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Background
Tachyarrhythmia refers to a group of cardiac rhythm disturbances characterized by an abnormally fast heart rate, typically exceeding 100 beats per minute. These arrhythmias originate either from the atria (supraventricular) or ventricles (ventricular) and may be regular or irregular. Depending on the rate, origin, and mechanism, they can range from benign to life-threatening.
II) Classification/Types
By Site of Origin:
- Supraventricular Tachyarrhythmias (SVT):
- Sinus tachycardia
- Atrial fibrillation
- Atrial flutter
- Atrioventricular nodal reentrant tachycardia (AVNRT)
- Atrioventricular reciprocating tachycardia (AVRT)
- Multifocal atrial tachycardia (MAT)
- Ventricular Tachyarrhythmias:
- Ventricular tachycardia (VT)
- Ventricular fibrillation (VF)
- Torsades de pointes
By Rhythm Regularity:
- Regular: Sinus tachycardia, AVNRT, VT
- Irregular: Atrial fibrillation, MAT, VF
By QRS Width:
- Narrow-complex (<120 ms): Supraventricular
- Wide-complex (≥120 ms): Ventricular or aberrantly conducted SVT
Pathophysiology
Tachyarrhythmias arise from abnormalities in impulse formation (automaticity), impulse conduction (reentry), or triggered activity (afterdepolarizations). Enhanced automaticity or reentry circuits can cause rapid repetitive depolarizations. Sustained tachycardia may reduce diastolic filling time and coronary perfusion, leading to hypotension, ischemia, or heart failure.
Epidemiology
- Prevalence increases with age, structural heart disease, and electrolyte disturbances
- Atrial fibrillation is the most common sustained arrhythmia globally
- VT and VF are leading causes of sudden cardiac death
Etiology
I) Causes
- Structural heart disease (e.g., ischemic cardiomyopathy, valvular disease)
- Electrolyte imbalances (e.g., hypokalemia, hypomagnesemia)
- Drug toxicity (e.g., digoxin, antiarrhythmics, sympathomimetics)
- Congenital conduction abnormalities (e.g., WPW syndrome)
- Thyrotoxicosis
- Pulmonary diseases (e.g., COPD → MAT)
- Fever, pain, anxiety, anemia (→ sinus tachycardia)
II) Risk Factors
- Coronary artery disease
- Heart failure
- Previous myocardial infarction
- Substance use (cocaine, amphetamines, alcohol)
- Chronic lung disease
- Family history of arrhythmias or sudden death
Clinical Presentation
I) History (Symptoms)
- Palpitations
- Dizziness or lightheadedness
- Syncope or near-syncope
- Dyspnea
- Chest discomfort
- Fatigue
- Sudden cardiac arrest (in malignant arrhythmias)
II) Physical Exam (Signs)
- Tachycardia (>100 bpm)
- Irregularly irregular rhythm (in AF)
- Hypotension
- Jugular venous distension
- S3 or S4 gallop
- Signs of heart failure (rales, edema)
- Pulse deficit (in rapid AF)
Differential Diagnosis (DDx)
- Anxiety/panic disorder
- Hyperthyroidism
- Anemia
- Sepsis
- Hypovolemia
- Pulmonary embolism
- Pheochromocytoma
- Structural heart disease
Diagnostic Tests
Initial Work-Up
- ECG: Identifies rhythm, QRS width, P-wave morphology
- Telemetry/Holter/Event monitor: For intermittent arrhythmias
- Electrolytes, TSH, Troponins: Rule out precipitating causes
- Echocardiography: Evaluate for structural heart disease
- Chest X-ray: Assess for cardiomegaly, pulmonary causes
- Cardiac MRI or CT: If myocarditis or infiltrative disease suspected
- Electrophysiology Study: For definitive diagnosis and ablation planning
Treatment
I) Initial Approach
- Assess hemodynamic stability (hypotension, altered mental status)
- If unstable: Immediate synchronized cardioversion (except in VF)
- If stable: Determine type of arrhythmia and treat accordingly
II) Medications
| Drug Class | Examples | Notes |
| Rate control agents | Metoprolol, Diltiazem, Digoxin | For AF/AFlutter, especially in elderly |
| Rhythm control agents | Amiodarone, Flecainide, Sotalol | For paroxysmal or symptomatic arrhythmias |
| Antiarrhythmics (Class I/III) | Procainamide, Lidocaine, Amiodarone | For VT/VF or WPW |
| Adenosine | Adenosine | Terminates AVNRT/AVRT; diagnostic utility |
| Anticoagulants | Warfarin, Apixaban, Rivaroxaban | In AF for stroke prevention (CHA₂DS₂-VASc score) |
| Electrolyte correction | Magnesium sulfate, Potassium | Torsades de pointes, prevention of VT |
Consults/Referrals
- Cardiology: For diagnostic clarification and management
- Electrophysiologist: For ablation or device therapy
- Neurology: Post-cardiac arrest or stroke due to arrhythmia
- Endocrinology: For thyroid-related arrhythmias
Patient Education, Screening, Vaccines, Education
- Recognize symptoms of arrhythmia
- Adherence to medications and follow-up
- Avoid stimulants (e.g., caffeine, decongestants, illicit drugs)
- Understand stroke risk and importance of anticoagulation in AF
Screening/Prevention
- Regular ECG in patients with palpitations or syncope
- Screening for arrhythmia in heart failure and post-MI patients
- Use of implantable monitors in unexplained syncope
Vaccinations
- Influenza and pneumococcal vaccines in elderly or heart failure patients
- COVID-19 vaccine per guidelines
Follow-Up
Short-Term
- Monitor ECG rhythm and rate control
- Repeat labs for electrolyte or drug monitoring
- Evaluate response to antiarrhythmic therapy
Long-Term
- Ongoing anticoagulation monitoring if indicated
- Periodic echocardiography for structural assessment
- Reassess need for ablation or ICD implantation
- Risk stratification for sudden cardiac death
Prognosis
- Varies by arrhythmia type and underlying condition
- Benign for isolated sinus tachycardia or AVNRT
- Poor prognosis if associated with structural heart disease or if untreated (e.g., VT, VF)
- Risk of complications:
- Sudden cardiac death
- Stroke (in atrial fibrillation)
- Heart failure
