Key result
Rapid atrial pacing induces major QRS changes in ~39% of patients with pre-existing BBB.
Why the study?
The characteristics of QRS morphology changes during rapid atrial pacing and supraventricular tachycardia in patients with pre-existing bundle branch block were not well defined.
Does rapid atrial pacing or supraventricular tachycardia cause changes in QRS morphology in patients with pre-existing bundle branch block?
Observational (n=59)
Does rapid atrial pacing or supraventricular tachycardia cause changes in QRS morphology in patients with pre-existing bundle branch block?
In patients with pre-existing bundle branch block, rate-related changes in QRS morphology during tachycardia are common and do not necessarily indicate ventricular tachycardia.
Rate-related QRS changes are common in pre-existing BBB during atrial pacing; supports rate-dependent aberrancy but leaves open validation in spontaneous SVT.
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 > or = 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.
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Datino et al. (2008) conducted an observational in Pre-existing bundle branch block (n=59). Rapid atrial pacing (RAP) vs. Sinus rhythm was evaluated on QRS morphology changes (minor and major configuration differences). Rapid atrial pacing induced minor QRS changes in 37% and major changes in 39% of patients with pre-existing bundle branch block, though none changed to a contralateral BBB pattern.
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