Electrocardiographic Differential Diagnosis of Wide Complex Tachycardia

Electrocardiographic Differential Diagnosis of Wide Complex Tachycardia

Amita Sudhir1 and William J. Brady2

1 Department of Emergency Medicine, University of Virginia School of Medicine, Charlottesville, VA, USA

2 Departments of Emergency Medicine and Medicine, University of Virginia School of Medicine, Charlottesville, VA, USA

Wide complex tachycardia (WCT) is an abnormally fast heart rate, demonstrating a widened QRS complex. In the adult patient, the ventricular rate is usually over 120 bpm and the QRS complex is prolonged to greater than 0.12 second in duration or width. In the infant and young child, the clinician should use age‐specific norms for rates when interpreting the electrocardiogram (ECG). The wide QRS complex is caused by abnormal depolarization of the ventricles because of one of three mechanisms – ectopic ventricular foci (i.e. premature ventricular contraction [PVCs] and/or ventricular tachycardia [VT]), aberrant conduction (i.e. supraventricular tachycardia [SVT] with aberrant conduction), or ventricular preexcitation (i.e. Wolff–Parkinson–White [WPW] syndrome). Thus, the differential diagnosis for WCT (Table 23.1) includes VT, SVT with aberrant conduction, and ventricular preexcitation syndrome‐related tachycardia. WCTs may be either regular or irregular. See Clinical Presentation Box 23.1.

See Management Box 23.1.

Ventricular Tachycardia

VT almost always presents with a widened QRS complex. In the adult, the QRS complex is most often greater than 0.12 second in width; in infants and very young children, the QRS complex may not appear “wide” by adult standards when, in fact, it is. In VT, the QRS complex can be described as monomorphic (i.e. one predominant shape for the QRS complexes; Figure 23.1) or polymorphic (more than one shape for the QRS complexes; Figure 23.2). The focus of VT is found most often in the ventricular myocardium. The very rare form of fascicular tachycardia is a form of VT with a narrow QRS complex; the QRS complex is narrow in this instance because of the rhythm focus being in the intraventricular conduction system. Monomorphic VT demonstrates QRS complexes that are uniform in appearance (i.e. all appear the same or very similar). This rhythm is often seen in patients with ischemic heart disease or in the setting of an active myocardial infarction. The wide complex is caused by depolarization occurring at an ectopic ventricular focus, outside the normal conducting system. Monomorphic VT is always regular (Figure 23.1).

Polymorphic VT is a form of VT in which the morphology of the QRS complexes varies from beat to beat (Figure 23.2). The variation in the QRS complexes can be minimal or maximal. One subtype of polymorphic VT is Torsades de Pointes (TdP) in which the QRS complexes appear to be twisting around an electrical baseline (Figure 23.2b and c). If the patient’s cardiac rhythm can be viewed in a supraventricular setting either before or after the TdP occurs, the QTc interval is usually prolonged. Polymorphic VT, including TdP, is generally irregular. This rhythm is seen in a range of settings, including acute coronary syndrome, toxicologic presentations, and early in cardiac arrest.

Supraventricular Tachycardia with Aberrancy

If there is a dysfunction (i.e. a block or delay in activation) in the intraventricular conduction system, then the electrical impulse is delayed or slowed as it passes through the ventricular myocardium, thus widening the QRS complex. For instance, a left bundle branch block (LBBB) can be present in a patient with an SVT. Owing to the presence of the LBBB, the SVT, even though it arises above the ventricles, will demonstrate a widened QRS complex. The SVT can include any supraventricular rhythm that is tachycardic, including sinus tachycardia, atrial fibrillation, paroxysmal supraventricular tachycardia (PSVT), and so on (Figures 23.323.5). The malfunction in the intraventricular conduction system can be permanent, as with a bundle branch block, or temporary because the abnormal conduction may only occur at higher heart rates. SVT with aberrancy may be regular or irregular, depending on the origin of the rhythm; sinus tachycardia and PSVT will be regular, while atrial fibrillation and multifocal atrial tachycardia (MAT) will be irregular.

Table 23.1 Differential diagnosis of wide complex tachycardia (WCT).

Ventricular tachycardia

  • Monomorphic ventricular tachycardia
  • Polymorphic ventricular tachycardia
Supraventricular tachycardia (SVT) with aberrant conduction

  • Sinus tachycardia
  • Atrial fibrillation
  • Atrial flutter
  • Paroxysmal supraventricular tachycardia (PSVT)
  • Multifocal atrial tachycardia (MAT)
  • Paroxysmal atrial tachycardia
Ventricular preexcitation‐related tachycardia

  • Atrial fibrillation
  • Wide complex tachycardia (antidromic tachycardia)
Other wide complex tachycardias

  • Pacemaker‐mediated tachycardia
  • Artifact mimicking WCT
Jul 15, 2023 | Posted by in ANESTHESIA | Comments Off on Electrocardiographic Differential Diagnosis of Wide Complex Tachycardia

Full access? Get Clinical Tree

Get Clinical Tree app for offline access