Monday 11th June 2007
Researchers have found that heart failure patients with low to low-normal serum potassium levels face increased risk of death. The study published in the latest issue of the European Heart Journal was conducted by Dr. Ali Ahmed and colleagues at the University of Alabama (UAB) in Birmingham.
For this first of its kind study, Dr. Ahmed and colleagues looked at 1,187 pairs of patients. Half of them had low potassium levels while the other half had normal levels. All the patients were balanced in all measured baseline covariates. The patients were all enrolled in the Digitalis Investigation Group, a large clinical trial of heart failure patients conducted in 302 centers in the US and Canada between 1991 and 1993.
Dr. Ahmed??s team was the first to directly examine the effect of long-term lack of potassium in a population of propensity-matched heart failure patients. ??Our findings showed that heart failure patients with low to low-normal (less than 4 mEq/L) potassium levels were more likely to die than those with higher levels (4 to 5.5 mEq/L) of potassium,? said Dr. Ahmed, an Associate Professor of Medicine in the Division of Gerontology, Geriatrics and Palliative Care and Director, Geriatric Heart Failure Clinics, at UAB.
??These patients were not significantly more likely to be hospitalized than the higher potassium group, suggesting that most low potassium associated deaths were sudden deaths due to ventricular arrhythmias,? he added.
Clinically, a level of 3.5 mEq/L of potassium is considered to be low. The researchers found that this level of potassium might in fact be too low and that the current standard is actually flawed. According to their findings, even patients with potassium levels below 4 mEq/L had increased risk of long-term mortality.
??It would appear that the threshold for low potassium, 3.5 mEq/L, needs to be raised for chronic heart failure and that any of these patient with a potassium level less than 4 mEq/L should be considered as having low potassium and thus at increased risk of death,? said Dr. Ahmed.
In his opinion, the link between low potassium levels and diuretics is of particular concern as the medication is common treatment for patients with heart failure and is also known to cause low potassium.
In a study last year, Dr. Ahmed and colleagues had found that extended heavy use of diuretics may increase long-term mortality. In their opinion, this might partly be on account of the low potassium levels caused by diuretic use. The previous study, just like the current one, was published in the European Heart Journal.
??Our findings suggest that low potassium levels in patients with chronic heart failure should be corrected and potassium should be maintained above 4 mEq/L,? said Dr. Ahmed. ??However, whether this should be maintained using potassium supplements or an aldosterone antagonist such as spironolactone is currently unknown. Spironolactone reduces mortality in heart failure patients, and also raises potassium levels. Potassium supplements, on the other hand, are commonly used, and yet their long-term effects on outcomes are unknown.?
