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Paroxysmal supraventricular arrhythmias during hypokalemic episodes in a patient with hypokalemic periodic paralysis/Hipokalemik periyodik paralizili bir hastada hipokalemik epizodlar sirasinda gelisen paroksismal supraventrikuler aritmiler.

Dear Editor,

A 21-year-old female patient was admitted to our hospital with severe muscle weakness, fatigue, unable to move all extremities and palpitation following a high carbohydrate meal. The patient described similar symptoms a week ago, which she recovered spontaneously in 48 hours. Her past and family history was unremarkable. Physical examination was notable for flaccid tetraparesis, decreased deep tendon reflexes, with sparing of the facial, oropharyngeal and respiratory muscles. Sensory testing was intact. Thyroid and other system examinations were unremarkable. Electrocardiography (ECG) on admission revealed supra-ventricular tachycardia (180 bpm) (Fig. 1A). Initial laboratory tests showed a potassium level of 2.67 mEq/L (normal range 3.5-5.1 mEq/L); all the other routine examinations and thyroid hormone levels were normal. She presented sinus rhythm after intravenous potassium replacement and diltia-zem (12.5 mg). Control potassium level showed 3.78 mEq/L. Electrophysiological study revealed dual AV nodal physiology, inability to induce any tachycardia and no ablation therapy. She discharged uneventfully. While she was asymptomatic for 2 months, the patient admitted to emergency room with palpitation again. ECG on admission showed atrial tachycardia (166 bpm) (Fig. 1B). In addition, biochemistry tests showed potassium level of 2.78 mEq/L. Her palpitation was resolved after intravenous potassium replacement again. She was referred for investigation of the reasons of hypokalemia. Serum potassium levels were normal in between emergency admissions. Also serum magnesium, sodium, calcium levels and thyroid function tests were in normal limits. Urinary potassium level was decreased (24 mEq/L). Urinary potassium/creatinine ratio was 0.50. Transtubular potassium gradient was 6.8 (normal range: 7-9). Arterial blood gas analysis showed no metabolic alkalosis. Serum renin, aldosterone and ACTH levels were normal. Adrenal gland imaging with computed tomography revealed normal findings. So, hypokalemic periodic paralysis was considered in differential diagnosis, which was confirmed by genetic testing (mutation in SCN4A, Arg669H). The patient was discharged with oral potassium supplement (potassium citrate 2.17 gr/ day plus potassium carbonate 2.0 gr/day) and avoidance of strenuous exercise and high carbohydrate diet. The 6-months follow-up was free of new paralysis and palpitation episodes.

Hypokalemic periodic paralysis is an autosomal dominant disorder which is accompanied by muscle weakness/paralysis and hypokalemia. Attacks can be induced by exercise, carbohydrate-rich meals and exposure to cold (1). In the heart, NaV channels are essential for the orderly progression of action potentials throughout the myocardium to stimulate rhythmic contraction. NaV 1.4 channels are expressed principally in the skeletal muscle cells, but there are some demonstrations that the SCN4A asubunit gene is expressed in normal human heart too (3).

[FIGURE 1 OMITTED]

As a result of increased duration of the action potential and refractory period, patients with hypokalemia are at increased risk for certain dysrhythmias like ventricular tachycardia. Extreme syncopal bradycardia and sinus arrest are rare findings in hypokalemia (4). In the literature, there was no association of hypokalemic periodic paralysis with supraventricular arrhythmias. Although it was a hypothesis, we thought that NaV 1.4 channels could play role in development of supraventricular tachycardias in such a case. So, this case is the first report regarding the occurrence of supraventricular tachycardias and hypokalemic periodic paralysis together.

References

(1.) Lin SH, Hsu YD, Cheng NL, Kao MC. Skeletal muscle dihydropyridine-sensitive calcium channel (CACNA1S) gene mutations in Chinese patients with hypokalemic periodic paralysis. Am J Med Sci 2005; 329: 66-70. [CrossRef]

(2.) Pereon Y, Lande G, Demolombe S, Nguyen The Tich S, Sternberg D, Le Marec H, et al. Paramyotonia congenita with an SCN4A mutation affecting cardiac repolarization. Neurology 2003; 60: 340-2. [CrossRef]

(3.) Kantola IM, Tarssanen LT. Familial hypokalemic periodic paralysis in Finland. J Neurol Neurosurg Psychiatry 1992; 55: 322-4. [CrossRef]

(4.) Maffe S, Signorotti F Perucca A, Bielli M, Hladnik U, Ragazzoni E, et al. Atypical arrhythmic complications in familial hypokalemic periodic paralysis. J Cardiovasc Med 2009; 10: 68-71. [CrossRef]

Ugur Canpolat, Hamza Sunman, Kudret Aytemir, Ali Oto

Department of Cardiology, Faculty of Medicine, Hacettepe University, Ankara-Turkey

Address for Correspondence/Yazisma Adresi: Dr. Ugur Canpolat

Hacettepe Universitesi Tip Fakultesi, Kardiyoloji Anabilim Dali, 06100 Sihhiye, Ankara-Turkiye

Phone: +90 312 305 17 80 Fax: +90 312 305 41 37

E-mail: dru_canpolat@yahoo.com

Available Online Date/Cevrimici Yayin Tarihi: 22.06.2012

doi: 10.5152/akd.2012.169
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Title Annotation:Letters to the Editors/Editore Mektuplar
Author:Canpolat, Ugur; Sunman, Hamza; Aytemir, Kudret; Oto, Ali
Publication:The Anatolian Journal of Cardiology (Anadolu Kardiyoloji Dergisi)
Article Type:Letter to the editor
Date:Sep 1, 2012
Words:710
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