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(Chest. 2001;120:840-846.)
© 2001 American College of Chest Physicians

A Transesophageal Echocardiographic Study on Risk Factors for Stroke in Elderly Patients With Atrial Fibrillation*

A Comparison With Younger Patients

Noriko Shinokawa, MD; Tadakazu Hirai, MD; Shutaro Takashima, MD; Tomoki Kameyama, MD; Keiko Nakagawa, MD; Hidetsugu Asanoi, MD and Hiroshi Inoue, MD

* From The Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Toyama, Japan.

Correspondence to: Hiroshi Inoue, MD, The Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan; e-mail: thirai{at}ms.toyama-mpu.ac.jp


   Abstract
TOP
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Study objectives: Atrial fibrillation (AF) becomes an increasingly important cause of stroke as patients get older. The aim of the study was to determine whether risk factors of cerebral embolism among elderly patients with AF differed from those of younger patients by using transesophageal echocardiography (TEE).

Design and setting: Cross-sectional study at a university hospital.

Methods: Cardiovascular lesions with the potential for thromboembolism in patients with AF were investigated using TEE. Left atrial spontaneous echocardiographic contrast (SEC), peak flow velocity in the left atrial appendage (LAA-flow), and aortic atherosclerosis of the thoracic aorta were assessed in 67 elderly (>= 70 years old) and 135 younger (< 70 years old) patients. All patients underwent either brain CT (n = 54) or MRI (n = 148) to assess presence of cerebral infarction.

Results: Cerebral infarction due to embolism was noted in 113 patients with AF. There was a higher prevalence of cerebral embolism in elderly patients when compared with younger patients (78% vs 45%; p < 0.001). Cerebral embolism found in younger patients was associated with high grade of SEC and lower LAA-flow (p < 0.05). In addition to these TEE findings, aortic atherosclerosis was more severe in elderly patients with cerebral embolism than in those without cerebral embolism (p < 0.0001). By multivariate logistic analysis, LAA-flow was an independent predictor of cortical infarction in younger patients, but not in elderly patients, whereas aortic atherosclerosis was a useful marker in predicting embolic risk in elderly patients.

Conclusions: TEE findings indicative of left atrial blood stasis were useful to identify the embolic risk of younger patients with AF, while atherosclerosis of the thoracic aorta appears to be an important marker for cerebral embolism in elderly patients.

Key Words: atrial fibrillation • embolism • transesophageal echocardiography


   Introduction
TOP
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Although atrial fibrillation (AF) is a major risk factor for ischemic cerebral events, the risk of stroke varies greatly depending on age and coexisting cardiovascular pathology.1 Clinical trials2 3 have shown that younger patients not complicated with hypertension or cardiovascular disease have a low risk of stroke, but the risk of stroke rises along with increasing age. Elderly patients who have diabetes, hypertension, or prior stroke have demonstrated a high annual stroke rate.1 4 Identification of these clinical diseases that increase the risk of stroke is important, but the pathophysiologic mechanisms linking clinical risk factors with thromboembolic risk remain elusive in many patients.

Transesophageal echocardiography (TEE) offers high-resolution images of the left atrium and its appendage as well as the thoracic aorta for evaluation of left atrial blood stasis and aortic atherosclerosis. Doppler echocardiographic measurement of blood flow velocity in the left atrial appendage (LAA-flow) and evaluation of left atrial spontaneous echocardiographic contrast (SEC) have been used to assess the degree of blood stasis in the left atrial appendage and the risk of thromboembolism.5 6 7 In clinical studies,8 9 an association between atherosclerotic disease of the thoracic aorta and cerebral infarction has been ascertained. In addition to being a direct cause of cerebral embolism, aortic atheroma has been shown to be a significant predictor of stroke and mortality,10 11 12 suggesting that aortic atherosclerosis diagnosed using TEE could be a marker of generalized atherosclerosis.13 Thus, TEE may provide a useful information to evaluate the risk of cerebral infarction, particularly in elderly subjects, who have cardiac and concomitant extracardiac risk factors. In this study, we assessed TEE findings to determine the risk of cerebral embolism, not of cerebral thrombosis, in younger and elderly patients with AF.


   Materials and Methods
TOP
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Study Patients
Over a 3-year period, 202 consecutive patients (118 men and 84 women; mean ± SD age, 64 ± 12 years) with electrocardiographically documented AF who were referred for cardiovascular assessment at our institution underwent TEE. The indications for TEE were evaluation of potential thromboembolic risk or identification of embolic source of recent stroke. Patients aged < 70 years or >= 70 years were categorized as younger or elderly patients, respectively. All patients underwent brain CT (n = 54) or MRI (n = 148) to determine the presence of cerebral infarction of cortical branch, which is considered to be presumably embolic infarction.14 Based on the CT or MRI, diagnosis of cortical infarction was made by neurologists aware of clinical data but not the findings of echocardiography.15 16 Baseline clinical characteristics, including systemic hypertension, hyperlipidemia, diabetes mellitus, and smoking habits, were determined from medical records and routine laboratory data.

Echocardiography
TEE was performed using a 5-MHz multiplane transducer (PEF-510MA; Toshiba Corporation; Tokyo, Japan) connected to an ultrasound imaging system (SSH-140A; Toshiba Corporation) according to the standard protocols. Multiple standard tomographic planes were imaged to determine left appendage flow, left atrial thrombi, left atrial SEC, and wall thickness of the descending thoracic aorta. All studies were recorded on videotape for subsequent analyses. No complications occurred during TEE.

Left atrial SEC was diagnosed by the presence of dynamic smoke-like echoes within the atrium and atrial appendage, distinct from background white noise caused by excessive gain. The severity of SEC was defined by the criteria of Fatkin et al.7 Briefly, it was graded from 0 to 4+ according to the following criteria: 0 = absence of echogenicity; 1+ = mild (minimal echogenicity only detectable with optimal gain settings transiently during the cardiac cycle); 2+ = mild to moderate (transient SEC without increased gain settings and more dense pattern than 1+); 3+ = moderate (dense swirling pattern during the entire cardiac cycle); and 4+ = severe (intense echodensity and very slow swirling patterns in the left atrial appendage, usually with similar density in the main cavity). In the following analyses, grades 3+ and 4+ were defined as high-grade SEC.

Left atrial appendage velocity profiles were obtained by pulsed-wave Doppler echocardiographic interrogation at the orifice of the appendage. Attempts were made to maintain the angle between the ultrasound beam and left atrial appendage flow (LAA-flow) within 30°. Peak outflow velocity signals within each R-R interval were averaged over a minimum of six cardiac cycles in each patient.

We performed a careful search for the intima-lumen interface and media-adventitia interface on the thoracic aorta and identified the thickest lesion of the intima-media complex in the aortic wall. Each patient’s aorta was graded in terms of the severity of atherosclerosis according to the grading system of Montgomery et al12 : grade 1 = no disease or intimal thickening; grade 2 = intimal thickening; grade 3 = atheroma < 5 mm; grade 4 = atheroma >= 5 mm; grade 5 = any mobile atheroma. The presence of aortic atheroma of the thoracic aorta (grades 3 to 5) was defined as severe atherosclerosis.

Statistical Analysis
Variables are presented as mean ± SD unless otherwise indicated. Statistical analyses were performed using software (SPSS version 8.01-J; SPSS; Chicago, IL). The significance of any difference in mean value was tested using unpaired Student’s t test, and the difference in proportions between two groups was tested using {chi}2 test. Mann-Whitney two-sample rank test was used for nonparametric distributions. Multivariate logistic regression analyses were used to determine independent predictors of cerebral embolic infarction in younger and elderly patients. Variables tested were high-grade (dense) SEC (>= grade 3), reduced LAA-flow (<= 20 cm/s), left atrial thrombi and aortic atherosclerosis (>= grade 3). Odds ratios are shown with 95% confidence intervals. A p value < 0.05 was considered statistically significant.


   Results
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Clinical Characteristics in Young vs Elderly Patients With AF
Of the 202 patients, 67 patients (33%) were elderly (mean age, 76 ± 5 years) and 135 patients (67%) were younger (mean age, 58 ± 8 years). The prevalences of hypertension and nonsmokers were significantly higher in elderly patients than in younger patients (Table 1 ). Other clinical variables did not differ between the two groups. As expected, elderly patients had cerebral embolism (cortical infarction) more frequently than younger patients (78% vs 45%; p = 0.001). Asymptomatic infarction with no definite neurologic signs or symptoms was found in 45% of elderly patients and 23% of younger patients. Thirty-six patients (54%) in the elderly group and 69 patients (51%) in the younger group received anticoagulation therapy with warfarin, and international normalized ratio (INR) at the time of TEE was not significantly different between the two groups (1.44 ± 0.47 in the elderly group vs 1.63 ± 0.70 in the younger group; p = 0.15). Aspirin was similarly used in 31% of the elderly patients and 30% of the younger patients (p = 0.80). Using univariate analyses, mitral stenosis emerged as a risk factor for cerebral embolism in the elderly patients, while permanent AF did so in the younger patients (Table 2 ).


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  		Table 1.. Background Characteristics*

 

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  		Table 2.. Univariate Analyses of Clinical Characteristics Related to Cerebral Embolism

 
As indicated in Table 3 , transthoracic echocardiographic characteristics did not differ between the elderly and younger groups. Erythrocyte sedimentation rate was significantly increased in elderly patients, although hematocrit and D-dimer levels were similar in both groups (Table 3) .


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  		Table 3.. Comparison of Echocardiographic and Hematologic Variables in Patients With and Without Cerebral Embolism*

 
Cerebral Embolism and TEE
Patients with cerebral embolism in the younger group had higher grade of left atrial SEC and lower LAA-flow than those without cerebral embolism (p < 0.05; Fig 1 , top). Presence of left atrial thrombi and severe atherosclerosis did not differ between younger patients with and without cerebral embolism. In contrast, the elderly group showed no significant differences in the grade of left atrial SEC, LAA-flow, and presence of left atrial thrombi formation between patients with and without cerebral embolism (Fig 1 , bottom). Alternatively, elderly patients with cerebral embolism had more severe atherosclerosis than those without cerebral embolism (p < 0.05). These were also true when patients with symptomatic cerebral embolism were compared with those without symptomatic or asymptomatic cerebral embolism. For example, 30 younger patients with symptomatic cerebral embolism had higher grade of left atrial SEC (2.0 ± 1.4 vs 0.8 ± 1.2; p < 0.05), and lower LAA-flow (27.3 ± 20.7 cm/s vs 42.6 ± 22.7 cm/s; p < 0.05) than younger patients without cerebral embolism. In contrast, 22 elderly patients with symptomatic cerebral embolism had similar grade of left atrial SEC (1.9 ± 1.1) and LAA-flow (30.6 ± 16.1 cm/s) as elderly patients without cerebral embolism (1.4 ± 1.5 and 34.9 ± 23.9 cm/s, respectively). Severe aortic atherosclerosis was more frequently seen in elderly patients with symptomatic embolism than in those without any embolism (68% vs 33%; p < 0.05).



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  		Figure 1.. TEE findings in younger patients (top) and elderly patients (bottom). LA = left atrial; severe atherosclerosis = atherosclersosis of descending thoracic aorta with atheroma. Open and solid bars represent patients without prior cerebral embolism and with prior cerebral embolism, respectively (mean ± SEM). *p < 0.05 vs patients without cerebral embolism.

 
Risk Stratification of Cerebral Embolism
Among all the clinical and echocardiographic variables determined in the present study, severe atherosclerosis found in the thoracic aorta was the only predictor of cerebral embolism in the elderly group, while reduced peak LAA-flow was an independent predictor of cerebral embolism in the younger group (Table 4 ). Other TEE variables did not provide any further information on the predictive value to characterize patients at risk for cerebral embolism.


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  		Table 4.. Multiple Logistic Analysis of TEE Factors Related to Cerebral Embolism*

 

   Discussion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
In the present study, we found that nearly half of the patients with cerebral infarction did not have apparent symptoms, and cerebral embolism was associated with lower LAA-flow in the younger group, but not in the elderly group. Alternatively, advanced lesions of atherosclerosis of the thoracic aorta emerged as a predictor of cerebral embolism in the elderly patients with AF.

Cerebral Infarction in AF
In this study, the prevalence of cerebral embolism was higher in the elderly group than in younger group, a consistent finding with the prior observations2 3 17 that the rate of ischemic stroke among patients with AF rose with increasing age. Small and large asymptomatic emboli were frequently observed in patients with AF. Indeed, 61 of 113 patients (54%) with cortical infarction were asymptomatic in the present study. TEE demonstrated that the grade of SEC was higher, and the peak LAA-flow velocity was lower in patients with cortical infarction than in those without cortical infarction,18 suggesting an association between left atrial blood stasis and systemic embolism in this type of cerebral infarction. Thus, it seems reasonable that most of cortical infarction among patients with AF was considered as embolism,19 although precise mechanism or mechanisms of cortical infarction remained undermined.

We found the significant difference in SEC grade between younger patients with and without cerebral embolism, but not between elderly patients with and without cerebral embolism. Left atrial SEC is an echogenic swirling pattern of blood flow with erythrocyte rouleaux formation, a marker of increased thromboembolic risk.20 It has been observed commonly in the left atrium and left atrial appendage in low-flow state, including AF and rheumatic mitral stenosis. In vitro studies20 21 demonstrated qualitative increases in blood echogenicity along with the decrease in blood flow rates. Accordingly, left atrial SEC was frequently associated with left atrial thrombi and embolic events.5 7 22 Indeed, a higher grade of SEC and lower peak LAA-flow velocity were found in the younger patients with cerebral cortical infarction in the present study, indicating that this specific subtype of infarction could be closely coupled with embolism from left atrial appendage in AF. On the other hand, the fact that there was no difference in the left appendage function between the elderly patients with and without cortical infarction suggests that multiple factors must be associated complicatedly with cerebral infarction of elderly patients with AF. These were also true when only patients with symptomatic cerebral embolism were included for analyses.

Cerebral Embolism and Aortic Atherosclerosis
Atherosclerotic changes in the thoracic aorta can be evaluated noninvasively with TEE. Montgomery et al12 reported that severe atherosclerosis of the thoracic aorta detected by TEE was an important risk factor for systemic atherosclerotic disease and its severity was correlated positively with ischemic cerebral stroke and mortality. In addition, clinical studies8 9 23 24 have shown that atherosclerosis of the thoracic aorta is an independent predictor of long-term neurologic events and mortality. Autopsy studies25 26 showed that the atherosclerotic involvement of the thoracic aorta was parallel to the extent and severity of atherosclerosis in the aortic arch and the carotid arteries. Therefore, patients with AF with severe atherosclerosis of the thoracic aorta could be susceptible to cerebral embolism arising from arterial lesions in the aortic arch as well as in the carotid system.19 24 26 Indeed, advanced atherosclerotic lesions of the thoracic aorta were observed more frequently in the elderly group than in the younger group of the present study. However, the distinct source and pathophysiologic mechanisms of cerebral embolism should be determined in future studies.

TEE in Patients With AF
Clinical trials2 3 4 have clearly demonstrated that anticoagulation with adjusted-dose warfarin (approximate target INR, 2.0 to 3.0) is effective in preventing the thromboembolic complications of AF. Since the risk of stroke rises with increasing age, long-term oral anticoagulation therapy is strongly recommended for elderly patients with AF. However, owing to the risk of serious bleeding and the need for close monitoring of INR levels, warfarin was used less frequently in elderly patients with AF in clinical practice.27 If TEE could be useful for stratifying embolic risk as shown in the previous studies as well as in the present study, it helps decide who should receive anticoagulation. Recently, the Stroke Prevention in Atrial Fibrillation III investigators28 have shown that the presence of echocardiographic abnormalities involving both left atrial appendage and aortic plaque was correlated with incidence of thromboembolism in high-risk patients with AF. Consistently, we found that older patients with aortic atherosclerosis were at high risk for embolism. Thus, assessment of embolic risk with TEE might improve management of patients with AF.

Study Limitations
There are several limitations of the present study. First, the diagnosis of thromboembolic infarction was based on assessment of brain CT or MRI retrospectively. TEE variables found at the onset of cerebral infarction were unclear in the present study. However, it is clinically difficult to have TEE at the onset of cerebral infarction, in particular, in patients with asymptomatic infarction. Second, most patients were receiving a combination of different medications, including aspirin or warfarin. These drugs may affect the incidence of cerebral infarction in both groups, but warfarin and aspirin were similarly used in the two groups. Intensity of anticoagulation in the present study was slightly weak as compared with that recommended in the United States.4 In Japan, low-intensity warfarin (INR, 1.5 to 2.1) is accepted for prevention of stroke in patients with AF.29 Third, the common carotid and vertebral arteries were not examined with ultrasonography, and the contribution of large-vessel atherosclerosis to cerebral infarction was not determined. Finally, prevalence of cerebral infarction was relatively high in both study groups. This could be attributed to patient selection in the present study. Although limited for these reasons, the present study suggests that factors outside the left atrium could contribute to the increased stroke risk in elderly patientswith AF.


   Acknowledgements
 
We thank Yoshiko Uchiyama, RMS, for assistance in collection and analysis of the data.


   Footnotes
 
Abbreviations: AF = atrial fibrillation; INR = international normalized ratio; LAA-flow = flow velocity in the left atrial appendage; SEC = spontaneous echocardiographic contrast; TEE = transesophageal echocardiography

Received for publication September 8, 2000. Accepted for publication March 21, 2001.


   References
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. . Atrial Fibrillation Investigators. (1994) Risk factors for stroke and efficacy of anti-thrombotic therapy in atrial fibrillation: analysis of pooled data from five randomized controlled trials. Arch Intern Med 154,1449-1457[Abstract]
  2. Ezekowitz, MD, Bridgers, SL, James, KE, et al (1992) Warfarin in the prevention of stroke associated with nonrheumatic atrial fibrillation. N Engl J Med 327,1406-1412[Abstract]
  3. . Stroke Prevention in Atrial Fibrillation Investigators (1994) Warfarin vs aspirin for prevention of thromboembolism in atrial fibrillation: Stroke Prevention in Atrial Fibrillation II study Lancet 343,687-691[CrossRef][ISI][Medline]
  4. . Stroke Prevention in Atrial Fibrillation Investigators (1996) Adjusted dose warfarin vs low intensity, fixed dose warfarin plus aspirin for high risk patients with atrial fibrillation: Stroke Prevention in Atrial Fibrillation III randomized clinical trial Lancet 348,633-638[CrossRef][ISI][Medline]
  5. Black, IW, Hopkins, AP, Lee, LCL, et al (1991) Left atrial spontaneous echo contrast: a clinical and echocardiographic analysis. J Am Coll Cardiol 18,398-404[Abstract]
  6. Pollick, C, Taylor, D (1991) Assessment of left atrial appendage function by transesophageal echocardiography: implications for the development of thrombus. Circulation 84,223-231[Abstract/Free Full Text]
  7. Fatkin, D, Kelly, RP, Feneley, MP (1994) Relations between left atrial appendage blood flow velocity, spontaneous echocardiographic contrast and thromboembolic risk in vivo. J Am Coll Cardiol 23,961-969[Abstract]
  8. Ferrari, E, Vidal, R, Chevallier, T, et al (1999) Atherosclerosis of the thoracic aorta and aortic debris as a marker of poor prognosis: benefit of oral anticoagulants. J Am Coll Cardiol 33,1317-1322[Abstract/Free Full Text]
  9. Stone, DA, Hawke, MW, LaMonte, M, et al (1995) Ulcerated atherosclerotic plaques in the thoracic aorta are associated with cryptogenic stroke: a multiplane transesophageal echocardiographic study. Am Heart J 130,105-108[CrossRef][ISI][Medline]
  10. Tunick, PA, Kronzon, I (1990) Protruding atherosclerotic plaque in the aortic arch of patients with systemic embolization: a new finding seen by transesophageal echocardiography. Am Heart J 120,658-660[CrossRef][ISI][Medline]
  11. . The French Study of Aortic Plaques in Stroke Group (1996) Atherosclerotic disease of the aortic arch as a risk factor for recurrent ischemic stroke N Engl J Med 334,1216-1221[Abstract/Free Full Text]
  12. Montgomery, DH, Ververis, JJ, McGorisk, G, et al (1996) Natural history of severe atheromatous disease of the thoracic aorta: a transesophageal echocardiographic study. J Am Coll Cardiol 27,95-101[Abstract]
  13. Fazio, GP, Redberg, RF, Winslow, R, et al (1993) Transesophageal echocardiographically detected atherosclerotic aortic plaque is a marker for coronary artery disease. J Am Coll Cardiol 21,144-150[Abstract]
  14. . Cerebral Embolism Task Force. (1989) Cardiogenic brain embolism: the second report of the Cerebral Embolism Task Force. Arch Neurol 46,727-743[Abstract]
  15. Damasio, H (1983) A computed tomographic guide to the identification of cerebral vascular territories. Arch Neurol 40,138-142[Abstract]
  16. Whisnant, JP, Basford, JR, Bernstein, EF, et al (1990) Classification of cerebrovascular disease. Stroke 21,637-676[Free Full Text]
  17. Laupacis, A, Albers, G, Dalen, J, et al (1995) Antithrombotic therapy in atrial fibrillation. Chest 108,352S-359S[Medline]
  18. Shinokawa, N, Hirai, T, Takashima, S, et al (2000) Relation of transesophageal echocardiographic findings of subtypes of cerebral infarction in patients with atrial fibrillation. Clin Cardiol 23,517-522[ISI][Medline]
  19. Lindgren, A, Roijer, A, Norrving, B, et al (1994) Carotid artery and heart disease in subtypes of cerebral infarction. Stroke 25,2356-2362[Abstract]
  20. Merino, A, Hauptman, P, Badimon, L, et al (1992) Echocardiographic "smoke" is produced by an interaction of erythrocytes and plasma proteins modulated by shear forces. J Am Coll Cardiol 20,1661-1668[Abstract]
  21. Siegel, B, Machi, J, Beitler, JC, et al (1983) Red cell aggregation as a cause of blood-flow echogenicity. Radiology 148,799-802[Abstract/Free Full Text]
  22. Leung, DYC, Black, IW, Cranney, GB, et al (1994) Prognostic implications of left atrial spontaneous echo contrast in nonvalvular atrial fibrillation. J Am Coll Cardiol 24,755-762[Abstract]
  23. Finkelhor, RS, Lamont, WE, Ramanavarapu, SK, et al (1995) Spontaneous echocardiographic contrast in the thoracic aorta: factors associated with its occurrence and its association with embolic events. Am Heart J 130,1254-1258[CrossRef][ISI][Medline]
  24. Blackshear, JL, Pearce, LA, Hart, RG, et al (1999) Aortic plaque in atrial fibrillation; prevalence, predictors, and thromboembolic implications. Stroke 30,834-840[Abstract/Free Full Text]
  25. Solberg, LA, Strong, JP (1983) Risk factors and atherosclerotic lesions: a review of autopsy studies. Arteriosclerosis 3,187-198[Abstract/Free Full Text]
  26. Khatibzadeh, M, Mitusch, R, Stierle, U, et al (1996) Aortic atherosclerotic plaques as a source of systemic embolism. J Am Coll Cardiol 27,664-669[Abstract]
  27. Brass, LM, Krumholz, HM, Scinto, JM, et al (1997) Warfarin useamong patients with atrial fibrillation. Stroke 28,2382-2389[Abstract/Free Full Text]
  28. Zabalgoitia, M, Halperin, JL, Pearce, LA, et al (1998) Transesophageal echocardiographic correlates of clinical risk of thromboembolism in nonvalvular atrial fibrillation: Stroke Prevention in Atrial Fibrillation III Investigators. J Am Coll Cardiol 31,1622-1626[Abstract/Free Full Text]
  29. . for the Japanese Nonvalvular Atrial Fibrillation-Embolism Secondary Prevention Cooperative Study GroupYamaguchi, T (2000) Optimal intensity of warfarin therapy for secondary prevention of stroke in patients with nonvalvular atrial fibrillation: a multicenter, prospective, randomized trial. Stroke 31,817-821[Abstract/Free Full Text]



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