What to do with a patient suspected of having a 3rd degree (third degree) heart block, particularly in the context of a Transient Ischemic Attack (TIA), after ordering a stat (immediate) Electrocardiogram (ECG)?

From the Guidelines

For a patient suspected of having a third-degree heart block in the context of a TIA, immediate intervention is necessary after confirming the diagnosis with a stat ECG, and the patient should be placed on continuous cardiac monitoring and have IV access established immediately. The patient should be administered atropine 0.5 mg IV as first-line therapy for symptomatic bradycardia, which can be repeated every 3-5 minutes up to a maximum of 3 mg 1. If atropine is ineffective, initiate transcutaneous pacing while arranging for urgent cardiology consultation for possible transvenous pacing. Dopamine (2-10 mcg/kg/min) or epinephrine (2-10 mcg/min) infusions can be used if atropine fails and pacing is unavailable or delayed. Some key points to consider in the management of third-degree heart block include:

• The decision to implant a pacemaker in a patient with abnormal AV conduction depends on the presence of symptoms related to bradycardia or ventricular arrhythmias and their prognostic implications 1.
• Symptomatic third-degree AV block is a class I indication for permanent pacing, whereas asymptomatic third-degree AV block is a class IIa indication 1.
• The guidelines suggest that pacing is indicated for type II second-degree AV block with a wide QRS, as it typically indicates diffuse conduction system disease and constitutes an indication for pacing even in the absence of symptoms 1. Simultaneously, address the TIA by obtaining neuroimaging (CT or MRI), administering aspirin 325 mg, and consulting neurology. Third-degree heart block represents complete failure of electrical impulse transmission from atria to ventricles, creating a dangerous situation where the ventricles beat independently at a slow rate (typically 20-40 beats per minute). This condition, especially in the context of a TIA, requires immediate attention as it can lead to hemodynamic instability, syncope, or cardiac arrest, while also potentially worsening neurological outcomes from the TIA due to decreased cerebral perfusion. It is essential to consider the patient's symptoms and the potential risks and benefits of pacing in the management of third-degree heart block, as outlined in the guidelines 1. The use of atropine, dopamine, or epinephrine, as well as the consideration of pacing, should be guided by the patient's clinical presentation and the results of the stat ECG. In general, the decision regarding implantation of a pacemaker must be considered with respect to whether AV block will be permanent, and reversible causes of AV block should be corrected first 1.

From the Research

Management of 3rd Degree Heart Block in the Context of TIA

• The patient is suspected of having a 3rd degree heart block, which is a cardiovascular emergency that requires prompt recognition and treatment 2.
• A stat EKG has been ordered to confirm the diagnosis and determine the location of the block and the presence of a functioning secondary pacemaker within the conduction system.
• The management of 3rd degree heart block includes accurate interpretation of the EKG, assessment of hemodynamic stability and systemic perfusion, and time-sensitive pharmacologic or procedural intervention 2.
• Patients presenting with 3rd degree AVB with ventricular escape rhythms can destabilize, and if no escape rhythm generates, patients can develop asystole and cardiac arrest 2.

Treatment Options

• Effective management includes administering IV atropine, attempting transcutaneous pacing, and placing a transvenous pacemaker 2.
• Emergent consultation with interventional cardiology is also recommended 2.
• In some cases, permanent pacemaker placement may be necessary, but it carries a risk of complications 3.

Considerations in the Context of TIA

• TIA is a risk factor for eventually having a stroke, and patients who have had a TIA are at increased risk of recurrent TIAs and stroke 4.
• The treatment following acute recovery from a TIA depends on the underlying cause, and patients with 3rd degree heart block may require additional interventions to manage their cardiovascular risk factors 4.
• Educating patients and inculcating lifestyle modifications are initial steps to minimize the prevalence of transient ischemic attack 4.

Clinical Presentation and Diagnosis

• 3rd degree heart block can present with symptoms such as hypotension, syncope, and bradycardia 2.
• The diagnosis is typically made based on the results of a 12-lead EKG, which can show a complete heart block with no atrial impulses reaching the ventricular conduction system 2.
• Other diagnostic tests, such as echocardiography and stress testing, may also be useful in evaluating patients with 3rd degree heart block 3, 5.