Final answer:
A second-degree heart block type I, also known as Mobitz type I or Wenckebach block, is a conduction abnormality characterized by a progressive lengthening in the PR interval on an electrocardiogram (ECG) until a beat is dropped.
Step-by-step explanation:
A second-degree heart block type I, also known as Mobitz type I or Wenckebach block, is a conduction abnormality characterized by a progressive lengthening in the PR interval on an electrocardiogram (ECG) until a beat is dropped. This is caused by a delay in the conduction of electrical impulses from the atria to the ventricles. In this type of heart block, there is a gradual prolongation of the PR interval until a beat is blocked and the QRS complex is missing. After the blocked beat, the cycle starts again.An example of a second-degree heart block type I would be a pattern of PR interval prolongation with an eventual dropped beat, followed by a reset of the cycle. This pattern can often be seen on an ECG.