[Electrocardiographic diagnosis and classification of acute coronary attacks]

In clinical practice the use of terms transmural and non-transmural infarction, based on the evaluation of the electrocardiogram is abandoned, as the correlation of an abnormal Q wave and transmural infarction and its absence in non-transmural ischaemic lesions is inadequate. A cardiac infarction with a Q wave and a non-Q wave infarction have certain different clinical and prognostic characteristics. A non-Q infarction is characterized during hospitalization usually by more frequent episodes of angina pectoris and a lower mortality than infarction with a Q wave. The depression of the ST segment in a standard electrocardiogram in acute coronary attacks is not a more benign phenomenon than its elevation. From the aspect of long-term prognosis the sub-group of patients specially at risk are those with marked depressions of the ST segment. A non-Q infarction, even if of smaller extent, is an unstable form of ischaemic heart disease and therefore in these patients more intense and post-hospitalization monitoring for a so-called vulnerable heart muscle is justified. The basic classification of the ECG in acute coronaries into infarctions with and without a Q wave is inadequate, unless based on the corresponding pathological correlate as patients with non-Q infarctions are not a homogeneous group. The way to obtain optimal electrocardiographic informations and their classification in acute myocardial infarction is to evaluate electrocardiograms where not only changes in the initial portion of the QRS complex are evaluated but also changes in its medium and end portions, changes of ST segments and T waves as well as their combinations, distribution and duration.