Second-degree block is a type of heart block where the electrical signals between the heart's upper chambers (atria) and lower chambers (ventricles) are partially interrupted. This condition can lead to missed heartbeats, which may cause symptoms like dizziness or fatigue. There are two main types: Mobitz Type I (Wenckebach) and Mobitz Type II, each with different patterns of missed beats. In Mobitz Type I, the electrical signals progressively lengthen until one is blocked, while in Mobitz Type II, the block occurs suddenly without warning. Treatment may involve monitoring or the placement of a pacemaker to help regulate the heart's rhythm.