Prediction of Risk of Thromboembolism by Plasma Brain
The purpose of this study was to assess a possible relationship between left atrial appendage function and plasma brain natriuretic peptide (BNP) levels in patients with nonvalvular atrial fibrillation. Transesophageal echocardiography and plasma BNP measurement were performed in 34 consecutive patients with chronic nonvalvular atrial fibrillation (age 69±9 years). Thirteen patients with a history of thromboembolism or echographically detected thrombus (E+ group), were compared with 21 atrial fibrillation patients without complications (E- group). The E+ group patients demonstrated greater impairment of left atrial appendage velocity and higher plasma BNP levels than the E- group patients (left atrial appendage velocity, 12±6 vs. 31±17 cm/s [p <0.05]; plasma BNP, 126±53 vs. 86±45 ng/L [p <0.05]). Overall analysis of the continuous variables with multiple logistic regression analysis revealed that BNP was a significant predictor of thromboembolism. The present data suggest the usefulness of measuring plasma BNP levels in detecting patients with a high risk for thromboembolic complications in nonvalvular atrial fibrillation.
Atrial fibrillation (AF) is a sustained arrhythmia commonly found in people in their 60s, and its incidence has been reported to be 2%-4% of this generation. In people ≥75 years, the incidence of AF has been reported to increase to 11.6%. Thromboembolism is an important complication of AF that causes deterioration in the patient's quality of life. Thus, proper selection of candidates for anticoagulation therapy among patients with AF is a matter of debate.
Transesophageal echocardiography (TEE) is a useful clinical tool both for identifying actual thrombi and for visualizing spontaneous echo contrast (SEC), which may predispose a patient to atrial thrombus formation. Left atrial appendage (LAA) flow velocity, measured by TEE, has been used as a functional parameter of the LAA. Several investigators have reported that patients with AF who have a low appendage blood flow velocity, reflecting impaired LAA function, have a higher risk of thromboembolism than patients with an appendage flow greater than 20 cm/s.
On the other hand, a biochemical approach to circulating blood enables us to assume thrombin activation and platelet aggregation in patients with either valvular or nonvalvular AF. However, abnormal values for these biochemical markers may not appear until thrombin is actually being activated, and more importantly, these abnormal values may not necessarily be of cardiac origin.
Brain natriuretic peptide (BNP), which increases in patients with heart disease such as congestive heart failure, dilated cardiomyopathy, hypertrophic cardiomyopathy, hypertensive heart disease, and lone AF, has been used as a biochemical parameter produced in the heart. Contrary to earlier theories that BNP is mainly secreted from the ventricular myocardium, we recently reported that the left atrium, not the left ventricle, is the main source of BNP in patients with AF. The major important findings in that study were that patients with AF show 1) significantly higher plasma BNP levels than control subjects; 2) a significant increase in BNP occurring between the coronary sinus and the anterior interventricular vein, reflecting atrial secretion of BNP; and 3) a significant decrease in both plasma BNP levels and atrial BNP production after direct current cardioversion of AF to sinus rhythm. However, the question of why a wide variation in plasma BNP levels was observed in patients with lone AF (ranging from 22-390 ng/L) remains unanswered. In the present study, we examined the question of whether plasma BNP levels are higher in patients with clinical evidence of thromboembolism than in patients without complications and, if so, whether plasma BNP levels correlate with left atrial function as represented by LAA flow.
The purpose of this study was to assess a possible relationship between left atrial appendage function and plasma brain natriuretic peptide (BNP) levels in patients with nonvalvular atrial fibrillation. Transesophageal echocardiography and plasma BNP measurement were performed in 34 consecutive patients with chronic nonvalvular atrial fibrillation (age 69±9 years). Thirteen patients with a history of thromboembolism or echographically detected thrombus (E+ group), were compared with 21 atrial fibrillation patients without complications (E- group). The E+ group patients demonstrated greater impairment of left atrial appendage velocity and higher plasma BNP levels than the E- group patients (left atrial appendage velocity, 12±6 vs. 31±17 cm/s [p <0.05]; plasma BNP, 126±53 vs. 86±45 ng/L [p <0.05]). Overall analysis of the continuous variables with multiple logistic regression analysis revealed that BNP was a significant predictor of thromboembolism. The present data suggest the usefulness of measuring plasma BNP levels in detecting patients with a high risk for thromboembolic complications in nonvalvular atrial fibrillation.
Atrial fibrillation (AF) is a sustained arrhythmia commonly found in people in their 60s, and its incidence has been reported to be 2%-4% of this generation. In people ≥75 years, the incidence of AF has been reported to increase to 11.6%. Thromboembolism is an important complication of AF that causes deterioration in the patient's quality of life. Thus, proper selection of candidates for anticoagulation therapy among patients with AF is a matter of debate.
Transesophageal echocardiography (TEE) is a useful clinical tool both for identifying actual thrombi and for visualizing spontaneous echo contrast (SEC), which may predispose a patient to atrial thrombus formation. Left atrial appendage (LAA) flow velocity, measured by TEE, has been used as a functional parameter of the LAA. Several investigators have reported that patients with AF who have a low appendage blood flow velocity, reflecting impaired LAA function, have a higher risk of thromboembolism than patients with an appendage flow greater than 20 cm/s.
On the other hand, a biochemical approach to circulating blood enables us to assume thrombin activation and platelet aggregation in patients with either valvular or nonvalvular AF. However, abnormal values for these biochemical markers may not appear until thrombin is actually being activated, and more importantly, these abnormal values may not necessarily be of cardiac origin.
Brain natriuretic peptide (BNP), which increases in patients with heart disease such as congestive heart failure, dilated cardiomyopathy, hypertrophic cardiomyopathy, hypertensive heart disease, and lone AF, has been used as a biochemical parameter produced in the heart. Contrary to earlier theories that BNP is mainly secreted from the ventricular myocardium, we recently reported that the left atrium, not the left ventricle, is the main source of BNP in patients with AF. The major important findings in that study were that patients with AF show 1) significantly higher plasma BNP levels than control subjects; 2) a significant increase in BNP occurring between the coronary sinus and the anterior interventricular vein, reflecting atrial secretion of BNP; and 3) a significant decrease in both plasma BNP levels and atrial BNP production after direct current cardioversion of AF to sinus rhythm. However, the question of why a wide variation in plasma BNP levels was observed in patients with lone AF (ranging from 22-390 ng/L) remains unanswered. In the present study, we examined the question of whether plasma BNP levels are higher in patients with clinical evidence of thromboembolism than in patients without complications and, if so, whether plasma BNP levels correlate with left atrial function as represented by LAA flow.