JS-NG-8: CASE REPORT: POSSIBLE NEW CHANNELOPATHY ASSOCIATED WITH ELEVATED ALDOSTERONE LEVELS

Abstract

Background: Potassium channelopathies are associated with prolonged QT cardiac syndrome. New potassium channelopathies in somatic cells, including KCNJ5 mutations, also underlie some forms of primary hyperaldosteronism. We present a first-in-human report of an association between a KCNQ1 loss of function mutation manifesting with life threatening-ventricular tachycardia (VT), severe hypokalemia and presumed hyperaldosteronism. Case Presentation: The patient is a 51-year-old Asian woman known for obesity, Wolff-Parkinson-White post ablation, and recurrent syncopal episodes with polymorphic VT due to prolonged QTc, requiring an implantable cardioverter defibrillator. On initial presentation for syncope, spontaneous hypokalemia was discovered at 3.1 mmol/L. She had multiple hospitalizations for torsade storms and persistent hypokalemia resistant to aggressive potassium supplementation until addition of spironolactone. Investigations revealed a suppressed plasma renin activity < 0.05 ng/L/s, serum aldosterone concentration at 302 pmol/L, and an aldosterone to renin ratio (ARR) > 6040. Repeated ARR was > 10980. Confirmatory saline suppression testing or adrenal vein sampling were not performed due to risk of recurrent VT associated with spironolactone cessation. A comprehensive evaluation for the etiology of this patient's clinical presentation revealed a mutation in the KCNQ1 gene type 1. Literature review: The voltage-dependent K(+) channel responsible for activating delayed K(+) current is composed of pore-forming KCNQ1 and regulatory KCNE1/3 subunits which loss of function predispose to sustained torsade de pointes. Animal models demonstrate that KCNQ1 and KCNE1 mRNAs are expressed in the zona glomerulosa of adrenal glands where potassium channels directly participate in the control of aldosterone production. Although KCNE3 is not expressed in mouse adrenals, its deletion is thought to cause activation of lymphocytes targeting adrenal glands, leading to hyperaldosteronism. Furthermore, administration of spironolactone to KCNE3 knockout mice ameliorates their QT prolongation and predisposition to VT. There have been no case reports of an association between KCNQ1/E1/E3 loss of function and hyperaldosteronism in humans. Conclusion: This raises the question if this mechanism can also be a component of human KCNQ1 and KCNE1/3-linked arrhythmogenesis and hyperaldosteronism. Alternatively, we can further speculate that patients with hyperaldosteronism who develop malignant arrhythmias during hypokalemia are subjects with impaired repolarization reserve as a consequence of variants in genes known to cause long QT syndrome. The variants, leading to subclinical ion channel dysfunction, are typically silent until unmasked by electrolytes abnormalities such as hypokalemia. To our knowledge, this case is a first report of a potentially novel channelopathy associated with hyperaldosteronism in humans. These findings are hypothesis generating and require further investigations.