Second-degree heart block

Second-degree heart block is a type of heart block, a condition where the electrical signals that control the heartbeat are partially or completely blocked from reaching the ventricles. In a second-degree heart block, some signals fail to reach the ventricles, leading to dropped or skipped beats. This condition is further divided into two types: Mobitz Type I (Wenckebach block) and Mobitz Type II.

Types

Mobitz Type I

Also known as Wenckebach block, Mobitz Type I is characterized by progressive prolongation of the PR interval on the ECG until a beat is dropped. This type of block is usually located in the AV node, and is generally considered less severe.

Mobitz Type II

Mobitz Type II heart block is characterized by dropped beats without progressive prolongation of the PR interval. This type of block is usually located below the AV node in the His-Purkinje system, and is considered more serious as it can progress to a complete heart block.

Symptoms

Symptoms of second-degree heart block may include palpitations, syncope, shortness of breath, and fatigue. However, some individuals may be asymptomatic.

Diagnosis

Diagnosis of second-degree heart block is typically made through an ECG, which can identify the dropped beats characteristic of this condition.

Treatment

Treatment for second-degree heart block depends on the type and severity of the condition. Mobitz Type I often does not require treatment, while Mobitz Type II may require a pacemaker.

See also

• Heart block
• Electrocardiography
• Pacemaker