Follow-up
ATRIAL FIBRILLATION, MAY, HEART
All patients completed the study and all patients in the intervention group reported full compliance to medication during the study period. Patients in the intervention group were given a mean daily dose of oral potassium supplement of 2,700 mg (~ 36 mmol) and mean dose of MRA of 23 mg. The mean difference in changes in p-K was 0.52 mmol/l (0.35; 0.69), P < 0.001 higher in the intervention as compared to the control group.The follow-up echocardiography was performed after a mean of 44 days (SD 18) after baseline, 47 days (SD 17) in the intervention group and 40 days (SD 18) in the control group (P = 0.22). Three patients were excluded from the final analysis: two due to poor image quality and one due to differences in rhythm at baseline and follow-up (sinus rhythm and atrial fibrillation) — Fig. 
Flowchart showing patient randomization in the POTCAST trial from June 1st 2020 until May 31st 2021 and derivation of study population in the current substudy
Changes in clinical characteristics and echocardiographic parameters between the intervention group (n = 25) and the control group (n = 22) from baseline to follow-up. Difference in changes is calculated as change in the intervention group relative to the control groupP-value for difference in mean change in the intervention group and the control groupDisplayed as mean (± SD) or number (%). A: Late diastolic mitral inflow velocity, E: early diastolic mitral inflow velocity, e’: Early diastolicmitral annular velocity, HR: Heart rate, LVEF: Left ventricular ejection fraction, GLS: Global Longitudinal Strain, MD: Mechanical dispersion, RV FWS: Right ventricular free wall strain, TAPSE: Tricuspid annular plane systolic excursion