From the Guidelines
Wide complex tachycardias are typically more dangerous and require immediate treatment, whereas narrow complex tachycardias can often be managed with vagal maneuvers or pharmacologic conversion. The distinction between wide and narrow complex tachycardias is crucial in guiding treatment and preventing misdiagnosis, which can lead to inappropriate treatment and potentially life-threatening consequences 1.
Key Differences
- Narrow complex tachycardias (QRS duration <120 ms) typically originate above the ventricles in the atria or AV node and include conditions like sinus tachycardia, atrial fibrillation, atrial flutter, and supraventricular tachycardia (SVT) 1.
- Wide complex tachycardias (QRS ≥120 ms) typically originate in or involve abnormal conduction through the ventricles and include ventricular tachycardia, ventricular fibrillation, and SVT with aberrant conduction 1.
Treatment Options
- For narrow complex tachycardias, treatment often includes:
- Vagal maneuvers
- Adenosine (6-12 mg IV push)
- Calcium channel blockers like diltiazem (0.25 mg/kg IV)
- Beta-blockers such as metoprolol (5 mg IV)
- Cardioversion for unstable patients 1
- For wide complex tachycardias, treatment may include:
- Amiodarone (150 mg IV over 10 minutes, followed by infusion)
- Lidocaine (1-1.5 mg/kg IV)
- Electrical cardioversion (synchronized at 100-200 joules biphasic) for unstable patients 1
Importance of Accurate Diagnosis
The distinction between wide and narrow complex tachycardias is critical, as misdiagnosis can lead to inappropriate treatment and potentially life-threatening consequences, such as giving verapamil to a patient with ventricular tachycardia mistaken for SVT, which could cause cardiovascular collapse 1.
From the Research
Wide vs Narrow Complex Tachycardias
- Wide complex tachycardias (WCTs) are characterized by a QRS complex duration of ≥120 ms, whereas narrow complex tachycardias have a QRS complex duration of <120 ms 2.
- The most important cause of WCT is ventricular tachycardia, but supraventricular tachycardia can also manifest with a wide QRS complex due to aberrancy or preexcitation 2, 3.
Differentiation of Wide Complex Tachycardias
- The primary goal of the initial ECG evaluation of every WCT is to determine whether the tachyarrhythmia has a ventricular or supraventricular origin 3.
- Differentiation between ventricular tachycardia and supraventricular tachycardia with a wide QRS complex is critical because the treatment for each is different, and improper therapy may have potentially lethal consequences 2, 4.
- Various methods, including traditional and contemporary approaches, have been developed to differentiate ventricular tachycardia and supraventricular wide complex tachycardia, including manually applied and automated methods 3.
Treatment of Wide Complex Tachycardias
- Calcium channel blockers have been shown to be effective in treating WCTs, particularly in patients without underlying ischemic heart disease 5.
- The treatment of WCTs in the emergency department (ED) is crucial, and ED physicians should be aware of the importance of accurate diagnosis and appropriate treatment, including the use of calcium channel blockers and other anti-arrhythmic medications 6.
- The accuracy of ED diagnosis and appropriateness of treatment for WCTs have been shown to be variable, with opportunities for improvement in care, including the control of heart rate and treatment of underlying conditions 6.