An electrocardiographic criterion to detect AV dissociation in wide QRS tachyarrhythmias.

A study was carried out on 12 patients with wide QRS tachycardia, 8 of whom presented with atrioventricular (AV) dissociation (Group A) and 4 with 1:1 AV association (Group B). This investigation aimed at assessing whether significant variations occurred in the QRS amplitude between the two groups. Group A showed more marked variations in QRS amplitude (31.7 +/- 13%) compared to Group B patients (6.2 +/- 1.2%) (p less than 0.001). The amplitude changes observed in Group A patients are probably related to variations in telediastolic volume resulting from the occasional contribution of the atrial systole. The findings suggest that variability in QRS amplitude during wide QRS tachyarrhythmias is a reliable sign of the presence of an AV dissociation. The possibility of diagnosing an AV dissociation on a surface ECG without visible P waves is an important finding, which though not pathognomonic of ventricular tachycardia, is a valid ECG criterion for assessing the ventricular origin of arrhythmias. This ECG criterion can be usefully applied in clinical practice along with others already used for the differential diagnosis of wide QRS tachyarrhythmias.