U wave features in body surface potential mapping in post-myocardial infarction patients.

BACKGROUND:The data on U wave features in post-myocardial infarction (MI) remain sparse. We employed 120-lead body surface potential mapping (BSPM) to explore the U wave in patients with remote MI. METHODS:Sixty post-MI patients and 46 healthy controls were examined. After signal averaging, the polarity changes of U wave related to the T wave were analyzed, and the spatial and temporal U wave parameters were computed. RESULTS:Four types of patterns based on T and U polarity were recognized. A pattern with positive T and U waves was related to better ventricular function. The study groups did not differ as regards to Tend-Uapex and Tapex-Uapex intervals whereas Uapex-Uend was significantly longer in MI patients (110 ± 20 ms vs. 100 ± 13 ms, P = 0.004). MI patients had significantly higher U wave maximum amplitude (70 ± 30 μV vs. 50 ± 20 μV, P < 0.001), and U integral area (3.96 ± 1.50 μV·s vs. 3.17 ± 0.99 μV·s, P = 0.002), but lower corresponding T wave parameter values, thus resulting into higher U/T maximum amplitude and area ratios (0.16 ± 0.10 vs. 0.09 ± 0.04, P < 0.001; and 0.13 ± 0.06 vs. 0.09 ± 0.03, P < 0.001). In comparison to 12-lead ECG, BSPM covering the entire thorax enhanced the detection of U waves. CONCLUSION:MI tends to increase the U amplitude and prolong the later part of U wave duration thus augmenting the U wave. The size and location of infarction were associated with specific T and U wave polarity patterns.