Complete atrioventricular block with QRS complexes of variable amplitude

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.