BACKGROUND: Thyroid stimulating hormone (TSH) abnormalities have been associated 
with various cardiac arrhythmias. Effect of TSH abnormalities on mortality and 
implantable cardioverter defibrillators (ICD) behavior in patients with 
cardiomyopathy has not been investigated.
METHODS: Our ICD database includes 1,445 patients between December 1997 and 
January 2008. TSH levels using the ultra sensitive assay were available in 371 
patients. Patients were classified based on TSH levels as: High TSH (N = 102, 
TSH > 5) and Low TSH (N = 26, TSH < 0.4). TSH groups were compared for 
mortality, appropriate and inappropriate ICD therapies.
RESULTS: A high or low TSH was an independent predictor of all-cause mortality: 
Hazard ratio (HR) 1.46 (95% CI 1.03-2.08), P = 0.033 and HR 1.76 (95% confidence 
interval 1.02-3.03), P = 0.043 respectively. TSH abnormalities were not 
associated with an increased incidence in appropriate or inappropriate ICD 
therapy.
CONCLUSION: A low or high TSH was associated with a higher mortality; however, 
neither were associated with appropriate or inappropriate ICD therapy after 
multivariate analysis. Univariate analysis demonstrated an association of high 
TSH and appropriate ICD therapy. However, multivariate analysis did not show 
this association. Therefore, we are concluding that TSH levels are predictors of 
all-cause mortality but not ICD therapy.