Cardiac Arrhythmias

• QRS complex is ventricular depolarization
• If there is a reversible or physiologic cause, treat as needed (e.g., sleep apnea causing bradycardia)
• If there are no underlying causes, do a 2D echo or transthoracic echocardiography to find out if there is structural heart disease (e.g., enlarged chambers that may cause a conduction problem such as infiltrative CM, endocarditis)
• If there is suspicion for CM that do not have specific patterns on 2D echo, advanced imaging or MRI can be done
• If there is no suspicion for cardiac disease, see if there are symptoms

  • If there are no symptoms, treatment is not needed
  • Because the treatment benefit is not very large
• If the symptoms are exercise related, exercise ECG testing is done

  • If with confirmed sinus node dysfunction (chronotropic incompetence or heart block), treat the patient following the algorithm
• If exercise ECG testing is not diagnostic, perform ambulatory ECG monitoring such as Holter monitoring
• Electrophysiology study (red box) is rather not done because it may cause more harm unless if it is performed for other reasons
• More often than not, treatment strategy doesn’t change when you diagnose SND, go straight to pacing
• Indications for permanent pacing in SND

  → Symptoms that are directly attributable to SND

  → Symptomatic sinus bradycardia because of essential medication therapy for which there is no alternative treatment

  → Tachy-brady syndrome and symptoms attributable to bradycardia

  → Symptomatic chronotropic incompetence

  → Patients with slow heart rate/ HR is not increasing despite exercise/activity
• → In patients with symptoms that are possibly attributable to SND, a trial of oral theophylline may be considered to increase heart rate and determine if permanent pacing may be beneficia
• In suspected sinus node dysfunction, confirm the symptoms and rule out reversible causes
• If symptoms correlate with bradycardia:

  • Oral theophylline may be given
  • Permanent pacing may be done
• If symptoms do not correlate or the patient is asymptomatic:

  • Observe only
• If patient has significant comorbidities:

  • Single chamber ventricular pacing may be done
• A single chamber pacing may cause asynchrony by making the RV depolarize ahead of the LV
• If the AV node is normal and there is a reason to avoid an RV lead:

  • Single chamber atrial pacing may be done
  • More often than not, especially in the elderly, dual chamber pacing is done with a program to minimize ventricular pacing
• Etiology AV Node Dysfunction

  → Iatrogenic

  → AV block in the presence of ischemia

  → Infectious

  → Autonomic and functional

  → Acquired blocks from infiltrative cardiomyopathies

  → Congenital AV block
• Senile degeneration or Lev’s disease is common
• Calcification of the aortic valve annulus can cause AV block since it is near the AV node
• After cardiac surgery, sometimes a momentary AV block occurs
• A pacing wire is left on the myocardium post-surgery so that pacing may be done even after the chest has been closed
• Transcatheter aortic valve replacement (TAVR) for aortic stenosis can lead to AV block, especially in the elderly
• Complication from catheter ablation:

  • Catheters are placed in the heart
  • When you burn it by ablation frequency or cryoablation, injured tissues will provoke fibrosis
  • Sometimes it can damage tissues near the AV node, resulting in complete heart block
• Patients for cardiac surgery or valve implantation via the percutaneous route are informed that they might be using pacemakers even after their surgeries later on
• Functional causes of AV block tend to be reversible

  → Autonomic, metabolic/endocrine, and drug-related

  ● Most other etiologies produce structural changes, typically fibrosis, in segments of the AV conduction axis that are generally permanent
• FIRST-DEGREE AV BLOCK

  ● All atrial impulses are conducted to the ventricle

  ● Prolonged PR interval (>200 ms) without the QRS dropping 📣

  ● AV delay usually occurs within the AV node (intranodal)

  
• SECOND-DEGREE AV BLOCK

  Intermittent failure of conduction between atrium and ventricle

  Types of Second-Degree AV Block

  Type I / Mobitz I / Wenckebach

  • Progressive PR interval prolongation until loss of conduction occurs

  Type II / Mobitz II

  • Fixed PR interval before loss of conduction
  • Some of these patients are candidates for permanent pacing because the block of the AV node is below the bundle of His (infranodal)
  • Usually associated with QRS widening
• THIRD-DEGREE AV BLOCK

  Complete heart block

  ● Complete interruption of conduction between atria and ventricles

  ● Complete dissociation of the natural atrioventricular (AV) pacing

  → P wave is pacing on its own, and the ventricles are conducting on its own 📣
• If there is a reversible or physiologic cause (e.g., medications, sleep apnea), treat as needed
• If patient improves, then just observe
• If not, consider Mobitz type II 2nd-degree AV block
• If the patient has Mobitz type II 2nd-degree AV block, do a transthoracic echocardiography to find out if there is structural heart disease
• If a structural problem is detected, do advanced imaging (MRI)
• If structural heart disease is not suspected from transthoracic echocardiography, treat for AV block
• If there is no suspicion for structural heart disease, determine where the AV block is and treat accordingly and based on symptoms
• Intranodal, treat
• Unclear (e.g., 2:1 AV block):

  • If with symptoms, treat already
  • If without symptoms, do exercise testing
  • If diagnostic for intranodal block, treat with pacemaker
  • If not diagnostic, check whether it is AV node in the surface ECG and observe
• AV Node (Mobitz type 1):

  • If symptomatic, treat
  • If asymptomatic, just observe
• In all types of AV block, permanent pacing class I is done