Fluctuating magnetic droplets immersed in a sea of quantum spin liquid.

The search of quantum spin liquid (QSL), an exotic magnetic state with strongly fluctuating and highly entangled spins down to zero temperature, is a main theme in current condensed matter physics. However, there is no smoking gun evidence for deconfined spinons in any QSL candidate so far. The disorders and competing exchange interactions may prevent the formation of an ideal QSL state on frustrated spin lattices. Here we report comprehensive and systematic measurements of the magnetic susceptibility, ultralow-temperature specific heat, muon spin relaxation (µSR), nuclear magnetic resonance (NMR), and thermal conductivity for NaYbSe2 single crystals, in which Yb3+ ions with effective spin-1/2 form a perfect triangular lattice. All these complementary techniques find no evidence of long-range magnetic order down to their respective base temperatures. Instead, specific heat, µSR, and NMR measurements suggest the coexistence of quasi-static and dynamic spins in NaYbSe2. The scattering from these quasi-static spins may cause the absence of magnetic thermal conductivity. Thus, we propose a scenario of fluctuating ferrimagnetic droplets immersed in a sea of QSL. This may be quite common on the way pursuing an ideal QSL, and provides a brand new platform to study how a QSL state survives impurities and coexists with other magnetically ordered states.

Aggravation of atrial arrhythmia by amiodarone during the perinatal period: A case report.

RATIONALE: Amiodarone, a broad-spectrum antiarrhythmic drug, is widely used for the clinical treatment of tachyarrhythmias because of its safety and efficacy. PATIENT CONCERNS: A 30-year-old woman presented with known paroxysmal atrial tachycardia and severe preeclampsia. Two days before admission, she had given birth to twins. She described her symptoms as a sudden palpitation at 10:20 accompanied by chest tightness and shortness of breath. DIAGNOSIS: Cardiac arrhythmia and acute left heart failure. INTERVENTIONS: Furosemide and sodium nitroprusside were administered to control the heart failure. At 16:20, 150 mg amiodarone (15 mg/min) was injected intravenously and continued at 1 mg/min. At 16:50, her electrocardiogram showed possible atrial tachycardia or atrial flutter with a ventricular rate of 206 beats/min. Administration of amiodarone was stopped at 17:23, and the medication was changed to esmolol. OUTCOMES: After 3 minutes, the palpitations stopped, the heart rate changed to a sinus rhythm, and the ventricular rate was 100 beats/min. Four days later, the patient underwent an electrophysiologic study and radiofrequency ablation. LESSONS: When amiodarone is used to treat atrial arrhythmia, the ventricular rate may accelerate, which can cause patients with borderline heart failure to develop acute heart failure or further deterioration of acute heart failure. For heart failure induced or mediated by atrial arrhythmias, short-term ß-blockers may be used to control the ventricular rate more quickly and effectively and to prevent the progression of heart failure.

Cryoballoon ablation for paroxysmal atrial fibrillation in a case of persistent left superior vena cava.

BACKGROUND: Atrial fibrillation (AF) usually originates from pulmonary veins (PVs) but can also be caused by pulmonary veins outside, such as the coronary sinus (CS), the superior vena cava (SVC), and the ligament of Marshall. CASE PRESENTATION: A 69-year-old male with a history of palpitations for 10 years was referred to our institute because of its recurrence for half a day. A dynamic electrocardiogram revealed sinus rhythm (SR) and paroxysmal AF. Echocardiography demonstrated normal cardiac structure, and physical examination results were unremarkable. However, computed tomography angiography (CTA) showed a persistent left superior vena cava (LSVC) but no indication of thrombosis in the left atria. A cryoablation catheter was inserted into the PV. After the PV was successfully isolated, AF was still observed. After cardioversion was synchronized, SR was detected, but AF occurred again in less than a minute. Finally, we observed ectopic atrial electrical activity originating from the LSVC and successfully ablated it. CONCLUSIONS: An LSVC may be a substrate for initiating or perpetuating atrial arrhythmia. Cryoballoon ablation can help treat AF originating from the LSVC.