A wide QRS-complex tachycardia may be of either ventricular origin or of supraventricular origin with preexisting or rate-dependent bundle-branch block. Distinction between the two has important causative, prognostic, and therapeutic implications. Although definitive diagnosis sometimes requires intracardiac electrophysiologic studies, much information can be obtained from careful examination of the surface ECG. We describe a patient who had both wide and narrow QRS-complex tachycardias in whom the correct diagnosis was made in this manner.
REPORT OF A CASE
A 28-year-old resident physician had experienced sporadic episodes of paroxysmal palpitations since the age of 15 years. These episodes were accompanied by dizziness but not by chest pain, shortness of breath, or syncope. The average frequency of these episodes was about once bimonthly. Between episodes, he was completely well. Physical examination showed no abnormalities. A chest roentgenogram, the initial ECG, and the M-mode and two-dimensional echocardiograms were normal. A diagnostic treadmill test was