Bradycardia Treatment

• Management of sinus bradycardia is not necessary unless with inadequate cardiac output and/or with life-threatening arrhythmia
• Observation and monitoring is recommended for hemodynamically stable patients
• Second-line therapy and transcutaneous pacing may be considered only when a patient with acute symptomatic bradycardia is unresponsive to Atropine

1st-Line Agent

Atropine

• Used for symptomatic sinus bradycardia, hypersensitive carotid sinus syndrome, and atrioventricular (AV) blocks
• Reverses cholinergic-mediated decrease in heart rate by exerting its parasympathomimetic effect on the myocardium
• Improves signs and symptoms and cardiac rate
• Use cautiously in patients with acute myocardial infarction or acute coronary ischemia
• May not be effective in patients who have undergone cardiac transplantation
• Temporizing measure for pending transcutaneous pacing

2nd-Line Agents

• Consider in patients with unsatisfactory response to Atropine and as temporizing measure while awaiting pacemaker insertion

Dopamine

• May be used in patients with symptomatic bradycardia, especially associated with hypotension, in whom Atropine may be inappropriate or after Atropine fails
• Dopamine infusion may be given in addition to Epinephrine or may be administered alone
• Has both alpha- and beta-adrenergic agonist actions

Epinephrine

• Epinephrine infusion may be used in patients with symptomatic bradycardia, especially associated with hypotension, in whom Atropine may be inappropriate or after Atropine and transcutaneous pacing fails
• Strong alpha- and beta-adrenergic agonist

Isoproterenol (Isoprenaline)

• May be considered for transient heart block but should be used with utmost caution
  • Not to be used in patients with acute MI
• Increases heart rate or atrioventricular-nodal conduction in patients with acute symptomatic bradyarrhythmia
• Nonselective beta agonist with chronotropic and inotropic effects

Other Agents

Aminophylline, Glucagon, Glycopyrrolate, Terbutaline, Theophylline

• Aminophylline should be considered in patients with bradycardia caused by MI, cardiac transplant or spinal cord injury  
• Consider Glucagon if the potential cause for bradycardia is a beta-blocker or calcium channel antagonist   
  • Vasoactive peptide that counteracts the effects of beta-blockers by activating hepatic adenyl cyclase which promotes glycogenesis

• Indication is determined by severity of bradycardia
• Recommended for patients with symptomatic sinus bradycardia, atrioventricular (AV) block, hypersensitive carotid sinus syndrome
• Pacing is recommended to correct bradyarrhythmias and enable pharmacological treatment in symptomatic patients with bradycardia-tachycardia form of SND if ablation is not preferred
• May be considered for patients at risk of asystole, hemodynamically unstable, and those unresponsive to Atropine
  • Also in patients ≥40 years old with recurrent unpredictable reflex syncope and/or documented symptomatic pauses due to sinus arrest or AV block, patients with history of syncope with asymptomatic pauses of >6 seconds secondary to sinus arrest, sinoatrial (SA) block, or AV block

Temporary Pacing

• Emergency intervention used during the interval prior to permanent pacemaker implantation or resolution of bradycardia

Transcutaneous Pacing

• Non-invasive intervention applicable for symptomatic bradycardias
• Recommended for patients who fail to respond to Atropine therapy or if hemodynamically unstable especially those with high-degree AV blocks
• May be performed if transvenous pacing is not available or possible
• Hemodynamic stability and ECG results should be monitored during pacing

Transvenous Pacing

• Invasive intervention involving the insertion of a temporary pacemaker wire to acquire venous access into the thoracic region
  • Most common insertion sites are the internal jugular vein and subclavian vein
• Performed if Atropine therapy and transcutaneous pacing fails
• Should be an option if immediate pacing is needed and pacing indications are expected to be reversible   
• May be performed as a bridge to permanent pacemaker implantation in patients where permanent implantation is not immediately possible such as in the case of a concomitant infection or not immediately available
• Should only be used in patients with high-degree AV block without escape rhythm, and life-threatening bradyarrhythmias
• Should be used for a minimum period necessary as back-up pacing or to provide hemodynamic support to prevent asystole in order to avoid complications

Permanent Pacemaker Implantation

• Prevents recurrence of syncope, improves symptoms, and increases survival rates
• Indications include:
  • Symptomatic sinus bradycardia
  • Symptomatic patients with AV block
    • Patients with intermittent or paroxysmal intrinsic 2nd- to 3rd-degree AV block
    • Patients with type I 2nd-degree AV block should be symptomatic if being considered
    • Patient with type II 2nd-degree  AV block with wide QRS interval should be considered regardless if symptomatic or not
  • Symptomatic SND
    • Symptomatic patients with bradycardia-tachycardia form of SND
  • Patients with unexplained syncope with abnormal findings in electrophysiological studies (EPS)
  • Patients with recurrent syncope accompanied by ventricular asystole of >3 seconds due to spontaneously occurring carotid sinus stimulation and pressure
• Also recommended for acute myocardial infarction patients with AV block, congenital AV block, and AV block associated with enhanced vagal tone
• May be considered in patients with neuromuscular diseases ie myotonic muscular dystrophy, Erb dystrophy, peroneal muscular atrophy with bifascicular block or any fascicular block, regardless if with symptoms or not
• May be considered in patients with SND with chronotropic incompetence and with symptoms during exercise 
• Should be excluded if bradycardia is due to reversible causes, asymptomatic 1st-degree atrioventricular block, asymptomatic 2nd-degree Mobitz I with supra-Hisian conduction block, or AV block expected to resolve

Modes of Pacing

Single Chamber Pacing

• Considered for patients needing a single-lead atrial sensing ventricular pacemaker

Dual Chamber Pacing

• Beneficial for patients with history of stroke, embolism, atrial fibrillation, reduced exercise capacity, pacemaker syndrome compared to single chamber pacing but with more complications recorded
• Preferred for patients with sinus node disease, acquired AV block when rate response is desired
  • Reduces risk of atrial fibrillation, stroke, pacemaker syndrome and improves overall quality of life
  • Programming of dual chamber pacing is recommended in symptomatic patients with SND to minimize unnecessary ventricular pacing    
• Recommended to reduce syncope in patients >40 years old with severe, unpredictable, recurrent syncope and with:   
  • Asystolic syncope during tilt testing or
  • Cardioinhibitory carotid sinus syndrome or 
  • Spontaneous documented symptomatic asystolic pauses >3 seconds or asymptomatic pauses >6 seconds secondary to sinus arrest or AV block  
• Dual chamber pacing with rate-responsive programming may be considered in symptomatic patients with SND with chronotropic incompetence

Atrial Antitachycardia Pacing 

• Programming of atrial antitachycardia pacing may be considered in patients with bradycardia-tachycardia form of SND

Endocardial Pacing

• Involves implantation of transvenous leads into the myocardium which have the ability to assess cardiac activity and provide therapeutic cardiac stimulation, and placement of a pulse generator commonly in the pectoral region   

Epicardial Pacing 

• Involves implantation of epicardial leads during minimally invasive thoracotomy or thoracoscopy or using robotic technique 
• Indicated in patients with congenital anomalies and without venous access to the heart or have an open shunt between the left and right sides of the circulation, recurrent device infections, occluded veins or in conjunction with open heart surgery