Radionuclide evaluations on significance of U waves in previous anterior myocardial infarction

With the aim of evaluating the clinical significance of negative U (NU) waves in previous anterior myocardial infarction (PAMI), myocardial infarction size and left ventricular function were examined using stress thallium-201 myocardial scintigraphy (TMS) and ECG-gated radionuclide ventriculography (RNVG), respectively, in 63 PAMI patients and 12 normal subjects. According to the polarity of U waves in left precordial leads (leads V4-6), the patients fell into three groups: positive U (PU) waves (n = 16), flat U (FU) waves (n = 18), and NU waves (n = 29). Total myocardial perfusion index (MPI) calculated on early and delayed TMS significantly varied in the following order: PU > FU > NU waves. When restricting MPI to the anterolateral segment, a similar tendency was seen on early images; on delayed images, however, the difference was not significant between the FU and NU groups because of the appearance of redistribution in the NU group. Global ejection fraction (EF) calculated on RNVG decreased in the order of PU, FU, and NU waves, with significant difference among the groups. For regional EF, a similar tendency was seen in the anteroseptal and apicoinferior segments; however, a significant decrease in EF was limited to the posterolateral segment in the NU group. In conclusion, NU waves have the potential to diagnose extensive myocardial infarction with significantly decreased left ventricular function involving the apex, as well as to reflect ischemia in the lateral wall. (Namekawa, K.)