Which AV conduction abnormality is commonly seen after an inferior myocardial infarction and can progress to more serious AV block?

Which AV conduction abnormality is commonly seen after an inferior myocardial infarction and can progress to more serious AV block?

• A. Second Degree Heart Block Type I (Wenckebach)
• B. First Degree Heart Block
• C. Second Degree Heart Block Type II
• D. Third Degree Heart Block

Answer: (B)

Inferior myocardial infarction often injures the AV node because the AV node is supplied by the right coronary artery in many people. This damage slows conduction through the AV node, so the ECG shows a prolonged PR interval with 1:1 atrial-to-ventricular conduction. That pattern is first-degree heart block. It’s the most common AV conduction disturbance seen with this type of MI and it reflects nodal (not infranodal) disease. Importantly, it can progress to more serious blocks if ischemia persists or worsens, which is why clinicians monitor closely and treat the underlying ischemia. Blocks like Mobitz II or complete heart block imply more extensive conduction system damage (often associated with anterior MI), so they’re less typical initially in inferior MI.

Inferior myocardial infarction often injures the AV node because the AV node is supplied by the right coronary artery in many people. This damage slows conduction through the AV node, so the ECG shows a prolonged PR interval with 1:1 atrial-to-ventricular conduction. That pattern is first-degree heart block. It’s the most common AV conduction disturbance seen with this type of MI and it reflects nodal (not infranodal) disease. Importantly, it can progress to more serious blocks if ischemia persists or worsens, which is why clinicians monitor closely and treat the underlying ischemia. Blocks like Mobitz II or complete heart block imply more extensive conduction system damage (often associated with anterior MI), so they’re less typical initially in inferior MI.