CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Ilan Goldenberg, MD* and
Arthur J. Moss, MD
* Heart Research Follow-Up Program, Box 653, University of Rochester Medical Center, Rochester, New York 14642 (Email: Ilan.Goldenberg{at}heart.rochester.edu).
We thank Dr. Kapoor for his interest in our study (1). He suggests that potassium-raising therapies should be added to the therapeutic regimen of patients with congenital long QT syndrome (LQTS) who carry mutations that lead to a reduction in the outward potassium current. This recommendation is based on the results of an early study by Compton et al. (2) that showed an improvement in several repolarization parameters after short-term administration of oral spironolactone and intravenous potassium chloride in 7 long QT syndrome type 2 (LQT2) patients, and on a more recent study by Etheridge et al. (3) that showed a significant reduction in the duration of the corrected QT interval in 8 LQT2 genotype carriers after longer-term (4-week) combined therapy of oral potassium chloride and spironolactone targeted to increase serum potassium levels to 1.5 mEq/l above baseline. These promising preliminary data, however, should be interpreted with caution because currently information regarding the clinical efficacy of potassium-increasing therapies in LQTS patients is not available, and an electrocardiographic response may not always correlate with clinical response in affected subjects.
After the study by Compton et al. (2), Drs. Mason, Moss, and their associates (unpublished data, November 2002) initiated a collaborative randomized, placebo-controlled trial of potassium supplement plus spironolactone versus placebo in LQT2 patients. The study used conservative potassium doses, as suggested by Compton et al. (2), but was terminated early because of safety issues involving potassium supplement-related hyperkalemia. Thus, until further data regarding the safety and efficacy of this therapeutic regimen are available, we are reluctant to recommend chronic potassium-spironolactone supplement in this population. We do, however, agree with Dr. Kapoor that it is important to avoid hypokalemia in LQTS patients, particularly among those with the LQT2 genotype, in whom efforts should be made to maintain serum potassium levels in the 4 to 5 mEq/l range.
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1. Goldenberg I, Moss AJ. Long QT syndome J Am Coll Cardiol 2008;51:2291-2300.[Abstract/Free Full Text]2. Compton SJ, Lux RL, Ramsey MR, et al. Genetically defined therapy of inherited long-QT syndrome. Correction of abnormal repolarization by potassium. Circulation 1996;94:1018-1022.[Abstract/Free Full Text] 3. Etheridge SP, Compton SJ, Tristani-Firouzi M, Mason JW. A new oral therapy for long QT syndrome: long-term oral potassium improves repolarization in patients with HERG mutations J Am Coll Cardiol 2003;42:1777-1782.[Abstract/Free Full Text]
Related Article
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Inherited Long QT Syndromes: Be Mindful of the Potassium Level
- John R. Kapoor
J. Am. Coll. Cardiol. 2008 52: 1605.
[Full Text]
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