Microvolt T-wave alternans, peak oxygen consumption, and outcome in patients with severely impaired left ventricular systolic function.
BACKGROUND
Abnormal microvolt T-wave alternans (MTWA) and low peak oxygen consumption (VO2) both predict poor outcome in heart failure. However, their independent predictive properties have not been assessed in large-scale cohorts.


METHODS
This was an observational prospective cohort study of 303 consecutive patients referred for metabolic stress testing. All had an ejection fraction < or = 40% and were considered candidates for transplantation. The exercise laboratory did not collect MTWA data from patients with implanted pacemakers or defibrillators. The primary end point was a composite of all-cause death or United Network for Organ Sharing status 1 transplantation.


RESULTS
During a 2.8-year period, there were 34 deaths and 17 transplantations. Patients with abnormal MTWA had a higher event rate of 23% (31 of 136) vs 12% (20 of 167), with an unadjusted hazard ratio (HR) of 1.90 (95% confidence interval [CI], 1.90-3.33; p = 0.03). The association remained significant after adjustment for 3 clinical variables (HR, 1.89; 95% CI, 1.05-3.39; p = 0.03). After adding peak VO2 to the model, the association was no longer significant (adjusted HR, 1.18; 95% CI, 0.64-2.17, p = 0.60). After accounting for peak VO2 and 28 other confounders in a matched propensity analysis, MTWA was not predictive (propensity-matched HR, 0.79; 95% CI, 0.37-1.66; p = 0.53).


CONCLUSIONS
These results confirm the association of abnormal MTWA with poor outcome amongst patients with impaired left ventricular systolic function. However, this association is markedly attenuated after accounting for peak VO2.
Gorodeski
Eiran Z
EZ
Department of Cardiovascular Medicine of Cleveland Clinic, Cleveland, Ohio 32610, USA.
Cantillon
Daniel J
DJ
Goel
Sachin S
SS
Kaufman
Elizabeth S
ES
Martin
David O
DO
Hsich
Eileen M
EM
Blackstone
Eugene H
EH
Lauer
Michael S
MS
D000328:Adult; D015331:Cohort Studies; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology; D016027:Heart Transplantation; D006801:Humans; D053208:Kaplan-Meier Estimate; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D018579:Patient Selection; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D013312:Stress, Physiological / Q000502:physiology; D013318:Stroke Volume / Q000502:physiology; D013599:Systole / Q000502:physiology*; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000503:physiopathology*