Correlation between inducibility of sustained ventricular tachycardia and QRS duration

Some studies provide a link between the width of QRS complexesand late potentials occurring at the end of the QRS complexin signal-averaged recordings. The purpose of this study wasto compare three methods of QRS duration measurement: the conventional12 lead ECG. the Frank vectorcardiogram (VCG) and the signal-averagedelectrocardiogram. The recordings were made at a similar timein 121 consecutive patients with the Cardionics PC-based system(ECG and VCG) and the ardionics high resolution ECG, based onmethods described by Simson. Patients with bundle branch blockwere excluded. All patients had presented a myocardial infarctionand were studied either for spontaneous ventricular arrhythmiasor systematically 3 to 6 weeks after an acute myocardial infarction. The signal-averaged ECG and VCG QRS durations were similar in41 patients without inducible ventricular arrhythmias and withnormal signal-averaged ECG but were longer (P<0·001)than the conventional ECG QRS duration. In 36 patients withspontaneous and inducible ventricular tachyarrhythmias, theQRS duration was significantly longer on signal-averaged ECGthan on VCG (P<0·05) and longer on VCG than on conventionalECG (P<0·05). The QRS duration was also significantly(P<0·001) longer with the three techniques in patientswith spontaneous ventricular tachycardia (VT) than in patientswithout spontaneous and inducible VT. A QRS duration on VCG 110 ms and on conventional ECG 100 ms had a sensitivity of93% and 77% and a specificity of 83% and 85% respectively forpredicting an abnormal signal-averaged ECG. In conclusion, the measurement of QRS duration with the conventionalECG, VCG or the signal-averaged ECG could be a simple methodto detect the patients with myocardial infarction prone to VT.