Sodium Channelopathy Underlying Familial Sick Sinus Syndrome With Early Onset and Predominantly Male Characteristics

Background-Sick sinus syndrome (SSS) is a common arrhythmia often associated with aging or organic heart diseases but may also occur in a familial form with a variable mode of inheritance. Despite the identifcation of causative genes, including cardiac Na channel (SCN5A), the pathogenesis and molecular epidemiology of familial SSS remain undetermined primarily because of its rarity. Methods and Results-We genetically screened 48 members of 15 SSS families for mutations in several candidate genes and determined the functional properties of mutant Na channels using whole-cell patch clamping. We identifed 6 SCN5A mutations including a compound heterozygous mutation. Heterologously expressed mutant Na channels showed loss-of-function properties of reduced or no Na current density in conjunction with gating modulations. Among 19 family members with SCN5A mutations, QT prolongation and Brugada syndrome were associated in 4 and 2 individuals, respectively. Age of onset in probands carrying SCN5A mutations was signifcantly less (mean±SE, 12.4±4.6 years; n=5) than in SCN5A-negative probands (47.0±4.6 years; n=10; P<0.001) or nonfamilial SSS (74.3±0.4 years; n=538; P<0.001). Meta-analysis of SSS probands carrying SCN5A mutations (n=29) indicated profound male predominance (79.3%) resembling Brugada syndrome but with a considerably earlier age of onset (20.9±3.4 years). Conclusions-The notable pathophysiological overlap between familial SSS and Na channelopathy indicates that familial SSS with SCN5A mutations may represent a subset of cardiac Na channelopathy with strong male predominance and early clinical manifestations

An Angiotensin Receptor Blocker and Spironolactone Enabled A Withdrawal from Furosemide and KCl in A Patient with Pseudo-Bartter\u27s Syndrome

A 30-year-old woman with pseudo-Bartter\u27s syndrome was referred to our department because of hypokalemic symptoms caused by outrageous abuse of furosemide and by KCl infusion administered to compensate for it. As an attempt to break this vicious cycle, we first tried to change furosemide with azosemide, a long-lasting loop diuretics, to avoid acute excessive diuresis and excretion of potassium. Administration of losartan effectively attenuated the concentration of extremely activated plasma aldosterone. Administration of spironolactone reduced aldosterone breakthrough induced by losartan and the patient was released from both furosemide and KCl. Blocking renin-angiotensin-aldosterone system demonstrated to be an effective treatment for pseudo-Bartter\u27s syndrome by the improvement of the total body potassium level which was decreased before treatment

Rivaroxaban Therapy Resulting in the Resolution of Right Atrial Thrombosis Resistant to Ordinary Control with Warfarin in a Patient with Atrial Fibrillation

A 72-year-old man with non-valvular atrial fibrillation and metastatic liver and lung cancer after surgery for colon cancer developed thrombosis in the right atrium one month after decreasing the dose of warfarin due to the introduction of double anti-platelet therapy for coronary stent implantation. Restoring the warfarin dose with ordinary control for two months did not result in any changes in the size of the thrombus; however, the subsequent substitution of rivaroxaban (oral treatment with a direct Factor Xa inhibitor) for warfarin ultimately resolved the thrombosis

Rivaroxaban Therapy Resulting in the Resolution of Right Atrial Thrombosis Resistant to Ordinary Control with Warfarin in a Patient with Atrial Fibrillation

A 72-year-old man with non-valvular atrial fibrillation and metastatic liver and lung cancer after surgery for colon cancer developed thrombosis in the right atrium one month after decreasing the dose of warfarin due to the introduction of double anti-platelet therapy for coronary stent implantation. Restoring the warfarin dose with ordinary control for two months did not result in any changes in the size of the thrombus; however, the subsequent substitution of rivaroxaban (oral treatment with a direct Factor Xa inhibitor) for warfarin ultimately resolved the thrombosis

Postural Orthostatic Tachycardia in a Patient with Type 2 Diabetes with Diabetic Neuropathy

24-year-old Japanese man with type 2 diabetes mellitus and diabetic neuropathy was admitted to our ward to evaluate the cause of orthostatic intolerance. During a head-up tilt test, his heart rate increased from 105 to 155 beats/minute within 3 minutes, and chest discomfort began. He was diagnosed with postural orthostatic tachycardia syndrome (POTS), and orthostatic intolerance disappeared after β-blocker treatment. Scintigraphy using123I-metaiodobenzylguanidine showed decreased cardiac uptake. Power spectral analysis of heart rate variability for 24 hours in Holter electrocardiography demonstrated decreases in both sympathetic and parasympathetic nervous system activities, with a greater decrease in parasympathetic activity than sympathetic activity. The relative sympathetic hyperactivity in the present patient with diabetic neuropathy seemed to be related to POTS

Cardiogenic Shock due to Left Ventricular Outflow Obstruction and Complete Atrioventricular Block in a Patient with Hypertrophic Cardiomyopathy with Acute Myocarditis

A 67-year-old woman was referred to our hospital with a sudden syncopal attack. She suffered from cardiogenic shock due to left ventricular (LV) outflow stenosis with simultaneous complete atrioventricular (AV) block. An endomyocardial biopsy of the left ventricle demonstrated myocardial disarray and myocardial fibrous and edematous tissue with infiltration of mononuclear cells. Cardiac magnetic resonance imaging (cMRI) detected a damaged septal area that was likely associated with the conduction disturbance. The diagnosis was hypertrophic cardiomyopathy accompanied by acute myocarditis. Although the LV outflow stenosis was transient, the complete AV block was persistent, thus requiring permanent pacemaker implantation

Relationships Between Clinical Characteristics and Decreased Plakoglobin and Connexin 43 Expressions in Myocardial Biopsies From Patients With Arrhythmogenic Right Ventricular Cardiomyopathy

Reduced expressions of plakoglobin and connexin 43 have been reported in the myocardium of patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). However, the relationships between these expression abnormalities and the clinical features of ARVC remain unknown. The expressions of plakoglobin and connexin 43 in myocardial biopsy specimens from 10 patients with confirmed ARVC, and 13 control patients without ARVC (non-ARVC; hypertrophic cardiomyopathy, n = 7; dilated cardiomyopathy, n = 6), were examined by immunostaining to evaluate the relationships between these expressions and the clinical characteristics of ARVC. The ratios of plakoglobin/N-cadherin and of plakoglobin/connexin 43 expressions were significantly lower in the ARVC group than in the control group. Significantly more patients had decreased plakoglobin expression in the ARVC group than in the control group (9/10 versus 7/13; P = 0.0376). Sustained ventricular tachycardia occurred more frequently in patients with ARVC and with decreased expressions of both plakoglobin and connexin 43 than in those with decreased expression of plakoglobin alone (5/5 versus 1/4, P = 0.048). Decreased expressions of both connexin 43 and plakoglobin in the myocardium might be associated with the development of arrhythmia in ARVC