Broad Complex Tachycardia (BCT)

Introduction

Broad Complex Tachycardia (BCT) is a term used to describe a rapid heart rate (typically over 100 beats per minute) that originates from the ventricles or involves an abnormal conduction pathway, resulting in a QRS complex duration greater than 120 milliseconds. It is crucial to differentiate between life-threatening and benign causes of BCT, as it often requires urgent medical intervention.

Causes of BCT

There are two primary categories of Broad Complex Tachycardia: 1. Ventricular Tachycardia (VT) – This arises from the ventricles and is frequently associated with structural heart disease. 2. Supraventricular Tachycardia (SVT) with Aberrancy – This occurs when an atrial-origin tachycardia presents with a broad QRS complex due to abnormal conduction, such as bundle branch block or accessory pathways (e.g., Wolff-Parkinson-White syndrome).

Key Features to Differentiate VT from SVT with Aberrancy

• VT is more likely if:
  • Age > 35 years
  • History of ischemic heart disease, heart failure, or cardiomyopathy
  • AV dissociation (atria and ventricles functioning independently)
  • Concordance in precordial leads (all QRS complexes in V1-V6 are positive or negative)
  • QRS duration > 160 ms
• SVT with aberrancy is more likely if:
  • Previous episodes of SVT
  • Normal heart structure
  • Initiation by sudden atrial tachycardia

Diagnosis and Investigations

• ECG (Electrocardiogram) is the most important test for classifying BCT.
• Electrolyte levels (especially potassium and magnesium) should be checked.
• Echocardiography to assess structural heart disease.
• Cardiac MRI may be useful in unclear cases.

Management Strategies

Emergency Management (If Unstable Patient)

• Immediate synchronized cardioversion
• Advanced cardiac life support (ACLS) protocols

Pharmacological Treatment (Stable Patient)

1. For VT
   • First-line: Amiodarone (IV infusion)
   • Alternative: Lidocaine, Procainamide (used in specific cases)
2. For SVT with Aberrancy
   • Adenosine (may reveal underlying SVT if QRS narrows temporarily)
   • Beta-blockers or calcium channel blockers (for rate control)

Long-term Management

• Implantable Cardioverter Defibrillator (ICD) for high-risk VT patients.
• Catheter Ablation for recurrent tachyarrhythmias.
• Lifestyle Modifications (e.g., avoiding triggers, managing hypertension, and heart disease).

Conclusion

Broad Complex Tachycardia is a serious condition requiring rapid evaluation and appropriate management to reduce the risk of fatal arrhythmias. Proper differentiation between VT and SVT with aberrancy is essential for optimal treatment.

Source recommendations

1. American Heart Association (AHA) Guidelines on Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death

1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549
2. https://pubmed.ncbi.nlm.nih.gov/29097320/
3. https://www.sciencedirect.com/science/article/pii/S2405500X22010945
4. https://pubmed.ncbi.nlm.nih.gov/29084733/
5. https://www.hrsonline.org/guidance/clinical-resources/2017-ahaacchrs-guideline-management-patients-ventricular-arrhythmias-and-prevention-sudden-cardiac

2. European Society of Cardiology (ESC) Guidelines for the Management of Supraventricular Tachycardia

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Supraventricular-Tachycardia
2. https://academic.oup.com/eurheartj/article/41/5/655/5556821
3. https://pubmed.ncbi.nlm.nih.gov/31504425/
4. https://www.acc.org/Latest-in-Cardiology/ten-points-to-remember/2019/09/10/12/36/2019-ESC-Guidelines-for-Supraventricular-Tachycardia
5. https://pubmed.ncbi.nlm.nih.gov/14563598/

3. ESC Guidelines for the Diagnosis and Management of Ventricular Arrhythmias

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death
2. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549
3. https://pubmed.ncbi.nlm.nih.gov/26320108/
4. https://www.jacc.org/doi/10.1016/j.jacep.2022.12.008
5. https://pubmed.ncbi.nlm.nih.gov/36017572/