What is the clinical significance of a PR interval greater than 200 milliseconds?

A PR interval greater than 200 milliseconds is clinically significant as it indicates a first-degree atrioventricular (AV) block. The PR interval reflects the time taken for electrical impulses to travel from the atria through the AV node to the ventricles. A prolonged PR interval suggests that there is a delay in this conduction through the AV node, which is characteristic of first-degree AV block.

In first-degree AV block, every atrial impulse is transmitted to the ventricles, but the prolonged interval indicates a slower conduction, rather than a complete block. This condition is often asymptomatic and can be found incidentally on an electrocardiogram (ECG), but it is essential to recognize it as it may be associated with various underlying conditions or lead to more severe heart block in some patients.

Other options provided do not correctly relate to a PR interval exceeding 200 milliseconds. For instance, ventricular hypertrophy would typically manifest through changes in the QRS complex morphology rather than the PR interval. Atrial fibrillation is characterized by an irregularly irregular rhythm and absence of distinct P waves, not by a prolonged PR interval. Myocardial infarction primarily affects the ST segment and can show various changes in the ECG but does not directly cause a PR