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Figure 4 Triphasic QT Interval ("Bumps-Ahead Sign") in Patients With Bradyarrhythmia-Induced Torsade de Pointes
(A) Long-standing sinus bradycardia after MAZE operation and mitral valve replacement in a 60-year-old woman treated with low-dose beta-blockers, vasodilators, and furosemide and potassium supplements. Her potassium serum levels were 5 mEq/l. The "bumps-ahead sign" (the triphasic wave with a very late positive component) are seen in leads V2 to V6. Note that the QT interval in leads with clearly defined T waves (lead I and aVL) is 500 ms. In contrast, if one uses the terminal wave of the "bump sign" to calculate the QT interval, much longer values (of about 680 ms) are obtained. (B) An 89-year-old female patient admitted with syncope in the absence of drugs. Trace B1 shows sinus rhythm with complete atrioventricular block (AVB) and a wide QRS escape rhythm with extremely low rate (average <15 beats/min). In trace B2 the ventricular rate is faster (37 beats/min), but the bradyarrhythmia is complicated by torsade de pointes. (C) Recordings from leads V2 to V3 in a female patient with atrial fibrillation and slow ventricular rate (AVB related to aortic valve replacement). In traces B2 and C1, arrowheads denote the late positive component of the triphasic "bump." The 2-way arrows show that the amplitude of the late component of the "hump" increases just before the onset of torsade or after pauses.
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