Robert A. Mackey

T-WAVE ALTERNANS AND SUDDEN DEATH IN EPHESUS. Robert A. Mackey¹, Phyllis K. Stein², Washington University Department of Biology, St. Louis, MO¹, Washington University School of Medicine HRV Lab, St. Louis, MO².

Background: T-wave alternans (TWA) seen during treadmill stress testing is associated with malignant arrhythmias and sudden cardiac death (SCD). Less is known about the predictive value of TWA recorded on Holter monitors.

Methods: To determine if Holter TWA is associated with SCD, patients from the EPHESUS study who died (N=29 no SCD, N=19 SCD) were matched on age, gender, and diabetes with N=51 controls alive at the end of follow up (mean 618 days). N=71 Holter recordings proved to be available (N=12 SCD, N=17 CD death, N=42 controls). Mean age was 64± 12 yrs, 51 M, 20 F and 83% of cases and 76% of controls were on β-blockers. Maximum TWA for each Holter channel and the HR at the time of max TWA were determined using GE Medical Systems Holter PC software MARS V 7.03. Results were evaluated via t-tests and chi-square analyses (p<.05).

Results: Subjects were categorized as having significant TWA if the maximum level was >10µv at a heart rate >60 bpm. 79% of all subjects had significant TWA. There was no significant difference in maximum TWA between any of the study groups. Heart rates at maximum TWA tended to be lower among SCD (p=0.055) and were significantly lower in channel 2 in SCD compared to those who died but not suddenly [84±17 bpm (died no SCD), 71±10 bpm (SCD), p=0.016]. There was also a trend for time of maximal TWA on channel 2 to be later than on channel 1 (p=0.051). Although there was no difference in TWA parameters for those on and not on β-blockers, those on β-blockers had their maximum TWA on channel 1 about 7 hours earlier in the day (6:02±5:06 vs. 12:51±7:00, p=0.004).

Conclusions: Although maximal TWA did not identify patients at higher risk of SCD, possibly due to the small sample size and inpatient population, maximal TWA was seen at lower heart rates among those who suffered SCD, suggesting differences in ambulatory TWA in high risk patients that would not have been seen during stress testing.