The threshold of renal insufficiency at which to restrict metformin is controversial. In the United Kingdom, National Institute for Health and Clinical Excellence guidelines suggest that metformin can be used down to an estimated glo- merular filtration of 30 mL min 1 (with a dose reduction advised at an estimated glomerular filtration Thiazolidinedione Current ACC/AHA guidelines for the management of heart failure recommend that thiazolidinediones be avoided or discontinued in patients with HF (Class III Rec- ommendation: Harm; Level of Evidence B). Similarly, sci- entific advisories caution against the use of rosiglitazone or pioglitazone in all patients with signs and symptoms of HF. Initiation of either agent is contraindicated in pa- tients with class III to IV HF. Other Medications There are inadequate data to make recommendations on other diabetic agents. Bozkurt et al Obesity and HF Obesity and Incident HF Multiple studies have established obesity as a risk fac- tor for the development of HF. Although the concept of cardiomyopathy relating to obesity has been described the strong, independent, incremental re- lationship between obesity as indexed by body mass in- dex (BMI) and HF incidence was only more recently estab- lished. 