Is ambulatory monitoring for "community-acquired" syncope economically attractive? A cost-effectiveness analysis of a randomized trial of external loop recorders versus Holter monitoring

An old diagnostic tool for new indications: inpatient Holter ECG for conditions other than syncope or stroke

Holter electrocardiography (ECG) assists in the diagnosis of arrhythmias. Its use in the inpatient setting has been described solely for the evaluation of stroke and syncope. Our aim was to assess its diagnostic value for other conditions in the internal medicine department. We included all hospitalized patients between 2018 and 2021 in a tertiary referral center. The primary outcome was a diagnostic Holter recording a new arrhythmia that led to a change in treatment. Overall, 289 patients completed a 24-h inpatient Holter ECG for conditions other than syncope or stroke, with 39 (13%) diagnostic findings. The highest diagnostic value was found in patients admitted for pre-syncope (19%), palpitations (18%), and unexplained heart failure exacerbation/dyspnea (17%). A low diagnostic yield was found for the evaluation of chest pain (5%). Heart failure with preserved ejection fraction (adjusted OR 2.3, 95% CI 1.1-5.4, p = 0.04), and baseline ECG with either a bundle branch block (AOR 4.2, 95% CI 1.9-9.2, p < 0.01) or atrioventricular block (first or second degree, AOR 5, 95% CI 2.04-12.3, p < 0.01) were among the independent predictors for a diagnostic test. Inpatient Holter ECG monitoring may have value as a diagnostic tool for selected patients with conditions other than syncope or stroke.

Clinical applications of heart rhythm monitoring tools in symptomatic patients and for screening in high-risk groups

Recent technological advances have facilitated and diversified the options available for the diagnosis of cardiac arrhythmias. Ranging from simple resting or exercise electrocardiograms to more sophisticated and expensive smartphones and implantable cardiac monitors. These tests and devices may be used for varying periods of time depending on symptom frequency. The choice of the most appropriate heart rhythm test should be guided by clinical evaluation and optimized following accurate characterization of underlying symptoms, 'red flags', risk factors, and consideration of cost-effectiveness of the different tests. This review provides evidence-based guidance for assessing suspected arrhythmia in patients who present with symptoms or in the context of screening, such as atrial fibrillation or advanced conduction disturbances following transcatheter aortic valve implantation in high-risk groups. This is intended to help clinicians choose the most appropriate diagnostic tool to facilitate the management of patients with suspected arrhythmias.

Monitoring and diagnosis of intermittent arrhythmias: evidence-based guidance and role of novel monitoring strategies

Technological advances have made diagnosis of heart rhythm disturbances much easier, with a wide variety of options, including single-lead portable devices, smartphones/watches to sophisticated implantable cardiac monitors, allowing accurate data to be collected over different time periods depending on symptoms frequency. This review provides an overview of the novel and existing heart rhythm testing options, including a description of the supporting evidence for their use. A description of each of the tests is provided, along with discussion of their advantages and limitations. This is intended to help clinicians towards choosing the most appropriate test, thus improving diagnostic yield management of patients with suspected arrhythmias.

Holter ECG for Syncope Evaluation in the Internal Medicine Department-Choosing the Right Patients

Physicians use Holter electrocardiography (ECG) monitoring to evaluate some patients with syncope in the internal medicine department. We questioned whether Holter ECG should be used in the presented setting. Included were all consecutive patients admitted with syncope to one of our nine internal medicine departments who had completed a 24 h Holter ECG between 2018 and 2021. A diagnostic Holter was defined as one which altered the patient’s treatment and met ESC/ACC/AHA diagnostic criteria. A total of 478 Holter tests were performed for syncope evaluation during admission to an internal medicine department in the study period. Of them, 25 patients (5.2%) had a diagnostic Holter finding. Sinus node dysfunction was the most frequent diagnostic recording (13 patients, 52%). In multivariant analysis, predictors for diagnostic Holter were older age (OR 1.35, 95% CI 1.08−1.68), heart failure with preserved ejection fraction (OR 4.1, 95% CI 1.43−11.72), and shorter duration to Holter initiation (OR 0.73, 95% CI 0.56−0.96). There was a positive correlation between time from admission to Holter and hospital stay, r(479) = 0.342, p < 0.001. Our results suggest that completing a 24 h Holter monitoring during admission to the internal medicine department should be restricted to patients with a high pre-test probability to avoid overuse and possible harm.

Syncope and electrocardiogram

INTRODUCTION

Suspected transient loss of consciousness (T-LOC) and syncope are common causes of hospitalization in older patients. Arrhythmias are the most common cardiac causes of syncope. Although a number of instrumental diagnostic procedures are usually routinely performed in patients with suspected syncope, a 12 leads electrocardiogram (ECG) is the only instrumental test recommended for the initial evaluation of these patients.

EVIDENCE ACQUISITION

In this paper current literature on this topic will be reviewed, including ECG diagnostic criteria and findings suggestive of cardiac syncope.

EVIDENCE SYNTHESIS

The ECG may disclose an arrhythmia associated with a high likelihood of syncope, avoiding further evaluations and permitting institution of specific treatment in 7% of patients referred to emergency department. When the cause of syncope remains uncertain after initial evaluation the next step is to assess the risk of major cardiovascular events or sudden cardiac death. An abnormal ECG selected patients with high probabiliry of cardiac syncope. ECG diagnostic criteria and ECG findings suggesting arrhythmic syncope are presented. Indications and potential clinical implications of ECG monitoring will be discussed too.

CONCLUSIONS

A careful, well-conducted medical history focused on the suspected syncopal event is crucial for the diagnosis. In this setting, the ECG is a mandatory diagnostic tool which, although normal in the majority of patients of syncope, has the potential to identify patients with high likelihood of cardiac syncope due to arrhythmic or cardiopulmonary disorder.

Evidence-Based Approach to Palpitations

Palpitations are a common presenting symptom in primary care, yet their cause can be difficult to diagnose due to their intermittent and sometimes infrequent nature. All patients presenting with a chief complaint of palpitations should undergo a detailed history, physical examination, and electrocardiogram (ECG). This alone can yield a probable diagnosis. Limited laboratory testing, ambulatory ECG monitoring, and cardiology referral are sometimes indicated. This article reviews current data and guidelines on how to evaluate palpitations in the primary care setting.

Evaluation and Management of Asymptomatic Bradyarrhythmias

Asymptomatic bradyarrhythmias involving sinus node dysfunction and atrioventicular blocks are frequently noted in clinical practice. Its prevalence is expected to rise as devices that are developed for monitoring cardiac rhythm for longer duration become more widely available. Episodes of bradyarrhythmia that are asymptomatic are considered to have a benign course compared with those that cause symptoms and do not necessitate further treatment. However, in certain cases, they can be a harbinger of future symptoms or cardiac manifestations of systemic diseases. The evaluation and risk stratification of individuals presenting with asymptomatic bradyarrhythmias is important not only for preventing implantation of unnecessary permanent pacing devices but also for reducing significant morbidity by implementing proper treatment as required. In this article, we will review the current evidence on the pathophysiology, diagnosis, evaluation and management of patients with asymptomatic bradyarrhythmias.

[Differential diagnostics of unclear syncope]

The clarification of syncope is a diagnostic challenge as possible causes often occur only intermittently. Therefore, a detailed and standardized anamnesis is essential as it 1) differentiates syncope from other transient losses of consciousness (TLOC) and 2) directly clarifies possible causes of syncope. The risk stratification plays a central and very important role in order to avoid unnecessary examinations in patients with benign syncope and to provide patients with life-threatening, mostly cardiac syncopal episodes with timely diagnostics and treatment. In cases where the cause of syncope is still unclear, a standardized approach is indicated using extended diagnostics, such as a tilt table examination, a carotid sinus pressure test, prolonged telemetric monitoring or clarification with an implantable loop recorder (ILR).

Diagnostic challenges in supraventricular tachycardia: anticipating value of natriuretic peptides

It is important not to overlook supraventricular tachycardia (SVT) in patients complaining of palpitation or tachycardia-related symptoms but with normal ECG and heart rate in emergency department or outpatient clinics. The severity and presentation of symptoms is highly variable and depends on features including heart rate, duration of tachycardia, underlying heart disease, and individual patient perception. Early measurement of natriuretic peptides in patients presenting with palpitation and/or tachycardia-related symptoms would guide the clinician to rule out tachycardia and/or SVT. High levels of natriuretic peptides within 30 min of postattack period would certainly increase the likelihood of SVT.

Holter Monitoring and Loop Recorders: From Research to Clinical Practice

Holter monitors are tools of proven efficacy in diagnosing and monitoring cardiac arrhythmias. Despite the fact their use is widely prescribed by general practitioners, little is known about their evolving role in the management of patients with cryptogenic stroke, paroxysmal atrial fibrillation, unexplained recurrent syncope and risk stratification in implantable cardioverter defibrillator or pacemaker candidates. New Holter monitoring technologies and loop recorders allow prolonged monitoring of heart rhythm for periods from a few days to several months, making it possible to detect infrequent arrhythmias in patients of all ages. This review discusses the advances in this area of arrhythmology and how Holter monitors have improved the clinical management of patients with suspected cardiac rhythm diseases.

The Cost-Effective Evaluation of Syncope

Syncope is a common clinical problem that carries a high socioeconomic burden. A structured approach in the evaluation of syncope with special emphasis on a detailed history, comprehensive physical examination that includes orthostatic vital signs, and an electrocardiogram, proves to be the most cost-effective approach. The need for additional testing and hospital admission should be based on the results of the initial evaluation and use of risk-stratification tools that help identify those syncope patients at highest risk for poor outcomes.

Syncope: the emergency department and beyond

Syncope is a common problem encountered by both emergency and internal medicine physicians. This review focuses on not only the assessment, risk stratification and management of the syncope patient, but also the latest thinking on diagnostic testing including more novel tools such as biomarkers and ambulatory patch monitor recording.

Use of event recorders and loop recorders in clinical practice: results of the European Heart Rhythm Association Survey

Several kinds of electrocardiogram monitoring systems are now available in the clinical practice. The aim of this European Heart Rhythm Association (EHRA) survey was to assess the use of different monitoring techniques in the evaluation of patients with unexplained syncope, palpitations, and in those with established diagnosis of atrial fibrillation. Forty-five centres in Europe answered the questionnaire and the majority (78%) were university hospitals. The answers showed a discrepancy between the recommended use of implantable loop recorders (ILRs) in patients with unexplained syncope and the use of this device in clinical practice. In most of the cases only a minority of patients (<20%) seemed to actually receive an ILR as a part of the diagnostic process in accordance to the current guidelines. Holter monitoring systems and external loop recorders seemed to be the preferred monitoring techniques both in patients with recurrent palpitations and in those with established diagnosis of atrial fibrillation.

Cryptogenic Stroke And Role Of Loop Recorder

Ischemic stroke is an important cause of morbidity and mortality when untreated. Identifying atrial fibrillation is important because atrial fibrillation ischemic related strokes are associated with an increased risk of disability and death compared with strokes of other etiologies and tend to recur without anticoagulation. However, atrial fibrillation detection can be difficult when it is asymptomatic and paroxistic and may be the underlying cause of some cryptogenic strokes or strokes of unknown origin. In this review, the different methods of cardiac monitoring to detect atrial fibrillation in patients with cryptogenic stroke are summarized, with a focus on loop recorder monitoring.

Troponin-I is a predictor of a delayed diagnosis of atrial fibrillation in acute ischemic stroke and transient ischemic attack

BACKGROUND

Prolonged cardiac monitoring detects higher rates of atrial fibrillation (AF) in ischemic stroke and transient ischemic attack (TIA) but is costly and has practical implications. The use of admission troponin-I (TnI) level to identify patients at high risk of delayed AF detection was investigated.

METHODS

Consecutive ischemic stroke and TIA cases presenting to our institute over a 13-month period were identified from the Irish Stroke and TIA Register. Electronic databases and case notes were examined. "Delayed" AF was diagnosed after a sinus rhythm admission electrocardiogram and no documented history. Group comparisons were made by AF status. The association between TnI and AF was investigated using a multivariate regression model.

RESULTS

A total of 185 cases (130 ischemic stroke) were analyzed. Mean age (standard deviation) was 73.3 (13.9) years, 47% female. Sixty-two cases (33.5%) had AF. The first documented presentation of AF was found in 21 cases, on admission electrocardiogram (n = 11) or inpatient telemetry (delayed, n = 10). TnI was higher in those with delayed AF than in those without AF (W = 194; P = .036). A higher proportion of those with an elevated TnI (30%) than those with a normal TnI (6.1%) had delayed diagnosis of AF (χ(2) = 6.41, P = .011). Having an abnormal TnI was a significant independent predictor of delayed AF detection (odds ratio, 5.8; P = .037).

CONCLUSIONS

TnI elevation is associated with a higher likelihood of subsequent AF diagnosis. Identification of these higher risk stroke and TIA cases for more intensive cardiac monitoring may improve stroke secondary prevention practices.

The use of external event monitoring (web-loop) in the elucidation of symptoms associated with arrhythmias in a general population

Objective

To correlate arrhythmic symptoms with the presence of significant arrhythmias through the external event monitoring (web-loop).

Methods

Between January and December 2011, the web-loop was connected to 112 patients (46% of them were women, mean age 52±21 years old). Specific arrhythmic symptoms were defined as palpitations, pre-syncope and syncope observed during the monitoring. Supraventricular tachycardia, atrial flutter or fibrillation, ventricular tachycardia, pauses greater than 2 seconds or advanced atrioventricular block were classified as significant arrhythmia. The association between symptoms and significant arrhythmias were analyzed.

Results

The web-loop recorded arrhythmic symptoms in 74 (66%) patients. Of these, in only 14 (19%) patients the association between symptoms and significant cardiac arrhythmia was detected. Moreover, significant arrhythmia was found in 11 (9.8%) asymptomatic patients. There was no association between presence of major symptoms and significant cardiac arrhythmia (OR=0.57, CI95%: 0.21-1.57; p=0.23).

Conclusion

We found no association between major symptoms and significant cardiac arrhythmia in patients submitted to event recorder monitoring. Event loop recorder was useful to elucidate cases of palpitations and syncope in symptomatic patients.

Syncope

Syncope is common representing approximately 3% of ED visits and up to 6% of hospital admissions, with a cost close to 2 billion dollars per year. Diagnostic testing is often poorly sensitive and evaluations commonly lack a standardized approach. A mindful and systematic approach can increase sensitivity and improve diagnostic accuracy. A thorough history and physical exam is paramount, as conclusions drawn from the history and exam will guide further assessment. Developing a strategy for the first and, if necessary, subsequent tests will improve the accuracy of identifying the etiology of syncope and reduce cost. Although syncope has a favorable prognosis, identification of patients with structural heart disease is critical, as these patients are at greatest risk for mortality. Several risk scoring systems have been developed to help separate high risk from low risk patients.

Syncope in the Elderly

A rapid change in ageing demographic is taking place worldwide such that healthcare professionals are increasingly treating old and very old patients. Syncope in the elderly is a challenging presentation that is under-recognised, particularly in the acute care setting. The reason for this is that presentation in the older person may be atypical: patients are less likely to have a prodrome, may have amnesia for loss of consciousness and events are frequently unwitnessed. The older patient thus may present with a fall rather than transient loss of consciousness. There is an increased susceptibility to syncope with advancing age attributed to age-related physiological impairments in heart rate and blood pressure, and alterations in cerebral blood flow. Multi-morbidity and polypharmacy in these complex patients increases susceptibility to syncope. Cardiac causes and more than one possible cause are also common. Syncope is a major cause of morbidity and mortality and is associated with enormous personal and wider health economic costs. In view of this, prompt assessment and early targeted intervention are recommended. The purpose of this article is to update the reader regarding the presentation and management of syncope in this rapidly changing demographic.

Benefits of monitoring patients with mobile cardiac telemetry (MCT) compared with the Event or Holter monitors

INTRODUCTION

This research is meant to establish if a patient monitored with mobile cardiac telemetry (MCT) sees different outcomes regarding diagnostic yield of arrhythmia, therapeutic management through the use of antiarrhythmic drugs, and cardiovascular costs incurred in the hospital setting when compared with more traditional monitoring devices, such as the Holter or the Event monitor.

MATERIALS AND METHODS

We conducted a retrospective analysis spanning 57 months of claims data from January 2007 to September 2011 pertaining to 200,000+ patients, of whom 14,000 used MCT only, 54,000 an Event monitor only, and 163,000 a Holter monitor only. Those claims came from the Truven database, an employer database that counts 2.8 million cardiovascular patients from an insured population of about 10 million members. We employed a pair-wise pre/post test-control methodology, and ensured that control patients were similar to test patients along the following dimensions: age, geographic location, type of cardiovascular diagnosis both in the inpatient and outpatient settings, and the cardiovascular drug class the patient uses.

RESULTS

First, the diagnostic yield of patients monitored with MCT is 61%, that is significantly higher than that of patients that use the Event monitor (23%) or the Holter monitor (24%). Second, patients naive to antiarrhythmic drugs initiate drug therapy after monitoring at the following rates: 61% for patients that use MCT compared with 39% for patients that use the Event and 43% for patients that use the Holter. Third, there are very significant inpatient cardiovascular savings (in the tens of thousands of dollars) for patients that undergo ablation, coronary artery bypass graft (CABG) and valve septa. Savings are more modest but nonetheless significant when it comes to the heart/pericardium procedure.

CONCLUSION

Given the superior outcome of MCT regarding both patient care and hospital savings, hospitals only stand to gain by enforcing protocols that favor the MCT system over the Event or the Holter monitor.

Role of extended external loop recorders for the diagnosis of unexplained syncope, pre-syncope, and sustained palpitations

AIMS

To assess the diagnostic yield of new external loop recorders (ELRs) in patients with history of syncope, pre-syncope, and sustained palpitations.

METHODS AND RESULTS

Since 2005, we have established a registry including patients who consecutively received ELR monitoring for unexplained syncope or pre-syncope/palpitations. The registry included 307 patients (61% females, age 58 ± 19 years, range 8-94 years) monitored by high-capacity memory ELR of two subsequent generations: SpiderFlash-A(®) (SFA(®), Sorin CRM), storing two-lead electrocardiogram (ECG) patient-activated recordings by loop-recording technique (191 patients, 54 patients with syncope, years 2005-09), and SpiderFlash-T(®) (SFT(®)), adding auto-trigger detection for pauses, bradycardia, and supraventricular/ventricular arrhythmias (116 patients, 38 patients with syncope, years 2009-12). All the patients previously underwent routine workup for syncope or palpitation, including one or more 24 h Holter, not conclusive for diagnosis. Mean monitoring duration was 24.1 ± 8.9 days. Among 215 patients with palpitations, a conclusive diagnosis was obtained in 184 patients (86% diagnostic yield for palpitation). Among 92 patients with syncope, a conclusive diagnosis was obtained in 16 patients (17% clinical diagnostic yield for syncope), with recording during syncope of significant arrhythmias in 9 patients, and sinus rhythm in 7 patients. Furthermore, asymptomatic arrhythmias were de novo detected in 12 patients (13%), mainly by auto-trigger detection, suggesting an arrhythmic origin of the syncope.

CONCLUSIONS

The diagnostic yield of ELR in patients with syncope, pre-syncope, or palpitation of unknown origin after routine workup was similar to implantable loop recorder (ILR) within the same timeframe, therefore, ELR could be considered for patients candidate for long-term ECG monitoring, stepwise before ILR.

ECG monitoring in syncope

Electrocardiographic (ECG) monitoring is a well-established procedure in the work-up of patients with syncope or for diagnosing arrhythmias. The investigation of syncope remains, however, challenging and physicians have an increasing armamentarium of diagnostic tools available and with advances in technology the role of these tools has to be continuously evaluated. The gold standard for the diagnosis of syncope is a symptom-ECG correlation, and while many studies have investigated the use and indications of both short-term and long-term monitoring; there is still some uncertainty in their clinical utility and practical approach. The use of ECG monitoring and other diagnostic tools is often subject to a "shot-gun approach" rather than a strict guideline algorithm. A systematic approach and selection of ECG monitoring tools helps permit an effective usage of the limited health care resources available for the management of unexplained syncope. In this review we aim to focus and clarify the role of short-term (Holter and external loop recorders) and long-term (implantable loop recorders) ECG monitoring in the diagnosis and management of patients with unexplained syncope.

A usability study of patients setting up a cardiac event loop recorder and BlackBerry gateway for remote monitoring at home

This article reports on a usability study of remote noninvasive cardiac testing in homes. We studied the Vitaphone 3100BT (Bluetooth®) event loop recorder (Vitaphone GmbH, Mannheim, Germany) and paired BlackBerry® Curve™ 8520 smartphone (Research In Motion, Ltd., Waterloo, ON, Canada). This application requires independent device set-up by patients in their own homes following receipt by mail out of the kit (instructions plus the event loop recorder and smartphone). The case studies of five participants, each with varying experience with technology, were documented as they interacted with the devices. Participants were videotaped following written instructions as they performed a "think aloud" procedure while completing 20 device set-up tasks. Interviews provided insight into how the independent device set-up and processes could be improved. This study concluded that gender, age, and familiarity with technology seemed to influence the participants' abilities to successfully set up these devices and that sending the kit by mail appeared to be an acceptable strategy to provide remote noninvasive cardiac diagnostic services. This study provides a foundation for future research assessing usability of mobile healthcare technology.

[Significance of diagnostic methods in the work-up of syncope]

After the initial evaluation including detailed history, physical examination, electrocardiogram, and orthostatic blood pressure measurements, risk stratification should follow, if the cause of syncope is still unclear in order to define the acuteness and extensiveness of the further diagnostic evaluation. The documentation of arrhythmia during syncope is the gold standard for diagnosis of arrhythmic syncope. The implantable loop recorder should be integrated early in the diagnostic work-up. In patients >40 years with otherwise unexplained syncope, carotid sinus massage is recommended. In suspected reflex-mediated syncope, the tilt test is able to confirm the diagnosis and gives information about the underlying pathomechanisms, while electrophysiological studies have still a proven indication in patients with previous myocardial infarction and preserved left ventricular function. The adenosine triphophate test has no clinical relevance in the diagnostics of syncope. Echocardiography plays an important role in the risk stratification by diagnosing structural cardiac disease. In patients experiencing syncope associated with exertion, exercise stress testing is indicated. Finally, a coronary angiogram should be performed, if ischemia triggered syncope is suspected. A routinely performed neurological evaluation is not recommended.

The Utility of Ambulatory Electrocardiographic Monitoring for Detecting Silent Arrhythmias and Clarifying Symptom Mechanism in an Urban Elderly Population with Heart Failure and Hypertension: Clinical Implications

Background: Atrial and ventriclar tachyarrhythmias, as well as bradyarrhythmias, in the elderly with heart failure (HF) and/or hypertension (HTN) have been well documented. However, the frequency of these arrhythmias, whether silent or symptomatic, and their association with subsequent cardiac events has not been well defi ned in patients 65 years or older with HF and other cardiovascular risk factors. Objective: To assess the value of 2 weeks of remote, transtelephonic cardiac monitoring for detecting arrhythmias in an elderly, urban population living with HF. Methods: Fi" y-four patients with a history of systolic HF and/or HTN were consented and enrolled. All wore an auto triggered cardiac loop monitor for 2 weeks that captures EKG data and both silent and symptomatic arrhythmias were recorded. Results: Mean age was 73 ± 6 years with 59% of subjects were females, 74% Hispanic, 22% black, and 4% white/other. All patients had HF and 94% had HTN. From the cardiac monitoring, 72% demonstrated ectopic atrial and ventricular activity, and 1 paroxysmal episode of atrial fi brillation was documented. In addition, 3 subjects had signifi cant non-sustained ventricular tachycardia, and 4 individuals had severe bradycardia recorded on cardiac monitoring. These 7 individuals underwent placement of an implantable cardioverter defi brillator (ICD) or pacemaker based on the documented arrhythmias which may have otherwise gone undetected. Conclusions: A substantial proportion of patients exhibited cardiac arrhythmias. Future morbidity was prevented because of the detection of arrhythmias on monitoring that led to specifi c therapies such as pacemaker or ICD implantation which otherwise may not have been implemented.

Frequency of serious arrhythmias detected with ambulatory cardiac telemetry

Ambulatory cardiac telemetry has been shown to be effective in establishing diagnoses in patients with suspected arrhythmias. A critical component of ambulatory telemetry is the immediate transfer of rhythm information to a central monitoring station without requiring patient action. The frequency with which potentially life-threatening events are detected using ambulatory telemetry has not previously been evaluated in a large patient population. All patients (n = 26,438) who underwent monitoring from April to December 2008 at a single service provider formed the patient population of this study. Arrhythmic events noted in these patients were defined as those requiring physician notification and those that represented potentially life-threatening arrhythmias. Of the 26,438 patients included in the study, 5,459 (21%) had arrhythmic events meeting physician notification criteria during a mean monitoring period of 21 days. Of these, 262 patients (1%) had arrhythmic events that could potentially be classified as emergent. These included 120 patients with wide complex tachycardia > or = 15 beats at > or = 120 beats/min, 100 patients with pauses > or = 6 seconds, and 42 patients with sustained heart rates <30 beats/min. An additional 704 patients (3%) had narrow complex tachycardia > or = 180 beats/min at rest. In conclusion, approximately 1% of patients who underwent ambulatory telemetry for routine clinical indications experienced life-threatening arrhythmic events over a 3-week monitoring period. Ambulatory cardiac telemetry could be potentially lifesaving in this group of patients.

The diagnosis of cardiac arrhythmias: a prospective multi-center randomized study comparing mobile cardiac outpatient telemetry versus standard loop event monitoring

INTRODUCTION

Ambulatory electrocardiographic monitoring systems are frequently used in the outpatient evaluation of symptoms suggestive of a cardiac arrhythmia; however, they have a low yield in the identification of clinically significant but infrequent, brief, and/or intermittently symptomatic arrhythmias. The purpose of this study was to compare the relative value of a mobile cardiac outpatient telemetry system (MCOT) with a patient-activated external looping event monitor (LOOP) for symptoms thought to be due to an arrhythmia.

METHODS AND RESULTS

The study was a 17-center prospective clinical trial with patients randomized to either LOOP or MCOT for up to 30 days. Subjects with symptoms of syncope, presyncope, or severe palpitations who had a nondiagnostic 24-hour Holter monitor were randomized. The primary endpoint was the confirmation or exclusion of a probable arrhythmic cause of their symptoms. A total of 266 patients who completed the monitoring period were analyzed. A diagnosis was made in 88% of MCOT subjects compared with 75% of LOOP subjects (P = 0.008). In a subgroup of patients presenting with syncope or presyncope, a diagnosis was made in 89% of MCOT subjects versus 69% of LOOP subjects (P = 0.008). MCOT was superior in confirming the diagnosis of clinical significant arrhythmias, detecting such events in 55 of 134 patients (41%) compared with 19 of 132 patients (15%) in the LOOP group (P < 0.001).

CONCLUSIONS

MCOT provided a significantly higher yield than standard cardiac loop recorders in patients with symptoms suggestive of a significant cardiac arrhythmia.

Using the net benefit regression framework to construct cost-effectiveness acceptability curves: an example using data from a trial of external loop recorders versus Holter monitoring for ambulatory monitoring of "community acquired" syncope

Background

Cost-effectiveness acceptability curves (CEACs) describe the probability that a new treatment or intervention is cost-effective. The net benefit regression framework (NBRF) allows cost-effectiveness analysis to be done in a simple regression framework. The objective of the paper is to illustrate how net benefit regression can be used to construct a CEAC.

Methods

One hundred patients referred for ambulatory monitoring with syncope or presyncope were randomized to a one-month external loop recorder (n = 49) or 48-hour Holter monitor (n = 51). The primary endpoint was symptom-rhythm correlation during monitoring. Direct costs were calculated based on the 2003 Ontario Health Insurance Plan (OHIP) fee schedule combined with hospital case costing of labour, materials, service and overhead costs for diagnostic testing and related equipment.

Results

In the loop recorder group, 63.27% of patients (31/49) had symptom recurrence and successful activation, compared to 23.53% in the Holter group (12/51). The cost in US dollars for loop recording was $648.50 and $212.92 for Holter monitoring. The incremental cost-effectiveness ratio (ICER) of the loop recorder was $1,096 per extra successful diagnosis. The probability that the loop recorder was cost-effective compared to the Holter monitor was estimated using net benefit regression and plotted on a CEAC. In a sensitivity analysis, bootstrapping was used to examine the effect of distributional assumptions.

Conclusion

The NBRF is straightforward to use and interpret. The resulting uncertainty surrounding the regression coefficient relates to the CEAC. When the link from the regression's p-value to the probability of cost-effectiveness is tentative, bootstrapping may be used.