Significance of QRS prolongation during diagnostic ajmaline test in patients with suspected Brugada syndrome.
BACKGROUND
Current consensus documents on Brugada syndrome recommend the diagnostic intravenous administration of a Na-channel blocker to be stopped when the QRS prolongs to > or =130% of baseline, presumably because of increased arrhythmic risk.


OBJECTIVE
This study sought to assess QRS prolongation during ajmaline testing and its relation to arrhythmic risk.


METHODS
We analyzed an electrocardiographic (ECG) database collected during ajmaline testing in 148 patients (92 men, age 36 +/- 15 years). The QRS was measured at baseline and during the 1st to 7th, 10th, and 15th minute after the beginning of ajmaline administration.


RESULTS
The average QRS prolongation was 36% +/- 16% (range 9% to 88%), not significantly different between positive (n = 30) and negative (n = 118) tests. QRS prolonged to > or =130% during 16 (55%) positive and 71 (61%) negative tests (P = .50), with no clinical side effects. The incidence of ventricular arrhythmias was not significantly different between patients with and without QRS prolongation. Short runs (3 to 8 complexes) of nonsustained ventricular tachycardia occurred in 3 patients with QRS prolongation > or =130%. In 40% of positive tests, prolongation > or =130% occurred earlier by >1 minute than diagnostic Brugada ECG changes, i.e., early termination of the test could possibly have resulted in false-negative outcomes.


CONCLUSIONS
QRS prolongation > or =130% occurs in >50% of all tests. In 40% of positive tests it occurs before diagnostic ECG changes. Always terminating the test when QRS prolongs > or =130% could possibly result in loss of important diagnostic information. It is appropriate to adjust the criteria for early termination of the test to the baseline QRS and possibly other factors.
Batchvarov
Velislav N
VN
Division of Cardiac and Vascular Sciences, St. George's University of London, London, England, United Kingdom. vbatchva@sgul.ac.uk
Govindan
Malini
M
Camm
A John
AJ
Behr
Elijah R
ER
D000328:Adult; D000404:Ajmaline; D000889:Anti-Arrhythmia Agents; D053840:Brugada Syndrome / Q000175:diagnosis* / Q000503:physiopathology; D003937:Diagnosis, Differential; D004562:Electrocardiography / Q000187:drug effects*; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000187:drug effects / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D011379:Prognosis; D012189:Retrospective Studies
D000889:Anti-Arrhythmia Agents; D000404:Ajmaline