Wenckebach

Wenckebach phenomenon
Synonyms	Mobitz Type I AV block
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The Wenckebach phenomenon, also known as Mobitz Type I AV block, is a type of atrioventricular block that occurs in the heart. It is characterized by a progressive lengthening of the PR interval on the electrocardiogram (ECG) until a QRS complex is dropped.

Pathophysiology

The Wenckebach phenomenon occurs due to a delay in the conduction of electrical impulses through the atrioventricular node (AV node). This delay is usually caused by increased vagal tone or ischemia affecting the AV node. As the conduction delay increases, the PR interval becomes progressively longer until an impulse fails to conduct, resulting in a dropped QRS complex.

Clinical Significance

Wenckebach phenomenon is often asymptomatic and may be found incidentally on an ECG. However, in some cases, it can cause symptoms such as dizziness, lightheadedness, or syncope. It is important to differentiate Wenckebach phenomenon from other types of AV block, such as Mobitz Type II or complete heart block, as the management and prognosis differ.

Diagnosis

Diagnosis of Wenckebach phenomenon is made using an ECG. The hallmark of this condition is the progressive prolongation of the PR interval followed by a non-conducted P wave, resulting in a dropped QRS complex. This pattern repeats cyclically.

Management

In most cases, no specific treatment is required for Wenckebach phenomenon, especially if the patient is asymptomatic. If symptoms are present, treatment may involve addressing the underlying cause, such as reducing vagal tone or treating ischemia. In rare cases, a pacemaker may be necessary if the block is associated with significant symptoms or hemodynamic compromise.

See Also

• Atrioventricular block
• Electrocardiogram
• Cardiac conduction system

External Links

• [Wenckebach phenomenon on MedlinePlus](https://medlineplus.gov/ency/article/000161.htm)
• [Wenckebach phenomenon on Mayo Clinic](https://www.mayoclinic.org/diseases-conditions/heart-block/symptoms-causes/syc-20373130)