From the Guidelines
Mobitz type 1 and Mobitz type 2 heart blocks are distinct forms of second-degree atrioventricular (AV) heart blocks with different mechanisms and clinical implications, and the primary difference lies in their location and risk of progression to complete heart block, with Mobitz type 2 requiring more aggressive management, such as pacemaker placement, as recommended by the 2018 ACC/AHA/HRS guideline 1.
Key Differences
- Mobitz type 1, also called Wenckebach phenomenon, is characterized by progressive prolongation of the PR interval on ECG until a beat is dropped, followed by a reset of the cycle, typically occurring at the AV node level and often being benign.
- Mobitz type 2 shows consistent PR intervals with sudden, unpredictable dropped beats without warning, usually indicating disease in the His-Purkinje system below the AV node and carrying a higher risk of progression to complete heart block.
Clinical Implications
- The distinction between Mobitz type 1 and Mobitz type 2 is clinically important because Mobitz type 2 often requires pacemaker placement, as stated in the 2018 ACC/AHA/HRS guideline, which recommends permanent pacing in patients with acquired second-degree Mobitz type II atrioventricular block, high-grade atrioventricular block, or third-degree atrioventricular block not attributable to reversible or physiologic causes, regardless of symptoms 1.
- In contrast, Mobitz type 1 can frequently be managed conservatively or with medication adjustments if the patient is symptomatic, although permanent pacing may be considered in patients with marked first-degree or second-degree Mobitz type I (Wenckebach) atrioventricular block with symptoms that are clearly attributable to the atrioventricular block, as recommended by the guideline 1.
Management
- Permanent pacing is recommended for patients with Mobitz type 2 heart block, regardless of symptoms, due to the higher risk of progression to complete heart block and the potential for symptomatic improvement with pacing, as stated in the 2018 ACC/AHA/HRS guideline 1.
- For patients with Mobitz type 1 heart block, management should be individualized based on symptoms and other clinical factors, with permanent pacing considered in select cases where symptoms are clearly attributable to the atrioventricular block.
From the Research
Mobitz 1 and Mobitz 2 Heart Blocks
The key differences between Mobitz 1 and Mobitz 2 heart blocks are:
- Definition: Mobitz 1, also known as Wenckebach or Luciani-Wenckebach, is a type of second-degree atrioventricular (AV) block characterized by progressive prolongation of the PR interval until a beat is dropped 2.
- Electrocardiogram (ECG) Characteristics: In Mobitz 1, the PR interval lengthens with each successive beat until a P wave is not conducted to the ventricles, resulting in a dropped beat. In contrast, Mobitz 2 is characterized by a sudden failure of conduction without prior prolongation of the PR interval.
- Clinical Significance: Mobitz 1 is often considered a more benign condition, whereas Mobitz 2 is associated with a higher risk of complete heart block and may require more urgent medical attention.
- Association with Underlying Conditions: Both types of heart blocks can be associated with underlying cardiac conditions, such as acute myocardial infarction and severe coronary artery disease, as reported in a case study of a patient with paroxysmal Mobitz Type-I atrioventricular block Luciani-Wenckebach conduction 2.