Nonrespiratory QRS amplitude variations related to PR interval length were observed in a case of complete atrioventricular (AV) block with narrow QRS complexes. This electrocardiographic pattern was studied, taking into consideration the greater deflection of the ventricular complexes (R- or S-wave) on each standard lead and by analyzing three groups of QRS (A,B,C) divided in relation to the different timing of the atrial systole. A significant variation appears in the entity of the mitral flow, as assessed by Doppler echocardiography evaluation, related to PR interval length, and a significant inverse correlation was found between QRS variability and ventricular diastolic filling.

In order to evaluate the incidence and prognostic significance of anterior precordial ST segment depression (decreases ST) in acute inferior myocardial infarction (MI), 158 patients with inferior MI were selected. In 90 patients (56.9%) an anterior decreases ST was associated with inferior lesion wave (group A), and in 68 patients (43.1%) only an ecg pattern of inferior myocardial infarction (group B) was present. No significant statistical differences were observed in mortality (group A 10% vs group B 10.2%), in compliances (group A 54.4% vs group B 47.0%) and in higher peak serum ck-levels (group A 83.3% vs group B 69.1%) in two groups during hospitalization period. In conclusion the anterior decreases ST during inferior MI should not be considered a negative prognostic sign. These favourable results are probably related to stringent criteria for ecg diagnosis of inferior myocardial infarction used and to exclusion of all patients with non contemporary evolution of anterior decreases ST and inferior lesion wave.

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.