[SCD-FORUM] 133E microvolt T- wave alternans Dr. Bigger

[SCD Symposium]

Dr. Roy,
I thought your essay on microvolt TWA was elegant and I agreed with all of your statements except the last sentence.
"Measurements of MTWA may be inaccurate in patients who have not withheld beta blockers and who have persistent atrial fibrillation or flutter and the contraindications are same as for a standard exercise stress test."
The multi-center study by Bloomfield et al. (J Am Coll Cardiol 2006; 47:456-463) did not discontinue beta-blockers (81% of the 549 patients were on beta-blockers for the MTWA test) and yet the MTWA test had excellent negative predictive accuracy.  Also, the 2-tiered strategy works in atrial fibrillation as well, the high-risk patients identified by LVEF in the first tier is not removed from the second tier in patients who have atrial fibrillation; thus, they get ICD prophylaxis ( the 2-tiered strategy works in this situation because AF doubles the risk of death in this high-risk subgroup (LVEF <0.31 and AF compared with LVEF <0.31 and no AFas shown by MADIT II investigators).  There are fewer "contraindications for a MTWA test and a standard exercise test because the level of effort is much lower for the MTWA test, just walking at a normal pace.  Happily, the 2-tiered stratgy using LVEF (tier 1) and MTWA (tier 2) works in almost all situations.
-- 
J Thomas Bigger, MD 
Professor of Medicine and of Pharmacology  
Columbia University  
630 West 168th Street, PH 9-103D  
New York, NY 10032  
USA  
212-305-5058 (phone)  
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jtb2 at columbia.edu