What is the management approach for Mobitz (Second-Degree Atrioventricular Block) type 2?

From the Guidelines

The management of Mobitz type 2 second-degree atrioventricular block typically requires permanent pacemaker implantation due to its high risk of progression to complete heart block. This recommendation is based on the most recent guidelines from the American College of Cardiology, American Heart Association, and Heart Rhythm Society, as outlined in the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1.

Key Considerations

• Temporary pacing may be needed in emergency situations while awaiting definitive treatment.
• Medications like atropine (0.5-1 mg IV) can be used as a temporizing measure in symptomatic patients, but its effect is often limited in this type of block.
• Isoproterenol (2-10 mcg/min IV) may also be considered in emergency situations to increase heart rate until pacing can be established.
• Unlike Mobitz type 1, Mobitz type 2 blocks occur below the AV node in the His-Purkinje system, making them less responsive to pharmacological interventions and more likely to cause symptomatic bradycardia or sudden progression to complete heart block.
• Patients should be monitored in a setting with cardiac telemetry until definitive treatment is provided.
• If the block is medication-induced (such as from beta-blockers, calcium channel blockers, or digoxin), the offending agent should be discontinued, though this alone is often insufficient treatment given the anatomical nature of the conduction disturbance.

Guideline Recommendations

• The 2018 ACC/AHA/HRS guideline recommends permanent pacing in patients with acquired second-degree Mobitz type II atrioventricular block, high-grade atrioventricular block, or third-degree atrioventricular block not caused by reversible or physiologic causes, regardless of symptoms 1.
• The guideline also emphasizes the importance of shared decision-making and patient-centered care in the management of patients with bradycardia and cardiac conduction delay 1.

Comparison with Older Guidelines

• Older guidelines, such as the 2007 European Society of Cardiology guidelines, also recommend permanent pacing for certain types of conduction disturbances, including Mobitz type II second-degree heart block associated with bundle branch block 1.
• However, the 2018 ACC/AHA/HRS guideline provides more comprehensive and up-to-date recommendations for the management of Mobitz type 2 second-degree atrioventricular block.

Overall, the management of Mobitz type 2 second-degree atrioventricular block requires a comprehensive approach that takes into account the patient's symptoms, underlying cardiac disease, and potential risks and benefits of treatment, as supported by the most recent guidelines 1.

From the Research

Management Approach for Mobitz Type 2 Second-Degree Atrioventricular Block

The management of Mobitz Type 2 second-degree atrioventricular block involves several key considerations, including the underlying cause of the block, the presence of symptoms, and the risk of progression to complete heart block.

• The distinction between Mobitz Type 2 and Type 1 block is descriptive, but the anatomic site of the block and the prognosis are of greater importance to the clinician 2.
• Mobitz Type 2 block is more likely to progress to complete heart block and Stokes-Adams arrest, and the site of the block is almost always below the AV node 2.
• Permanent pacemaker implantation is often indicated in patients with Mobitz Type 2 second-degree atrioventricular block, particularly those with symptoms or evidence of high-degree atrioventricular block 3, 4.
• The choice of pacing mode, such as ventricular demand pacing or dual-chamber pacing, depends on the individual patient's needs and underlying cardiac condition 4.
• Correctly identified Mobitz Type 2 AVB is invariably at the level of the His-Purkinje system and is an indication for a pacemaker 5.
• Permanent His-bundle pacing (PHBP) may be an optimal approach to the management of patients with Mobitz Type 2 atrioventricular block, particularly those with sick sinus syndrome or other conduction system diseases 6.

Key Considerations

• The presence of underlying cardiac conditions, such as coronary heart disease or valvular heart disease, may influence the management approach 3, 4.
• The patient's age, sex, and clinical setting should be taken into account when determining the site of the AV block and the prognosis 2.
• The width of the QRS complex on the surface electrocardiogram can provide information about the site of the AV block 2.
• The patient's symptoms, such as syncope or palpitations, should be carefully evaluated and managed accordingly 6.