Hot Line 1: POTCAST
30 Aug 2025
Hot Line ESC Congress 2025 Is there benefit from mid-to-high normal potassium levels in patients at high risk of ventricular arrhythmias implanted with an ICD?
Yesterday, Doctor Christian Jons (Rigshospitalet - Copenhagen University Hospital - Copenhagen, Denmark) presented key findings from the POTCAST trial. Explaining the rationale, he said: “There is some evidence from observational studies to suggest that low plasma potassium levels are associated with increased risk of ventricular arrhythmias and that potassium levels in the upper normal level have protective effects.1 We conducted the POTCAST trial to assess the benefits and risks of targeting mid-to-high normal potassium levels in patients at high risk of ventricular arrhythmias with an implantable cardioverter defibrillator (ICD).”
This open-label Danish trial included participants with an ICD or cardiac resynchronisation therapy defibrillator and baseline plasma potassium ≤4.3 mmol/l. They were randomised to a treatment regimen aiming at increasing plasma potassium level to 4.5–5.0 mmol/l, using dietary guidance, potassium supplements and/or mineralocorticoid receptor antagonist therapy, or to standard care. The primary endpoint was a composite of sustained ventricular tachycardia >125 bpm lasting >30 seconds, any appropriate ICD therapy, unplanned hospitalisation (>24 hours) due to arrhythmia or heart failure, and all-cause mortality.
Among 1,200 randomised patients, the mean age was 62.7 years and 19.8% were women. From mean baseline levels of 4.01 mmol/l, plasma potassium levels reached a mean of 4.36 mmol/l in the high-normal potassium group compared with 4.05 mmol/l in the control group after 6 months.
After median follow-up of 39.6 months, the primary endpoint was significantly lower in the high-normal potassium group than in the control group.
A primary outcome event occurred in 22.7% of patients in the high-normal potassium group and 29.2% in the control group (hazard ratio [HR] 0.76; 95% CI 0.61 to 0.95; p=0.015). The effect was consistent across prespecified subgroups, including ischaemic heart disease and heart failure. Any appropriate ICD therapy (shock therapy or anti-tachycardia pacing) was the main driver of the difference, occurring in 15.3% of participants in the high-normal potassium group and 20.3% in the control group (HR 0.75; 95% CI 0.57 to 0.80). A total of 5.7% in the high-normal potassium group and 6.8% in the control group died (HR 0.85; 95% CI 0.54 to 1.34).
Regarding safety outcomes, hospitalisation due to hyper- or hypokalaemia occurred in 1% of participants in both groups.
Senior author, Professor Henning Bundgaard (Rigshospitalet - Copenhagen University Hospital - Copenhagen, Denmark), said: “A treatment-induced increase in plasma potassium level of approximately 0.3 mmol/l significantly reduced the arrhythmia burden without increasing the combined risk of hyper- or hypokalaemia. The benefits occurred across cardiovascular disease types and regardless of the method used to increase potassium levels. We believe the time is right for clinicians to consider increasing potassium levels to the mid-to-high normal range as an inexpensive and widely available treatment strategy in patients with a broad spectrum of cardiovascular diseases associated with a high risk of ventricular arrhythmia.”
References
- Ferreira JP, et al. J Am Coll Cardiol. 2020;75:2836–2850.
