Author + information
- Received January 8, 1987
- Revision received March 11, 1987
- Accepted May 1, 1987
- Published online October 1, 1987.
- ↵*Address for reprints: J. Anthony Gomes, MD, Division of Cardiology, Section of Electrocardiography and Electrophysiology, The Mount Sinai Medical Center, 1 Gustave L. Levy Place, New York, New York 10029.
Forty patients with syncope of unknown origin underwent quantitative signal averaging of the surface QRS complex before invasive electrophysiologic testing with programmed ventricular stimulation. Of 34 patients without bundle branch block, 12 had inducible ventricular tachycardia (Group I) and 22 did not (Group II). The duration of low amplitude signals, the root mean square voltage of the terminal 40 ms and the signalaveraged QRS vector duration were measured in each case. One or more abnormal signal averaging variables were present in 92% of patients in Group I, but in only 27% of patients in Group II (p < 0.005). An abnormal root mean square voltage of the terminal 40 ms was the most significant distinguishing variable, being present in 83% of Group I patients and in only 14% of Group II patients (p < 0.005). The QRS vector duration was prolonged in 58% of Group I patients, but in only 9% of Group II patients (p < 0.05). Likewise, the duration of low amplitude signals was prolonged in 58% of Group I patients, but in only 19% of Group II patients (p < 0.05).
When compared with 24 hour ambulatory electrocardiographic monitoring, the presence of abnormal signal averaging variables was more predictive of inducible ventricular tachycardia. Seven (32%) Group II patients had 2 10 ventricular premature beats/h, couplets or episodes of nonsustained ventricular tachycardia; however, none had abnormal late potentials recorded. In contrast, three patients (25%) in Group I had 10 ventricular premature beats/h, although all in that group had one or more abnormal signal-averaged variables.
The sensitivity and specificity of the various signalaveraged variables ranged from 50 to 83% and from 82 to 91%, respectively. An abnormally low root mean square voltage of the terminal 40 ms had the highest sensitivity (82%) and specificity (91%) in distinguishing individuals with syncope of unknown origin who had inducible ventricular tachycardia. Thus, signal averaging of the surface QRS complex is a useful noninvasive technique for selecting patients with syncope of unknown origin who should undergo programmed ventricular stimulation.
- Received January 8, 1987.
- Revision received March 11, 1987.
- Accepted May 1, 1987.
- American College of Cardiology Foundation