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Effect of moderate potassium-elevating treatment in long QT syndrome: the TriQarr Potassium Study

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BACKGROUND: In long QT syndrome (LQTS), beta blockers prevent arrhythmias. As a supplement, means to increase potassium has been suggested. We set to investigate the effect of moderate potassium elevation on cardiac repolarisation.

METHODS: Patients with LQTS with a disease-causing KCNQ1 or KCNH2 variant were included. In addition to usual beta-blocker treatment, patients were prescribed (1) 50 mg spironolactone (low dose) or (2) 100 mg spironolactone and 3 g potassium chloride per day (high dose+). Electrocardiographic measures were obtained at baseline and after 7 days of treatment.

RESULTS: Twenty patients were enrolled (10 low dose and 10 high dose+). One patient was excluded due to severe influenza-like symptoms, and 5 of 19 patients completing the study had mild side effects. Plasma potassium in low dose did not increase in response to treatment (4.26±0.22 to 4.05±0.19 mmol/L, p=0.07). Also, no change was observed in resting QTcF (QT interval corrected using Fridericia's formula) before versus after treatment (478±7 vs 479±7 ms, p=0.9). In high dose+, potassium increased significantly from 4.08±0.29 to 4.48±0.54 mmol/L (p=0.001). However, no difference in QTcF was observed comparing before (472±8 ms) versus after (469±8 ms) (p=0.66) high dose+ treatment. No patients developed hyperkalaemia.

CONCLUSION: In patients with LQTS, high dose+ treatment increased plasma potassium by 0.4 mmol/L without cases of hyperkalaemia. However, the potassium increase did not shorten the QT interval and several patients had side effects. Considering the QT interval as a proxy for arrhythmic risk, our data do not support that potassium-elevating treatment has a role as antiarrhythmic prophylaxis in patients with LQTS with normal-range potassium levels.

TRIAL REGISTRATION NUMBER: NCT03291145.

Original languageEnglish
Article numbere001670
JournalOpen Heart
Volume8
Issue number2
ISSN2053-3624
DOIs
Publication statusPublished - Sep 2021

Bibliographical note

© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

    Research areas

  • Adult, Biomarkers/blood, Dose-Response Relationship, Drug, Electrocardiography, Electrocardiography, Ambulatory/methods, Female, Follow-Up Studies, Heart Rate/physiology, Humans, Long QT Syndrome/blood, Male, Potassium Chloride/administration & dosage, Potassium/blood, Prospective Studies

ID: 71930329