Electrocardiographic predictors of Brugada type response during Na channel blockade challenge

Aim To identify ECG predictors of Brugada type response during Na channel blockade challenge. Methods We studied prospectively 103 patients (M=76, 45 +/- 13 years) in whom ECGs were collected during ajmatine challenge. ECG recordings included the high right precordial leads (-2V(1) and -2V(2)). A positive response was defined by a > 0.2 mV J point or ST segment elevation and a down-sloping pattern of the ST segment in at least one right precordiat lead. Results Ajmaline challenge was positive in 48 (47%) of the 103 cases. Baseline J wave elevation was greater in -2V(1) (0.077 +/- 0.078 mV vs. 0.038 +/- 0.046 mV, P=0.003) and -2V(2) (0.149 +/- 0.103 mV vs. 0.043 +/- 0.088 mV, P < 0.001) in cases with a subsequent positive response. In contrast, ST segment elevation and T wave amplitudes were reduced in V-1, V-2 and V-3. Logistic regression showed that J wave elevation in -2V(2) and decreased T wave amplitude in V3 at baseline were independent predictors of a positive response. Baseline J wave elevation > 0.16 mV in -2V(2) had a specificity of 100%, a sensitivity of 40%, a positive predictive value of 100% and a negative predictive value of 28%. Conclusion J wave elevation > 0.16 mV in -2V(2) was the strongest predictor of a Brugada type response to Na channel blockade challenge when Brugada syndrome was suspected on a baseline ECG. (c) 2005 The European Society of Cardiology. Published by Elsevier Ltd. All rights reserved.