From the Guidelines
Immediate management of third-degree heart block requires prompt intervention with temporary pacing while preparing for permanent pacemaker implantation, as it is a life-threatening condition that can lead to hemodynamic compromise, syncope, or cardiac arrest. First, establish IV access and initiate continuous cardiac monitoring. Administer atropine 0.5-1 mg IV every 3-5 minutes (maximum 3 mg) if the patient is symptomatic with hypotension, though its effectiveness is limited in complete heart block, as noted in the 2019 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1. For symptomatic bradycardia unresponsive to atropine, start dopamine infusion at 5 to 20 mcg/kg/min IV or epinephrine infusion at 2-10 mcg/min while arranging for transcutaneous pacing, as recommended in the same guideline 1. Apply transcutaneous pacing pads and initiate pacing at 60-80 beats per minute, gradually increasing the output until electrical capture is achieved. For more stable management, transvenous temporary pacing should be established as soon as possible. Simultaneously, correct any underlying causes such as medication effects (beta-blockers, calcium channel blockers), electrolyte abnormalities, or myocardial ischemia. The decision to implant a permanent pacemaker is guided by the presence of symptoms and the prognostic implications, with symptomatic third-degree AV block being a class I indication for permanent pacing, as stated in the 2005 American Family Physician guidelines 1.
Some key points to consider in the management of third-degree heart block include:
- The importance of prompt intervention with temporary pacing to stabilize the patient
- The need to prepare for permanent pacemaker implantation as definitive management
- The role of atropine, dopamine, and epinephrine in managing symptomatic bradycardia
- The importance of correcting underlying causes such as medication effects or electrolyte abnormalities
- The consideration of permanent pacemaker implantation based on symptoms and prognostic implications, as discussed in the 2013 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities 1.
Overall, the management of third-degree heart block requires a comprehensive approach that includes immediate stabilization with temporary pacing, preparation for permanent pacemaker implantation, and correction of underlying causes, with the goal of improving morbidity, mortality, and quality of life for the patient.
From the Research
Immediate Management of 3rd Degree Heart Block
The immediate management of a patient with a 3rd degree heart block involves several key steps:
- Assessing the patient's hemodynamic stability 2
- Obtaining a stat EKG to confirm the diagnosis
- Administering atropine to patients with hemodynamically unstable bradycardia or atrioventricular block (AVB) 3, 2
- Considering the use of external transcutaneous pacemakers (EXTP) in patients who are unresponsive to atropine 4
- Preparing for potential transvenous pacemaker placement if necessary
Atropine Administration
Atropine is effective in treating patients with sinus bradycardia and hypotension, as well as those with ventricular arrhythmias and conduction disturbances 3. However, it is essential to use atropine with caution and careful medical supervision due to the risk of adverse effects 3. The response to atropine can vary, with some patients experiencing a complete response, while others may have a partial or no response 2.
Pacemaker Placement
The decision to place a temporary or permanent pacemaker depends on the patient's underlying condition and response to initial treatment. In some cases, external transcutaneous pacemakers may be used as a temporary measure until a transvenous pacemaker can be placed 4. The use of temporary pacemakers in children with 3rd degree heart block undergoing pacemaker placement is not always necessary and should be evaluated on a case-by-case basis 5.
Monitoring and Further Management
Patients with 3rd degree heart block require close monitoring and further management to prevent complications and improve outcomes. This may include coronary angiography to rule out underlying coronary artery disease 6, as well as ongoing assessment of the patient's hemodynamic stability and cardiac rhythm.