Is there benefit from mid-to-high normal potassium levels in patients with an ICD?

On Friday, the 29^th of August, 2025, at ESC Congress, Dr. Christian Jons (Rigshospitalet – Copenhagen University Hospital, Denmark) presented key findings from the Danish POTCAST trial. The study assessed whether targeting mid-to-high normal plasma potassium levels (4.5–5.0 mmol/l) could improve outcomes in patients at high risk of ventricular arrhythmias with an implantable cardioverter defibrillator (ICD).

In this open-label, randomised trial of 1,200 patients with baseline potassium ≤ 4.3 mmol / l, treatment strategies (dietary guidance, supplements, mineralocorticoid receptor antagonists) achieved an average increase of 0.3 mmol / l compared with standard care. 

After a median follow-up of nearly 40 months, the primary composite outcome (sustained VT, appropriate ICD therapy, arrhythmia / HF hospitalisation, or all-cause mortality) occurred in 22.7 % of patients in the high-normal potassium group versus 29.2 % in controls (HR 0.76; 95 % CI 0.61–0.95; p = 0.015). The difference was driven mainly by fewer appropriate ICD therapies. Importantly, rates of hospitalisation due to hyper- or hypokalaemia were low and similar (1 %). 

According to senior author Professor Henning Bundgaard, “A treatment-induced increase in potassium of ~ 0.3 mmol/l significantly reduced arrhythmia burden without added safety concerns. We believe the time is right for clinicians to consider targeting mid-to-high normal potassium as a simple, inexpensive, and widely available treatment strategy in high-risk patients.”

Key highlights from the POTCAST Trial:

• Randomised 1,200 ICD patients with baseline Kn ≤ 4.3 mmol / l
• Intervention: dietary guidance, supplements, MRA vs. standard care
• Achieved + 0.3 mmol / l increase in potassium
• Primary outcome reduced: 22.7 % vs 29.2 % (HR 0.76; p = 0.015)
• Fewer appropriate ICD therapies (15.3 % vs 20.3 %)
• No excess in hyper- / hypokalaemia hospitalisations (1 % in both groups)