From the Guidelines
Yes, hyperkalemia can cause bradycardia, as evidenced by the most recent study in 2021 1. Hyperkalemia, defined as a serum potassium level above 5.5 mEq/L, affects cardiac conduction by altering the resting membrane potential of cardiac cells. As potassium levels rise, the heart's electrical system becomes progressively impaired. Initially, hyperkalemia causes peaked T waves on ECG, but as levels increase further, it leads to PR interval prolongation, QRS widening, and eventually bradycardia or even asystole in severe cases. The mechanism involves potassium's effect on sodium channels, causing them to remain in an inactivated state and slowing cardiac depolarization. Key points to consider in the management of hyperkalemia include:
- The risk of mortality, cardiovascular morbidity, progression of CKD, and hospitalization is increased in patients with hyperkalemia, especially those with CKD, HF, and diabetes 1.
- A U-shaped curve exists between serum K+ and mortality, with both hyperkalemia and hypokalemia associated with adverse clinical outcomes 1.
- Treatment of hyperkalemia-induced bradycardia requires urgent lowering of potassium levels through interventions such as calcium gluconate to stabilize cardiac membranes, insulin with glucose to shift potassium intracellularly, sodium bicarbonate if acidosis is present, and potentially dialysis in severe cases 1.
- Patients with bradycardia due to hyperkalemia may require temporary cardiac pacing until potassium levels normalize. It is essential to note that the optimal range for serum K+ concentrations varies according to individual patient comorbidities, such as CKD, HF, or diabetes 1. In patients with CKD, compensatory mechanisms may result in tolerance to elevated circulating K+, and several studies have suggested that hyperkalemia is a less threatening condition in CKD 1. However, the most critical consideration is to prioritize the management of hyperkalemia to prevent life-threatening complications, such as bradycardia and cardiac arrest, as supported by the latest evidence from 2021 1.
From the Research
Hyperkalemia and Bradycardia
- Hyperkalemia can cause bradycardia, as evidenced by a study published in 2022 2, which found that severe bradycardia is an under-studied manifestation of hyperkalemia, potentially associated with adverse outcomes.
- The study 2 described emergency department patients who presented with severe bradycardia and severe hyperkalemia, and found that cardiovascular and renal comorbidities were common among these patients.
- Another study published in 2019 3 reported a case of synergistic bradycardia caused by hyperkalemia, renal failure, and beta blocker use, highlighting the importance of considering multiple causes of bradycardia in patients with hyperkalemia.
Mechanisms and Risk Factors
- Hyperkalemia can alter the cellular transmembrane potential and cause life-threatening arrhythmias, including bradycardia 4.
- Patients with decreased renal excretion, excess potassium intake, or potassium shifting from the intra- to the extracellular space are at risk of developing hyperkalemia, which can increase the risk of morbidity and mortality 4.
- Heart failure patients with comorbid renal insufficiency and/or diabetes mellitus are at increased risk of developing hyperkalemia, which can constitute a common reason for insufficient up-titration, down-titration, or discontinuation of prognostically relevant heart failure medications 4.
Clinical Management
- The treatment of hyperkalemia has evolved, with new oral potassium binders and other agents available to enhance treatment opportunities 5, 6, 4.
- Patients with hyperkalemia should be monitored closely, as it is associated with adverse outcomes, and new therapies have demonstrated effective control, offering hope for potential use in patients who would benefit from diet or medications associated with an increase in serum potassium 6.