title: "Indeterminate" microvolt T-wave alternans tests predict high risk of death or sustained ventricular arrhythmias in patients with left ventricular dysfunction.
abstract: OBJECTIVE
  This study tested the hypothesis that an "indeterminate" microvolt T-wave alternans (MTWA) test, when due to ectopy, unsustained MTWA, or low exercise heart rate (HR), has prognostic significance similar to a positive MTWA test.
  
  
  BACKGROUND
  MTWA testing, used to stratify risk of sudden or total mortality in patients with structural heart disease, has been limited by a substantial number of "indeterminate" tests. Indeterminate tests are due to patient factors--excessive ventricular ectopy during exercise, unsustained MTWA, or failure to achieve a HR of 105 beats/min for 1 min--or technical factors such as a noisy recording or an exercise protocol that causes an excessively rapid rise in HR.
  
  
  METHODS
  Patients in sinus rhythm with left ventricular ejection fraction < or =0.40 underwent MTWA exercise tests, analyzed with the spectral method and classified by a computerized interpretation algorithm. The primary end point was all-cause mortality or documented non-fatal sustained ventricular arrhythmia (SVA). "Indeterminate" tests were reviewed jointly by 2 readers blinded to subsequent events to determine the primary reason for indeterminacy.
  
  
  RESULTS
  Participants (N = 549) were 56 +/- 13 years and 71% male; 49% had ischemic cardiomyopathy. There were 40 deaths and 11 non-fatal SVA. Most (94%) indeterminate results were due to patient factors. The 2-year rate for death or SVA was 17.8% in patients with an "indeterminate" MTWA test compared with 12.3% in those with a positive test.
  
  
  CONCLUSIONS
  In patients with left ventricular dysfunction, an "indeterminate" MTWA test due to patient factors predicted death or SVA at least as well as a positive test.
authors.affiliation: Heart and Vascular Research Center, MetroHealth Campus of Case Western Reserve University, Cleveland, Ohio 44109-1998, USA. ekaufman@metrohealth.org
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Kaufman
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Bloomfield
authors.forename: Richard C
authors.initials: RC
authors.lastname: Steinman
authors.forename: Pearila B
authors.initials: PB
authors.lastname: Namerow
authors.forename: Ottorino
authors.initials: O
authors.lastname: Costantini
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cohen
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Bigger
mesh_terms: D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000209:etiology*; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D018570:Risk Assessment; D018487:Ventricular Dysfunction, Left / Q000150:complications* / Q000401:mortality*