501
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Vasquez JM, Vu A, Schultz JS, Vullev VI. Fluorescence enhancement of warfarin induced by interaction with β-cyclodextrin. Biotechnol Prog 2009; 25:906-14. [DOI: 10.1002/btpr.188] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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502
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Kirchhof P, Bax J, Blomstrom-Lundquist C, Calkins H, Camm AJ, Cappato R, Cosio F, Crijns H, Diener HC, Goette A, Israel CW, Kuck KH, Lip GY, Nattel S, Page RL, Ravens U, Schotten U, Steinbeck G, Vardas P, Waldo A, Wegscheider K, Willems S, Breithardt G. Early and comprehensive management of atrial fibrillation: Proceedings from the 2nd AFNET/EHRA consensus conference on atrial fibrillation entitled 'research perspectives in atrial fibrillation'. Europace 2009; 11:860-85. [DOI: 10.1093/europace/eup124] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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503
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Singer DE, Chang Y, Fang MC, Borowsky LH, Pomernacki NK, Udaltsova N, Go AS. Should patient characteristics influence target anticoagulation intensity for stroke prevention in nonvalvular atrial fibrillation?: the ATRIA study. Circ Cardiovasc Qual Outcomes 2009; 2:297-304. [PMID: 20031854 DOI: 10.1161/circoutcomes.108.830232] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Randomized trials and observational studies support using an international normalized ratio (INR) target of 2.0 to 3.0 for preventing ischemic stroke in atrial fibrillation. We assessed whether the INR target should be adjusted based on selected patient characteristics. METHODS AND RESULTS We conducted a case-control study nested within the ATRIA cohort's 9217 atrial fibrillation patients taking warfarin to define the relationship between INR level and the odds of thromboembolism (TE; mainly stroke) and of intracranial hemorrhage (ICH) relative to INR 2.0 to 2.5. We identified 396 TE cases and 164 ICH cases during follow-up. Each case was compared with 4 randomly selected controls matched on calendar date and stroke risk factors using matched univariable analyses and conditional logistic regression. We explored modification of the INR-outcome relationships by the following stroke risk factors: prior stroke, age, and CHADS(2) risk score. Overall, the odds of TE were low and stable above INR 1.8. Compared with INR 2.0 to 2.5, the relative odds of TE increased strikingly at INR <1.8 (eg, odds ratio, 3.72; 95% CI, 2.67 to 5.19, at INR 1.4 to 1.7). The odds of ICH increased markedly at INR values >3.5 (eg, odds ratio, 3.56; 95% CI: 1.70 to 7.46, at INR 3.6 to 4.5). The relative odds of ICH were consistently low at INR <3.6. There was no evidence of lower ICH risk at INR levels <2.0. These patterns of risk did not differ substantially by history of stroke, age, or CHADS(2) risk score. CONCLUSIONS Our results confirm that the current standard of INR 2.0 to 3.0 for atrial fibrillation falls in the optimal INR range. Our findings do not support adjustment of INR targets according to previously defined stroke risk factors.
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Affiliation(s)
- Daniel E Singer
- Clinical Epidemiology Unit, General Medicine Division, Massachusetts General Hospital, Boston, MA 02114, USA.
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504
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Bushnell CD, Colón-Emeric CS. Secondary stroke prevention strategies for the oldest patients: possibilities and challenges. Drugs Aging 2009; 26:209-30. [PMID: 19358617 DOI: 10.2165/00002512-200926030-00003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Older adults are not only at higher risk of experiencing stroke, but also have multiple co-morbidities that make treatment for secondary stroke prevention challenging. Very few clinical trials specifically related to secondary stroke prevention treatment efficacy have focused on the oldest-old (>or=85 years) and, therefore, evidence-based recommendations for treatment specific to this population are not available. Some of the special considerations for stroke prevention treatments in older patients include careful titration of blood-pressure-lowering drugs to avoid hypotension, the risk of haemorrhagic stroke with HMG-CoA reductase inhibitors (statins) and weighing the risk of recurrent ischaemia versus bleeding in patients taking antiplatelet or anticoagulant therapy. The risk of peri-procedural complications appears to be high with both carotid angioplasty and stenting and carotid endarterectomy in older patients with carotid stenosis. Other common issues in older patients include adverse drug events, recognizing the risk of dementia, depression and osteoporosis and deciding when to discontinue secondary stroke prevention. In this review, we provide the practitioner with the evidence related to specific approaches to secondary stroke prevention in older patients, and identify the knowledge gaps that currently limit our ability to appropriately treat this vulnerable population.
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Affiliation(s)
- Cheryl D Bushnell
- Department of Neurology, Wake Forest University Health Sciences, Winston-Salem, North Carolina 27157, USA.
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505
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Fang MC, Panguluri P, Machtinger EL, Schillinger D. Language, literacy, and characterization of stroke among patients taking warfarin for stroke prevention: Implications for health communication. PATIENT EDUCATION AND COUNSELING 2009; 75:403-410. [PMID: 19171448 PMCID: PMC2740646 DOI: 10.1016/j.pec.2008.12.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 12/04/2008] [Accepted: 12/05/2008] [Indexed: 05/26/2023]
Abstract
OBJECTIVE Warfarin is a medication commonly prescribed to prevent strokes associated with certain medical conditions such as atrial fibrillation; however, little is known about how people taking warfarin perceive the goal of therapy and how they describe strokes. We assessed the stroke-related health literacy of anticoagulated patients to inform ways in which to improve health communication among people taking warfarin. METHODS We conducted a mixed-methods study of an ethnically and linguistically diverse sample of people taking warfarin to prevent stroke (N=183) and measured literacy using the short-form Test of Functional Health Literacy in Adults. We asked participants to (1) describe their indication for warfarin, and (2) describe a stroke. Transcribed answers were coded as concordant or discordant with established indications for warfarin and definitions of stroke. RESULTS Forty-three percent of participants provided a discordant response when describing their indication for warfarin. Only 9.3% reported that the purpose of taking warfarin was to prevent stroke. Not speaking English [OR=2.4 (1.1-5.6)] and less than a college education [OR=3.3 (1.4-7.3)] were independently associated with discordant answers about warfarin. Nearly 40% of subjects had inaccurate perceptions of stroke, and only one-third of subjects described a symptom or sign of stroke. Among English and Spanish-speaking participants, inadequate literacy was strongly associated with discordant responses about stroke [OR=5.8 (2.1-15.6)]. CONCLUSION Among high-risk people taking warfarin to prevent stroke, significant gaps in stroke-related health literacy exist. These gaps likely represent mismatches in the ways clinicians teach and patients learn. PRACTICE IMPLICATIONS Since stroke risk awareness and early recognition of the signs and symptoms of stroke are critical aspects of stroke prevention and treatment, clinicians should more strongly link warfarin therapy to stroke prevention and ensure that patients know the presenting symptoms and signs of stroke. Public health communication strategies regarding stroke prevention need to target individuals with limited literacy and limited English proficiency.
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Affiliation(s)
- Margaret C Fang
- Division of Hospital Medicine, University of California, San Francisco, CA 94143, United States.
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506
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Jacobs LG, Billett HH, Freeman K, Dinglas C, Jumaquio L. Anticoagulation for stroke prevention in elderly patients with atrial fibrillation, including those with falls and/or early-stage dementia: A single-center, retrospective, observational study. ACTA ACUST UNITED AC 2009; 7:159-66. [DOI: 10.1016/j.amjopharm.2009.06.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2009] [Indexed: 11/25/2022]
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507
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Connolly SJ, Pogue J, Hart RG, Hohnloser SH, Pfeffer M, Chrolavicius S, Yusuf S. Effect of clopidogrel added to aspirin in patients with atrial fibrillation. N Engl J Med 2009; 360:2066-78. [PMID: 19336502 DOI: 10.1056/nejmoa0901301] [Citation(s) in RCA: 763] [Impact Index Per Article: 50.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND Vitamin K antagonists reduce the risk of stroke in patients with atrial fibrillation but are considered unsuitable in many patients, who usually receive aspirin instead. We investigated the hypothesis that the addition of clopidogrel to aspirin would reduce the risk of vascular events in patients with atrial fibrillation. METHODS A total of 7554 patients with atrial fibrillation who had an increased risk of stroke and for whom vitamin K-antagonist therapy was unsuitable were randomly assigned to receive clopidogrel (75 mg) or placebo, once daily, in addition to aspirin. The primary outcome was the composite of stroke, myocardial infarction, non-central nervous system systemic embolism, or death from vascular causes. RESULTS At a median of 3.6 years of follow-up, major vascular events had occurred in 832 patients receiving clopidogrel (6.8% per year) and in 924 patients receiving placebo (7.6% per year) (relative risk with clopidogrel, 0.89; 95% confidence interval [CI], 0.81 to 0.98; P=0.01). The difference was primarily due to a reduction in the rate of stroke with clopidogrel. Stroke occurred in 296 patients receiving clopidogrel (2.4% per year) and 408 patients receiving placebo (3.3% per year) (relative risk, 0.72; 95% CI, 0.62 to 0.83; P<0.001). Myocardial infarction occurred in 90 patients receiving clopidogrel (0.7% per year) and in 115 receiving placebo (0.9% per year) (relative risk, 0.78; 95% CI, 0.59 to 1.03; P=0.08). Major bleeding occurred in 251 patients receiving clopidogrel (2.0% per year) and in 162 patients receiving placebo (1.3% per year) (relative risk, 1.57; 95% CI, 1.29 to 1.92; P<0.001). CONCLUSIONS In patients with atrial fibrillation for whom vitamin K-antagonist therapy was unsuitable, the addition of clopidogrel to aspirin reduced the risk of major vascular events, especially stroke, and increased the risk of major hemorrhage. (ClinicalTrials.gov number, NCT00249873.)
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508
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509
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Robert-Ebadi H, Le Gal G, Righini M. Use of anticoagulants in elderly patients: practical recommendations. Clin Interv Aging 2009; 4:165-77. [PMID: 19503778 PMCID: PMC2685237 DOI: 10.2147/cia.s4308] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Elderly people represent a patient population at high thromboembolic risk, but also at high hemorrhagic risk. There is a general tendency among physicians to underuse anticoagulants in the elderly, probably both because of underestimation of thromboembolic risk and overestimation of bleeding risk. The main indications for anticoagulation are venous thromboembolism (VTE) prophylaxis in medical and surgical settings, VTE treatment, atrial fibrillation (AF) and valvular heart disease. Available anticoagulants for VTE prophylaxis and initial treatment of VTE are low molecular weight heparins (LMWH), unfractionated heparin (UFH) or synthetic anti-factor Xa pentasaccharide fondaparinux. For long-term anticoagulation vitamin K antagonists (VKA) are the first choice and only available oral anticoagulants nowadays. Assessing the benefit-risk ratio of anticoagulation is one of the most challenging issues in the individual elderly patient, patients at highest hemorrhagic risk often being those who would have the greatest benefit from anticoagulants. Some specific considerations are of utmost importance when using anticoagulants in the elderly to maximize safety of these treatments, including decreased renal function, co-morbidities and risk of falls, altered pharmacodynamics of anticoagulants especially VKAs, association with antiplatelet agents, patient education. Newer anticoagulants that are currently under study could simplify the management and increase the safety of anticoagulation in the future.
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Affiliation(s)
- Helia Robert-Ebadi
- Division of Angiology and Hemostasis, Department of Internal Medicine, Geneva University Hospital and Faculty of Medicine, Geneva, Switzerland.
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510
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Haas S. Rivaroxaban -- an oral, direct Factor Xa inhibitor: lessons from a broad clinical study programme. Eur J Haematol 2009; 82:339-49. [PMID: 19187276 PMCID: PMC2730547 DOI: 10.1111/j.1600-0609.2009.01230.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2009] [Indexed: 01/10/2023]
Abstract
Anticoagulants are recommended for the prevention and treatment of venous thromboembolism (VTE), prevention of stroke in patients with atrial fibrillation (AF) and secondary prevention in patients with acute coronary syndrome (ACS). There is a clinical need for novel anticoagulants offering improvements over current standard of care, such as fixed oral dosing and no need for routine monitoring. Rivaroxaban, an oral, once-daily, direct Factor Xa inhibitor, has recently completed the RECORD phase III programme for the prevention of VTE in patients undergoing total hip or knee replacement (THR or TKR), an indication for which it is approved in Europe and Canada. It is being investigated in large-scale phase III studies for VTE treatment and prevention of stroke in patients with AF, and phase III studies will soon commence for secondary prevention in patients with ACS. Phase I studies demonstrated that no routine anticoagulation monitoring was required, while phase II studies suggested that fixed daily doses had a wide therapeutic window. The four RECORD studies consistently showed that rivaroxaban was significantly more effective than enoxaparin in the prevention of VTE after THR and TKR, with a similar safety profile. This review describes the development of this novel anticoagulant, from bench to bedside.
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Affiliation(s)
- Sylvia Haas
- Institut für Experimentelle Onkologie und Therapieforschung, Technische Universität München, Munich, Germany.
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511
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Rose AJ, Berlowitz DR, Frayne SM, Hylek EM. Measuring quality of oral anticoagulation care: extending quality measurement to a new field. Jt Comm J Qual Patient Saf 2009; 35:146-55. [PMID: 19326806 DOI: 10.1016/s1553-7250(09)35019-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
BACKGROUND Oral anticoagulation with warfarin is an increasingly common medical intervention. Despite its efficacy, warfarin is difficult to manage, contributing to potential for patient harm. Efforts to measure the quality of oral anticoagulation care have focused disproportionately on the identification of ideal candidates for warfarin therapy, with comparatively little effort in measuring the quality of oral anticoagulation care once therapy has begun. To address this gap in the literature, a MEDLINE search was conducted for all papers relevant to possible quality measures in oral anticoagulation care, including measures of structure, process, and outcomes of care. LIMITATIONS, CONCERNS, AND CHALLENGES OF QUALITY MEASUREMENT IN ORAL ANTICOAGULATION Because they do not have intrinsic significance, measures of structure and process should be strongly related to outcomes that matter to merit our interest. Consensus guidelines may provide useful guidance to practicing clinicians but may not represent valid process measures. Outcome measures must be studied with databases that provide sufficient statistical power to reliably demonstrate real differences between providers or sites of care. CONCLUSION Oral anticoagulation care, a common and serious condition, is in need of a program of quality measurement. This article suggests a research agenda to begin such a program. Previous research has established the evidence for anticoagulant therapy across a broad spectrum of indications and has helped to achieve consensus on the optimal target intensity for various indications. The next task will be to use this body of evidence to develop valid measures of the structure, process, and outcomes of oral anticoagulation care. Quality indicators provide a framework for quality improvement, two goals of which are to maximize the effectiveness of therapy and to minimize harm.
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Affiliation(s)
- Adam J Rose
- Center for Health Quality, Outcomes and Economic Research, Bedford VA Medical Center, Bedford, MA, USA.
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512
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Abstract
Atrial fibrillation (AF) and congestive heart failure are common conditions and each predisposes to the development of the other. Basic research using animal models of the two conditions continues to yield insights that may improve therapies. The role of medical therapies aimed at the underlying structural changes in AF continues to be a subject of ongoing studies. Cardiac resynchronization therapy is effective in appropriately selected patients with both sinus rhythm and AF. Catheter ablation is emerging as a potential alternative to antiarrhythmic drug therapy, but large randomized trials will be needed to assess its role.
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513
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Lippi G, Favaloro EJ, Salvagno GL, Franchini M. Laboratory assessment and perioperative management of patients on antiplatelet therapy: from the bench to the bedside. Clin Chim Acta 2009; 405:8-16. [PMID: 19351529 DOI: 10.1016/j.cca.2009.03.055] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Revised: 03/25/2009] [Accepted: 03/29/2009] [Indexed: 01/29/2023]
Abstract
The contribution of platelets in the pathophysiology of thromboses has established antiplatelet therapy as a cornerstone for prevention or treatment of these disorders. However, patients on antiplatelet drugs undergoing surgery face the life-threatening dilemma between the risk of perioperative thrombosis by ceasing therapy and restoring platelet function versus the risk of surgical bleeding by its continuation. According to their mechanism of action, antiplatelet drugs can be conventionally classified as agents that inhibit cyclooxygenase, block the platelet adenosine diphosphate P2Y12 receptor, inhibit phosphodiesterase, or block platelet glycoprotein IIb/IIIa. Although several tests have been developed to assess platelet inhibition by most of these compounds, studies to date have not been able to reliably evaluate the diagnostic efficiency of these tests to predict hemorrhage and/or blood loss, and accordingly perioperative assessment of drug-induced platelet inhibition cannot be recommended as yet. Although several management options are available to counteract the hemorrhagic risk of surgical patients using antiplatelet agents, perioperative discontinuation of these drugs is the preferable choice wherever possible. The use of platelet transfusions should be limited where necessary to the treatment of major, life-threatening bleeding. The contribution of newer hemostatic agents, such as desmopressin and recombinant activated factor VII, is yet to be fully determined, and there remain many challenges and unresolved issues in the clinical care of these patients.
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Affiliation(s)
- Giuseppe Lippi
- Sezione di Chimica Clinica, Dipartimento di Scienze Biomediche e Morfologiche, Università di Verona, Italy.
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514
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515
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516
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Abstract
BACKGROUND Little is known about how patterns of warfarin dose management contribute to percentage time in the therapeutic International Normalized Ratio (INR) range (TTR). OBJECTIVES To quantify the contribution of warfarin dose management to TTR and to define an optimal dose management strategy. PATIENTS/METHODS We enrolled 3961 patients receiving warfarin from 94 community-based clinics. We derived and validated a model for the probability of a warfarin dose change under various conditions. For each patient, we computed an observed minus expected (O - E) score, comparing the number of dose changes predicted by our model to the number of changes observed. We examined the ability of O - E scores to predict TTR, and simulated various dose management strategies in the context of our model. RESULTS Patients were observed for a mean of 15.2 months. Patients who deviated the least from the predicted number of dose changes achieved the best INR control (mean TTR 70.1% unadjusted); patients with greater deviations had lower TTR (65.8% and 62.0% for fewer and more dose changes respectively, Bonferroni-adjusted P < 0.05/3 for both comparisons). On average, clinicians in our study changed the dose when the INR was 1.8 or lower/3.2 or higher (mean TTR: 68%); optimal management would have been to change the dose when the INR was 1.7 or lower/3.3 or higher (predicted TTR: 74%). CONCLUSIONS Our observational study suggests that INR control could be improved considerably by changing the warfarin dose only when the INR is 1.7 or lower/3.3 or higher. This should be confirmed in a randomized trial.
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Affiliation(s)
- A J Rose
- Center for Health Quality, Outcomes, and Economic Research, Bedford VA Medical Center, Bedford, MA 01730, USA.
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517
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Jug B, Vene N, Salobir BG, Šebeštjen M, Šabovic M, Keber I. Procoagulant State in Heart Failure With Preserved Left Ventricular Ejection Fraction. Int Heart J 2009; 50:591-600. [DOI: 10.1536/ihj.50.591] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Borut Jug
- Department of Vascular Diseases, Clinic of Internal Medicine, University Clinical Center Ljubljana
| | - Nina Vene
- Department of Vascular Diseases, Clinic of Internal Medicine, University Clinical Center Ljubljana
| | | | - Miran Šebeštjen
- Department of Vascular Diseases, Clinic of Internal Medicine, University Clinical Center Ljubljana
| | - Mišo Šabovic
- Department of Vascular Diseases, Clinic of Internal Medicine, University Clinical Center Ljubljana
| | - Irena Keber
- Department of Vascular Diseases, Clinic of Internal Medicine, University Clinical Center Ljubljana
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518
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Khoo CW, Lip GYH. Initiation and persistence of warfarin or aspirin as thromboprophylaxis in chronic atrial fibrillation in general practice. J Thromb Haemost 2008; 6:1622-4. [PMID: 18680537 DOI: 10.1111/j.1538-7836.2008.03115.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Affiliation(s)
- C W Khoo
- University Department of Medicine, City Hospital, Birmingham, UK
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519
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Lopes RD, Piccini JP, Hylek EM, Granger CB, Alexander JH. Antithrombotic therapy in atrial fibrillation: guidelines translated for the clinician. J Thromb Thrombolysis 2008; 26:167-74. [PMID: 18807225 DOI: 10.1007/s11239-008-0272-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Accepted: 09/02/2008] [Indexed: 10/21/2022]
Abstract
Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice, accounting for approximately one-third of hospitalizations for cardiac rhythm disturbances. The highest incidence of AF is in patients 70-80 years old and other high-risk populations. Although the diagnosis of AF is usually straightforward, effective treatment strategies are less well implemented. This is particularly true for antithrombotic therapy, which is very effective at preventing thromboembolic complications of AF. Stroke is the most significant morbidity in AF patients. The yearly risk of stroke increases from 1.5% for AF patients aged 50-59 to 23% for those aged 80-89. Ischemic strokes secondary to AF carry twice the risk of death when compared with strokes from other causes. We provide a practical and useful review of the most recent American College of Cardiology/American Heart Association/European Society of Cardiology guidelines-based care and future directions of antithrombotic therapy for patients with AF.
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Affiliation(s)
- Renato D Lopes
- Duke Clinical Research Institute, Duke University Medical Center, Durham, NC 27710, USA
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520
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521
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Abstract
INTRODUCTION Atrial fibrillation (AF) is the most common, sustained rhythm disturbance. The prevalence of AF is increasing as people live longer. Common conditions such as hypertension and ischaemic heart disease play an important role in the development of AF. The presence of AF is associated with increased morbidity and mortality from stroke and heart failure, particularly in patients with structural heart disease. SOURCES OF DATA This article provides evidence-based information on the key aspects of managing AF which is based on major guidelines, landmark clinical trials and meta-analyses. AREAS OF AGREEMENT It is well recognized that both rate control and rhythm control are important strategies for the management of AF, but each approach should be chosen according to individual patient circumstances. A vast majority of elderly, relatively asymptomatic patients will benefit from ventricular rate control. Embolic stroke remains a major complication of AF. Yet, anticoagulation with warfarin remains underprescribed, especially in the elderly due to the presumed risk of bleeding. The technique of catheter ablation continues to improve and is generally successful in younger patients with relatively normal hearts. AREAS OF CONTROVERSY There are clinically relevant differences among published schemes designed to stratify stroke risk in patients with AF. The CHADS2 score is currently the most simple system to give some initial estimate of stroke risk in AF patients, but could significantly underestimate this risk, particularly in those who fall in the 'intermediate' risk category. GROWING POINTS AND AREAS TIMELY FOR DEVELOPING RESEARCH Novel antiarrhythmic agents, including atrial specific agents with improved efficacy and safety profile, are currently under development. New antithrombotic agents with efficacy similar to warfarin which do not require regular INR testing appear to be promising, but there are lack of data about their long-term safety. There is increasing evidence that inflammation and fibrosis may play a major role in the initiation and maintenance of AF. Statins by means of their pleotropic effects and angiotensin-converting enzyme inhibitors and angiotensin receptor blockers by preventing atrial remodelling may prove useful in preventing the development of AF. However, there is insufficient evidence to expand the use of these agents to a wider patient population at risk of AF. It needs to be seen if strategies towards primary and secondary prevention with treatment of underlying heart disease and modification of risk factors have a larger effect than specific interventions in preventing the burden of AF in the general population.
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Affiliation(s)
- Abhay Bajpai
- Ground Floor, Jenner Wing, St George's, University of London, Cranmer Terrace, Tooting, London SW170RE, UK
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522
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Dimitrova NA, Dimitrov GV, Bonow RO, Carabello BA, Erwin JP, Guyton RA, O’Gara PT, Ruiz CE, Skubas NJ, Sorajja P, Sundt TM, Thomas JD. Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres. J Am Coll Cardiol 1988; 63:e57-185. [PMID: 2460319 DOI: 10.1016/j.jacc.2014.02.536] [Citation(s) in RCA: 1837] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.
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Affiliation(s)
- N A Dimitrova
- CLBA, Centre of Biology, Bulgarian Academy of Sciences, Sofia
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