Intermittent Regional Delay of Left Ventricular Activation: The Influence of Such a Delay on the Standard Electrocardiogram; Report of 33 Cases

Abstract

In the 33 cases reported changing sequence of left ventricular activation caused the ventricular complexes to change their shape in continuous electrocardiographic strips. The influence of such a change on both normal and abnormal electrocardiographic patterns is shown. The cases suggest that time relationship of left ventricular regional activation significantly contributes to the variability of the normal electrocardiogram at all ages, including its “positional” characteristics; that a normal aging process in the conductive tissue causes progressive left superior delay with progressive leftward shift of the electrical axis during lifetime, contributing to the prevalence of left axis shift at older age. It is shown that left superior regional delay may produce anterior and possibly obscure posterior infarction patterns. It tends to augment or produce left ventricular hypertrophy and “strain” pattern in limb leads and lessen or obliterate left ventricular hypertrophy and “strain” pattern in the chest leads. Left superior delay may obscure right ventricular hypertrophy in the electrocardiogram. It may normalize primary T wave changes. It may transform the incomplete into complete left bundle branch block pattern with left axis shift. In the 33 cases reported changing sequence of left ventricular activation caused the ventricular complexes to change their shape in continuous electrocardiographic strips. The influence of such a change on both normal and abnormal electrocardiographic patterns is shown. The cases suggest that time relationship of left ventricular regional activation significantly contributes to the variability of the normal electrocardiogram at all ages, including its “positional” characteristics; that a normal aging process in the conductive tissue causes progressive left superior delay with progressive leftward shift of the electrical axis during lifetime, contributing to the prevalence of left axis shift at older age. It is shown that left superior regional delay may produce anterior and possibly obscure posterior infarction patterns. It tends to augment or produce left ventricular hypertrophy and “strain” pattern in limb leads and lessen or obliterate left ventricular hypertrophy and “strain” pattern in the chest leads. Left superior delay may obscure right ventricular hypertrophy in the electrocardiogram. It may normalize primary T wave changes. It may transform the incomplete into complete left bundle branch block pattern with left axis shift.