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Ratio of Late to Early T-Wave Peak Amplitude in 24-h Electrocardiographic Recordings as Indicator of Symptom History in Patients With Long-QT Syndrome Types 1 and 2

Matti Viitasalo, MD^_*,_*, Lasse Oikarinen, MD^_*, Heikki Swan, MD^_*, Kathryn A. Glatter, MD, Heikki Väänänen, MSc, Heidi Fodstad, MSc, Nipavan Chiamvimonvat, MD, Kimmo Kontula, MD, Lauri Toivonen, MD, FACC^_* and Melvin M. Scheinman, MD, FACC^||

^_* Department of Cardiology, Helsinki University Central Hospital, Helsinki, Finland
Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland
Department of Cardiology, University of California, Davis, California
Laboratory of Biomedical Engineering, Helsinki University of Technology, Espoo, Finland
^|| Department of Medicine, Cardiac Electrophysiology, University of California, San Francisco, California

View larger version (44K): [in a new window]   Figure 1 Electrocardiographic signals before, at times of maximal T2- to T1-wave amplitude ratios, and after the events of maximal T2- to T1-wave amplitude ratio in an unaffected subject (first panel), a long-QT syndrome type 1 (LQT1) patient (second panel), and an LQT2 patient (third panel). The two lower panels with a continuous electrocardiographic signal during a 20-s period show an episode of a prominent T2-wave in an LQT1 patient (modified lead V5). Note that the T2-wave is present in 24 beats only, the arrows showing the first and the last beat with the T2-wave.

View larger version (24K): [in a new window]   Figure 2 Data from 24-h electrocardiographic recordings during normal daily activities in the long-QT syndrome type 1 (LQT1) and 2 (LQT2) groups showing maximal QT intervals (two higher lines) and QT intervals at stable heart rates (two lower lines) in symptomatic (solid lines) and asymptomatic (broken lines) patients. Separate data points show the QT versus RR intervals at the moment of maximal T2- to T1-wave amplitude ratios in symptomatic (closed symbols) and asymptomatic (open symbols) patients.

View larger version (87K): [in a new window]   Figure 3 (Top panels) High T2- to T1-wave amplitude ratios during 24-h electrocardiographic (ECG) recordings in an unaffected subject (a), in three long-QT syndrome type 1 (LQT1) patients (b, c, and d), and in an LQT2 patient (e) (paper speed 25 mm/s). Baseline ECG recordings (leads V1 to V6, paper speed 50 mm/s) of the same patients are shown in the lower panels. Note that only the LQT2 patient exhibits bifid T waves in the baseline ECG recording.

View larger version (15K): [in a new window]   Figure 4 Odds ratios and 95% confidence intervals for the risk of long-QT syndrome (LQT)-related symptoms, according to the tertile of maximal T2- to T1-wave amplitude ratio and the QTc interval. The y axis is on a log scale. The reference group is tertile 1. (A) In LQT type 1 (LQT1) patients, the maximum T2 to T1 amplitude ratio was 3 or more in tertile 3 and 2 or less in tertile 1. (B) In LQT type 2 (LQT2) patients, the corresponding ratio was 2.4 or more in tertile 3 and 1.5 or less in tertile 1.