Accelerated junctional

Vomiting is common in patients with digitalis overdose. Hyperkalemia may be caused by acute digitalis overdose or severe poisoning, whereas hypokalemia may be present in patients as a result of long-term diuretic treatment. (Digitalis does not cause hypokalemia.) A variety of cardiac rhythm disturbances may occur, including sinus bradycardia, AV block, atrial tachycardia with block, accelerated junctional rhythm, premature ventricular beats, bidirectional ventricular tachycardia, and other ventricular arrhythmias. 

Unifocal or multiform ventricular premature contractions, ventricular tachycardia, atrioventricular dissociation, accelerated junctional rhythm, and atrial tachycardia with block... 

B. With chronic intoxication, visual disturbances, weakness, sinus bradycardia, atrial fibrillation with slowed ventricular response rate or junctional escape rhythm, and ventricular arrhythmias (ventricular bigeminy or trigeminy, ventricular tachycardia, bidirectional tachycardia, and ventricular fibrillation) are common. Accelerated junctional tachycardia and paroxysmal atrial tachycardia with block are frequently seen. Hypokalemia and hypomagnesemia from chronic diuretic use may be evident and appear to worsen the tachyarrhythmias. 

IV. Diagnosis is based on a history of recent overdose or characteristic arrhythmias (eg, bidirectional tachycardia and accelerated junctional rhythm) in a patient receiving chronic therapy. Hyperkalemia suggests acute ingestion but may also be seen with very severe chronic poisoning. Senim potassium levels higher than 5.5 mEq/L are associated with severe poisoning. 

Similarly, some systems identify an event sensed on the ventricular channel of the pacemaker which is not preceded by an atrial event, either paced or sensed, as a premature ventricular contraction (PVC). PVC s have a very definite implication for the clinician. The pacemaker s definition is far more specific as the pacemaker cannot analyze the morphology of the complex. Hence, nonphysiologic make-break electrical potentials associated with an internal insulation failure or conductor fracture will also be identified as PVCs as will accelerated junctional rhythms or episodes of atrial undersensing but with intact AV nodal conduction. Some systems may also identify runs of ventricu-... 

Need to differentiate accelerated junctional rhythm from accelerated idioventricular rhythm (a possibly life-threatening arrhythmia)... 

Accelerated junctional rhythm and an accelerated Idioventricular rhythm appear similar but have different causes. To distinguish between them, closely examine the duration of the QRS complex, and then look for P waves. 

May be no symptoms because accelerated junctional rhythm has the same rate as sinus rhythm. 

Treatment for accelerated junctional rhythm involves identifying and correcting the underlying cause. 

Atrial and ventricular rhythms regular atrial rate 40 to 60 beats/minute ventricular rate usually 40 to 60 beat minute (60 to 100 beat minute is accelerated junctional rhythm). 

Imidazole antimycotics, ketoconazole, clotrimazole, and miconazole are potent inhibitors of various cytochrome P450-isoenzymes that also affect the metabolism of retinoids. They were fust shown to inhibit the metabolism of RA in F9 embryonal carcinoma cells. When tested in vitm liarazole, a potent CYP-inhibitor, suppressed neoplastic transformation and upregulated gap junctional communication in murine and human fibroblasts, which appeared to be due to the presence of retinoids in the serum component of the cell culture medium. Furthermore, liarazole magnified the cancer chemopreventive activity of RA and (3-carotene in these experiments by inhibiting RA-catabolism as demonstrated by absence of a decrease in RA-levels in the culture medium in the presence of liarazole over 48 h, whereas without liarazole 99% of RA was catabolized. In vivo, treatment with liarazole and ketoconazole reduced the accelerated catabolism of retinoids and increased the mean plasma all-irans-RA-concentration in patients with acute promyelocytic leukemia and other cancels. 

Fig. 5.5 SEM surface view and cross section of an electrodeposited, ca. 1 p.m thick, CdSe/li film subjected to accelerated photocorrosion by the apphcation of -0.1 V vs. Pt bias in polysulfide solution under a focused, high-power (1 W cm ) solar illumination for 30 min. The coherence of the as-deposited film morphology is evident. The authors emphasize that, even in this situation, the liquid junction nature prevents the flow of high leakage currents during the process (as it might be the case with a solid junction). (Reprinted from [99], Copyright 2009, with permission from Elsevier)...

The foregoing text highlights the fact that at the interface between electrolytic solutions of different concentrations (or between two different electrolytes at the same concentration) there originates a liquid junction potential (also known as diffusion potential). The reason for this potential lies in the fact that the rates of diffusion of ions are a function of their type and of their concentration. For example, in the case of a junction between two concentrations of a binary electrolyte (e.g., NaOH, HC1), the two different types of ion diffuse at different rates from the stronger to the weaker solution. Hence, there arises an excess of ions of one type, and a deficit of ions of the other type on opposite sides of the liquid junction. The resultant uneven distribution of electric charges constitutes a potential difference between the two solutions, and this acts in such a way as to retard the faster ion and to accelerate the slower. In this way an equilibrium is soon reached, and a steady potential difference is set up across the boundary between the solutions. Once the steady potential difference is attained, no further net charge transfer occurs across the liquid junction and the different types of ion diffuse at the same rate. 

Much of the discussion of this subsection has been based on the behavior of hydrogenated diodes annealed under reverse bias. Annealing under forward bias has also been studied, though less extensively, and some of the observations have suggested the possibility of a new type of thermal breakup of BH complexes, namely BH + e— B + H° (Tavendale et al., 1985, 1986a). These authors reported breakup of BH in a few hours at 300 K under forward bias, both in Schottky diodes and in n+-p junctions. However, in a similar experiment with an n+-p junction, Johnson (1986) found a slight buildup of BH under forward-bias anneal. Available details of the various experiments are too sketchy to allow useful speculation on the reasons for the different outcomes or possible mechanisms for accelerated breakup. 

Zeng R, Li X, and Gorodeski GI [2004] Estrogen abrogates transcervical tight junctional resistance by acceleration of Occludin modulation. J Clin Endocrinol Metab 89 5145-5155... 

The liquid junction potential always acts in such a way that the motion of ions that move rapidly is retarded, while the motion of the slower ions is accelerated. Accordingly, equilibrium is soon attained (within a few milliseconds of the two solutions being joined via a membrane), thus allowing a constant value of Ej to be recorded. The absolute magnitude of Ej will depend on the concentrations (again, strictly the activities) of the constituent ions in the two half cells, on the charges of each ion and on the relative rates of movement across the membrane. 

Since the Hamiltonian for atoms in accelerated optical lattices is similar to the Legett Hamiltonian for current-biased Josephson junctions [37], the present theory has been extended to describe effects of current modulations on the rate of macroscopic quanmm tunneling in Josephson junctions in Ref. [11]. 

If two electrolyte solutions that are of different concentrations but in the same solvent contact each other at a junction, ion transfers occur across the junction (Fig. 6.3). If the rate of transfer of the cation differs from that of the anion, a charge separation occurs at the junction and a potential difference is generated. The potential difference tends to retard the ion of higher rate and accelerate the ion of lower rate. Eventually, the rates of both ions are balanced and the potential difference reaches a constant value. This potential difference is called the liquid junction potential (LJP) [10]. As for the LJP between aqueous solutions, the LJP between non-aqueous solutions can be estimated using the Henderson equation. Generally the LJP, Lj-, at the junction Ci MX(s) c2 NY(s) can be expressed by Eq. (6.1) ... 

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