1. Department of Medicine, University of Naples, Italy
2. Department of Internal Medicine, Division of Hypertension, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, U.S.A.
3. Department of Internal Medicine, Division of Cardiovascular Diseases, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, U.S.A.
4. Division of Medicine, University of Naples, Italy; Department of Medicine-0682, University of California at San Diego, Gilman Drive 9500, La Jolla, CA 92093, U.S.A.