Interim analysis
An interim analysis was performed with data from the trial to check the assumptions made in the sample size calculation. For this, at least 25 patients had to be included in both arms that had reached three months follow-up. We expected to find a larger difference between the arms in the proportion of patients with resistant hypertension at this time point due to the shorter follow-up time, as compared to results after 12 months of follow-up. At the time of the interim analysis, 27 patients in the intervention+SoC arm and 28 patients in the SoC arm were analyzed. In the intervention+SoC arm, the proportion of patients with resistant hypertension decreased to 75% and in the SoC arm to 59%. This decrease in resistant hypertension was higher than expected. However, there was a reversed improvement in resistant hypertension, with a difference between the two arms of 16% in the proportion of patients with resistant hypertension with a lower proportion of resistant hypertension in the SoC arm as compared to the intervention+SoC arm. Given these interim findings and difficulties with the inclusion and visits of patients due to COVID-19 restrictions, the inclusion of patients was stopped by the researchers before reaching the required number of patients to determine the efficacy of the intervention. However, because of ethical considerations, the complete protocol was carried out for patients already included in the trial.