title: Temporal variations in microvolt T-wave alternans testing after acute myocardial infarction.
abstract: BACKGROUND
  Microvolt T-wave alternans (TWA) have been accepted as a tool for assessing vulnerability to ventricular tachyarrhythmias. There is lack of data concerning prospective temporal variations in TWA measurements after acute myocardial infarction (AMI). We analysed the temporal patterns of TWA in post-AMI patients.
  
  
  RESULTS
  TWA tests were performed <1 month (TWA_early) and 6 months (TWA_late) after AMI in 51 consecutive patients treated with successful percutaneous coronary intervention (PCI). Twenty seven patients (53%) had anterior wall infarctions and 24 (47%) had inferior/lateral wall infarctions. TWA was measured during a treadmill manual exercise protocol and defined as positive, negative and indeterminate. Group A included patients with TWA negative in both tests and Group B included those with TWA abnormal (positive or indeterminate) at first or second determinations. TWA_early was negative, positive and indeterminate in 38 (74.6%), 8 (15.6%) and 5 (9.8%) patients, respectively, whereas TWA_late was negative, positive and indeterminate in 30 (58.9%), 14 (27.4%) and 7 (13.7%) patients, respectively. TWA_early was classified as normal in 74.6% and abnormal in 25.4% of the cases, and TWA_late was normal in 58.9% and abnormal in 41.1%. TWA tests were concordant in 36 patients (70.6%) and discordant 15 patients (29.4%). At TWA_late, 10 patients (19.6%) changed from TWA negative to TWA abnormal and 4 patients (7.8%) from TWA abnormal to TWA negative. After TWA_early+TWA_late, 45% of the patients had 1 test classified as abnormal. Left ventricular ejection fraction was <50% in 22% of Group A and 52% of Group B (P = 0.037).
  
  
  CONCLUSIONS
  In the era of primary PCI, temporal changes in TWA measurements may occur frequently during the first 6 months post-AMI. These findings should be considered in risk stratification strategies following AMI.
authors.affiliation: Cardiology Department, Santa Marta Hospital, Lisbon, Portugal. mmoliveira@clix.pt
authors.forename: Mário Martins
authors.initials: MM
authors.lastname: Oliveira
authors.forename: António
authors.initials: A
authors.lastname: Fiarresga
authors.forename: Nuno
authors.initials: N
authors.lastname: Pelicano
authors.forename: Nogueira
authors.initials: N
authors.lastname: da Silva
authors.forename: Ana Teresa
authors.initials: AT
authors.lastname: Timóteo
authors.forename: Isabel
authors.initials: I
authors.lastname: Carlos
authors.forename: Sofia
authors.initials: S
authors.lastname: Silva
authors.forename: Jorge
authors.initials: J
authors.lastname: Quininha
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015906:Angioplasty, Balloon, Coronary; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology* / Q000628:therapy; D018570:Risk Assessment; D013997:Time Factors