In first-degree AV block (1*AVB), what is true about the QRS complexes?

In first-degree AV block, also known as first-degree atrioventricular block, the distinguishing characteristic is that there is a delay in conduction through the AV node, but all impulses from the atria successfully reach the ventricles. This results in the presence of QRS complexes for every atrial impulse, meaning that there are no dropped QRS complexes. The PR interval is prolonged, typically greater than 200 milliseconds, but since every atrial impulse is conducted to the ventricles, QRS complexes remain present.

Understanding this condition helps clarify why the other options don't apply. Dropped QRS complexes would indicate a higher degree of block, such as in second-degree AV block, where some atrial impulses are not conducted to the ventricles. A wide QRS complex often occurs in conditions that involve intraventricular conduction delays, but in first-degree AV block, the QRS may still be normal in width unless there are other underlying conduction abnormalities. Lastly, absent QRS complexes would suggest a complete failure of conduction, which is not characteristic of first-degree AV block since the QRS complexes are still present.