Research published in the European Heart Journal suggests that patients with heart failure (HF) with low to low-normal serum potassium levels are at increased risk of dying.
Lead investigator Dr Ali Ahmed, of the University of Alabama at Birmingham, USA, said: “Our findings showed that HF patients with low to low-normal (<4.0mEq/l) potassium levels were more likely to die than those with higher levels (4.0–5.5mEq/l) of potassium. These patients were not significantly more likely to be hospitalised than the higher potassium group, suggesting that most low potassium associated deaths were sudden deaths due to ventricular arrhythmias.”
Dr Ahmed and team studied 6,845 HF patients in the Digitalis Investigation Group trial with serum potassium levels at 5.5mEq/l. The researchers calculated propensity scores for each patient and used these to match 1,187 patients with low potassium to 1,187 with normal potassium levels.
Over a median follow-up of 37 months, there were 441 deaths from any cause among the low-potassium patients (1,330/10,000 person-years) compared with 379 among the normal-potassium patients (1,103/10,000 person-years; hazard ratio =1.25, p=0.006).
Cardiovascular mortality was also higher in the low-potassium group, at 356 deaths (1,074/10,000 person-years) versus 297 deaths (864/10,000 person-years; HR=1.13, p=0.009), as was hospitalisation for cardiovascular events (HR=1.13, p=0.082).
“It would appear that the threshold for low potassium, 3.5mEq/l, needs to be raised for chronic HF and that any of these patients with a potassium level less than 4mEq/l should be considered as having low potassium and thus at increased risk of death,” Dr Ahmed commented.
He added that the findings suggest that low potassium levels in patients with HF should be corrected and potassium should be maintained at above 4.0mEq/l.
“However, whether this should be maintained using potassium supplements or an aldosterone antagonist such as spironolactone is currently unknown.
“Spironolactone reduces mortality in HF 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.”
Eur Heart J 2007;28:1334-43