Cardiac sarcoidosis (CS) can be silent in most patients with extrapulmonary sarcoidosis. Atrioventricular (AV) block is the most common clinical presentation, but it can also present as fatal ventricular arrhythmias and sudden cardiac death. Endomyocardial biopsy is the gold standard; however, it is not sensitive since CS can involve the myocardium in a patchy distribution. Our case depicts a female who presented with syncope; however, her hospital course was complicated by multiple cardiac arrests. Her initial laboratory tests, including an autoimmune workup, were unremarkable. Cardiac magnetic resonance and fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging revealed intramyocardial delayed enhancement of the basal anteroseptal (non-ischemic distribution) and patchy foci of increased uptake in the anteroseptal and inferior myocardial region, respectively. The patient was started on intravenous methylprednisolone, and her condition slowly improved. Post-discharge, the patient followed in the outpatient clinic with a repeat FDG-PET scan revealing resolution of myocardial FDG uptake. She also underwent bronchoscopy with lymph node biopsy showing granulomas and endobronchial biopsy confirming pulmonary sarcoidosis.

Bradycardia, renal failure, atrioventricular (AV) blockade, shock, and hyperkalemia (BRASH) syndrome is an uncommon and relatively new entity that results from synergy between AV nodal blockade and renal failure leading to a vicious cycle of hypotension, profound bradycardia, and hyperkalemia. Classically, this syndrome is seen in a patient taking AV nodal blocking agents and underlying renal insufficiency. We are presenting a case of a 76-year-old female with a medical history of essential hypertension and non-insulin-dependent type 2 diabetes mellitus presented to the emergency room with a chief complaint of dizziness and generalized weakness. The patient was taking metoprolol tartrate 200 mg twice a day, amlodipine 10 mg once daily, clonidine 0.1 mg twice daily, enalapril 20 mg twice daily, and Metformin 750 mg twice daily. On presentation, the patient had symptomatic bradycardia resistant to atropine with heart rate in 30s and hypotension resistant to volume expansion. The laboratory results showed that the patient also had acute kidney injury and severe resistant hyperkalemia. The whole presentation raised the suspicion of BRASH syndrome. The patient was started on peripheral dopamine infusion for bradycardia and symptomatic hypotension. Nephrology was consulted, and the patient was started on urgent dialysis for resistant hyperkalemia. The patient was admitted to the cardiovascular intensive care unit, and all antihypertensive medication, including beta-blockers, were stopped. The patient clinically improved on the next day, the dopamine infusion was stopped, and the patient remained vitally stable. The patient was eventually discharged home with cardiology and nephrology follow-up. The purpose of this case report is to help with the early diagnosis of this under-recognized and new clinical condition and to discuss the pathophysiology and management.

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The relative influence of momentum diffusivity and thermal diffusivity, in terms of the Prandtl number (Pr), on the finite-amplitude instability of a non-isothermal annular Poiseuille flow (NAPF) is analyzed. The limiting value of the growth of instabilities under nonlinear effects is studied by deriving a cubic Landau equation. Emphasis is given especially on studying the impact of the low Prandtl number and the curvature parameter (C) on the bifurcation and the pattern variation of the secondary flow for both axisymmetric and non-axisymmetric disturbances. The finite-amplitude analysis predicts that in contrast to NAPF of water or fluid with Pr ≥ O(1) where the flow is supercritically unstable, the NAPF of low Pr fluids, particularly liquid metals, has shown both supercritical and subcritical bifurcation in the vicinity as well as away from the critical point. The nonlinear interaction of different harmonics for the liquid metal predicts a lower heat transfer rate than those by the laminar flow model, whereas for a fluid with Pr > 2, it is the other way. The maximum heat transfer takes place for the considered minimum value of C. For fluids with low Pr, a probable lower critical Rayleigh number is obtained. The corresponding variation in neutral stability curves as a function of wavenumber reveals that the instability that is supercritical for some wavenumber may be subcritical or vice versa at other nearby wavenumbers. The structural feature of the pattern of the secondary flow under the linear theory differs significantly from those of the secondary flow under nonlinear theory away from the bifurcation point. This is a consequence of the intrinsic interaction of different harmonics that are responsible for the stabilizing or the destabilizing nature of different components in the disturbance kinetic energy balance.

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