Significance of T-wave inversion triggered by spontaneous atrial premature beats in patients with long QT syndrome

In patients with the long QT syndrome (LQTS), a sudden increase in heart rate can cause T-wave alternans (TWA) with beat-to-beat alternating polarity of T wave. We hypothesized that LQTS patients at high risk for torsades de pointes (TdP) may exhibit momentary atrial or sinoatrial premature beat-induced T-wave inversion (APB-TWI). The purpose of this study was to assess the association of APB-TWI with TdP history and with microvolt TWA. Twenty-four–hour continuous 12-lead electrocardiograms (ECGs) were recorded in 18 healthy subjects and 39 consecutive patients with LQTS types 1 (n = 21), 2 (n = 4), 3 (n = 4), and unidentified (n = 10). Peak TWA was determined by the modified moving average method. The 39 LQTS patients were divided into 2 groups: 10 LQTS patients with TdP history (TdP group) and 29 without (non-TdP group). None of the healthy subjects showed APB-TWI, whereas 38.5% of the LQTS patients (15/39) exhibited APB-TWI. The incidences of APB-TWI and TWA ≥42 μV were significantly higher in the TdP group than in the non-TdP group (APB-TWI: 80% vs 24.1%, P = .006; TWA ≥42 μV: 100% vs 65.5%, P = .04). APB-TWI was inferior in sensitivity for an association with TdP history to TWA ≥42 μV (80% vs 100%) but superior in specificity (75.9% vs 51.7%). Patients with APB-TWI exhibited significantly higher TWA values than those without [median (interquartile range) 73 (55–106.5) vs 48 (37.5–71.8) μV, P = .02]. APB-TWI is an easily measurable ECG pattern and is strongly associated with TdP history as well as TWA ≥42 μV in LQTS patients. APB-TWI and TWA may share pathophysiological mechanisms.