observed in lead V1 is a critical component for making an accurate diagnosis of VT.