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Summary:Early repolarization (ER) is an enigma. The purpose of this review is to reemphasize the overall electrocardiographic (ECG) pattern of this normal ST variant which continues to challenge the clinician because of its similarity to the current of injury potential to myocardium or an acute pericarditis. The data were provided from the studies identified through computerized searches of Medline, Toxline, Oxford, Agricola, and Bios Afterdark, Cumulative index, and a review of bibliographies of relevant articles on the related subjects. Early repolarization has elevated, upward, concave ST segments, located commonly in precordial leads, with reciprocal depression in aVR, tall, peaked and slightly asymmetrical T waves with notch, and slur on the R wave. The other accompanying features in the ECG are vertical axis, shorter and depressed P-R interval, abrupt transition, counterclockwise rotation, presence of U waves, and sinus bradycardia. Males dominate and patients are often younger than 50 years of age. The incidence of 1 to 2% is found equally common in all races. Degree and incidence of ST elevation decrease as age advances. Exercise or isoproterenol administration may normalize the ST segment. Early repolarization is a benign condition. If the ECG conforms to a classical pattern of ER on serial ECGs, it would exclude the unnecessary hazards of present day revascularization therapy for myocardial infarction such as primary angioplasty or thrombolytic therapy, or aggressive management of acute pericarditis, and so forth. This review concludes with a discussion of comparative ECG features of ER, pericarditis, and myocardial infarction, and provides an algorithm for diagnostic management of patients suffering from these conditions. Key words: ST segment in early repolarization, race and early repolarization, early repolarization and myocardial infarction, early repolarization and pericarditis, arrhythmia in early repolarization, PR interval and early repolarization. early repolarization and gender

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BACKGROUND: Nicotine, the active agent in tobacco, is released into the circulation during cigarette smoking. It elevates plasma catecholamines, heart rate, and arterial blood pressure; produces coronary spasm; and increases myocardial work and oxygen demand with concomitant reduction in oxygen supply. This may generate cardiac arrhythmias that might contribute to an increased incidence of sudden death due to smoking. It is hypothesized that acute administration of nicotine will induce cardiac arrhythmias, and this experimental study was planned with an aim to assess arrhythmogenic activity as a result of acute administration of nicotine. METHODS: Nicotine was administered in different doses intravenously in 16 anesthesized dogs, and 52 experiments were carried out at weekly intervals. In each experiment, continuing anesthesia and after nicotine administration. They were scrutinized by two experienced electrocardiographers at intervals of 1, 2, 3, 4, 5, 10, 15, and 30 minutes. RESULTS: Data revealed nonsignificant arrhythmias with doses of 2.5, 5.0, and 10.0 mg/kg of intravenous nicotine. The dose of 50 µg/kg induced supraventricular arrhythmias, atrioventricular junctional arrhythmias, and ventricular arrhythmias. Supraventricular bradycardia in 30 (83%; P <.0001), supraventricular arrhythmia in 30 (83%; P <.0001), sinus arrest in 18 (50%; P <.003), atrial ectopics in 24 (67%; P <.0004), and atrial tachycardia in 98 experiments (25%; P <.021). These results were statistically significant. In 18 experiments, sinus arrest was observed to be missing P waves and QRS complexes for a period corresponding to 4:1-10:1 SA block, lasting 2-6 seconds, within 3 seconds of injection. Occurrence of wandering pacemaker was observed in 6 experiments, atrial flutter in 2, and atrial fibrillation in 2, but these incidents were not significant. Atrioventricular junctional arrhythmias consisted of escape beats in 9 subjects (25%; P <.02), premature contractions in 12 (33%; P <.005), first-degree heart block in 9 (25%; P <.02), second degree heart block in 9 (25%; P <.02) and atrioventricular dissociation in 9 (25%; P <.02). All arrhythmias in this category were significant. Ventricular arrhythmias consisted of ventricular premature contractions that were unifocal in 32 subjects (89%; P <.0001), multifocal in 30 (83%; P <.0001), bigeminy in 28 salvos in 18 (50%; P <.003). Sustained ventricular tachycardia (> 30 beats) in 12 experiments (33%; P <.005) proved significant. The dose of 100 µg/kg induced fatal ventricular flutter and ventricular fibrillation. The dog expired and experiments with that dose were not repeated. CONCLUSION: Data reveal dose-dependent arrhythmogenecity of nicotine in dogs. Smaller doses of nicotine did not produce significant arrhythmias. Higher doses, bioequivalent to smoking two standard cigarettes, may generate cardiac arrhythmias of simple to severe nature. Further work in human beings may confirm whether nicotine in cigarette smoke will generate similar cardiac arrhythmias especially in patients with auto...

Astrocyte plays a pivotal role in synaptic transmission with neuron. It maintains the ionic concentration in synapse to regulate signals from one cell to another. Calcium known as second messenger plays an important role in signal transduction. There are so many physiological processes that affect the cytosolic calcium concentration [ Ca 2+]i like calcium buffering, flow of calcium ion through channels, etc. The modeling of calcium signaling in astrocytes has become more sophisticated. The modeling effort has provided insight to understand the cell contraction. Main objective of this work is to study the effect of voltage-gated calcium channel on calcium profile under excess buffer approximation in the form of diffusion equation. A mathematical model is developed in the form of diffusion equation for the calcium profile. The model incorporates the important physiological parameter like diffusion coefficient association rate constant, etc. Appropriate boundary conditions have been framed. Finite element method is employed to solve the problem. A MATLAB program has been developed for the entire problem and simulated to compute the numerical results.

Summary:The diagnosis of constrictive pericarditis remains a challenge because its physical findings and hemodynamics mimic restrictive cardiomyopathy. Various diagnostic advances over the years enable us to differentiate between these two conditions. This review begins with a case report of constriclive pericarditis, followed by a brief history and discussions of etiologies. Clinical features, radiologic, electrocardiographic, angiographic findings, and hemodynamics of constrictive pericarditis are reviewed. The echocardiographic findings are detailed and the recent advances in Doppler flow velocity patterns of pulmonary, mitral, tricuspid valves and hepatic veins are reported. Nuclear ventriculograms depict rapid ventricular filling in constrictive pericarditis and differentiate it from restrictive cardiomyopathy. Endomyocardial biopsy helps further in recognizing the various types of restrictive cardiomyopathies. Computed tomography and magnetic resonance imaging delineate abnormal pericardial thickness in constrictive pericarditis. Association of characteristic hemodynamic changes and abnormal pericardial thickness > 3 mm usually confirms the diagnosis of constrictive pericarditis. Effusive and occult varieties of constrictive pericarditis are briefly described. This review concludes with emphasizing the importance of pericardial resection.

In this paper a finite element model is developed to study cytosolic calcium concentration distribution in astrocytes for a two-dimensional steady-state case in presence of excess buffer. The mathematical model of calcium diffusion in astrocytes leads to a boundary value problem involving elliptical partial differential equation. The model consists of reaction–diffusion phenomena, association and dissociation rates and buffer. A point source of calcium is incorporated in the model. Appropriate boundary conditions have been framed. Finite element method is employed to solve the problem. A MATLAB program has been developed for the entire problem and simulated to compute the numerical results. The numerical results have been used to plot calcium concentration profiles in astrocytes. The effect of EGTA, BAPTA and σCa influx on calcium concentration distribution in astrocytes is studied with the help of numerical results.

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