Abstract 2858: Microvolt T Wave Alternans Does Not Add Incremental Prognostic Value To Peak Oxygen Consumption In Patients With Severely Impaired Left Ventricular Systolic Function
Background: It is unknown whether Microvolt T Wave Alternans (MTWA) add incremental prognostic value to peak oxygen consumption (peak VO2) in patients with severely impaired left ventricular systolic function.
Methods: We collected MTWA data using the Heartwave system (Cambridge Heart) from 303 consecutive patients with left ventricular ejection fraction ≤ 40% referred for metabolic stress testing. The median EF for all patients was 20%. MTWA was considered abnormal if it was positive or indeterminate. Patients were followed for a combined end point of all-cause mortality or urgent cardiac transplantation (UNOS status 1). Vital status was ascertained using the Social Security Death Index, and transplant outcome through electronic chart review.
Results: During a mean follow-up time of 2.8 years there were 30 deaths and 18 urgent cardiac transplants. In a univariate analysis abnormal MTWA had a significant association with the composite end point (HR 1.90 [95% CI 1.08 –3.33], p = 0.03). After adjustment for peak VO2 this relationship became non-significant (HR 1.32 [95% CI 0.74 –2.34], p = 0.34). Peak VO2 data was also dichotomized at a cutoff of ≥14 or > 14. Stratification by MTWA did not add any incremental prognostic value to peak VO2 (Figure⇓). Receiver operator curves were constructed for the composite endpoint. There was no difference between the performance of peak VO2 alone versus peak VO2 and MTWA together (c-statistic 0.73 vs. 0.74, p = 0.54). MTWA alone performed worse (c-statistic 0.60).
Conclusions: In patients with severely impaired left ventricular systolic function, abnormal MTWA does not add incremental prognostic value to peak VO2.