Rate-related changes in QRS morphology in patients with fixed bundle branch block: implications for differential diagnosis of wide QRS complex tachyca

Tomás Datino, Jesús Almendral*, Esteban González-Torrecilla, Felipe Atienza, Francisco J. García-Fernández, Ángel Arenal, Leonardo Atea and Francisco Fernández-Avilés
Cardiology Department, Hospital General Universitario, Gregorio Marañón, Doctor Esquerdo 46, Madrid 28007, Spain
Received 3 December 2007; revised 15 June 2008; accepted 8 July 2008; online publish-ahead-of-print 29 July 2008.

* Corresponding author. Tel/Fax: +34 915 868 276, Email: almendral@secardiologia.es

See page 2319 for the editorial comment on this article (doi:10.1093/eurheartj/ehn391)



Aims: To analyse QRS morphology in response to rapid atrial pacing (RAP) and supraventricular tachycardia (SVT) in patients with pre-existing bundle branch block (BBB).

Methods and results: We prospectively studied 59 patients in sinus rhythm (SR), with QRS 120 ms, and no pre-excitation. Trains of RAP were introduced at increasing rates until atrioventricular block. QRS during SR and last QRS complex of each RAP train were compared on the 12-leads. Previously described criteria for minor and major configuration differences were used to identify QRS changes. During RAP minor QRS changes were seen in 22 (37%) and major changes in 23 (39%) subjects. One patient showed major axis shifts and no one showed a change to the contralateral BBB pattern. QRS changes were significantly and independently related to RAP rate and type of BBB (more frequent if right-BBB). Of 14 subjects (24%) with SVT, 13 displayed the same QRS changes during RAP.

Conclusion: In patients with organic BBB, important changes in QRS morphology, except for a change in the contralateral BBB, can appear during RAP and SVT. Thus, in these patients, a change in QRS morphology during tachycardia does not necessarily imply that it is ventricular tachycardia.


Key Words: Tachycardia • Bundle branch block • Diagnosis • Wide QRS complex tachycardia • Electrocardiography


Comentario de incirculation.net:
Differential diagnosis of wide QRS tachycardia under scrutiny

6 October 2008

MedWire News: The standard approach to the differential diagnosis of wide QRS tachycardia in patients with fixed bundle branch block (BBB) is flawed and may cause some patients to be wrongly diagnosed with ventricular tachycardia, say researchers.

The claim is made by Spanish cardiologists based on a prospective study of patients with fixed BBB and reported in the European Heart Journal.

It is widely held that the differentiation of wide QRS tachycardia in patients with preexisting wide QRS complex is simple: If the QRS complexes during tachycardia are identical to those in sinus rhythm, the tachycardia is supraventricular tachycardia (SVT); if they are different, the arrhythmia is ventricular in origin.

“This concept may be too simplistic and has not been tested in a systematic way,” write Tomás Datino (Hospital General Universitario, Madrid) and co-authors.

For this study, Datino et al analyzed QRS morphology during incremental rapid atrial pacing in 59 patients in sinus rhythm and QRS =120 ms but no pre-excitation.

On pacing, minor QRS changes were seen in 37% of subjects and major changes in 39%, the researchers report. One patient showed major axis shifts and none showed a change to the contralateral BBB pattern.

QRS changes were significantly and independently related to pacing rate and BBB type, being more frequent in those with right BBB. Furthermore, of 14 subjects with SVT, 13 displayed the same QRS changes during pacing.

Based on their observations Datino et al conclude: “If the 12-lead ECG morphology of a wide QRS tachycardia is different to that during sinus rhythm, but with the same BBB pattern, it does not necessarily imply that the tachycardia is ventricular.”

In an accompanying editorial, Hein Wellens (Cardiovascular Research Institute Maastricht, The Netherlands) remarked: “To make the correct diagnosis in a wide QRS tachycardia remains a challenge.

“In patients with the same type of BBB during sinus rhythm and tachycardia, there may be differences in QRS configuration without implying that the tachycardia is ventricular.”

Eur Heart J 2008; 29: 2351–2358