Q wave, S-T segment, and T wave myocardial infarction. Useful clinical distinction

Abstract

Abundant experimental and clinical evidence now suggests that the presence or absence of 0 waves on surface electrocardiography does not permit distinction between pathologic transmural and subendocardial myocardial infarction. It has been recommended, therefore, that use of certain electrocardiographic descriptors of myocardial Infarction be avoided. One hundred fourteen consecutive patients with first myocardial infarction were studied. The lack of development of 0 waves accompanying acute myocardial infarction delineated a group of patients with low in-hospital mortality. Left ventricular ejection fraction was less after 0 wave (0.48 ± 0.16) than after non-Q wave (0.67 ± 0.10) infarction (p <0.0001). Left ventricular end-diastolic pressure was greater after 0 wave (16.1 ± 5.9 mm Hg) than after non-Q wave (11.7 ± 2.7mm Hg) infarction (p <0.02). Fixed thallium perfusion scintigraphic defects were more common in survivors of 0 wave (98 percent [41 of 42]) than In survivors of non-Q wave (64 percent [seven of 11]) Infarction (p < 0.002). Objectively demonstrable myocardial ischemia was more common after non-Q wave (68 percent [13 of 19]) than after 0 wave (32 percent [16 of 50]) Infarction (p <0.01). The incidence of late cardiac events (sudden death plus reinfarction) did not differ after 0 wave or non-Q wave infarction. Q wave, S-T segment, and T wave myocardial infarctions differ physiologically, clinically, and prognostically. It is of little consequence to the clinician managing patients whether such useful electrocardiographic descriptors also accurately define groups that differ anatomically with regard to the thickness of the injured myocardial wall.