6. History of atrial fibrillation, mitral valve prolapse, significant heart murmur or vascular bruit. 7. Prolonged QTc interval (Bazett's) at screening (for females > 450 msec and for males > 430 msec). If the QTc interval is prolonged on the initial ECG, then complete two additional ECGs 5 minutes apart and take the average QTc measurements of all three ECGs to evaluate this criteria. If averaged QTc exceeds the safety criteria, the subject should be excluded. 8. Female subjects currently receiving hormone replacement therapy (HRT). 9. Positive for HIV, hepatitis B virus or hepatitis C virus assays at screening.