Understanding Tachycardia on ECG

Introduction

Tachycardia is a condition where the heart beats faster than normal, typically over 100 beats per minute (bpm) in adults. It can be classified as either physiological (e.g., exercise-induced) or pathological (due to disease). The primary method of diagnosing tachycardia is through an electrocardiogram (ECG).

Types of Tachycardia

There are several types of tachycardia, including:

1. Sinus Tachycardia

   • Originates from the sinoatrial (SA) node (the heart’s natural pacemaker)
   • Usually a response to fever, anxiety, dehydration, or exercise
   • ECG Findings: Regular rhythm, P waves present before each QRS complex, rate > 100 bpm

2. Supraventricular Tachycardia (SVT)

   • Originates above the ventricles (in the atria or AV node)
   • Can present suddenly and cause palpitations, dizziness, or even fainting
   • ECG Findings: Narrow QRS complexes (<120 ms), regular rhythm, P waves may be hidden or abnormal

3. Atrial Fibrillation (AFib) with Rapid Ventricular Response (RVR)

   • Irregular and rapid atrial activity
   • ECG Findings: No distinct P waves, irregularly irregular QRS complexes, varying R-R intervals

4. Atrial Flutter

   • Rapid, organized atrial rhythm
   • ECG Findings: “Sawtooth” flutter waves, atrial rate ~250-350 bpm

5. Ventricular Tachycardia (VT)

   • Originates from the ventricles
   • Can be life-threatening and lead to ventricular fibrillation
   • ECG Findings: Wide QRS complexes (>120 ms), absence of P waves, rapid rate >100 bpm

Diagnosing Tachycardia on ECG

When evaluating tachycardia on ECG, consider: 1. Heart Rate: Is it greater than 100 bpm? 2. Rhythm Regularity: Is the rhythm regular or irregular? 3. QRS Complex Duration: - Narrow QRS (<120 ms) suggests a supraventricular origin - Wide QRS (>120 ms) suggests ventricular origin 4. Presence of P Waves: Helps determine the origin of tachycardia

Treatment Approaches

• Sinus Tachycardia: Treat underlying causes (e.g., dehydration, fever, anxiety)
• SVT: Vagal maneuvers (e.g., carotid massage, Valsalva), medications (adenosine, beta-blockers), catheter ablation for recurrent cases
• Atrial Fibrillation: Rate control (beta-blockers, calcium channel blockers), rhythm control (antiarrhythmics, cardioversion), anticoagulation if needed
• Ventricular Tachycardia: Emergency defibrillation if unstable, antiarrhythmic drugs (amiodarone, lidocaine), implantable cardioverter-defibrillator (ICD) for long-term management

Conclusion

Detecting and diagnosing tachycardia on ECG is crucial for determining appropriate treatment. If you experience palpitations, dizziness, or fainting, consult a cardiologist immediately.

Source recommendations

1. American Heart Association Guidelines on Tachycardia

1. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/tachycardia--fast-heart-rate
2. https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/algorithms
3. https://www.ahajournals.org/doi/10.1161/cir.0000000000000311
4. https://cpr.heart.org/-/media/cpr-files/cpr-guidelines-files/algorithms/algorithmacls_tachycardia_200612.pdf
5. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549

2. European Society of Cardiology Guidelines on Arrhythmias

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death
2. https://academic.oup.com/eurheartj/article/43/40/3997/6675633
3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Supraventricular-Tachycardia
4. https://pubmed.ncbi.nlm.nih.gov/36017572/
5. https://www.ahajournals.org/doi/10.1161/01.cir.0000091380.04100.84