New research at UAB indicates that optimum range for serum potassium for heart-failure patients, one of the most sensitive populations to changes in potassium levels in the blood, is between 4 and 5 mEq per liter. The study, published this month online in the International Journal of Cardiology, is the first to define the safe optimal upper limit of serum potassium levels for heart failure patients.
"Our findings show that compared with serum potassium levels 4 to 4.9 mEq per liter, levels 5 to 5.5 mEq per liter were relatively safe in patients with chronic heart failure receiving diuretics and ACE inhibitors," said Mustafa Ahmed, M.D., a physician-scientist in the UAB Division of General Internal Medicine and the study's lead investigator.
Potassium is an electrolyte that is essential for normal heart function, and low serum potassium may cause life-threatening irregular heart rhythms.
"We have previously demonstrated that serum potassium levels less than 4 mEq per liter may increase the risk of death in patients with chronic heart failure," said Ali Ahmed, M.D., MPH, director of UAB's Geriatric Heart Failure Clinic, associate professor in the Division of Gerontology, Geriatrics and Palliative Care Medicine and the study's senior investigator. "However, less was known about the safe upper limit of serum potassium in patients with chronic heart failure.
"Although serum potassium levels 5 to 5.5 mEq per liter were relatively safe, it may be prudent to keep serum potassium levels between 4 and 5 mEq per liter in patients with chronic heart failure. This is important as heart failure patients are often more sensitive to changes in serum potassium levels than the general population," Ahmed said.
Ahmed and colleagues matched 548 patients with mildly elevated serum potassium levels (5 to 5.5 mEq per liter) with 1,629 patients with normal serum potassium levels (4 to 4.9 mEq per liter) from the Digitalis Investigation Group trial. All-cause mortality occurred in 36 percent of the patients with normal serum potassium levels versus 38 percent of patients with mildly elevated serum potassium levels.
The research was supported through a grant from the National Heart, Lung and Blood Institute, one of the National Institutes of Health, and a generous gift from Jean B. Morris of Birmingham.
Ahmed's co-researchers were Mustafa Ahmed, M.D., James Ekundayo, M.D. DrPH, Marjan Mujib, MBBS, Ruth Campbell, M.D., Paul Sanders, M.D., Gilbert Perry, M.D., Inmaculada Aban, Ph.D., all from UAB; Bertram Pitt, University of Michigan; George Bakris, M.D., University of Chicago; Thomas Love, Ph.D., Case Western Reserve University; and Wilbert Aronow, M.D., New York Medical College.