Relationship between prothrombin activation fragment F1.2 and international normalized ratio in patients with atrial fibrillation. Stroke Prevention in Atrial Fibrillation Investigators

AutoMLP: A Framework for the Acceleration of Multi-Layer Perceptron Models on FPGAs for Real-Time Atrial Fibrillation Disease Detection

Cardiovascular diseases are a leading cause of death globally, and atrial fibrillation (AF) is a common arrhythmia that affects many people. Detecting AF in real-time using hardware acceleration can prompt timely medical intervention. Multi-layer perceptron (MLP) has demonstrated the ability to detect AF accurately. However, implementing MLP on Field-Programmable Gate Array (FPGA) for real-time detection poses challenges due to the complex hardware design requirements. This study presents a novel framework for generating hardware accelerators to detect AF in real-time using MLP on FPGA. The framework automates evaluating MLP model topology, data type, and bit-widths to generate parallel acceleration. The generated solutions are evaluated using two AF datasets, PhysioNet MIT-BIH atrial fibrillation (AFDB) and China Physiological Signal Challenge 2018 (CPSC2018), regarding execution time, resource utilization, and accuracy. The evaluation results demonstrate that the hardware MLP can achieve a speedup higher than 1500× and around 25000× lower energy consumption than an embedded CPU. These satisfactory results prove the framework's suitability and convenience for the online detection of AF in an accelerated and automatic way through FPGA hardware implementation.

An in situ inferior vena cava ligation-stenosis model to study thrombin generation rates with flow

BACKGROUND

Blood flow-induced shear stress affects platelet participation in coagulation and thrombin generation. We aimed to develop an in vivo model to characterize thrombin generation rates under flow.

METHODS

An in situ inferior vena cava (IVC) ligation-stenosis model was established using C57BL/6 mice. Wild type C57BL/6 mice were fed normal chow diet for two weeks before experiments. On the day of experiments, mice were anesthetized, followed by an incision through the abdominal skin to expose the IVC, which was then ligated (followed by reperfusion through a stenosis for up to 2 h). IVC blood flow rate was monitored using a Transonic ultrasound flow meter. In sham animals, the IVC was exposed following the same procedure, but no ligation was applied. Thrombin generation following IVC ligation was estimated by measuring mouse plasma prothrombin fragment 1-2 concentration. Mouse plasma factor Va concentration was measured using phospholipids and a modified prothrombinase assay. Blood vessel histomorphology, vascular wall ICAM-1, von Willebrand Factor, tissue factor, and PECAM-1 expression were measured using immunofluorescence microscopy.

RESULTS

IVC blood flow rate increased immediately following ligation and stenosis formation. Sizable clots formed in mouse IVC following ligation and stenosis formation. Both plasma factor Va and prothrombin fragment 1-2 concentration reduced significantly following IVC ligation/stenosis, while no changes were observed with ICAM-1, von Willebrand Factor, tissue factor and PECAM-1 expression.

CONCLUSION

Clot formation was successful. However, the prothrombin-thrombin conversion rate constant in vivo cannot be determined as local thrombin and FVa concentration (at the injury site) cannot be accurately measured. Modification to the animal model is needed to further the investigation.

Assessment of Coagulation and Hemostasis Biomarkers in a Subset of Patients With Chronic Cardiovascular Disease

Measurement of a single marker of coagulation may not provide a complete picture of hemostasis activation and fibrinolysis in patients with chronic cardiovascular diseases. We assessed retrospective orders of a panel which included prothrombin fragment 1.2 (PF1.2), thrombin: antithrombin complexes, fibrin monomers, and D-dimers in patients with heart assist devices, cardiomyopathies, atrial fibrillation and intracardiac thrombosis (based on ordering ICD-10 codes). During 1 year there were 117 panels from 81 patients. Fifty-six (69%) patients had heart assist devices, cardiomyopathy was present in 17 patients (21%) and 29 patients (36%) had more than 1 condition. PF1.2 was most frequently elevated in patients with cardiomyopathy (61.1%) compared to those with cardiac assist devices (15.7%; P = 0.0002). D-dimer elevation was more frequent in patients with cardiac assist devices (98.8%) compared to those patients with cardiomyopathy (83.3%; P = 0.014). Patients with cardiomyopathy show increases of PF1.2 suggesting thrombin generation. In contrast, elevations of D-dimers without increase in other coagulation markers in patients with cardiac assist devices likely reflect the presence of the intravascular device and not necessarily evidence of hemostatic activation.

The Relationship Between Prolidase Activity and Atrial Electromechanical Changes in Patients with Paroxysmal Atrial Fibrillation

Background:

Tissue fibrosis increases in the structure of the atrial tissue of atrial fibrillation patients. Prolidase enzyme regulates collagen synthesis. There may be an association between electrocardiography (ECG) findings and prolidase activity.

Objective:

This study investigated the association between atrial conduction time and prolidase activity, a collagen synthesis enzyme, and P-wave dispersion (PWD) in patients with Paroxysmal Atrial Fibrillation (PAF).

Methods:

Exclusion criteria included the age of <18 years, heart failure, diabetes, hypertension, hyperlipidemia, malignancy, cerebrovascular disease, chronic respiratory distress, osteoporosis, rheumatoid arthritis, renal disease, cirrhosis, and other types of arrhythmia. Patients diagnosed with PAF within 48 hours were considered to have a definite diagnosis. PWD was calculated using a 12-lead ECG, and inter- and intraatrial electromechanical delay (EMD) was assessed using tissue Doppler imaging and conventional echocardiography. Serum prolidase levels were measured in both groups.

Results:

A total of 43 patients with PAF (20 female, 23 male; mean age, 46.8 ± 5.7 years) and 42 healthy volunteers (21 female, 21 male; mean age, 43.9 ± 5.1 years) were included in the study.

:

Inter- and intraatrial EMD, PWD, minimum P-wave (Pmin), and maximum P-wave (Pmax) measurements were significantly higher (39.7 ± 2.7, 35.7 ± 2.3, p < 0.001; 13.2 ± 2.6, 8.5 ± 1.9, p < 0.001; 47.1 ± 11, 24.1 ± 7.1, p < 0.001; 69.8 ± 8.8, 66.7 ± 10.2, p < 0.130; 114.8 ± 13, 93.6 ± 8.6, p < 0.001, respectively) and serum prolidase levels were significantly lower in patients with PAF compared to healthy controls (3.96 ± 1.2, 8.5 ± 3.56, p < 0.001). In patients with PAF, correlation analysis showed a negative correlation between prolidase levels and intra- and interatrial EMD, PWD, and Pmax (r = -0.41, p < 0.05; r = -0.54, p < 0.05; r = -0.62, p < 0.05; r = -0.49, p < 0.05, respectively). Interatrial EMD showed a significant positive correlation with intraatrial EMD, Pmax, and PWD in patients with PAF (r = 0.90, p < 0.05; r = 0.574, p < 0.05; r = 0.43, p < 0.05, respectively). Additionally, the level of high-sensitivity C-reactive protein (hs-CRP) was significantly higher in patients with PAF (6.6 ± 8, 1.8 ± 1.6, p < 0.001).

Conclusion:

The decreased plasma prolidase activity in patients with PAF may explain the irregularity of the collagen metabolism of different extracellular components and may indicate the onset of atrial remodeling. Changes in PWD, interatrial EMD, and serum prolidase level may predict PAF before diagnosis.

Performance of an Implantable Cardiac Monitor to Detect Atrial Fibrillation: Results of the DETECT AF Study

INTRODUCTION

Reliable detection and monitoring of atrial fibrillation (AF) is essential for accurate clinical decision making, which can now be done continuously with the introduction of implantable cardiac monitors (ICM) The DETECT AF study evaluated the performance of the Confirm DM2102 ICM (St. Jude Medical, St. Paul, MN, USA) to accurately detect and monitor AF.

METHODS

Ninety patients previously implanted with the ICM and with either suspected or known paroxysmal AF were enrolled at 12 centers in Germany and The Netherlands. At least 2 weeks after ICM implant, patients wore a Holter monitor for 4 days, while the ICM monitored for AF episodes lasting at least 2 minutes. Holter monitor data was analyzed by a blinded, independent core laboratory and compared to the ICM AF detections. Patient and episode sensitivity (SE), specificity (SP), positive predictive value (PPV), and negative predictive (NPV) were calculated using standard analysis and a generalized estimation equation method where appropriate.

RESULTS

A total of 79/90 subjects (61% male, 65.7 ± 9.6 years old) were included in the analysis, totaling 6,894 hours of Holter monitoring. Using a per patient analysis SE was 100%, PPV was 64.0%, SP was 85.7%, and NPV was 100%. Using a per episode analysis, SE was 94.0% and PPV was 64.0%. With an AF duration analysis, the SE was 83.9%, PPV was 97.3%, SP was 99.4% with an NPV of 98.5%.

CONCLUSION

The SJM Confirm DM2102 can accurately and repeatedly detect paroxysmal AF episodes of at least 2 minutes in length.

Increased Level of Thrombotic Biomarkers in Patients with Atrial Fibrillation Despite Traditional and New Anticoagulant Therapy

The aim of this study was to examine the effect of the traditional oral anticoagulant, warfarin (W), and new anticoagulants, apixaban (A) and rivaroxaban (R), on the level of thrombotic biomarkers in patients with atrial fibrillation (AF). Circulating plasma levels of von Willebrand factor (vWF), prothrombin fragment 1.2 (F1.2), microparticle tissue factor (MP-TF), and plasminogen activator inhibitor (PAI-1) were analyzed as potential markers of clot formation in 30 patients with AF prior to ablation surgery. Patients with AF were divided into 2 groups based on their usage (n = 21) and nonusage (n = 9) of any oral anticoagulant. Furthermore, those on anticoagulants were divided based on their use of newer (R and A, 16) or traditional (W, 4) anticoagulants. A statistical increase (P < .05) in the levels of vWF, MP-TF, and PAI-1 were seen in anticoagulated patients with AF, whereas F1.2 and PAI-1 were increased in nonanticoagulated patients with AF compared to normal. There was no statistical difference (P > .05) in levels of any thrombotic biomarker between patients treated with the traditional anticoagulant, W, and those treated with new anticoagulants, R and A. Our data suggest that, despite the use of traditional or newer anticoagulants, prothrombotic biomarkers are still generated at increased levels in patients with AF. Further studies to confirm these findings are warranted.

Association of Brachial-Ankle Pulse Wave Velocity With Cardiovascular Events in Atrial Fibrillation

BACKGROUND

Atrial fibrillation (AF) and increased arterial stiffness share several risk factors and the 2 diseases often coexist. However, the prognostic value of increased arterial stiffness remains uncertain in the AF population. We evaluated whether brachial-ankle pulse wave velocity (baPWV), a marker of arterial stiffness, can predict cardiovascular events, and determined that the baPWV is a more favorable prognostic marker compared with conventional clinical and echocardiographic markers in patients with AF.

METHODS

We enrolled 167 patients with persistent AF. Arterial stiffness was assessed using baPWV. Cardiovascular events were defined as cardiovascular death, nonfatal stroke, nonfatal myocardial infarction, and hospitalization for heart failure. The relative risk of cardiovascular events was analyzed using Cox regression models. An improvement in model prediction was determined using the -2 log likelihood ratio statistic.

RESULTS

During a median 26-month follow-up, 42 (24.9%) cardiovascular events were observed. The baPWV emerged as an independent predictor of cardiovascular events (adjusted hazard ratio: 1.152; 95% confidence interval: 1.054-1.259; P = 0.002) in the multivariate analysis. Furthermore, the addition of baPWV to a Cox model comprising standard clinical, biochemical, and echocardiographic parameters improved the prediction of adverse cardiovascular events (P < 0.001).

CONCLUSIONS

In patients with AF, a high baPWV is associated with increased cardiovascular events and improve the prediction of adverse cardiovascular events. Hence, baPWV might be included when examining patients with AF for prediction of adverse cardiovascular outcomes.

Prognostic role of left atrial strain and its combination index with transmitral E-wave velocity in patients with atrial fibrillation

Left atrial (LA) strain can reflect LA remodeling and is reduced in atrial fibrillation (AF) patients with prior stroke. This study sought to examine the ability of LA strain in predicting subsequent stroke event in AF and also evaluated whether E/LA strain could predict cardiovascular (CV) events in these patients. In 190 persistent AF patients, we performed comprehensive echocardiography with assessment of LA strain. There were 69 CV events including 19 CV death, 32 hospitalizations for heart failure, 3 myocardial infarctions, and 15 strokes during an average follow-up of 29 months. Multivariate analysis showed old age, chronic heart failure, increased left ventricular (LV) mass index, and increased E/LA strain were associated with CV events and decreased LA strain was associated with subsequent stroke event. The addition of E/LA strain and LA strain to a model containing CHA2DS2-VASc score and LV function significantly improved the values in predicting CV events and subsequent stroke event, respectively. In conclusion, E/LA strain and LA strain were respectively useful in predicting CV events and subsequent stroke event in AF. E/LA strain and LA strain could provide incremental values for CV outcome and subsequent stroke outcome prediction over conventional clinical and echocardiographic parameters in AF, respectively.

Association of the Ratio of Early Mitral Inflow Velocity to the Global Diastolic Strain Rate with a Rapid Renal Function Decline in Atrial Fibrillation

The ratio of early mitral inflow velocity (E) to the global diastolic strain rate (E'sr) has been correlated with left ventricular filling pressure and predicts adverse cardiac outcomes in atrial fibrillation (AF). The relationship between the E/E'sr ratio and renal outcomes in AF has not been evaluated. This study examined the ability of the E/E'sr ratio in predicting progression to the renal endpoint, which is defined as a ≥ 25% decline in the estimated glomerular filtration rate in patients with AF. Comprehensive echocardiography was performed on 149 patients with persistent AF, and E'sr was assessed from three standard apical views using the index beat method. During a median follow-up period of 2.3 years, 63 patients (42.3%) were reaching the renal endpoint. Multivariate analysis showed that an increased E/E'sr ratio (per 10 cm) (hazard ratio, 1.230; 95% confidence interval, 1.088 to 1.391; p = 0.001) was associated with an increased renal endpoint. In a direct comparison, the E/E'sr ratio outperformed the ratio of E to early diastolic mitral annular velocity (E') in predicting progression to the renal endpoint in both univariate and multivariate models (p ≤ 0.039). Moreover, adding the E/E'sr ratio to a clinical model and echocardiographic parameters provided an additional benefit in the prediction of progression to the renal endpoint (p = 0.006). The E/E'sr ratio is a useful parameter and is stronger than the E/E' ratio in predicting the progression to the renal endpoint, and it may offer an additional prognostic benefit over conventional clinical and echocardiographic parameters in patients with AF.

Effects of anticoagulation on markers of activation of clotting following major orthopedic surgery

INTRODUCTION

This study examines makers of activation of clotting following three chemoprophylactic regimens used for prevention of postoperative venous thromboembolic disease (TED) following high-risk surgery for TED.

METHODS

Patients having elective primary knee or hip replacement surgery received variable dose warfarin (target international normalized ratios 2.0-2.5), 1 mg warfarin daily starting 7 days preoperatively or aspirin 325 mg daily starting on the day of surgery. Twelve patients in each group were treated for 28 ± 2 days. Thrombin-antithrombin (T-AT) and prothrombin fragment F1 + 2 were measured at baseline and postoperative days 3 and 28 ± 2.

RESULTS

Thrombin-antithrombin and F1 + 2 on postoperative day 3 were equal for the study groups. By days 28 ± 2, variable dose warfarin therapy group suppressed production of F1 + 2 (P = 0.002) with no difference in the T-AT accumulation. F1 + 2 for other patients overlapped the normal range.

CONCLUSION

The signals of activated clotting following surgery did not differentiate the three regimens on postoperative day 3. Variable dose warfarin was associated with suppression of F1 + 2 after 1 month of therapy, with no effect on accumulation of T-AT. Fixed low-dose warfarin started 7 days prior to surgery and aspirin are not inferior on postoperative day 3, but appear to be inferior over a longer treatment.

An unusual complication of atrial fibrillation ablation: case report

The authors report a complication of catheter ablation that, to their knowledge, has never been previously reported. A 63-year-old man had undergone successful transvenous catheter thermoablation for atrial fibrillation. The patient remained well until 3 days prior to further admission when he noticed itching in the right frontal area of his scalp. On palpating his scalp, he discovered a metallic body projecting out of it and he proceeded to extract 20 cm of wire from his head. The following day a progressive left hemiplegia developed, and the patient experienced a deteriorating level of consciousness. A CT scan of the brain showed a right frontotemporal intraparenchymal hemorrhage and revealed a metallic structure in the middle of the hematoma. The hematoma was evacuated and a decompressive craniotomy was performed. The guidewire was identified, but it was only possible to extract part of it. It was covered by fibrous tissue, secondary to inflammatory reaction. To the authors' knowledge, this is the first report of guidewire-induced brain hemorrhage. The guidewire apparently had not been removed and had spontaneously migrated from the heart to the brain and beyond to the scalp where it then exited the patient's head. The patient had been well before he attempted to pull out the wire. Earlier identification of the iatrogenic complication of a retained guidewire might have prevented the fatal outcome in this case.

How does Chronic Atrial Fibrillation Influence Mortality in the Modern Treatment Era?

Atrial fibrillation (AF) continues to impose a significant burden upon healthcare resources. A sustained increase in the ageing population and better survival from conditions such as ischaemic heart disease have ensured that both the incidence and prevalence of AF continue to increase significantly. AF can lead to complications such as embolism and heart failure and these acting in concert with its associated co-morbidities portend increased mortality risk. Whilst some studies suggest that the mortality risk from AF is due to the "bad company it keeps" i.e. the associated co-morbidities rather than AF itself; undoubtedly some of the mortality is also due to the side-effects of various therapeutic strategies (anti-arrhythmic drugs, bleeding side-effects due to anti-coagulants or invasive procedures). Despite several treatment advances including newer anti-arrhythmic drugs and developments in catheter ablation, anti-coagulation remains the only effective means to reduce the mortality due to AF. Warfarin has been used as the oral anticoagulant in the treatment of AF for many years but suffers from disadvantages such as unpredictable INR levels, bleeding risks and need for haematological monitoring. This has therefore spurred a renewed interest in research and clinical studies directed towards developing safer and more efficacious anti-coagulants. We shall review in this article the epidemiological features of AF-related mortality from several studies as well as the cardiovascular and non-cardiac mortality mechanisms. We shall also elucidate why a rhythm control strategy has appeared to be counter-productive and attempt to predict the likely future impact of novel anti-coagulants upon mortality reduction in AF.

Occult left atrial ball-like thrombus in a patient referred for surgical removal of suspected cerebellum tumor

BACKGROUND

Atrial fibrillation and related cardio-embolic cerebrovascular accidents are two well-defined major healthcare problems worldwide. It has been approximated that 2.2 million people in America and 4.5 million in European Union have paroxysmal or persistent atrial fibrillation. And atrial fibrillation itself is an independent long-term risk factor of stroke. We present a case of patient referred to our center for surgical removal of suspected cerebellum tumor, a case that had a rather unexpected ending.

CASE REPORT

A 58-year-old male patient with a history of atrial fibrillation, congestive heart failure (NYHA II/III), stable coronary artery disease, diabetes type 2 and hyperlipidemia presented with vertigo, headaches, mainly during physical activity and increased tiredness. Performed computer tomography revealed two lesions in the cerebellum and in the left lateral chamber. The diagnosis of a proliferative disease of the cerebellum was established and patient was referred to the Neurosurgical Department. Fortunately, before the operation the echocardiography was performed, which revealed two lesions in left atrium. The decision of the Heart Team was to refer the patient for an open-heart surgery, in which two thrombi were removed. Neurosurgeons decided to withdraw from further surgery and proceed with head MRI and conservative treatment, deciding that the lesion in the cerebellum was most likely an ischemic area.

CONCLUSIONS

Looking at the brain lesion should always be done from the whole patient's perspective. And using mutlimodality imaging may lead to appropriate diagnosis, correct course of therapeutic action and unexpected ending of a rather non-extraordinary case.

Risk of new-onset atrial fibrillation in elderly patients with the overlap syndrome: a retrospective cohort study

OBJECTIVE

Co-existence of obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD) is referred to as overlap syndrome. Overlap patients have greater degree of hypoxia and pulmonary hypertension than patients with OSA or COPD alone. Studies showed that elderly patients with OSA alone do not have increased risk of atrial fibrillation (AF) but it is not known if overlap patients have higher risk of AF. To determine whether elderly patients with overlap syndrome have an increased risk of AF.

METHODS

In this single center, community-based retrospective cohort analysis, data were collected on 2,873 patients > 65 years of age without AF, presenting in the year 2006. Patients were divided into OSA group (n = 60), COPD group (n = 416), overlap syndrome group (n = 28) and group with no OSA or COPD (n = 2369). The primary endpoint was incidence of new-onset AF over the following two years. Logistic regression was performed to adjust for heart failure (HF), coronary artery disease, hypertension (HTN), cerebrovascular disease, cardiac valve disorders, diabetes mellitus, hyperlipidemia, chronic kidney disease (CKD) and obesity.

RESULTS

The incidence of AF was 10% in COPD group, 6% in OSA group and 21% in overlap syndrome group (P < 0.05). After adjusting for age, sex, HF, CKD, and HTN, patients with overlap syndrome demonstrated a significant association with new-onset AF (OR = 3.66, P = 0.007). HF, CKD and HTN were also significantly associated with new-onset AF (P < 0.05).

CONCLUSION

Among elderly patients, the presence of overlap syndrome is associated with a marked increase in risk of new-onset AF as compared to the presence of OSA or COPD alone.

Atrial Fibrillation Ablation: Do We Really Need Preprocedural Imaging?

Atrial fibrillation is the most common human arrhythmia, causing significant mortality and morbidity. Because of the potential for complications, it is important that procedures be made as safe and effective as possible by combining safe procedural planning with effective therapy delivery. To change the current approach, large randomized studies are needed to guide the selection of patients who may safely undergo ablation without transesophageal echocardiography to exclude thrombus. For institutions routinely using computed tomography and magnetic resonance imaging to assess pulmonary vein anatomy before procedures, the possibility of excluding intracardiac thrombi using these imaging modalities should be considered.

Metabolic stress, reactive oxygen species, and arrhythmia

Cardiac arrhythmias can cause sudden cardiac death (SCD) and add to the current heart failure (HF) health crisis. Nevertheless, the pathological processes underlying arrhythmias are unclear. Arrhythmic conditions are associated with systemic and cardiac oxidative stress caused by reactive oxygen species (ROS). In excitable cardiac cells, ROS regulate both cellular metabolism and ion homeostasis. Increasing evidence suggests that elevated cellular ROS can cause alterations of the cardiac sodium channel (Na(v)1.5), abnormal Ca(2+) handling, changes of mitochondrial function, and gap junction remodeling, leading to arrhythmogenesis. This review summarizes our knowledge of the mechanisms by which ROS may cause arrhythmias and discusses potential therapeutic strategies to prevent arrhythmias by targeting ROS and its consequences. This article is part of a Special Issue entitled "Local Signaling in Myocytes".

Is there a role for bi-atrial pacing resynchronisation therapy in the management of drug-refractory atrial fibrillation in patients unsuitable for left atrial ablation?

BACKGROUND

This retrospective cohort study evaluated whether long term outcome of atrial resynchronisation therapy using bi-atrial pacing (BiaP) to treat atrial fibrillation (AF) was effective in patients deemed unfit for left atrial (LA) ablation procedures.

METHODS AND RESULTS

The patient population comprised 2 groups: those deemed suitable for left LA ablation (n=14) and those who were not (n = 17). Both groups underwent BiaP and outcomes were evaluated by comparing symptoms, AF duration, admissions and antiarrhythmic drugs (AAD) for an equal period of time pre and post implantation. Median follow-up was 24 months (range 8-66 months) for the unsuitable group and 31 months (range 7-84 months) for the suitable group. Efficacy in reduction of both AF and symptoms was similar (P = 0.44) in both groups (unsuitable group: 13/17; suitable group: 8/14). There was significant improvement in median AF episodes/week pre and post BiaP in both groups (unsuitable group AF reduction: 5 days/week, P = 0.001; suitable group AF reduction: 4.9 days/week, P = 0.03); the improvement was similar in both groups (P = 0.33). There was a significant reduction in the median number of admissions for AF in both groups (unsuitable group: P = 0.003; suitable group: P = 0.01) and this reduction was also similar (P = 0.70). The median number of AAD was also reduced to a similar degree (P = 0.83) in both groups (suitable group: P = 0.004; unsuitable group: P = 0.001).

CONCLUSIONS

Atrial resynchronisation therapy is effective in the long term management of drug-resistant AF in patients unsuitable for LA ablation, leading to significant reductions in symptoms, AF duration, admissions and AAD.

[Class I antiarrhythmic drugs: mechanisms, contraindications, and current indications]

Class I antiarrhythmic drugs are sodium channel inhibitors that act by slowing myocardial conduction and, thus, interrupting or preventing reentrant arrhythmia. Due to proarrhythmic effects and the risk of ventricular tachyarrhythmia, class I antiarrhythmics should not be administered in patients with structural heart disease. Nevertheless, there remains a broad spectrum of arrhythmias--among the most common being atrial fibrillation--that can successfully be treated with class I antiarrhythmic drugs. This review gives an overview on the classification, antiarrhythmic mechanisms, indications, side effects, and application modes of class I antiarrhythmic drugs.

Ablation of atrial fibrillation with the Epicor system: a prospective observational trial to evaluate safety and efficacy and predictors of success

Background

High intensity focused ultrasound (HIFU) energy has evolved as a new surgical tool to treat atrial fibrillation (AF). We evaluated safety and efficacy of AF ablation with HIFU and analyzed predictors of success in a prospective clinical study.

Methods

From January 2007 to June 2008, 110 patients with AF and concomitant open heart surgery were enrolled into the study. Main underlying heart diseases were aortic valve disease (50%), ischemic heart disease (48%), and mitral valve disease (18%). AF was paroxysmal in 29%, persistent in 31%, and long standing persistent in 40% of patients, lasting for 1 to 240 months (mean 24 months). Mean left atrial diameter was 50 ± 7 mm. Each patient underwent left atrial ablation with the Epicor system prior to open heart surgery. After surgery, the patients were treated with amiodarone and coumadin for 6 months. Follow-up studies including resting ECG, 24 h Holter ECG, and echocardiography were obtained at 6 and 12 months.

Results

All patients had successful application of the system on the beating heart prior to initiation of extracorporeal circulation. On average, 11 ± 1 ultrasound transducer elements were used to create the box lesion. The hand-held probe for additional linear lesions was employed in 83 cases. No device-related deaths occurred. Postoperative pacemaker insertion was necessary in 4 patients. At 6 months, 62% of patients presented with sinus rhythm. No significant changes were noted at 12 months. Type of AF and a left atrial diameter > 50 mm were predictors for failure of AF ablation.

Conclusion

AF ablation with the Epicor system as a concomitant procedure during open heart surgery is safe and acceptably effective. Our overall conversion rate was lower than in previously published reports, which may be related to the lower proportion of isolated mitral valve disease in our study population. Left atrial size may be useful to determine patients who are most likely to benefit from the procedure.

Image quality of coronary 320-MDCT in patients with atrial fibrillation: initial experience

OBJECTIVE

Noninvasive coronary angiography has generally been contraindicated in patients with atrial fibrillation because of the difficulty in synchronizing an irregular heartbeat with table gantry movement. The objective of this study was to evaluate and compare the quality of 320-MDCT images obtained in patients with atrial fibrillation and in a control group of patients in sinus rhythm.

MATERIALS AND METHODS

Two reviewers were blinded to the patient groups and evaluated images of 15 coronary artery segments for each patient using 320-MDCT. The images were printed on glossy paper and scored subjectively as 1 or 2, meaning of diagnostic quality, or 3, meaning poor quality.

RESULTS

No statistical difference between the groups was noted in patient age: The mean age of the patients with atrial fibrillation was 67 years (age range, 52-82 years) and that of the patients in sinus rhythm was 59 years (36-86 years) (p = 0.3). Scores of 1 and 2 (diagnostic quality) were assigned to 100% in sinus rhythm and 96% in atrial fibrillation (p < 0.05). Scores of 3 were seen only in the atrial fibrillation group (7/175, 4%). Segment 15, the distal circumflex artery, was the segment that was most frequently assigned a score of 3 (2/7, 28.6%). A discrepancy in the two reviewers' scores was seen in 25 segments (7%), requiring joint consensus. The segments that most frequently required consensus reading were segments 12 and 15. The overall mean image quality score for all three coronary arteries in atrial fibrillation was 1.25 +/- 0.47 (SD) and 1.08 +/- 0.26 in sinus rhythm (p < 0.001). The median effective dose was 19.28 and 13.55 mSv in the atrial fibrillation and sinus rhythm groups, respectively.

CONCLUSION

The analysis of our initial experience shows that imaging in patients with atrial fibrillation is possible using 320-MDCT, with images of most segments obtained being of diagnostic quality. Segment 15 was the most difficult to see on 320-MDCT because of the small caliber of the vessel; poor visualization of that segment mostly occurred in the setting of a dominant right coronary arterial system.

Current Concepts in Ablation of Atrial Fibrillation

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. It occurs particularly frequently in cardiac surgical patients and is associated with significant excess mortality and morbidity. Pharmacological management of AF is relatively ineffective and associated with significant side effects and complications. Clinicians have therefore pursued more definitive treatment options, both catheter based and surgical, to treat patients with AF. Surgical techniques designed to cure AF have developed in parallel with an improved understanding of the pathophysiological processes underlying this condition. This review describes the rationale behind current surgical approaches to AF and summarizes the results achieved with current techniques.

Fibrinolytic and coagulation pathways after laparoscopic and open surgery: a prospective randomized trial

BACKGROUND

Tissue injury poses increased risk for postoperative thromboembolic complications. Laparoscopic surgery, by causing limited tissue injury, is associated with lower risk for thromboembolism than is open surgery. We conducted a prospective randomized study in order to detect potentially existing differences in activation of coagulation and fibrinolytic pathways between open and laparoscopic surgery.

METHODS

Forty patients with chronic cholelithiasis were randomly assigned to undergo open (group A) or laparoscopic cholecystectomy (group B). Blood samples were taken preoperatively, at the end of the procedure, and at 24 and 72 h postoperatively. Prothrombin time (PT), activated partial thromboplastin time (APTT), international normalized ratio (INR), platelets (PLT), soluble fibrin monomer complexes (F.S. test), fibrin degradation products (FDP), D-dimers (D-D), and fibrinogen (FIB) were measured and compared within each group and between groups: Thrombin-antithrombin complexes (TAT) and prothrombin fragments (F1 + 2) were measured at 24 and 72 h postoperatively.

RESULTS

Demographics were comparable between groups. Immediately postoperatively, TAT and F1 + 2 were significantly higher in group A (p < 0.05). They also increased significantly postoperatively as compared with preoperative levels within each group (p < 0.05). D-dimers were significantly higher in group A (p < 0.01) immediately postoperatively. D-dimers also increased significantly postoperatively in group B as compared with preoperative levels (p < 0.001). FIB decreased slightly in both groups at 24 h postoperatively but there was a significant increase in group A (p < 0.01). Soluble fibrin monomer complexes (SFMC) were detected twice in group A and only once in group B. FDP levels over 5 μg/ml were detected more often in group A (p < 0.05). There was not any case of thromboembolism or abnormal bleeding.

CONCLUSIONS

Open surgery leads to higher activation of the clotting system than do laparoscopic procedures. Although of a lower degree, hypercoagulability is still observed in patients undergoing laparoscopic surgery and therefore routine thromboembolic prophylaxis should be considered.

Alterations of hemostasis after laparoscopic and open surgery

BACKGROUND

After tissue injury caused by trauma or surgery, alterations of hemostasis are observed and there is a risk for postoperative thromboembolic complications. Laparoscopic surgery, by causing limited tissue injury, appears to be associated with a lower risk for thromboembolism than open surgery. We conducted a prospective randomized study in order to detect potentially existing differences in activation of coagulation and fibrinolytic pathways between open and laparoscopic surgery.

METHODS

Forty patients suffering from chronic cholelithiasis were randomly assigned to undergo open (group A n = 20) or laparoscopic cholecystectomy (group B n = 20) by the same surgical and anesthesiology team. Demographic data were comparable. Blood samples were taken (a) preoperatively, (b) at the end of the procedure, (c) 24 h postoperatively and (d) 72 h postoperatively. The following parameters were measured and compared within each group and between groups: platelets (PLT), soluble fibrin monomer complexes (SFMC), fibrin degradation products (FDP), D-dimers (D-D), fibrinogen (FIB), activated partial thromboplastin time (APTT), prothrombin time (PT). Thrombin-antithrombin III complexes (TAT) were measured at 24 and 72 h postoperatively. Prothrombin fragment 1 + 2 (F1 + 2) was measured at 24 and 72 h postoperatively in 11 patients of group A and 13 patients of group B, respectively.

RESULTS

Demographics were comparable between groups. Immediately postoperatively, TAT and F1 + 2 were significantly higher in group A as compared to group B (p < 0.05). They also increased significantly postoperatively as compared to preoperative levels within each group (p < 0.05). D-dimers were significantly higher in group A as compared to group B (p < 0.01) immediately postoperatively. D-dimers also increased significantly postoperatively in group B as compared to preoperative levels (p < 0.001). FIB decreased slightly in both groups at 24 h postoperatively but there was a significant increase in group A as compared to group B (p < 0.01). SFMC were detected twice in group A and only once group B. FDP levels over 5 mug/ml were detected more often in group A than in group B (p < 0.05). No patient from either group suffered thromboembolism or abnormal bleeding as a postoperative complication.

CONCLUSIONS

Open surgery as compared to laparoscopic procedures leads to activation of the clotting system of a higher degree. Although of a lower degree, hypercoagulability is still observed in patients undergoing laparoscopic surgery and, therefore, routine thromboembolic prophylaxis should be considered.

Atrial fibrillation and the postoperative cardiac surgery patient

Atrial fibrillation (AF) is the most common dysrhythmia that affects adults, with an estimated 2.2 million people diagnosed in the United States and 4.5 million in the European Union. The development of postoperative AF is associated with negative patient outcomes. This article provides critical care nurses with an understanding of the etiology of AF, risk factors associated with the development of it, and current treatment options for this dysrhythmia. In addition to the medical management of AF, an overview of preventive protocols, nursing implications, and patient education is provided.

CT of the Pulmonary Veins

Atrial fibrillation (AF) is a common cardiac rhythm disturbance and its incidence is increasing. Radiofrequency catheter ablation (RFCA) is a highly successful therapy for treating AF, and its use is becoming more widespread; however, with its increasing use and evolving technique, known complications are better understood and new complications are emerging. Computed tomography (CT) of the pulmonary veins, or more correctly, the posterior left atrium (LA), has an established role in precisely defining the complex anatomy of the LA and pulmonary veins preablation and has an expanding role in identifying the myriad of possible complications postablation. The purposes of this article are: to review AF and RFCA; to discuss CT evaluation of the LA and pulmonary veins preablation; and to review the complications of RFCA focusing on the role of CT postablation.

The Mitral L Wave A Marker of Advanced Diastolic Dysfunction in Patients With Atrial Fibrillation

BACKGROUND

The prominent mid-diastolic filling wave (mitral L wave) indicates advanced diastolic dysfunction in patients in sinus rhythm. The aim of the present study was to determine the clinical implications of the mitral L wave in patients with atrial fibrillation (AF).

METHODS AND RESULTS

Ninety-nine consecutive non-valvular chronic persistent AF patients were enrolled. The mitral L wave was defined as a distinct mid-diastolic flow velocity following the E wave with a peak velocity>20 cm/s. The prevalence of the L wave in AF patients (34/99, 34%) was significantly higher than that observed in patients in sinus rhythm during the same study period (23/946, 2.4%, p<0.001). Patients with AF and L wave were older, more frequently female and had a slower heart rate, shorter isovolumic relaxation times, larger E wave velocities and lower early diastolic mitral annulus velocity (E') resulting in the higher E/E' compared to those without L waves. The left atrial volume index was significantly larger in patients with an L wave. The Valsalva maneuver decreased, and leg elevation increased, the amplitude of the L wave in the subset of patients who received these procedures.

CONCLUSIONS

The appearance of the mitral L wave in AF is relatively common, and its presence indicates advanced diastolic dysfunction, including elevated filling pressures and distended noncompliant LA.

The potential of D-dimer levels as a useful clinical marker of clotting state after the return of sinus rhythm

Fibrin d-dimers levels have been advocated as a useful clinical marker of thrombogenesis. It is accepted that patients with atrial fibrillation (AF) are characterized by increased levels of plasmatic d-dimers. AF is a high risk factor for hypercoagulability, with a substantial risk of thromboembolism. The most effective way of minimizing the increased thromboembolic risk and treating patients’ symptoms is to return the heart rhythm to sinus rhythm by electrical or chemical cardioversion. However, cardioversion of AF itself leads to a further increased risk of thromboembolism. A marker of coagulation activation would be useful to identify patients at the highest thromboembolic risk after cardioversion in AF patients. Indicators of hypercoagulability, such as d-dimers, appear to be a useful parameter for assessing the degree of hypercoagulability of AF patients after cardioversion. Mean changes in plasma d-dimers levels could be used as a useful clinical marker of the clotting state after the return of atrial systole.

Dementia in subjects with atrial fibrillation: hemostatic function and the role of anticoagulation

BACKGROUND

Atrial fibrillation (AF) is associated with cognitive impairment and dementia, perhaps through encouraging a prothrombotic state and cardioembolism.

OBJECTIVES

We wished to test the hypotheses that hemostatic function is altered in subjects with AF who develop dementia, and that long-term warfarin anticoagulation is protective against this complication.

PATIENTS AND METHODS

Recruitment was from an observational cohort study of AF. Baseline assessment included measurement of plasma fibrinogen, fibrin D-dimer, prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complexes (TAT), von Willebrand factor and tissue plasminogen activator. We assessed cognitive function after 3 years' follow-up using the 13-item modified Telephone Interview for Cognitive Status (TICSm) and the short form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE).

RESULTS

Of the 218 subjects assessed, 145 (66%) were prescribed warfarin. Forty-nine (22%) met TICSm/IQCODE criteria for dementia. D-dimer, F1+2 and TAT levels were higher in AF subjects with dementia compared with those without (medians 81 vs. 60 ng mL(-1), P = 0.008; 0.76 vs. 0.49 nmol L(-1), P = 0.006; and 1.78 vs. 1.44 microg L(-1), P = 0.003, respectively). These associations became of borderline statistical significance following adjustment for age. Logistic regression showed a trend towards warfarin use being independently associated with reduced prevalence of dementia (odds ratio 0.52, P = 0.08).

CONCLUSIONS

We found evidence of increased thrombin generation and fibrin turnover in subjects with AF and dementia compared with those without dementia. Long-term warfarin use may be protective against the development of dementia in subjects with AF.

Prognostic implications of atrial fibrillation in patients undergoing myocardial perfusion single-photon emission computed tomography

OBJECTIVES

The aim of this research was to determine whether presence of atrial fibrillation (AF) provides incremental prognostic information relative to myocardial perfusion single-photon emission computed tomography (MPS) with respect to risk of cardiac death (CD).

BACKGROUND

The prognostic significance of AF in patients undergoing MPS is not known.

METHODS

A total of 16,048 consecutive patients undergoing MPS were followed-up for a mean of 2.21 +/- 1.15 years for the development of CD. Of those, 384 patients (2.4%) had AF. Cox proportional hazards method was used to compare clinical and perfusion data for the prediction of CD in patients with and without AF.

RESULTS

Atrial fibrillation was a significant predictor of CD in patients with normal (1.6% per year vs. 0.4% per year in non-AF patients), mildly abnormal (6.3% per year vs. 1.2% per year), and severely abnormal MPS (6.4% per year vs. 3.7% per year) (p < 0.001 for all). By multivariable analysis, AF patients had worse survival (p = 0.001) even after adjustment for the variables most predictive of CD: age, diabetes, shortness of breath, use of vasodilator stress, rest heart rate, and the nuclear variables. In the 4,239 patients with left ventricular ejection fraction evaluated by gated MPS, AF demonstrated incremental prognostic value not only over clinical and nuclear variables, but also over left ventricular ejection in predicting CD (p = 0.014).

CONCLUSIONS

The presence of AF independently increases the risk of cardiac events over perfusion and function variables in patients undergoing MPS. Patients with AF have a high risk of CD, even when MPS is only mildly abnormal. Whether patients with AF and mildly abnormal MPS constitute a group more deserving of early referral to cardiac catheterization is a question warranting further study.

Non-valvular atrial fibrillation and stroke: Implications for nursing practice and therapeutics

Atrial fibrillation (AF) is the most common sustained cardiac rhythm disturbance and is increasing in prevalence due to the ageing of the population, and rates of chronic heart failure. Haemodynamic compromise and thromboembolic events are responsible for significant morbidity and mortality in Australian communities. Non-valvular AF is a significant predictor for both a higher incidence of stroke and increased mortality. Stroke affects approximately 40,000 Australians every year and is Australia's third largest killer after cancer and heart disease. The burden of illness associated with AF, the potential to decrease the risk of stroke and other embolic events by thromboprophylaxis and the implications of this strategy for nursing care and patient education, determine AF as a critical element of nursing practice and research. A review of the literature was undertaken of the CINAHL, Medline, EMBASE and Cochrane Databases from 1966 until September 2002 focussing on management of atrial fibrillation to prevent thrombotic events. This review article presents key elements of this literature review and the implications for nursing practice.

Effects of Anticoagulation Intensity on Hemostatic Markers in Patients With Non-Valvular Atrial Fibrillation

BACKGROUND

Elevation of hemostatic markers may account for the increased risk of ischemic stroke in patients with non-valvular atrial fibrillation (NVAF). The aim of this study was to determine the effects of anticoagulation intensity on hemostatic markers in patients with NVAF.

METHODS AND RESULTS

In 509 patients with NVAF, comprising 263 patients treated with warfarin and 246 patients without warfarin, the hemostatic markers of prothrombin fragment F1.2 (F1.2), fibrin D-dimer, platelet factor 4 (PF4), and beta-thromboglobulin were determined and compared with those in 111 patients with sinus rhythm. F1.2 was inversely related with anticoagulation intensity and D-dimer increased with age. All hemostatic markers, except F1.2, were greater in patients with NVAF than in patients with sinus rhythm. F1.2 and D-dimer were significantly lower in patients with international normalized ratio (INR) > or =1.5 than in NVAF patients without warfarin and were not different between NVAF patients with INR of 1.5-1.9 and with INR > or =2.0.

CONCLUSIONS

Low intensity of anticoagulation (INR 1.5-1.9) suppresses the elevated concentration of F1.2 and D-dimer in patients with NVAF, and might be favorable in Japanese patients with NVAF in view of the balance between prevention of thromboembolism and the adverse effect by warfarin (ie, bleeding).