Her ECG is shown again here. It demonstrates normal sinus rhythm with a rate of 95/minute (the RR intervals vary between 60 and 0.72 seconds), a normal PR interval and a normal QRS duration. As in the previous patient, there is a prominent U wave (or notched T wave) seen best in the V leads and the QT/U interval is prolonged, measuring 580msec, with a corrected QT interval, (using an averaged RR interval of 0.66 seconds) of 610 msec. Unlike the ECG of the previous patient, the amplitude of the U wave does not exceed that of the T wave and her serum electrolytes, measured at the time of this tracing, were normal with a serum potassium of 4.6 mM. This ECG is characteristic of the congenital long QT syndrome and, in retrospect, the patient should have been admitted to the hospital to rule out the possibility that the feinting episode(s) had been caused a potentially life threatening cardiac arrhythmia. Unfortunately, this diagnosis was not considered and she was not admitted to the hospital. Rather, she was given an appointment to be seen in the neurology clinic and sent home. She died suddenly the next day.