Title: The electrocardiographic predictors of bradycardia-induced Torsade de Pointes in patients with acquired atrioventricular block
Abstract: Purpose: Predictors of Torsades de Pointes (TDP) in bradyarrhythmia-induced acquired LQTS have not been well defined. We sought to find the electrocardiographic predictors of TDP in patients with acquired atrioventricular block (AVB) and QT prolongation. Methods: We analyzed 12-lead electrocardiogram (ECG) of 19 patients who had AVB and experienced episodes of TdP. The ECG repolarization parameters of sinus rhythm in patients with TdP were compared with those of 76 age- and sex- matched controls with AVB but without TDP. Results: A total of 19 patients (14 females, 67.1±14.9 years old) who experienced TDP during AVB were included. TDP was initiated by PVCs with a long-short sequence of activation in 14 patients. The average cycle length of the long sequence was 2.3±0.6 times longer than the cycle length of short sequence. Patients with TDP showed a significantly longer QT interval (725.7±92.0 vs. 523.5±93.7ms, p=0.001) and T peak to end interval (333.9±60.8 vs. 148.3±77.2ms, p=0.001) compared with those without TdP. In morphology analysis, patients with TDP showed higher prevalence of notched T wave with T2 larger than T1 by 3mm (47.4% [9/19] vs. 3.9% [3/76], p=0.001), triphasic T wave (26.3% [5/19] vs. 1.3% [1/76]), reverse asymmetry (21.1% [4/19] vs. 0% [0/76], p=0.001), and T wave alternans (36.8% [7/19] vs. 0% [0/72], p=0.001). An algorithm combining these morphology parameters was useful for differentiating patients with TDP from those without events with a high sensitivity (84.2%) and specificity (97.4%). Figure 1 Figure 1 Conclusions: An algorithm combining specific morphology of T waves was useful identifying subjects at risk of developing TDP in patients with AVB.