Temporal variation in T wave alternans positivity post-MI: Implications for risk assessment.
Derek V Exner
Authors: Ryan Mitchell; Henry Duff; Wayne Tymchak; Jamie McMeekin; Katherine Kavanagh; For the REFINE Investigators; Derek V Exner; George Veenhuyzen; Satish Raj; Sandeep Aggarwal
8:00 - 6:00

Prophylactic implantable cardioverter defibrillator (ICD) therapy reduces mortality in patients with LV dysfunction post-MI. However, widespread ICD use is limited by cost. Identifying post-MI patients most & least likely to benefit from an ICD is important for maximizing cost-effectiveness. Assessment of beat-to-beat changes in cardiac repolarization (T-wave alternans; TWA) is a non-invasive technique that may be useful in determining the risk of serious arrhythmias post-MI. Test results are characterized as positive (significant TWA at heart rate (HR) <110 bpm), negative (no TWA at this HR), or indeterminate. Prior studies indicate that TWA positivity early (<1 month) post-MI does not predict the development of serious arrhythmias, while positivity late (6-12 months) post-MI does. The optimal timing of TWA evaluation is unclear, but is vital for accurate risk assessment. The aim of this analysis was to describe temporal patterns of TWA in patients with LV dysfunction post-MI. Results. The average age of the 60 patients was 58 years, 84% were male, 64% had suffered an anterior MI & the mean baseline LV ejection fraction was 0.38 (0.09). Appropriate medical therapy (94% ASA, 87% ACE inhibitor, 87% beta-blocker, 74% statin) was used. Few (3%)patients received amiodarone. TWA treadmill assessments were performed serially (4, 8, & 16 weeks) post-MI using commercial equipment (Cambridge Heart). Most (98%) patients had at least 2 of the 3 assessments. At week 4, 44% of the patients were TWA positive, 47% negative & 9% indeterminate. At week 8, 71% of patients were persistently TWA positive, negative or indeterminate. Most remaining patients changed from TWA negative to positive (14%) or from positive to negative (12%). At week 16, 78% of patients were persistently TWA positive, negative or indeterminate vs week 8. Remaining patients largely changed from negative to positive (10%) or from positive to negative (5%). Conclusion. Significant individual variation in TWA results are observed over the initial 16 weeks post-MI. Future studies are needed to determine the optimum timing of TWA assessment in this population & the prognostic significance of temporal changes in TWA.