What are the causes and management of tachycardia?

Causes and Management of Tachycardia

Tachycardia is primarily caused by physiological responses, pathological conditions, or medication effects, and should be managed by first identifying and treating the underlying cause rather than treating the tachycardia itself to reduce morbidity and mortality.

Types and Causes of Tachycardia

Sinus Tachycardia

• Physiological causes 1:

  • Exercise
  • Emotional stress
  • Pain
  • Anxiety
  • Fever

• Pathological causes 1, 2:

  • Infection/fever
  • Dehydration
  • Anemia
  • Heart failure
  • Hyperthyroidism
  • Hypovolemia
  • Hypotension/shock

• Medication/substance-induced 1, 2:

  • Stimulants (caffeine, alcohol, nicotine)
  • Beta-agonists (albuterol, salmeterol)
  • Anticholinergics (atropine)
  • Catecholamines
  • Recreational drugs (amphetamines, cocaine, ecstasy, cannabis)
  • Anticancer treatments (anthracyclines like doxorubicin)

Inappropriate Sinus Tachycardia (IST)

• Unexplained sinus tachycardia (>100 bpm at rest, average >90 bpm over 24 hours) 1
• Possible mechanisms: dysautonomia, neurohormonal dysregulation, intrinsic sinus node hyperactivity 1

Supraventricular Tachycardias (SVTs)

• Atrioventricular nodal reentrant tachycardia (AVNRT)
• Atrioventricular reciprocating tachycardia (AVRT)
• Atrial tachycardia (focal and multifocal)
• Atrial flutter
• Junctional tachycardia
• Accessory pathway-mediated tachycardias 1, 3, 4

Diagnostic Approach

1. 12-lead ECG assessment 1, 2:

   • QRS duration (narrow vs. wide complex)
   • Rhythm regularity
   • P-wave presence and morphology
   • Relationship between P waves and QRS complexes

2. Laboratory evaluation 2:

   • Complete blood count (anemia)
   • Basic metabolic panel (electrolyte abnormalities)
   • Thyroid function tests
   • Toxicology screen if substance use suspected

3. Additional testing for persistent or recurrent episodes:

   • 24-hour Holter monitoring
   • Event recorder
   • Echocardiography if structural heart disease suspected 2, 3

Management Algorithm

1. Hemodynamically Unstable Tachycardia

• Immediate synchronized cardioversion regardless of type 2

2. Hemodynamically Stable Tachycardia

A. Physiological Sinus Tachycardia

• Identify and treat underlying cause 1, 2:
  • Treat infection/fever with antipyretics
  • Correct dehydration with fluid resuscitation
  • Treat anemia
  • Manage hyperthyroidism
  • Discontinue offending medications if possible

B. Inappropriate Sinus Tachycardia (IST)

1. First-line therapy 1, 2:

   • Beta blockers (metoprolol) - titrate to achieve heart rate control
   • Monitor for side effects (hypotension, bradycardia)

2. Alternative therapy if beta blockers contraindicated/not tolerated 2:

   • Non-dihydropyridine calcium channel blockers (diltiazem, verapamil)
   • Caution: Avoid in patients with heart failure, sick sinus syndrome, or second/third-degree AV block 5

3. Newer agent 1:

   • Ivabradine (reasonable for ongoing management in symptomatic IST)

4. Combination therapy 1:

   • Beta blockers plus ivabradine may be considered

5. Last resort 1, 2:

   • Sinus node modification by catheter ablation (76% acute success rate, 66% long-term)
   • Potential complications: pericarditis, phrenic nerve injury, SVC syndrome, need for permanent pacing

C. Supraventricular Tachycardia (AVNRT, AVRT, AT)

1. Acute termination 3, 4:

   • Vagal maneuvers first (Valsalva, carotid sinus massage)
   • If unsuccessful: Adenosine 6mg IV rapid push
   • Caution: Use adenosine carefully in patients with severe coronary artery disease 1

2. Alternative acute treatments 1, 3, 4:

   • Non-dihydropyridine calcium channel blockers (diltiazem, verapamil)
   • Beta blockers (metoprolol)

3. Long-term management 3, 4:

   • Beta blockers or calcium channel blockers for prevention
   • Class IC antiarrhythmics (flecainide, propafenone) in absence of structural heart disease
   • Class III antiarrhythmics (amiodarone, sotalol) with cardiologist consultation
   • Catheter ablation (95% success rate, <5% recurrence) for recurrent episodes

D. Atrial Flutter/Fibrillation

1. Rate control 3:

   • Beta blockers or calcium channel blockers
   • Anticoagulation based on stroke risk

2. Rhythm control 1:

   • DC cardioversion
   • Pharmacologic conversion (ibutilide, flecainide)
   • Caution: Ibutilide should not be used in patients with EF <30% due to risk of polymorphic VT 1

Special Considerations

1. Wolff-Parkinson-White Syndrome:

   • Avoid verapamil, diltiazem, and adenosine in patients with atrial fibrillation and accessory pathway 5, 4
   • Expedient referral to cardiologist for ablation 6, 4

2. Wide-complex tachycardia:

   • Never use verapamil in undiagnosed wide-complex tachycardia (risk of hemodynamic deterioration and ventricular fibrillation) 5
   • IV amiodarone preferred for impaired LV function 1

3. Tachycardia-induced cardiomyopathy:

   • Can develop with incessant tachycardia 7
   • Requires aggressive management to prevent long-term cardiac damage

4. Monitoring response:

   • Target resting heart rate between 60-80 bpm 2
   • Consider referral to electrophysiologist if symptoms persist despite therapy 2

By systematically identifying the type of tachycardia and addressing underlying causes, most cases can be effectively managed with appropriate pharmacological therapy or catheter ablation when indicated.