Value of D-Dimer in Risk Stratification for Thromboembolism in Patients With Atrial Fibrillation and Low CHA2DS2-VASc Score

Atrial fibrillation (AF) can cause thrombi formation and subsequent emboli deposition in systemic arteries, leading to various organ ischemia and infarction. Anticoagulation therapy can reduce the risk of thrombus formation and embolization, and is initiated based on a patient's risk score, which is frequently estimated with the CHA2DS2-VASc score. We present a case of thromboembolism (TE) where a low CHA2DS2-VASc score suggested a low-moderate risk of systemic embolization, but an elevated plasma D-dimer value prompted further investigation which revealed an intracardiac thrombus with renal embolism. The patient is a 63-year-old male with past medical history of hypertension and AF treated with ablation 2 years prior presenting with sharp right flank pain of 5-hour duration. Primary workup and imaging were unrevealing at the time, and a low CHA2DS2-VASc score was suggestive of aspirin therapy. However, an elevated D-dimer of 289 ng/mL and a transient increase in creatinine pointed to possible etiology of embolic origin. The diagnosis was confirmed with computed tomography (CT) with contrast and transesophageal echocardiogram, revealing renal infarcts and the source of the emboli, respectively. The patient was treated with heparin and transitioned to apixaban prior to discharge with full resolution of symptoms. Through this case, we wish to show D-dimer's predictive value of TE, as well as its potential benefit in risk assessment in patients with AF.

Useful indices of thrombogenesis in the exclusion of intra-cardiac thrombus

Background

Cardioversion in patients with atrial fibrillation (AF) can cause cardioembolic stroke, and effective clinical management is necessary to reduce morbidity and mortality. Currently, transesophageal echocardiography (TEE) is the accepted standard to diagnose cardiogenic thromboemboli; however, a negative TEE does not eliminate the possibility of left atrial thrombus. The objective of this study was to evaluate the diagnostic value of supplementing the TEE with additional noninvasive markers to ensure thrombus absence.

Methods

A prospective study was conducted on 59 patients who underwent TEE for suspected intra‐cardiac thrombi. The TEE indications included acute ischemic stroke (45.7%) and AF or flutter (59.3%). D‐dimer level and white blood cell counts were assessed.

Results

A negative D‐dimer level (<200 ng/mL) excluded the presence of intra‐cardiac thrombi. Groups with either negative (n = 14) or positive (n = 45) D‐dimer levels had comparable clinical characteristics. Comparing positive D‐dimer–level patients with thrombus (n = 7) and without thrombus (n = 33), patients with thrombus had reduced left atrial appendage (LAA) velocity (P = .0024), reduced left ventricular ejection fraction (LVEF) (P = .0263), increased neutrophil percent (P = .0261), decreased lymphocyte percent (P = .0216), and increased monocyte counts (P = .0220). The area under the receiver operating characteristic (ROC) curve for thrombus diagnostics was larger for combinations of clinical and biochemical data than for each parameter individually.

Conclusions

Supplementing the gold standard TEE with the analysis of LAA velocity, noninvasive LVEF, D‐dimer, and hemostatic markers provided additional useful diagnostic information. Larger studies are needed to further validate the efficacy of supplementing the TEE to better assess patients for intra‐cardiac thrombi.

Embolic Stroke Diagnosed by Elevated D-Dimer in a Patient With Negative TEE for Cardioembolic Source

We report a case of cerebrovascular accident with thromboembolic stroke etiology in a patient who had atrial flutter and negative transesophageal echocardiography (TEE) results. The increased D-dimer levels (1877 ng/mL) initiated referral for magnetic resonance imaging and magnetic resonance angiography of the brain that showed classic recanalization of an embolic thrombus in the angular branch of the left middle cerebral distribution. The D-dimer level of this patient was normalized after 3 months of anticoagulation therapy. Although TEE is considered the gold standard for evaluation of cardiac source of embolism, exclusion of intracardiac thrombus with TEE alone does not eliminate the risk of thromboembolic events. This case highlights the utility of D-dimer as a potential adjunct in the decision-making process to guide investigation of thromboembolism, determine subsequent therapy, and hence reduce the risk of embolic stroke recurrence.

Can α-lipoic acid mitigate progression of aging-related decline caused by oxidative stress?

Aging is progressively deteriorating physiological function that leads to increasing risks of illness and death. Increases in life expectancy and the aging of a large segment of the population have made age-related disability and morbidity increasingly important issues. Supplements such as α-lipoic acid may have antiaging effects by positively affecting oxidative stress, cognitive function, and cardiovascular function.

The D-dimer assay: a possible tool in the evaluation of atrial thrombosis

Atrial fibrillation (AF) is a common arrhythmia seen in clinical practice, and affects more than 4% of the population older than 60 years of age. Peripheral thromboembolism contributes significantly to the observed morbidity and mortality. Symptomatic AF, before cardioversion to normal sinus rhythm, requires either exclusion of atrial thrombi using transesophageal echocardiography (TEE) or the conventional use of three weeks of adequate anticoagulation. The exclusion of atrial thrombi by TEE, a nontomographic technique but comparable with conventional treatment of AF in outcomes, has inherent limitations due to the complex three-dimensional multilobed anatomy of the left atrial appendage, where the majority of atrial thrombi arise. Also, the conventional treatment of three weeks of therapeutic anticoagulation before cardioversion reportedly does not always eliminate atrial thrombi. Plasma D-dimer constitutes an antigen-antibody reaction to the dimeric final degradation product of a mature clot. An elevated fibrin D-dimer has a high sensitivity for intravascular thrombosis and, hence, may improve the evaluation of a patient with AF before cardioversion in addition to a TEE. A case is presented in which a positive D-dimer resulted in performing TEE to document atrial thrombosis and the complications of previous bacterial endocarditis. In the present case, this involved aortic root abscess formation and acute aortic regurgitation because of flailing of the noncoronary cusp that resulted in recurrent pulmonary edema.

Characteristics of patients with cervical spinal injury requiring permanent pacemaker implantation

Acute cervical spinal cord injury frequently results in bradydysrhythmia, which may lead to hypotension and asystole. Such symptoms are more common in the first 2 weeks after the injury. Treatment modalities include atropine, epinephrine, aminophylline, and pacemaker insertion. The criteria for pacemaker use in this population are not well defined. We describe characteristics of 3 patients who required permanent, transvenous pacemaker implantation for recurrent symptoms. In 2 of the 3 patients, transcutaneous pacing failed to provide adequate protection. Transcutaneous pacemakers are not reliable, as was the case of these patients, and early consideration for transvenous pacemaker insertion may be indicated, especially in hemodynamically unstable patients. In this report, all 3 patients required permanent pacemaker implantation.

Latex D-dimer signal in in situ femoral vein thrombus in swine and effect of minidose exogenous tissue plasminogen activator bolus

STUDY OBJECTIVES

We created in situ femoral vein thrombi in swine to investigate the response of the latex d-dimer signal to acute in situ venous thrombosis, and to determine the minimum dose of exogenous bolus tissue plasminogen activator (t-PA) required to significantly elevate the d-dimer signal.

STUDY DESIGN

We studied seven swine (20 to 22 kg) under pentobarbital anesthesia. A 6-cm segment of the proximal femoral vein was surgically exposed and briefly ligated. Thrombin, 250 U, was then injected into the isolated femoral vein segment to create an in situ clot. After clot formation was documented to be complete between the ligatures, they were then released. D-dimer levels were then measured every 15 min for 1 h before and 1 h after clot formation with ligatures released. Time-response curves to establish timing of peak t-PA effect were performed, and then escalating dose-response curves of d-dimer level to minidose t-PA were plotted.

RESULTS

After formation of the clot, the release of ligatures resulted in no change in d-dimer levels over 1 h (p = 0.62) in all swine. When a time-response curve to exogenous t-PA bolus in the presence of femoral clot was plotted, there was a maximal increase in d-dimer signal at 30 min after bolus t-PA administration. The subsequent dose-response curves for escalating fivefold boluses of minidose t-PA showed an increase in d-dimer signal at doses of 0.8 mg (p = 0.03) and 4 mg (p = 0.003).

CONCLUSION

We conclude the following: (1) in situ femoral vein clot formation does not elevate d-dimer signal for 1 h after ligature release; (2) minidose t-PA boluses of 0.8 mg and 4 mg significantly elevated the latex d-dimer signal above baseline; and (3) there is a potential role of minidose t-PA in enhancing the d-dimer signal in in situ deep venous thrombosis.

Effects of acute volume loading and hemorrhage on intestinal vascular capacitance: a mechanism whereby capacitance modulates cardiac output

BACKGROUND

Changes in intestinal vascular capacitance during acute volume loading and hemorrhage have not been described.

OBJECTIVES

To determine the effects of volume loading and hemorrhage on the intestinal vascular pressure-volume relationship and cardiac output.

PATIENTS AND METHODS

In 11 alpha-chloralose-anesthetized dogs, a pneumatic portal venous constrictor and catheter were positioned to increase and measure portal venous pressure (Ppv), respectively. Relative changes in intestinal blood volume (IBV) were determined by blood-pool scintigraphy and expressed as the percentage change from control values (taken as 100%). Ppv-IBV relationships were constructed by graded portal vein constriction.

RESULTS

IBV and cardiac output increased by 60 6% and 178 48%, respectively, and Ppv increased from 5.8 0.9 mmHg to 13.2 1.8 mmHg after initial volume loading (40 mL/kg of an isotonic glucose-saline solution over 7 min). IBV gradually decreased and reached near-control values after 75 min. In seven dogs, hemorrhage (sufficient to decrease mean aortic pressure by 56 4%) decreased IBV and cardiac output to 88 4% and 52 3% of control values, respectively, and Ppv decreased to 3.2 0.8 mmHg.

CONCLUSIONS

A sigmoid function curve defined the relationship between cardiac output and IBV. Cardiac output remained constant over a wide range (between approximately 95% and 135% of control IBV). Outside this range, insufficient dilation or constriction resulted in a marked increase or decrease in venous pressures and cardiac output. These data indicate that vasculature capacitance modulates cardiac output during acute volume loading and hemorrhage, thereby maintaining cardiac output relatively constant over a wide range of total vascular blood volume.