[Clinical observation on pause-dependent long QT syndrome and torsade de pointes ventricular tachycardia].

Ten patients with long QT syndromes (LQTs) and torsade de pointes (Tdp) were evaluated. The following features were noticed: (1) Serum potassium concentration was reduced in 5 of 10 patients (50.0%, mean value 3.0 mmol/L); (2) The QT interval (mean value 0.50s) was significantly prolonged in all patients; (3) A flat and wide T wave, an abnormal increase in U wave amplitude close to the end or the peak of the T wave and these changes were accentuated by pause or a sudden deceleration in ventricular rhythm; (4) The critical beat of Tdp inevitably started after the peak of the T wave of a markedly prolonged QT interval. Cycle lengths preceding torsade de pointes were shown in a pattern of short cycle-long QT-"late premature ventricular contraction" initiating sequence changes.