Paroxysmal AV block Cardiac Pacing

European Society of Cardiology : Indications for Cardiac Pacing

Indications-"ESC Guidelines on Syncope (Diagnosis and Management of)".

• The major factors predicting the efficacy of pacing in preventing syncope recurrence are an established relationship between symptoms and bradycardia and the absence of associated hypotensive susceptibility .
  • When this relationship is less established, or some hypotensive mechanism is present, syncope can recur in a minority of patients.
  • Pacing is not indicated in unexplained syncope without evidence of any conduction disturbance.
  • Less than half of the patients with bifascicular BBB and syncope have a final diagnosis of cardiac syncope, albeit the probability is different among the types of BBB.
  • Elderly patients with bifascicular BBB and unexplained syncope after a reasonable workup might benefit from empirical pacemaker implantation,especially if syncope is unpredictable (with no or short prodromes) or has occurred in the supine position or during effort. "ESC Guidelines on Syncope (Diagnosis and Management of)".

• Milena et al conducted a 4 year study to study the efficacy of cardiac pacing in patients with documented paroxysmal AV block.
  • The endpoints of the study focused on syncope recurrence and time taken till first recurrence of presyncope.
  • Recurrence was only seen in patients without structural heart disease and the mechanism was related to hypotension, onset of atrial fibrillation or reflex mediated.
  • Significantly lower recurrence rates were seen in patients with documented paroxysmal AV block and it was also concluded that cardiac pacing could be offered more confidently to patients with structural heart disease."Syncope in patients paced for atrioventricular block. | Semantic Scholar".

• The Syncope Unit Project -2 (SUP-2 ) studied carried about by Brignole et al included patients with a history of recurrent syncope and positive findings on carotid sinus massage/ tilt table testing/ implantable loop recorders.
  • Such patients were fitted with dual chamber pacemakers and recurrence rates were followed up.
  • Using a standardized algorithm in their approach, they came to the conclusion that pacing can be can be offered to patients with positive findings on carotid sinus massage/ tilt table testing/ implantable loop recorders.
  • An efficacy of 3 years was maintained.
  • Furthermore, similar results were also found in those with intrinsic AV block patients and in tilt table positive asystolic reflex syncope patients.
  • The ISSUE 3 study also produced similar results where TT- negative asystolic reflex syncope patients were concerned.

Pacing in Reflex Syncope-"ESC Guidelines on Syncope (Diagnosis and Management of)".

2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: Recommendations for Temporary pacing

Recommendations for Temporary Pacing for Bradycardia Attributable to Atrioventricular Block

"1. For patients with second-degree or third-degree atrioventricular block associated with symptoms or hemodynamic compromise that is refractory to medical therapy, temporary transvenous pacing is reasonable to increase heart rate and improve symptoms. (Level of Evidence: B-NR 2.For patients who require prolonged temporary transvenous pacing, it is reasonable to choose an externalized permanent active fixation lead over a standard passive fixation temporary pacing lead.(Level of Evidence: B-NR) 3. For patients with second-degree or third-degree atrioventricular block and hemodynamic compromise refractory to antibradycardic medical therapy, temporary transcutaneous pacing may be considered until a temporary transvenous or PPM is placed or the bradyarrhythmia resolves.(Level of Evidence: B-R) "

• The cause of atrioventricular block must be taken into account when considering the timing and necessity of temporary pacing. For example, in the setting of an MI,initial focus on primary reperfusion rather than temporary pacing for rate support may be associated with improved outcomes.
• The safety of prolonged temporary pacing with an externalized active fixation permanent pacing lead has been demonstrated over the past 10 years.

• Temporary transvenous pacing should therefore be used for the minimum duration necessary to provide hemodynamic support or back-up pacing to prevent asystole and should be placed by the most experienced available operator.
• If atrioventricular block is felt to be irreversible, and the means to place a permanent pacing system is available, it may be best for the patient to avoid temporary pacing and proceed directly to permanent system implantation.
• Use of an active fixation permanent pacing lead externalized and connected to a reusable PPM generator (sometimes referred to as a “temporary PPM”) has been introduced as a means of allowing more prolonged temporary pacing for pacemaker-dependent patients who have a contraindication to PPM implantation, such as infection.
• A primary use is for bridging therapy in patients who have undergone CIED extraction for infection and require prolonged antibiotic treatment.
• Patients receiving long-term antibiotics who will be receiving a new pacemaker benefit from externalized devices during the course of therapy.
• Other advantages include ability to mobilize patients who would otherwise be confined to bedrest in an intensive care unit setting.
• No infections have been reported with the use of reusable sterilized pacemakers.

==2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay:Chronic Therapy/Management of Bradycardia Attributable to Atrioventricular Block==

Chronic Therapy/Management of Bradycardia Attributable to Atrioventricular Block

Recommendations for General Principles of Chronic Therapy/Management of Bradycardia Attributable to Atrioventricular Block

"1. In patients with first-degree atrioventricular block or second-degree Mobitz type I (Wenckebach) or 2:1 atrioventricular block which is believed to be at the level of the atrioventricular node, with symptoms that do not temporally correspond to the atrioventricular block, permanent pacing should not be performed. (Level of Evidence: C-LD 2.In asymptomatic patients with first-degree atrioventricular block or second-degree Mobitz type I (Wenckebach) or 2:1 atrioventricular block which is believed to be at the level of the atrioventricular node, permanent pacing should not be performed.(Level of Evidence: C-LD)

• The presence or absence of symptoms is a major determinant on whether permanent pacing will be required in the setting of bradycardia associated with atrioventricular block.
• In addition to symptoms, there are 3 additional clinical issues that must be considered when deciding on the use of permanent pacing in patients with atrioventricular block.
  • First, the site of atrioventricular block is critical because patients with infranodal disease who then later develop complete heart block will be dependent on unreliable ventricular escape rhythms.
  • Second, significant amounts of right ventricular pacing are potentially deleterious.
  • Finally, patients with atrioventricular block may have an associated systemic disease that leads to progressive atrioventricular block or has additional risk for ventricular arrhythmias.

• Improvement in atrioventricular conduction suggests that the site of block is at the atrioventricular node, whereas worsening atrioventricular conduction suggests infranodal block. If the symptoms do not clearly correspond to the episodes of atrioventricular block, the risks associated with the pacemaker in the absence of clear benefit make the overall risk-benefit ratio unfavorable.
• In patients who have second-degree Mobitz type I (Wenckebach) or 2:1 atrioventricular block but with symptoms of dizziness or presyncope or even syncope that do not temporally correspond to the episode of atrioventricular block, it is unclear whether permanent pacing will improve symptoms or alleviate them.
• If the level of the block is at the atrioventricular node, then sudden progression to a higher degree of atrioventricular block is unlikely.
• If the symptoms do not correlate with the episodes of first-degree or second-degree Mobitz type I atrioventricular block, the episodes would be considered unrelated and a pacemaker would not be indicated.
• Given the procedural and long-term risks of PPMs, in the absence of mitigating circumstances, for patients with first-degree or second-degree Mobitz type I (Wenckebach) atrioventricular block that does not clearly correspond to symptoms, further monitoring and follow up should be implemented.
• Although a narrow QRS complex suggests that the block is at the level of the atrioventricular node, there are instances where it has been determined to be infranodal during an EPS.
• Symptoms may be difficult to correlate but ambulatory electrocardiographic monitoring or a treadmill exercise test may be useful.
• Improvement in atrioventricular conduction suggests that the site of block is at the atrioventricular node, whereas worsening atrioventricular conduction suggests infranodal block. If the symptoms do not clearly correspond to the episodes of atrioventricular block, the risks associated with the pacemaker in the absence of clear benefit make the overall risk-benefit ratio unfavorable.