Second-degree first-degree AV block is a partial interruption of electrical excitation between the atria and ventricles. It usually manifests as a gradual lengthening of conduction time until one atrial excitation cannot be transmitted to the ventricles, and its ECG manifests as a gradual lengthening of the PR interval until the QRS wave cluster is dislodged.
Strictly speaking, the medical term for second degree type I AV block is second degree type I AV block, also known as Man or Mohs type I. It is the most common type of second degree AV block.
Second degree type I AV block is a milder form of AV block, some patients are clinically asymptomatic and some patients have clinical symptoms such as palpitations, dizziness, weakness and decreased blood pressure, which require intensive investigations and interventions under medical supervision to prevent progression of the disease to third degree AV block