Patients with advanced heart failure (HF) and insulin-treated diabetes have about a fourfold greater risk of dying compared with non-diabetic HF and non-insulin treated diabetic HF patients.
Dr. Gregg C. Fonarow from the Ahmanson-UCLA Cardiomyopathy Center in Los Angeles said "The magnitude of the effect was pretty surprising."
Previous studies have shown that diabetes is associated with a moderate increase in mortality risk in HF patients. "But none of these prior studies have really looked at the way the diabetic patients had been treated with regard to insulin and oral medications, so this really is a new and dramatic finding," Dr. Fonarow added.
Among a cohort of 554 patients with advanced systolic HF, 132 (23.8%) had diabetes. Forty-three (32.6%)were on insulin therapy and 89 (67.4%) were non-insulin treated diabetics.
One-year survival rates were 89.7% for non-diabetic patients and 85.8% for non-insulin-treated diabetic patients compared with 62.1% for insulin-treated diabetic patients (p<0.00001).
On multivariate analysis, insulin therapy was an independent predictor of mortality and "highly statistically significantly so," Dr. Fonarow said. The hazard ratio was 4.30. Non-insulin treated diabetes was not an independent predictor of death.
"There may be residual confounders," he continued, "so we can’t be sure that it is the insulin itself leading to this dramatic increase in mortality risk, but certainly there is an urgent need for further investigation to see whether we should try to avoid insulin in these patients."
"In the near term," Dr. Fonarow concluded, "clinicians need to recognize that heart failure patients with diabetes who are treated with insulin are at particularly high risk for mortality and deserve increased attention."
Am Heart J 2005