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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A major consequence of atrial fibrillation (AF) is stroke. For stroke prevention in AF, the American Heart Association recommends aspirin, 325 mg/d, for low-risk patients. For all others, anticoagulation with warfarin to a target INR of 2 to 3 is recommended if warfarin is not contraindicated. Approximately 0.3% of patients receiving warfarin suffer intracranial hemorrhage. For restoration of sinus rhythm in recent AF, direct current cardioversion is the treatment of choice if a trial of antiarrhythmic drug therapy has failed or is contraindicated. Potential complications include thromboembolism, ventricular arrhythmia, and pulmonary edema. Permanent pacemakers can be used to control conduction disturbances such as sick sinus syndrome and to prevent paroxysmal AF. Radiofrequency AV nodal ablation provides symptomatic relief for some patients with chronic or paroxysmal AF. Surgical techniques are also being developed for AF. These include left atrial isolation and the corridor and maze procedures.
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PMID:Atrial fibrillation: preventing thromboembolism and choosing nondrug therapies. 967 97

From 1993 to 1998, a total of 100 consecutive pediatric patients with tachycardia (45 male and 55 female, aged 1 year 10 months to 17 years, 11+/-4 year) who underwent electrophysiological study were reviewed. Eleven of them were younger than 5 years. Two had tachycardia-related cerebrovascular accident. Congenital heart disease was found in 12 patients. After propofol anesthesia, the clinical tachycardia could not be induced in three (two atrial tachycardia and one AV nodal re-entrant tachycardia) and became nonsustained in five (atrial tachycardia). Mechanical ablation occurred in three and two had subsequent recurrences. Among the 85 cases who received radiofrequency ablation, the overall final success rate of RF ablation for all diagnoses was 94% with a diagnosis-specific success rate ranging from 100 to 57%. Tachycardia cardiomyopathy was noted in four (three atrial tachycardia and one junctional ectopic tachycardia) and all regressed after successful ablation. Success in two patients with left posterioseptal accessory pathway could only be achieved by delivering the energy at the middle cardiac vein. Two patients with right atrial isomerism had an 'AV nodal-to-AV nodal tachycardia' which was eliminated by ablation. Total recurrence rate was 13% but final success was achieved in all during re-study except the three patients who refused re-intervention. The atrial tachycardia developed in postoperative congenital heart disease was associated with the lowest success rate (57%) and highest recurrence rate (25%). Procedure-related complications occurred in four; two with transient brachial palsy, one with first-degree AV block and one with blood loss requiring blood transfusion. In conclusion, the experience of this single center confirmed the efficacy and safety of radiofrequency catheter ablation in treating pediatric arrhythmias, but the limitations in postoperative arrhythmias and the effects of propofol on tachycardia induction (especially the atrial tachycardia) need to be improved.
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PMID:Radiofrequency catheter ablation of tachycardia in children with and without congenital heart disease: indications and limitations. 1071 30

The electrocardiographic patterns recorded from seven patients with isorhythmic A-V dissociation fall into two distinct groups. In pattern I, the P wave fluctuates cyclically back and forth across the QRS complex. The mechanism responsible for this type of A-V synchronization represents a typical biologic feedback control system. The P-R interval is a determinant of stroke volume, which in turn influences the arterial blood pressure. The blood pressure has an inverse effect on the discharge frequency of the S-A node through the baroreceptor reflex. The S-A nodal frequency then affects the P-R interval, to close the feedback loop. In pattern II, the P wave is in a fairly constant position relative to the QRS complex. It is usually coincident with the QRS complex or appears on the ST segment or first half of the T wave. The mechanism producing synchronization in pattern II type of isorhythmic dissociation has not been established conclusively.
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PMID:The mechanism of synchronization in isorhythmic A-V dissociation. II. Clinical studies. 1199 9

The combined role of atrial pacing lead location and AV timing on cardiovascular performance has not been defined. This study tested the hypothesis that atrial pacing lead location can change the dependence of LA and LV hemodynamics on AV timing in vivo. Dogs anesthetized with isoflurane (n = 8) were instrumented for measurement of hemodynamics including LA pressure, LA volume, and pulmonary venous bloodflow. Data were recorded during normal sinus rhythm, and atrial overdrive pacing from the right atrial appendage (RAA), proximal coronary sinus (CS), and LA lateral wall (LAW). The AV node was then ablated and measurements repeated during synchronous ventricular pacing and during dual chamber pacing from each atrial lead location at various AV delays (20, 60, 120, 180, 240, and 350 ms). Hemodynamics during intrinsic sinus rhythm and overdrive atrial pacing from different sites were similar. In contrast, ventricular or dual chamber pacing caused significant (P < 0.05) changes in cardiac output with different AV timing during RAA (3.5 +/- 0.2 vs 2.9 +/- 0.2 L/min at 120 and 350 ms, respectively) and LAW pacing but not CS pacing. A significant interaction between atrial lead location and AV delay was observed for changes in stroke volume, pulmonary venous blood transport, LA volume, and LV preload. The results indicate that the atrial contribution to cardiac output depends on AV timing and atrial lead location in isoflurane-anesthetized dogs with AV nodal conduction block.
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PMID:Atrial pacing lead location alters the effects of atrioventricular delay on atrial and ventricular hemodynamics. 1269 89

Atrial fibrillation (AF) affects about 2% of the general population and 8%-11% of those older than 65 years. The demand for effective therapeutic strategies for AF is anticipated to increase substantially as the proportion of the elderly population increases. Atrioventricular nodal ablation accompanied by permanent pacemaker implantation is an established option in elderly patients with intractable arrhythmia and poor ventricular rate control. However, it renders most patients pacemaker dependent and does not eliminate symptoms associated with loss of atrial transport or reduce the risk of stroke. The considerable limitations of rhythm or rate control strategies prompted interest in preventative atrial pacing, which may reduce the incidence of AF by either eliminating the triggers and/or by modifying the substrate of AF. Atrial or dual-chamber pacing has been proven to prevent or delay progression to permanent AF in elderly patients with sinus node dysfunction as compared with ventricular pacing. Patients with advanced atrial conduction delay may benefit from atrial resynchronization pacing. There may be additional benefits associated with the use of particular sites of pacing, specific pacing algorithms designed to target potential triggers of AF, and pace-termination of atrial tachycardia. Preventive and antitachycardia pacing algorithms incorporated in implantable cardioverter-defibrillators and pacemakers are currently under investigation and may offer a valuable alternative to antiarrhythmic drug therapy in elderly patients with left ventricular dysfunction at high risk of proarrhythmia or worsening heart failure. The evolution of hybrid therapy, in which two or more different strategies are employed in the same patient, may be the most effective approach to management of AF.
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PMID:Atrial pacing for the prevention and termination of atrial fibrillation. 1241 45

Certain embolic cerebrovascular accidents can be explained by the development of paroxysmal atrial fibrillation. When noninvasive complementary investigations are negative, programmed atrial stimulation can be proposed to detect increased atrial vulnerability. The objective of this study was to evaluate the reliability of this method performed via a transoesophageal approach in 59 subjects presenting with an embolic cerebrovascular accident and who were in sinus rhythm at the time of the accident. Seven of these patients had a history of paroxysmal atrial fibrillation (AF) or atrial tachycardia (AT) (group I). Three of these seven patients also presented AV nodal reentrant junctional tachycardia. The other 52 patients had no history of arrhythmia and their Holter recording did not reveal any episodes of sustained atrial tachycardia (group II). Transoesophageal programmed atrial stimulation used up to 2 extrastimuli under baseline conditions and during Isuprel infusion. The following results were obtained: sustained atrial tachycardia (> 1 min) was induced in all patients of group 1, 3 of them also presented inducible junctional tachycardias. 14 patients of group II (27%) presented inducible supraventricular tachycardia: atrial tachycardia in 7 cases. Patients in group II with inducible AT presented either heart disease (n = 3) or minor abnormalities on the Holter recording (runs of atrial premature complexes or sinus pauses (n = 3). Two of these patients subsequently developed sustained atrial fibrillation during follow-up. In 25 patients with normal Holter recording and no heart disease, programmed atrial stimulation induced junctional tachycardia in 4 cases. In conclusion, transoesophageal electrophysiological investigation is a useful way to identify various forms of supraventricular tachycardia able to explain an embolic cerebrovascular accident. The considerable incidence of inducible AV nodal reentrant junctional tachycardia must be emphasized, while the incidence of atrial fibrillation is much lower than during intracardiac investigations.
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PMID:[Value of transesophageal programmed atrial stimulation in the evaluation of unexplained cerebrovascular accidents]. 1255 33

Complete situs inversus is a rare syndrome, with overall frequency estimated at 1/10,000 births, resulting from abnormal rotation of the cardiac tube during embryogenesis, of unknown mechanism. Recent studies suggest that left-right asymmetry defects are likely to be due to genetic abnormalities in the lefty, nodal, i.v., HAND, ZIC3, Shh, ACVR2B and/or Pitxz genes. In dextrocardia with situs inversus the heart is structurally normal in 90-95% of cases, in contrast to dextroversion (dextrocardia with situs solitus), which has a high incidence of structural cardiac defects. Atrial septal defect is one of the most common congenital cardiac anomalies in adults. Diagnosis is based on clinical manifestations and simple complementary diagnostic exams like abdominal and thoracic radiography and electrocardiogram. Prognosis in isolated dextrocardia depends on the congenital cardiac defects present. By contrast, in dextrocardia with situs inversus life expectancy is similar to that of the general population. The authors present the case of a 64-year-old German man admitted to the emergency care unit with a diagnosis of embolic stroke due to atrial fibrillation with fast ventricular rate. As clinical history could not be assessed due to language limitations, routine admission tests were performed. They revealed complete situs inversus with corrected ostium secundum atrial septal defect. Finally, the anatomic, pathologic, embryologic and etiologic features of complete situs inversus and related abnormalities of the cardiac structures are presented. Special emphasis is given to genetic abnormalities, the study of which has seen great advances since the 1990s thanks to new techniques of DNA analysis.
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PMID:A case of complete situs inversus. 1271 13

Atrial fibrillation (AF) is the most common sustained arrhythmia in adults, and its incidence and prevalence increase progressively with age. As a result, AF-associated morbidity and mortality increase with age. Therefore, because even asymptomatic AF markedly increases the risk of stroke and other embolic events, aggressive treatment is warranted in order to avoid the potentially devastating sequelae of this condition. Goals for the treatment of AF in the elderly population should primarily focus on alleviation of symptoms and prevention of strokes, while minimizing potential toxic effects of polypharmacy. Rate control should be optimized with atrioventricular (AV) nodal- blocking agents. The decision of anticoagulation should be individualized for each patient, balancing the risk of stroke against the risk for major bleeding complications. In elderly patients without symptoms, rate control and anticoagulation is the preferred method of treatment. Antiarrhythmic therapy to maintain sinus rhythm is generally reserved for patients with significant symptoms attributable to AF. However, simply maintaining sinus rhythm has not been proven to decrease stroke risk; therefore, long-term anticoagulation is recommended even in patients who are in sinus rhythm on antiarrhythmic drugs. AV nodal ablation with implantation of a pacemaker is a safe and excellent method of rate control for elderly patients who do not respond adequately to pharmacotherapy. Other invasive procedures, such as pulmonary vein isolation and Cox-Maze operations, are associated with high risks of complications in the elderly and are generally not recommended. Postoperative AF is common in the elderly population, and its development in high-risk patients should be anticipated and promptly treated to avoid potential hemodynamic compromise and prolonged hospitalization.
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PMID:Atrial Fibrillation in the Elderly. 1294 Dec 4

African-American (AA) women with breast cancer have higher mortality rates than Caucasian woman, and some studies have suggested that this disparity may be partly explained by unequal access to medical care. The purpose of this study was to analyze racial differences in patterns and costs of care and survival among women treated for invasive breast cancer at a large academic medical center. Subjects included 331 AA and 257 Caucasian women diagnosed with stage I-III breast cancer between 1994 and 1997. Clinical, socio-demographic, and cost data were obtained from the medical record, cancer registry, and hospital financial database. Data were collected on the use of cancer directed treatments (surgery, radiation, chemo and hormonal therapy) up to 1-year post-diagnosis. Survival analyses compared disease-free and overall survival by race adjusting for age, stage, nodal involvement, ER/PR status and a diagnosis of hypertension, diabetes, heart disease and cerebral vascular accident. There were no significant racial differences in treatment utilization and costs. The mean total 1-year treatment costs were US 16,348 dollars for AAs and US 15,120 dollars for Caucasians. While AAs had a significantly higher unadjusted relative risk (RR) of recurrence 2.09 (95% CI: 1.41-3.10) and death 1.56 (95% CI: 1.09-2.25), the multivariate adjusted analyses resulted in no significant differences in recurrence 1.38 (95% CI: 0.85-2.26) or death 1.06 (95% CI: 0.64-1.75). There was no obvious racial disparity in treatment and costs noted. Our findings support the theory that equal treatments produce equal outcomes. Improvement in screening may have an important impact on survival among minority women with breast cancer.
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PMID:Racial disparities in treatment and survival of women with stage I-III breast cancer at a large academic medical center in metropolitan Detroit. 1595 57

We discuss in detail techniques for modelling flows due to finite and infinite arrays of beating cilia. An efficient technique, based on concepts from previous 'singularity models' is described, that is accurate in both near and far-fields. Cilia are modelled as curved slender ellipsoidal bodies by distributing Stokeslet and potential source dipole singularities along their centrelines, leading to an integral equation that can be solved using a simple and efficient discretisation. The computed velocity on the cilium surface is found to compare favourably with the boundary condition. We then present results for two topics of current interest in biology. 1) We present the first theoretical results showing the mechanism by which rotating embryonic nodal cilia produce a leftward flow by a 'posterior tilt,' and track particle motion in an array of three simulated nodal cilia. We find that, contrary to recent suggestions, there is no continuous layer of negative fluid transport close to the ciliated boundary. The mean leftward particle transport is found to be just over 1 mum/s, within experimentally measured ranges. We also discuss the accuracy of models that represent the action of cilia by steady rotlet arrays, in particular, confirming the importance of image systems in the boundary in establishing the far-field fluid transport. Future modelling may lead to understanding of the mechanisms by which morphogen gradients or mechanosensing cilia convert a directional flow to asymmetric gene expression. 2) We develop a more complex and detailed model of flow patterns in the periciliary layer of the airway surface liquid. Our results confirm that shear flow of the mucous layer drives a significant volume of periciliary liquid in the direction of mucus transport even during the recovery stroke of the cilia. Finally, we discuss the advantages and disadvantages of the singularity technique and outline future theoretical and experimental developments required to apply this technique to various other biological problems, particularly in the reproductive system.
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PMID:Discrete cilia modelling with singularity distributions: application to the embryonic node and the airway surface liquid. 1747 55


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