Which of the following is a normal AH interval value?

Which of the following is a normal AH interval value?

• A. 50-120 ms
• B. 200-300 ms
• C. 5-20 ms
• D. 130-140 ms

Answer: (A)

AH interval measures the conduction time from atrial activation to the His bundle, reflecting AV nodal conduction. In a normal heart, this interval typically runs about 50 to 120 milliseconds, representing the expected AV nodal delay that allows atrial contraction to precede ventricular activation. The range 50-120 ms matches this normal interval, making it the correct value. Values like 200-300 ms indicate a marked delay through the AV node, which is abnormal; 5-20 ms is unrealistically short for AV nodal conduction; 130-140 ms is slightly prolonged beyond the upper normal limit. So, the normal AH interval is 50-120 ms.

AH interval measures the conduction time from atrial activation to the His bundle, reflecting AV nodal conduction. In a normal heart, this interval typically runs about 50 to 120 milliseconds, representing the expected AV nodal delay that allows atrial contraction to precede ventricular activation. The range 50-120 ms matches this normal interval, making it the correct value. Values like 200-300 ms indicate a marked delay through the AV node, which is abnormal; 5-20 ms is unrealistically short for AV nodal conduction; 130-140 ms is slightly prolonged beyond the upper normal limit. So, the normal AH interval is 50-120 ms.