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Association between potassium level and outcomes in heart failure with reduced ejection fraction: a cohort study from
Lauren B Cooper1,2, Lina Benson3, Robert J Mentz2
1Inova Heart & Vascular Institute, Falls Church, VA, USA.
Insights
The optimal potassium level for heart failure patients is 4.2 mmol/L. Both low potassium (hypokalemia) and high potassium (hyperkalemia) increase mortality risk, with hypokalemia linked to long-term and hyperkalemia to short-term outcomes.
Area of Science:
- Cardiology
- Clinical Biochemistry
- Public Health
Background:
- Potassium levels (hyperkalemia and hypokalemia) are common in heart failure patients and linked to adverse outcomes.
- The ideal potassium range for patients with heart failure and reduced ejection fraction remains undetermined.
Purpose of the Study:
- To identify the optimal baseline potassium range in patients with heart failure and reduced ejection fraction (ejection fraction < 40%).
- To investigate the association between baseline potassium levels and short-term and long-term mortality in this patient group.
Main Methods:
- Utilized data from the Swedish Heart Failure Registry (2006-2012) including 13,015 patients.
- Employed Cox regression models, including stratified and restricted cubic spline analyses, to assess the relationship between potassium levels and all-cause mortality at 30 days, 12 months, and maximal follow-up.
Main Results:
- The potassium level associated with the lowest mortality risk was 4.2 mmol/L, with risk increasing significantly at levels above and below this value.
- Hypokalemia (<3.5 mmol/L) and hyperkalemia (>5.0 mmol/L) were more prevalent in patients with poorer kidney function and more severe heart failure.
- Adjusted analyses revealed that hypokalemia independently predicted increased mortality at 12 months and maximal follow-up, while hyperkalemia predicted increased mortality at 30 days.
Conclusions:
- The relationship between potassium levels and mortality in heart failure patients is U-shaped, with an optimal level of 4.2 mmol/L.
- Hypokalemia is associated with increased long-term mortality, whereas hyperkalemia is associated with increased short-term mortality in heart failure patients.
Aims:
Hyperkalaemia and hypokalaemia are common in heart failure and associated with worse outcomes. However, the optimal potassium range is unknown. We sought to determine the optimal range of potassium in patients with heart failure and reduced ejection fraction (< 40%) by exploring the relationship between baseline potassium level and short- and long-term outcomes using the Swedish Heart Failure Registry from 1 January 2006 to 31 December 2012.
Methods And Results:
We assessed the association between baseline potassium level and all-cause mortality at 30 days, 12 months, and maximal follow-up, in uni- and multivariable stratified and restricted cubic spline Cox regressions. Of 13 015 patients, 93.3% had potassium 3.5-5.0 mmol/L, 3.7% had potassium <3.5 mmol/L, and 3.0% had potassium >5.0 mmol/L. Potassium <3.5 mmol/L and >5.0 mmol/L were more common with lower estimated glomerular filtration rate and heart failure of longer duration and greater severity. The potassium level associated with the lowest hazard risk for mortality at 30 days, 12 months, and maximal follow-up was 4.2 mmol/L, and there was a steep increase in risk with both higher and lower potassium levels. In adjusted strata analyses, lower potassium was independently associated with all-cause mortality at 12 months and maximal follow-up, while higher potassium levels only increased risk at 30 days.
Conclusion:
In this nationwide registry, the relationship between potassium and mortality was U-shaped, with an optimal potassium value of 4.2 mmol/L. After multivariable adjustment, hypokalaemia was associated with increased long-term mortality but hyperkalaemia was associated with increased short-term mortality.
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