Long-term risk of recurrent atrial fibrillation as documented by an implantable monitoring device

Relevance of electrical remodeling in human atrial fibrillation: results of the Asymptomatic Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial mechanisms of atrial fibrillation study

BACKGROUND

In animal models of atrial fibrillation (AF), changes in atrial electrophysiological properties are associated with the development of AF. Their relevance to human AF is unclear.

METHODS AND RESULTS

The Asymptomatic Atrial Fibrillation and Stroke Evaluation in Pacemaker Patients and the Atrial Fibrillation Reduction Atrial Pacing Trial enrolled 2580 patients receiving a dual-chamber pacemaker, who were older than the age of 65 and had a history of hypertension, but no history of AF. Serial noninvasive electrophysiological testing was performed over 2 years in a subgroup of 485 patients. There were no differences in the clinical characteristics between patients with and those without device-detected atrial tachyarrhythmias during the first year. Patients with atrial tachyarrhythmias had longer paced (153±29 versus 145±28 ms; P=0.046) and sensed (128±46 versus 118±25 ms; P=0.06) P-wave durations and were more likely to have AF induced during electrophysiological testing (23.5% versus 13.6%; P=0.03). They had similar corrected sinus node recovery times at 90 bpm (388±554 versus 376 ± 466 ms; P=0.86), atrial effective refractory periods at 90 bpm (250±32 versus 248±36 ms; P=0.70), and rate-adaptive shortening of the atrial effective refractory periods (14±13 versus 12±14 ms; P=0.11). There were no significant differences in the change in electrophysiological properties over 2 years between patients with and those without atrial tachyarrhythmias.

CONCLUSIONS

Prolonged P-wave duration, but not differences in atrial effective refractory periods, was associated with the development of atrial tachyarrhythmias in pacemaker patients.

Proportion of patients with implanted permanent pacemakers with atrial fibrillation receiving appropriate medical prophylaxis in North Wales

BACKGROUND

Atrial fibrillation (AF) is associated with an increased long-term risk of stroke, heart failure, and mortality. Previous studies have demonstrated the suboptimal use of anticoagulation therapy in patients with AF.

METHODS

A retrospective survey of patients (N = 1,113) fitted with dual-chamber pacemakers found 71 patients (age 69 ± 35, mean ± standard deviation) with atrial tachycardia and AF (defined as >5 minutes per day). Their medical records and anticoagulation status were investigated and used to stratify each patient for stroke risk with the Birmingham 2009 schema (CHA(2)DS(2)-VASc) and assessed to determine the rate of appropriate thromboembolism (TE) prophylaxis prescription.

RESULTS

The most common overall concomitant risk factor for stroke was hypertension (54%), followed by age ≥75 (51%), being female and previous stroke/transient ischemic attack/TE (39%). The average CHA(2)DS(2)-VASc score was 3.7 ± 1.6. Fifty-six percent of the patients were not receiving appropriate anticoagulation therapy.

CONCLUSION

This study demonstrates an underutilization of the oral anticoagulant warfarin in patients with known AF and that the clinicians may not be regarding current stroke risk factors when adopting a thromboprophylaxis strategy.

Atrial fibrillation in the elderly

This review discusses atrial fibrillation according to the guidelines of Brazilian Society of Cardiac Arrhythmias and the Brazilian Cardiogeriatrics Guidelines. We stress the thromboembolic burden of atrial fibrillation and discuss how to prevent it as well as the best way to conduct cases of atrial fibrillatios in the elderly, reverting the arrhythmia to sinus rhythm, or the option of heart rate control. The new methods to treat atrial fibrillation, such as radiofrequency ablation, new oral direct thrombin inhibitors and Xa factor inhibitors, as well as new antiarrhythmic drugs, are depicted.

Persistent atrial fibrillation is associated with a poor prognosis in patients with atrioventricular block and dual-chamber pacemaker

BACKGROUND

The prognostic significance of development of persistent atrial fibrillation (AF) in patients with atrioventricular (AV) block and dual chamber (DDD) pacemakers has not been separately investigated. We sought to determine whether persistent AF influences clinical outcome in these patients.

METHODS

Three hundred-eight consecutive patients with second- or third-degree AV block and implanted a DDD pacemaker were followed for 36 ± 20 months and retrospectively divided into two groups. Thirty-four patients who developed persistent AF formed persistent AF group, and 278 patients who remained free of this arrhythmia control group. Clinical and outcome data of the two groups were compared. The primary outcome was cardiovascular death.

RESULTS

The primary outcome occurred more often among the patients in the persistent AF group (6.8% per year) than among those in the control group (2.9% per year; P = 0.028). This difference was primarily because of higher rate of heart failure-related deaths in the persistent AF group (P = 0.009). Secondary outcomes, hospitalization for heart failure and paroxysmal AF episode ≥5 minutes, occurred also more often among the patients in the persistent AF group (P = 0.008 and P < 0.001, respectively), although the risk of nonfatal stroke was similar in both groups (P = 0.628).

CONCLUSION

In patients with second- or third-degree AV block and DDD pacemaker, the development of persistent AF is associated with an increased risk of cardiovascular death and heart failure.

Daily distribution of atrial arrhythmic episodes in sick sinus syndrome patients: implications for atrial arrhythmia monitoring

AIMS

Disorders such as paroxysmal atrial fibrillation (AF) and atrial tachyarrhythmias (AT) are difficult to investigate because of their intermittent, and sometimes asymptomatic, nature. The aim of this study was to investigate the daily temporal distribution of AT/AF episodes--onset and occurrence--by analysing data from 250 pacemaker-implanted, brady-tachy syndrome patients who have been enrolled in the Burden II Study.

METHODS AND RESULTS

Data were analysed accounting for the mode switch list which includes date, time, and duration of each mode switch episode. Chi-squared tests for goodness of fit were used to determine whether AT/AF episode were uniformly distributed. The population analysed in the present study suggests the occurrence of a circadian rhythm of paroxysmal AF episodes, similar to that described for other cardiovascular diseases, with clustering of events in the morning from 08:00 and (to a lesser degree) in the afternoon (03:00 to 18:00). The relative risk of AT/AF onset is 13% higher during daytime, 40% lower at night (P < 0.000001).

CONCLUSION

The use of monitoring devices based on daily electrocardiogram (ECG) recording could be optimized with these data, thus increasing the probability to detect AT/AF episodes.

Subclinical atrial fibrillation and the risk of stroke

BACKGROUND

One quarter of strokes are of unknown cause, and subclinical atrial fibrillation may be a common etiologic factor. Pacemakers can detect subclinical episodes of rapid atrial rate, which correlate with electrocardiographically documented atrial fibrillation. We evaluated whether subclinical episodes of rapid atrial rate detected by implanted devices were associated with an increased risk of ischemic stroke in patients who did not have other evidence of atrial fibrillation.

METHODS

We enrolled 2580 patients, 65 years of age or older, with hypertension and no history of atrial fibrillation, in whom a pacemaker or defibrillator had recently been implanted. We monitored the patients for 3 months to detect subclinical atrial tachyarrhythmias (episodes of atrial rate >190 beats per minute for more than 6 minutes) and followed them for a mean of 2.5 years for the primary outcome of ischemic stroke or systemic embolism. Patients with pacemakers were randomly assigned to receive or not to receive continuous atrial overdrive pacing.

RESULTS

By 3 months, subclinical atrial tachyarrhythmias detected by implanted devices had occurred in 261 patients (10.1%). Subclinical atrial tachyarrhythmias were associated with an increased risk of clinical atrial fibrillation (hazard ratio, 5.56; 95% confidence interval [CI], 3.78 to 8.17; P<0.001) and of ischemic stroke or systemic embolism (hazard ratio, 2.49; 95% CI, 1.28 to 4.85; P=0.007). Of 51 patients who had a primary outcome event, 11 had had subclinical atrial tachyarrhythmias detected by 3 months, and none had had clinical atrial fibrillation by 3 months. The population attributable risk of stroke or systemic embolism associated with subclinical atrial tachyarrhythmias was 13%. Subclinical atrial tachyarrhythmias remained predictive of the primary outcome after adjustment for predictors of stroke (hazard ratio, 2.50; 95% CI, 1.28 to 4.89; P=0.008). Continuous atrial overdrive pacing did not prevent atrial fibrillation.

CONCLUSIONS

Subclinical atrial tachyarrhythmias, without clinical atrial fibrillation, occurred frequently in patients with pacemakers and were associated with a significantly increased risk of ischemic stroke or systemic embolism. (Funded by St. Jude Medical; ASSERT ClinicalTrials.gov number, NCT00256152.).

Comparison of Microlife BP A200 Plus and Omron M6 blood pressure monitors to detect atrial fibrillation in hypertensive patients

INTRODUCTION

Self-monitoring home blood pressure (BP) devices are currently recommended for long-term follow-up of hypertension and its management. Some of these devices are integrated with algorithms aimed at detecting atrial fibrillation (AF), which is common essential hypertension. This study was designed to compare the diagnostic accuracy of two widely diffused home BP monitoring devices in detecting AF in an unselected population of outpatients referred to a hypertension clinic because of high BP.

METHODS

In 503 consecutive patients the authors simultaneously compared the accuracy of the Microlife(®) BP A200 Plus (Microlife) and the OMRON(®) M6 (OMRON) home BP devices, in detecting AF.

RESULTS

Systolic and diastolic BP as well as heart rate (HR) values detected by the two devices were not significantly different. Pulse irregularity was detected in 124 and 112 patients with the OMRON M6 and Microlife BP A200 Plus devices, respectively. Simultaneous electrocardiogram (ECG) recording revealed that pulse irregularity was due to AF in 101 patients. Pulse irregularity detected by the OMRON M6 device corresponded to AF in 101, to supraventricular premature beats in 18, and to frequent premature ventricular beat in five patients, respectively. Pulse irregularity detected by the Microlife BP A200 Plus device corresponded to AF in 93, to supraventricular premature beats in 14, and to ventricular premature beats in five patients. The sensitivity for detecting AF was 100%, the specificity was 92%, and diagnostic accuracy 95% for the OMRON M6 and 100%, 92%, and 95 for the Microlife BP A200 Plus, respectively. AF was newly diagnosed by ECG recordings in 47 patients, and was detected in all patients by the OMRON device, and in 42 patients by the Microlife device.

CONCLUSION

These results indicate that OMRON M6 is more accurate than Microlife BP A200 Plus in detecting AF in patients with essential hypertension. Widespread use of these devices in hypertensive patients could be of clinical benefit for the early diagnosis and treatment of this arrhythmia and related consequences.

Comprehensive risk reduction in patients with atrial fibrillation: emerging diagnostic and therapeutic options--a report from the 3rd Atrial Fibrillation Competence NETwork/European Heart Rhythm Association consensus conference

While management of atrial fibrillation (AF) patients is improved by guideline-conform application of anticoagulant therapy, rate control, rhythm control, and therapy of accompanying heart disease, the morbidity and mortality associated with AF remain unacceptably high. This paper describes the proceedings of the 3rd Atrial Fibrillation NETwork (AFNET)/European Heart Rhythm Association (EHRA) consensus conference that convened over 60 scientists and representatives from industry to jointly discuss emerging therapeutic and diagnostic improvements to achieve better management of AF patients. The paper covers four chapters: (i) risk factors and risk markers for AF; (ii) pathophysiological classification of AF; (iii) relevance of monitored AF duration for AF-related outcomes; and (iv) perspectives and needs for implementing better antithrombotic therapy. Relevant published literature for each section is covered, and suggestions for the improvement of management in each area are put forward. Combined, the propositions formulate a perspective to implement comprehensive management in AF.

Navigating the fine line between benefit and risk in chronic atrial fibrillation: rationale and design of the Standard versus Atrial Fibrillation spEcific managemenT studY (SAFETY)

BACKGROUND

Health outcomes associated with atrial fibrillation (AF) continue to be poor and standard management often does not provide clinical stability. The Standard versus Atrial Fibrillation spEcific managemenT studY (SAFETY) compares the efficacy of a post-discharge, nurse-led, multi-disciplinary programme to optimise AF management with usual care.

METHODS

SAFETY is a prospective, multi-centre, randomised controlled trial with blinded-endpoint adjudication. A target of 320 hospitalised patients with a chronic form of AF will be randomised (stratified by "rate" versus "rhythm" control) to usual post-discharge care or the SAFETY Intervention (SI). The SI involves home-based assessment, extensive clinical profiling and the application of optimal gold-standard pharmacology which is individually tailored according to a "traffic light" framework based on clinical stability, risk profile and therapeutic management. The primary endpoint is event-free survival from all-cause death or unplanned readmission during 18-36 months follow-up. Secondary endpoints include rate of recurrent hospital stay, treatment success (i.e. maintenance of rhythm or rate control and/or application of anti-thrombotic therapy without a bleeding event) and cost-efficacy.

RESULTS

With study recruitment to be completed in early 2012, the results of this study will be available in early 2014.

CONCLUSIONS

If positive, SAFETY will represent a potentially cost-effective and readily applicable strategy to improve health outcomes in high risk individuals discharged from hospital with chronic AF.

Cardiac workup of ischemic stroke

Stroke is the leading cause of disability in developed countries and the third cause of mortality. Up to 15-30% of ischemic strokes are caused by cardiac sources of emboli being associated with poor prognosis and high index of fatal recurrence. In order to establish an adequate preventive strategy it is crucial to identify the cause of the embolism. After a complete diagnostic workup up to 30% of strokes remain with an undetermined cause, and most of them are attributed to an embolic mechanism suggesting a cardiac origin.There is no consensus in the extent and optimal approach of cardiac workup of ischemic stroke. Clinical features along with brain imaging and the study of the cerebral vessels with ultrasonography or MRI/CT based angiography can identify other causes or lead to think about a possible cardioembolic origin.Atrial fibrillation is the most common cause of cardioembolic stroke. Identification of occult atrial fibrillation is essential. Baseline ECG, serial ECG('s), cardiac monitoring during the first 48 hours, and Holter monitoring have detection rates varying from 4 to 8% each separately. Extended cardiac monitoring with event loop recorders has shown higher rates of detection of paroxysmal atrial fibrillation.Cardiac imaging with echocardiography is necessary to identify structural sources of emboli. There is insufficient data to determine which is the optimal approach. Transthoracic echocardiography has an acceptable diagnostic yield in patients with heart disease but transesophageal echocardiography has a higher diagnostic yield and is necessary if no cardiac sources have been identified in patients with cryptogenic stroke with embolic mechanism.

[Surgical atrial fibrillation ablation therapy and postoperative monitoring]

Atrial fibrillation represents the most common atrial arrhythmia seen in clinical practice. The surgical treatment of atrial fibrillation is recommended in symptomatic patients as well as in asymptomatic patients at low postoperative risk. As a "stand alone" procedure, surgical ablation therapy is indicated after failed catheter ablation therapy, which occurs increasingly due to the high number of catheter-based ablation techniques. In order to gain acceptance among patients as well as referring cardiologists, the surgical ablation procedure ought to be performed in a minimally invasive fashion and with a very high success rate. When applied in an interdisciplinary approach by cardiologists/electrophysiologists and cardiothoracic surgeons, both ablative techniques have the potential to treat atrial fibrillation effectively and in the long-term. In order to document the true heart rhythm after ablation therapy, intermittent "snapshot" ECG documentation ought to be avoided. Small leadless devices that can be implanted subcutaneously enable full heart rhythm disclosure with documentation of atrial arrhythmias. The modern technique of implantable loop recorders permits individualized treatment for each patient.

How to use implantable loop recorders in clinical trials and hybrid therapy

Epidemiological studies show that atrial fibrillation (AF) is associated with a doubling of mortality, even after adjustment for confounders. AF can be asymptomatic, but this does not decrease the thromboembolic risk of the patient. Office ECGs, occasional 24-h Holter recordings and long-term ECG event recording might not be sensitive and accurate enough in patients with AF, especially in those with paroxysmal episodes. In one study, 7 days of continuous monitoring with event recorders detected paroxysmal AF in 20 of 65 patients with a previous negative 24-h Holter recording. Over the last decade, enormous improvements have been made in the technology of implantable devices, which can now store significant information regarding heart rhythm. The first subcutaneous implantable monitor (Reveal XT, Medtronic) was validated for continuous AF monitoring by the XPECT study. The dedicated AF detection algorithm uses irregularity and incoherence of R–R intervals to identify and classify patterns in ventricular conduction. Its sensitivity in identifying patients with AF is >96%. Numerous clinical data from continuous monitoring of AF have recently been published. The first applications of this technology have been in the field of surgical and catheter AF ablation. With regard to cryptogenic stroke, an international randomized trial is ongoing to compare standard care with standard care plus the implantable cardiac monitor for AF detection in patients discharged with the diagnosis of cryptogenic stroke: the Crystal AF trial. Continuous AF monitoring provides an optimal picture of daily AF burden, both symptomatic and asymptomatic. Implantable cardiac monitors have high sensitivity, enable better assessment of therapy success and may guide further AF therapy.

Efficacy of low interatrial septum and right atrial appendage pacing for prevention of permanent atrial fibrillation in patients with sinus node disease: results from the electrophysiology-guided pacing site selection (EPASS) study

BACKGROUND

The role of pacing sites and atrial electrophysiology on the progression of atrial fibrillation (AF) to the permanent form in patients with sinus node dysfunction (SND) has never been investigated. The aim of the study was to investigate the relationship between atrial electrophysiology and the efficacy of atrial pacing at the low interatrial septum (IAS) or at the right atrial appendage (RAA) to prevent persistent/permanent AF in patients with SND.

METHODS AND RESULTS

The Electrophysiology-Guided Pacing Site Selection (EPASS) Study was a prospective, controlled, randomized study. Atrial refractoriness, basal and incremental conduction times from the RAA to the coronary sinus ostium were measured before implantation, and the difference (ΔCTos) was calculated. Patients with ΔCTos ≥ 50 ms (study group) and those with ΔCTos <50 ms (control group) were randomly assigned to RAA or IAS with algorithms for continuous atrial stimulation "on." The primary end point was time to development of permanent or persistent AF within a 2-year follow-up in the study group, IAS versus RAA. Data were analyzed by intention to treat. One hundred two patients (77 ± 7 years, 44 mol/L) were enrolled, 69 (68%) in the study group and 33 (32%) in the control group. Of these, 97 ended the study, respectively, randomly assigned: 29 IAS versus 36 RAA and 18 IAS versus 14 RAA. After a mean follow-up of 15 ± 7 (median, 17) months, 11 (16.6%) patients in the study group met the primary end point: 2 IAS versus 9 RAA (log rank=3.93, P=0.047).

CONCLUSIONS

In patients with SND and intra-atrial conduction delay, low IAS pacing was superior to RAA pacing in preventing progression to persistent or permanent AF.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00239226.

Detection of atrial high-rate events by continuous home monitoring: clinical significance in the heart failure-cardiac resynchronization therapy population

AIMS

Uncertainty exists over the importance of device-detected short-duration atrial arrhythmias. Continuous atrial diagnostics, through home monitoring (HM) technology (BIOTRONIK, Berlin, Germany), provides a unique opportunity to assess frequency and quantity of atrial fibrillation (AF) episodes defined as atrial high-rate events (AHRE).

METHODS AND RESULTS

Prospective data from 560 heart failure (HF) patients (age 67 ± 10 years, median ejection fraction 27%) patients with a cardiac resynchronization therapy (CRT) device capable of HM from two multi-centre studies were analysed. Atrial high-rate events burden was defined as the duration of mode switch in a 24-h period with atrial rates of >180 beats for at least 1% or total of 14 min per day. The primary endpoint was incidence of a thromboembolic (TE) event. Secondary endpoints were cardiovascular death, hospitalization because of AF, or worsening HF. Over a median 370-day follow-up AHRE occurred in 40% of patients with 11 (2%) patients developing TE complications and mortality rate of 4.3% (24 deaths, 16 with cardiovascular aetiology). Compared with patients without detected AHRE, patients with detected AHRE>3.8 h over a day were nine times more likely to develop TE complications (P= 0.006). The majority of patients (73%) did not show a temporal association with the detected atrial episode and their adverse event, with a mean interval of 46.7 ± 71.9 days (range 0-194) before the TE complication.

CONCLUSION

In a high-risk cohort of HF patients, device-detected atrial arrhythmias are associated with an increased incidence of TE events. A cut-off point of 3.8 h over 24 h was associated with significant increase in the event rate. Routine assessment of AHRE should be considered with other data when assessing stroke risk and considering anti-coagulation initiation and should also prompt the optimization of cardioprotective HF therapy in CRT patients.

Clinical characteristics of patients with asymptomatic recurrences of atrial fibrillation in the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico-Atrial Fibrillation (GISSI-AF) trial

BACKGROUND

Atrial fibrillation (AF) is a common arrhythmia that frequently recurs after restoration of sinus rhythm. In a consistent percentage of cases, AF recurrences are asymptomatic, thus making its clinical management difficult in relation to both therapeutic efficacy and thromboembolic risk.

METHODS

The GISSI-AF trial enrolled 1,442 patients in sinus rhythm with previous AF episodes. Patients were randomized to valsartan or placebo and followed for 12 months. To improve the likelihood of detecting arrhythmic recurrences, arrhythmic follow-up was based on both programmed or symptom-related control visits and transtelephonic electrocardiographic transmissions. The present post hoc analysis was performed on 1,638 arrhythmic episodes that occurred in 623 patients.

RESULTS

Asymptomatic AF recurrences were present in 49.5% of patients. In multivariable analysis, asymptomatic AF recurrences were significantly associated with a longer duration of qualifying arrhythmias (odds ratio [95% CI] 1.57 (1.26-1.97), P < .0001). A lower ventricular response (P < .001) and a longer duration of the arrhythmic recurrence (P < .001) characterized asymptomatic episodes. Patients with asymptomatic events were more likely to be in AF at the time of electrocardiographic control at the end of the 12-month follow-up (adjusted odds ratio [95% CI] 4.9 (2.8-8.4), P < .001). Moreover, a higher CHADS(2) (Congestive heart failure, history of Hypertension, Age≥75 years, Diabetes mellitus, and past history of Stroke or TIA doubled) score and a more frequent use of amiodarone, calcium-channel blockers, and digitalis characterized patients with asymptomatic, whereas 1C drugs were more often used in subjects with symptomatic recurrences.

CONCLUSION

Asymptomatic AF recurrences were frequent in the GISSI-AF study population in patients who were more likely to develop persistent-permanent AF and were characterized by an increased thromboembolic risk.

The efficacy of intraoperative atrial radiofrequency ablation for atrial fibrillation during concomitant cardiac surgery-the Surgical Atrial Fibrillation Suppression (SAFS) Study

INTRODUCTION

Studies assessing radiofrequency ablation (RFA) for atrial fibrillation (AF) performed at the time of concomitant cardiac surgery have reported high success rates. The efficacy of this treatment has primarily been determined by a single electrocardiogram (ECG) or 24-h Holter monitor at follow-up. We sought to assess the true efficacy of this procedure using prolonged cardiac rhythm monitoring.

METHODS

One hundred patients with paroxysmal (n = 47) and persistent AF (n = 53) requiring cardiac surgery were enrolled. Patients were clinically reviewed 6 weeks post-operatively and were monitored with 7-day Holter with full disclosure, 6 months post-surgery. A cohort of 50 patients also underwent 7 day Holter monitoring preoperatively. AF recurrence was defined as >30 s of AF.

RESULTS

At 6 months, 75% of patients were in sinus rhythm according to a single ECG. However, only 62% of patients were free from AF on 7-day Holter; all AF episodes in these patients were asymptomatic. The procedure resulted in a significant decrease in AF burden from 56.2% at baseline to 27.5% at 6 months follow-up, (p < 0.001). Predictors of AF recurrence were (1) pre-operative AF duration; (2) persistent compared with paroxysmal AF; (3) increasing left atrial diameter and (4) requirement for mitral valve surgery.

CONCLUSIONS

Surgical RFA for the treatment of AF, during concomitant cardiac surgery, is a successful procedure and significantly reduces AF burden. However, 13% of patients have asymptomatic AF episodes only identified with continuous monitoring. This has important implications for post-operative anti-arrhythmic and anticoagulant management and for the definition of surgical AF ablation success.

Atrial fibrillation with symptoms other than palpitations: incremental diagnostic sensitivity with at-home tele-cardiology assessment for emergency medical service

BACKGROUND

Clinical presentation of atrial fibrillation (AF) is usually represented by palpitations; nevertheless, atypical presentation of AF with symptoms other than palpitations may be not uncommon in elderly patients. This study therefore aimed to evaluate incremental diagnostic value of tele-medicine at-home assessment in patients who called emergency medical service (EMS).

METHODS

A total of 27,841 consecutive EMS patients referred for suspected heart disease underwent ECG assessment with a mobile ECG-recorder device. ECGs were transmitted with mobile-phone support to a tele-cardiology 'hub' active 24/7 where a cardiologist read the ECGs. Rate of prevalence of AF, age of patients, and symptoms were analysed.

RESULTS

AF was diagnosed in 11.67% of patients who underwent ECG examination. Typical symptoms were complained by 6.56% of whole patients, only 14.05% of patients with AF: rate of subjects with AF and typical symptoms significantly decreased with age (<65 years 29.58%, 65-75 years 17.06%, >75 years 10.35%, p < 0.001). Number needed to diagnose an AF with atypical presentation (number needed to treat) decreased from 45 (<65 years) to 9 (65-75 years) and 5 (>75 years) (p < 0.001). Tele-cardiology support increased the rate of at-home diagnosis of AF from two-fold (in 40-year-olds) up to four-fold (60-year-olds) and seven-fold (70-year-olds).

CONCLUSIONS

AF with symptoms other than palpitations is a common finding in elderly EMS patients. Tele-cardiology support improves the sensitivity of diagnosis of AF in elderly EMS patients and is useful in at-home identification of subjects with AF and atypical presentation.

Improving stroke risk stratification using the CHADS2 and CHA2DS2-VASc risk scores in patients with paroxysmal atrial fibrillation by continuous arrhythmia burden monitoring

BACKGROUND AND PURPOSE

In patients with atrial fibrillation (AF), stroke risk stratification schema do not consider AF parameters. The aim of the study is to assess the impact of combining risk factors with continuous AF burden monitoring.

METHODS

In this retrospective study 568 patients implanted with a DDDR-P pacemaker (AT-500; Medtronic) and a history of AF were continuously monitored for 1 year.

RESULTS

During follow-up, 14 patients (2.5%) had a thromboembolic event. Patients were divided into 3 groups: AF burden ≤5 minutes per day (AF-free; n=223 [39%]), AF burden >5 minutes but <24 hours per day (AF-5 minutes; n=179 [32%]), and AF burden ≥24 hours (AF-24 hours; n=166 [29%]). Patients were also classified according to CHADS2 and CHA2DS2-VASc risk scores. The discrimination ability of each risk score was evaluated performing a logistic regression analysis and calculating the corresponding C-statistic. The addition of AF burden improved C-statistics: for CHADS2 from 0.653 (P=0.051) to 0.713 (P=0.007); for CHA2DS2-VASc, from 0.898 (P<0.0001) to 0.910 (P<0.0001).

CONCLUSIONS

The CHA2DS2-VASc score had a high sensitivity to predict thromboembolism. Implementation of device data on AF presence/duration/burden has the potential to contribute to improved clinical risk stratification and should be tested prospectively.

Atrial fibrillation care: challenges in clinical practice and educational needs assessment

BACKGROUND

Current debates around the choice of management strategy for patients with atrial fibrillation (AF) combined with limited efficacy and frequent adverse effects of current pharmacotherapies cause uncertainty and confusion, challenging optimal care delivery to AF patients.

OBJECTIVES

To determine gaps in knowledge, skill, and competencies of Canadian physicians caring for patients with AF as well as underlying causes of these gaps.

METHODS

A mixed-method approach --consisting of qualitative (semistructured interviews) and quantitative data collection techniques (online survey) --was conducted. Findings were triangulated to ensure the reliability and trustworthiness of findings. The combined sample (n = 161) included 43 family physicians/general practitioners, 23 internal medicine specialists, 48 cardiologists, 28 emergency physicians, 14 neurologists, and 5 patients.

RESULTS

Gaps and barriers impeding optimal care were related to an unclear definition of AF, uncertainty of its pathophysiology, and knowledge gaps across the care continuum, including screening, diagnosis, and treatment. Clinical decision-making, individualized patient therapy, communication with patients and between professionals, and application of guidelines were found to be particularly challenging. These issues are discussed in the context of the newly revised Canadian Cardiovascular Society (CCS) AF Guidelines.

CONCLUSIONS

Educational gaps exist across the entire continuum of care. Results from this study, along with the 2011 CCS guidelines for AF management, provide direction for solutions through physician education and professional development.

Pathophysiological mechanisms of atrial fibrillation: a translational appraisal

Atrial fibrillation (AF) is an arrhythmia that can occur as the result of numerous different pathophysiological processes in the atria. Some aspects of the morphological and electrophysiological alterations promoting AF have been studied extensively in animal models. Atrial tachycardia or AF itself shortens atrial refractoriness and causes loss of atrial contractility. Aging, neurohumoral activation, and chronic atrial stretch due to structural heart disease activate a variety of signaling pathways leading to histological changes in the atria including myocyte hypertrophy, fibroblast proliferation, and complex alterations of the extracellular matrix including tissue fibrosis. These changes in electrical, contractile, and structural properties of the atria have been called "atrial remodeling." The resulting electrophysiological substrate is characterized by shortening of atrial refractoriness and reentrant wavelength or by local conduction heterogeneities caused by disruption of electrical interconnections between muscle bundles. Under these conditions, ectopic activity originating from the pulmonary veins or other sites is more likely to occur and to trigger longer episodes of AF. Many of these alterations also occur in patients with or at risk for AF, although the direct demonstration of these mechanisms is sometimes challenging. The diversity of etiological factors and electrophysiological mechanisms promoting AF in humans hampers the development of more effective therapy of AF. This review aims to give a translational overview on the biological basis of atrial remodeling and the proarrhythmic mechanisms involved in the fibrillation process. We pay attention to translation of pathophysiological insights gained from in vitro experiments and animal models to patients. Also, suggestions for future research objectives and therapeutical implications are discussed.

New approaches to atrial fibrillation management: treat the patient, not the ECG

Atrial fibrillation causes a significant burden on patients and the health care system. The main goals of atrial fibrillation therapy are to improve symptoms and reduce morbidity. There have been significant recent developments in both stoke prophylaxis and rhythm/rate control. The results of the ACTIVE W study emphasize the importance of effective oral anticoagulant therapy in patients with moderate-to-high risk for stroke. The RE-LY study showed superiority of dabigatran, an oral direct thrombin inhibitor, over warfarin in the prevention of stroke, or systemic embolism. Dronedarone, a new antiarrhythmic drug with multiple class effects, has been recently approved by the US Food and Drug Administration for the treatment of atrial fibrillation. Dronedarone has moderate rhythm and rate control efficacy; however, dronedarone significantly reduced cardiovascular hospitalization, cardiovascular death, and stroke in the large ATHENA trial. There is also an important shift in the paradigm of the goals of atrial fibrillation therapy. Instead of focusing solely on the electrocardiographic outcomes of treatment and considering "rhythm versus rate control," one needs to consider "symptom control" as well as patient well-being. This review will suggest that patient based outcomes rather than ECG-based outcomes should be the primary goals of treatment. Original reports and reviews on specific topics were identified through Medline. Randomized controlled trials were selected as the primary source of information. Analysis included critical review of the evidence available to date.

Performance of an implantable automatic atrial fibrillation detection device: impact of software adjustments and relevance of manual episode analysis

AIMS

Implantable loop recorders (ILRs) with specific atrial fibrillation (AF) detection algorithms (ILR-AF) have been developed for continuous AF monitoring. We sought to analyse the clinical value of a new AF monitoring device and to compare it to serial 7-day Holter.

METHODS AND RESULTS

Sixty-four consecutive patients suffering from paroxysmal AF were included in this prospective analysis and received an ILR-AF. Manual electrogram analysis was performed for each automatically detected episode and each was categorized into one of three possible diagnoses: 'no AF', 'definite AF', and 'possible AF' (non-diagnostic). Analysis was performed separately before and after a software upgrade that was introduced during the course of the study. A subgroup of patients (51 of 64) underwent AF catheter ablation with subsequent serial 7-day Holter in comparison with the ILR-AF. A total of 333 interrogations were performed (203 before and 130 after software upgrade). The number of patients with AF misdetection was significantly reduced from 72 to 44% following the software upgrade (P = 0.001). The number of patients with non-diagnostic interrogations went from 38 to 16% (P = 0.001). Compared with serial 7-day Holter, the ILR-AF had a tendency to detect a higher number of patients with AF recurrences (31 vs. 24%; P = 0.125).

CONCLUSIONS

The rate of AF detection on ILR-AF may be higher compared with standard AF monitoring. However, false-positive AF recordings hamper the clinical value. Developments in device technology and device handling are necessary to minimize non-diagnostic interrogations.

Paroxysmal atrial fibrillation in cryptogenic stroke

INTRODUCTION

Paroxysmal atrial fibrillation (PAF) is perhaps the most underdiagnosed mechanism of apparent cryptogenic stroke (CS). Various studies have shown that increasing the duration of monitoring can increase the diagnosis of PAF in CS.

METHODS

We compared demographic and risk factors for ischemic stroke across different TOAST (Trial of ORG 10172 in Acute Stroke Treatment) stroke subtypes to look for clinical differences between other subtypes and CS and subsequently performed periodic Holter monitoring and imaging studies in apparent CS patients.

RESULTS

Of the 298 patients with ischemic stroke, 17% had CS. Periodic holter monitoring enabled diagnosis of PAF in 29% of patients. Five of 51 patients with CS had recurrent ischemic stroke and all 5 were demonstrated as PAF on repeated Holter monitoring.

CONCLUSIONS

Long-term periodic rhythm monitoring in patients with apparent CS showed PAF in a significant percentage of CS patients, which altered subsequent treatment.

[Detection of atrial fibrillation after stroke]

Approximately every fourth stroke results from cardiac embolism. Atrial fibrillation has been recognized as a common cause for thromboembolic stroke. Detection of unknown atrial fibrillation is an important clinical challenge, as anticoagulation may effectively reduce the risk of recurrent ischemic stroke. In all patients with a cryptogenic stroke 24-h Holter monitoring should be performed in addition to a standard ECG to detect paroxysmal atrial fibrillation. In addition, it is useful to pay attention to atrial fibrillation during continuous bedside ECG monitoring on the stroke unit and in pacemaker interrogation. The indication for longer ECG monitoring by implantable loop recorders may be considered individually based on the expected probability of atrial fibrillation. The potential benefit of these devices is currently being evaluated in clinical trials.

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.

Wireless remote monitoring of atrial fibrillation using reconstructed 12-lead ECGs

Remote surveillance is important for patients with atrial fibrillation (AF). Atrial signal recognition with conventional monitoring devices is difficult; remote AF detection is predominantly accomplished by R-R interval analysis. Twelve lead ECG (12L) displays atrial activity and remains the gold standard for AF diagnosis. CardioBip is a portable wireless patient-activated event monitor providing signal reconstruction of a 12L waveform (12CB) using 5 leads and patient-specific transformation matrices. We hypothesized that atrial signal analysis with 12CB can detect atrial activity and improve AF detection.

METHODS

18 patients with AF undergoing DC cardioversion (CV) were studied. Separate 12-lead P and QRS patient-specific transformation matrices were created at baseline AF. Multiple wireless 12CB transmissions were performed 3-7 days before and up to 2 weeks after CV. Rhythm was confirmed with 12-lead ECGs (12L). In SR the number of leads with visible P waves (atrial signal > 0.05 mV), and P wave polarity were analyzed. In AF, the number of leads with AF signal were compared (fibrillatory [f] waves >0.025 mV).

RESULTS

Fourteen of 18 patients successfully cardioverted to SR and 4 failed; thus, 14 SR and 22 AF transmissions were analyzed. SR P wave was visible on 141/168 leads on 12L and 137/168 on 12CB (126 true pos [TP] and 11 false pos [FP] relative to 12L; p=0.26). In 126 leads with P waves in both 12L and 12CB, the methods agreed on P wave polarity in 125. In AF, F waves were visible in 178/264 leads on 12L and 189/264 leads on 12CB (144 TP, 45 FP; p=0.27). All 5 AF relapses were successfully detected by 12CB based on atrial activity.

CONCLUSION

12CB is not inferior to 12L in detecting atrial signal in SR and AF, and shows excellent potential for remote wireless monitoring of AF patients.

Principles of Anticoagulation and New Therapeutic Agents in Atrial Fibrillation

Anticoagulation is required in cardiac arrhythmias, specifically atrial fibrillation (AF) and atrial flutter, to reduce the risk of thromboembolism. Principles of anticoagulation of both AF and atrial flutter are similar because the location and nature of the arrhythmias are similar. Approximately 2 million people in the United States are affected by AF, and the prevalence is expected to exceed 10 million by the year 2050. Warfarin is known to reduce stroke risk by 68% in patients with AF and is the most effective agent for this indication, although it is not without risk. Antithrombotic therapy with antiplatelets or anticoagulants is recommended for most patients with AF. This review discusses the principles of anticoagulation and the mechanism of action, pharmacologic profile, and phase of development of the therapeutic agents used as anticoagulants.

Challenges in the classification of atrial fibrillation

The incidence and prevalence of atrial fibrillation (AF) are increasing worldwide. AF is of public health importance because it accounts for substantial morbidity, mortality, and health-care costs. AF may be transient initially, but many patients have progressive disease marked by increasing frequency and duration of episodes. Various classification schemes for AF have been proposed, although current guidelines are based on temporal rhythm-based patterns. We discuss existing schemes for the classification of AF, focusing on the advantages and limitations of the pattern-based scheme, in the context of new knowledge about AF pathophysiology, AF patterns, and clinical outcomes. Furthermore, we address gaps in knowledge that present opportunities to re-examine the current pattern-based classification of AF. A future classification scheme should ideally combine elements such as the risk of stroke, an assessment of symptoms, and the degree of impairment of the atrial substrate.

The long- and short-term impact of elevated body mass index on the risk of new atrial fibrillation the WHS (women's health study)

OBJECTIVES

The purpose of this study was to characterize the relationship between changes in body mass index (BMI) and incident atrial fibrillation (AF) in a large cohort of women.

BACKGROUND

Obesity and AF are increasing public health problems. The importance of dynamic obesity-associated AF risk is uncertain, and mediators are not well characterized.

METHODS

Cases of AF were confirmed by medical record review in 34,309 participants in the Women's Health Study. Baseline and updated measures of BMI were obtained from periodic questionnaires.

RESULTS

During 12.9 +/- 1.9 years of follow-up, 834 AF events were confirmed. BMI was linearly associated with AF risk, with a 4.7% (95% confidence interval [CI]: 3.4 to 6.1, p < 0.0001) increase in risk with each kilogram per square meter. Adjustment for inflammatory markers minimally attenuated this risk. When updated measures of BMI were used to estimate dynamic risk, overweight (hazard ratio [HR]: 1.22; 95% CI: 1.02 to 1.45, p = 0.03), and obesity (HR: 1.65; 95% CI: 1.36 to 2.00; p < 0.0001) were associated with adjusted short-term increases in AF risk. Participants becoming obese during the first 60 months had a 41% adjusted increase in risk of the development of AF (p = 0.02) compared with those maintaining BMI <30 kg/m(2). The prevalence of overweight and obesity increased over time. The adjusted proportion of incident AF attributable to short-term elevations in BMI was substantial (18.3%).

CONCLUSIONS

In this population of apparently healthy women, BMI was associated with short- and long-term increases in AF risk, accounting for a large proportion of incident AF independent of traditional risk factors. A strategy of weight control may reduce the increasing incidence of AF. (Women's Health Study [WHS]: A Randomized Trial of Low-Dose Aspirin and Vitamin E in the Primary Prevention of Cardiovascular Disease and Cancer; NCT00000479).

[Atrial fibrillation. New aspects for diagnosis and follow-up]

Continuous rhythm monitoring is the gold standard of objective rhythm assessment in patients with atrial fibrillation, thus, facilitating accurate detection of symptomatic and asymptomatic atrial fibrillation. This is of scientific and clinical interest for the understanding of this arrhythmia, the establishment of evidence-based therapeutic approaches, the definition of clinically indicated monitoring strategies, and for decision-making about oral anticoagulation. This article illustrates the importance of continuous monitoring of atrial fibrillation and presents developing technologies with their advantages and limitations as well as initial clinical experience.

Performance of a New Leadless Implantable Cardiac Monitor in Detecting and Quantifying Atrial Fibrillation Results of the XPECT Trial

Background— Current methods for detecting atrial fibrillation (AF) have limited diagnostic yield. Continuous monitoring with automatic arrhythmia detection and classification may improve detection of symptomatic and asymptomatic AF and subsequent patient treatment. The study purpose was to quantify the performance of the first implantable leadless cardiac monitor (ICM) with dedicated AF detection capabilities.

Methods and Results— Patients (n=247) with an implanted ICM (Reveal XT, Medtronic Inc, Minneapolis, Minn) who were likely to present with paroxysmal AF were selected. A special Holter device stored 46 hours of subcutaneously recorded ECG, ICM markers, and 2 surface ECG leads. The ICM automatic arrhythmia classification was compared with the core laboratory classification of the surface ECG. Of the 206 analyzable Holter recordings collected, 76 (37%) contained at least 1 episode of core laboratory classified AF. The sensitivity, specificity, positive predictive value, and negative predictive value for identifying patients with any AF were 96.1%, 85.4%, 79.3%, and 97.4%, respectively. The AF burden measured with the ICM was very well correlated with the reference value derived from the Holter (Pearson coefficient=0.97). The overall accuracy of the ICM for detecting AF was 98.5%.

Conclusions— In this ICM validation study, the dedicated AF detection algorithm reliably detected the presence or absence of AF and the AF burden was accurately quantified. The ICM is a promising new diagnostic and monitoring tool for the clinician to treat AF patients independently of symptoms. Long-term studies are needed to evaluate the clinical benefits of the technology.

Clinical Trial Registration— clinicaltrials.gov Identifier NCT00680927.

Adjuvant therapy for atrial fibrillation

Atrial fibrillation (AF) is the most common heart rhythm disorder, with increasing prevalence in the aging US population and affecting more than 2.3 million people. Current approaches for managing AF are rate- or rhythm-control strategies, both using anti-thrombotic therapy to prevent thromboembolism. While great advances have been made in understanding the pathophysiology of AF, few new strategies have shown promise in prevention or treatment of AF. Recent data suggest that non-antiarrhythmic medication may be useful in modifying the substrate that allows AF precipitation and perpetuation. This article reviews the data on the role of these agents in the prevention and management of AF as an adjunct to standard therapy.