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Ann Thorac Surg 2007;83:2118-2121
© 2007 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Absence of Correlation Between Symptoms and Rhythm in "Symptomatic" Atrial Fibrillation

Section of Cardiothoracic Surgery, Department of Surgery, University of Cincinnati, Cincinnati, Ohio

Accepted for publication February 26, 2007.

^_* Address correspondence to Dr Mehall, Section of Cardiothoracic Surgery, University of Cincinnati, 231 Albert B. Sabin Way, PO Box 670558, Cincinnati, OH 45367 (Email: john.mehall{at}uc.edu).

Presented at the Poster Session of the Fifty-third Annual Meeting of the Southern Thoracic Surgical Association, Tucson, AZ, Nov 8–12, 2006.

	Abstract

Top Abstract Introduction Material and Methods Results Comment References

 
Background: Symptoms are widely used as a means of assessment and follow-up of patients with atrial fibrillation. This study assessed the correlation between symptoms and cardiac rhythm in patients being evaluated for operative therapy for atrial fibrillation.

Methods: Seven days of preoperative continuous outpatient home electrocardiographic monitoring was performed on 50 patients with symptomatic atrial fibrillation. Cardiac rhythm was continuously monitored automatically, while patients recorded their symptoms electronically. Correlations were then drawn between symptomatic events and actual rhythm, and between atrial fibrillation episodes and symptoms.

Results: Fifty patients (37 men) with symptomatic atrial fibrillation were monitored for a combined 356 days (mean, 7.1 days). Patients were average age of 69 years old. Intermittent atrial fibrillation was reported by 36 patients, and 14 believed their atrial fibrillation was continuous. During monitoring, all patients had periods of both atrial fibrillation and normal sinus rhythm. Of the 552 documented episodes of atrial fibrillation, 467 (85%) were asymptomatic, and 85 (15%) episodes were symptomatic. Patients indicated that they experienced atrial fibrillation symptoms 163 times. Of the 163 symptomatic events, 85 (52%) were actual atrial fibrillation, 64 (42%) were sinus rhythm, and 14 (6%) were other rhythms. The ability of an individual patient to accurately identify atrial fibrillation ranged from 0% to 100%.

Conclusions: Patient-reported symptoms of atrial fibrillation had poor correlation with actual rhythm. The lack of correlation between symptoms and rhythm underscores the importance of continuous home monitoring for accurately quantifying preoperative atrial fibrillation burden and for postoperative follow-up.

	Introduction

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Atrial fibrillation represents a major health burden, and its occurrence places patients at increased risk of both stroke and death. Because antiarrhythmic pharmacotherapy is often ineffective, much attention is now being directed towards finding a curative therapy using electrical isolation of various parts of the atria through both catheter-based and surgical approaches. Unfortunately, it is difficult to compare the effectiveness of different therapeutic strategies owing to the tremendous variation in ablation modalities, lesion sets used for isolation/ablation, methods of assessment before and after the procedure, and inconsistent reporting of these variables in the literature.

To date, most attention has been paid to patients with symptoms that are thought related to or caused by atrial fibrillation. Although patients with both symptomatic and asymptomatic atrial fibrillation have similar increased risks of stroke and death, patients with symptoms are more likely to seek medical attention for their atrial fibrillation and have thus been better studied.

It has become an assumption that patients with symptomatic atrial fibrillation are able to accurately determine the presence of atrial fibrillation from the presence or absence of symptoms. Subjective querying of patients for the presence of symptoms has been used extensively as a mechanism of follow-up in many studies, including those which established the Cox Maze III as the gold standard of surgical treatment [1]. However, new research has questioned the assertion that patient-reported symptoms are an accurate reflection of actual cardiac rhythm [2–6]. Previous studies demonstrating a lack of correlation between symptoms and rhythm and a high incidence of asymptomatic atrial fibrillation used intermittent transtelephonic electrocardiograms or 24-hour Holter monitoring. In this study, we used continuous home monitoring to evaluate the correlation between symptoms and rhythm.

Patients with symptomatic atrial fibrillation undergoing periodic physical examination are found to be in asymptomatic atrial fibrillation 20% of the time; the incidence is even higher in studies using Holter monitoring, transtelephonic monitoring, or event recorders [2]. An increased posttreatment incidence of asymptomatic atrial fibrillation has also been observed after catheter ablation of atrial fibrillation [3]. Given the increasing awareness of asymptomatic atrial fibrillation and the potential unreliability of patient-reported symptoms as a means of postintervention follow-up, we conducted the following study to define the extent of correlation between patient-reported symptoms and actual cardiac rhythm.

	Material and Methods

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The Institutional Review Board of the University of Cincinnati approved the study protocol, the consent form, and the process. We studied 50 consecutive patients who were being evaluated for elective surgical treatment of their atrial fibrillation. Patients were placed on continuous home electrocardiographic monitoring (CardioNet, San Diego, CA) for 7 to 10 days preoperatively to assess their burden of atrial fibrillation and to determine the degree of correlation between their symptoms and rhythm.

The continuous home monitoring system records uninterrupted electrocardiograms for the entire monitoring period. The monitoring system makes a note of any changes in rhythm and records these changes as an event. The system also records heart rates above or below preset limits or wide complex/ventricular arrhythmias. Each change from normal sinus rhythm to a nonsinus rhythm is automatically recorded and is considered an automatically triggered arrhythmia event. For purposes of this study, conversion from normal sinus rhythm to atrial fibrillation was considered an automatically triggered atrial fibrillation event.

During the monitoring period, patients recorded their perceived rhythm electronically using buttons on the monitor to indicate when they believed that they were experiencing atrial fibrillation. These symptomatic episodes were recorded in real time with the corresponding cardiac rhythm and are considered patient-triggered symptomatic events. Collectively, the automatically triggered atrial fibrillation events and patient-triggered events represent the total number of atrial fibrillation related events. Patient-triggered events that were actually atrial fibrillation were true-positives, and patient-triggered events that were not atrial fibrillation were false-positives.

The home monitoring data were analyzed to determine the presence or absence of atrial fibrillation and other cardiac arrhythmias, the frequency and duration of atrial fibrillation episodes, the presence or absence of symptoms, and the correlation between symptomatic episodes and cardiac rhythm. The accuracy of patient reporting of symptoms was assessed for atrial fibrillation events triggered automatically and for patient-triggered symptomatic events. We also assessed the accuracy of patients’ preoperative characterizations of their atrial fibrillation as either intermittent or continuous.

	Results

Top Abstract Introduction Material and Methods Results Comment References

 
Fifty patients (37 men) with symptomatic atrial fibrillation were monitored for a mean 7.1 days per patient (range, 6 to 10 days; combined 356 days). Patients were an average age of 69 years old (range, 41 to 72 years). All patients were on both an antiarrhythmic and an anticoagulation regimen.

Thirty-six patients reported that their atrial fibrillation was intermittent, and 14 perceived their atrial fibrillation as continuous. Monitoring documented 552 occurrences of atrial fibrillation, for a mean of 1.6 episodes daily per patient (range, 0 to 75) and a mean of 11 episodes per patient during the monitored period. All patients were found to have at least some occurrences of atrial fibrillation during the monitored period. In addition, all patients were found to have some periods of normal sinus rhythm, including all 14 patients who reported having continuous atrial fibrillation.

A total of 1256 events were recorded through 356 days of monitoring. Of these, 163 were patient-recorded symptomatic events and 1093 were automatically recorded arrhythmia events. Of the 1093 automatically recorded arrhythmia events, 630 events were related to atrial fibrillation, 417 were electrocardiographic artifact or other undistinguishable rhythm, 28 were ventricular arrhythmias, including premature ventricular contractions, and 18 were other rhythms. Of the 630 events related to atrial fibrillation, 163 were patient-triggered symptomatic events and 552 were automatically triggered atrial fibrillation events. Atrial fibrillation occurred 552 times during the collective monitored period (mean, 1.6 events per day; range, 0 to 75). Of these 552 automatically triggered atrial fibrillation events, patients reported symptoms 85 times (15%) and 467 (85%) were undetected by patients (Fig 1).

View larger version (35K): [in this window] [in a new window]   Fig 1. Distribution of all recorded atrial fibrillation events. (SR = sinus rhythm.)

The positive predictive value of a symptom actually being atrial fibrillation is only 52%. The ability of an individual patient to accurately identify atrial fibrillation ranged from 0% to 100%. There was no statistically significant difference in accuracy between patients who believed their atrial fibrillation to be intermittent versus continuous with respect to their ability to accurately identify atrial fibrillation episodes, although this likely reflects the small number of patients in the continuous group. There was a trend towards increased recognition of atrial fibrillation episodes among patients with fewer atrial fibrillation episodes. Some form of ventricular ectopy was present in 28 patients, most often premature ventricular contractions. Three patients, however, were found to have unsuspected ventricular tachyarrhythmias.

	Comment

Top Abstract Introduction Material and Methods Results Comment References

 
An accurate and complete understanding of a patient’s cardiac rhythm and atrial fibrillation burden is essential to obtaining the correct preoperative diagnosis, deciding on appropriate treatments, and in determining the actual results of a treatment strategy. To date, however, the most common form of preprocedure assessment and postprocedure follow-up for patients undergoing treatment for atrial fibrillation has been patient reporting of symptoms. As this study demonstrates, patient reporting of symptoms lacks the accuracy and precision necessary for accurate rhythm determination and further confuses attempts to draw meaningful conclusions from the literature.

The recognition of asymptomatic atrial fibrillation has existed for more than a decade [2]. Even in those patients with symptomatic atrial fibrillation, the ratio of asymptomatic to symptomatic episodes has been found to be as high as 12:1 when using intermittent 24-hour Holter monitoring [2, 4]. Conversely, when patients with known paroxysmal atrial fibrillation reported their symptoms, one third of reported symptomatic atrial fibrillation episodes were actually normal sinus rhythm [5]. Despite the frequent absence of symptoms, short, intermittent episodes of atrial fibrillation identify patients who are more than twice as likely to die or have a stroke [6]. Because of these factors, the American College of Cardiology/American Heart Association/European Society of Cardiology Guidelines for the Management of Patients with Atrial Fibrillation [7] recommend lifelong antiarrhythmic or rate control therapy and anticoagulation therapy once atrial fibrillation recurs beyond the initial episode.

The recognition of the lack of correlation between symptoms and rhythm is increasing in the electrophysiology literature [3, 8, 9]. Nergardh and Frick [8] found a poor agreement between perceived rhythm and spot electrocardiograms in patients undergoing cardioversion for persistent atrial fibrillation. In patients who had undergone catheter ablation, daily transtelephonic monitoring more than doubled the accurate detection of asymptomatic atrial fibrillation episodes to 27.8% compared with the combined strategy of spot electrocardiograms and one-time 24-hour Holter monitoring [10]. This same study found that 50% of patients experienced at least one asymptomatic episode of atrial fibrillation. Hindricks and colleagues [3] concluded that when evaluating atrial fibrillation therapy, "A symptom-only based follow-up would substantially overestimate the success rate."

Unfortunately, almost all of the literature currently published on the effectiveness of surgical or catheter-based ablation for atrial fibrillation uses either symptom-based follow-up or spot electrocardiograms. Although the Cox Maze III is widely regarded as the gold standard for operative treatment of atrial fibrillation, the long-term follow-up study used patient-reported symptoms as the initial follow-up mechanism [1]. Patients who reported having no symptoms were considered cured, and no further follow-up was performed. Electrocardiograms of patients reporting symptoms were reviewed. The present study clearly demonstrates that most patients cannot reliably identify their cardiac rhythm, nor can they accurately correlate their symptoms to their cardiac rhythm.

The significantly higher percentage of automatically recorded asymptomatic atrial fibrillation episodes seen in this study is likely skewed by several factors:

1 Patients who had many episodes of atrial fibrillation a day may not have always recorded when they experienced symptoms;

2 Atrial fibrillation episodes that occurred during sleep might not have been noticed by the patient, and

3 Long periods of atrial fibrillation that were interrupted by electrocardiographic artifact caused the monitor to record a new episode of atrial fibrillation once it reacquired the electrocardiogram.

However, despite these limitations in automatically recorded episodes of atrial fibrillation, when patients indicated that they were experiencing atrial fibrillation, they were correct only half of the time. This study also identified three patients with clinically significant ventricular tachyarrhythmias that were unsuspected.

The Society of Thoracic Surgeons is attempting to clarify the literature of atrial fibrillation by drafting guidelines for reporting the results of operative interventions for atrial fibrillation. Precise and complete reporting of clinical data will be an important step towards making the atrial fibrillation literature meaningful. Equally important is appropriate preprocedure and postprocedure rhythm assessment. As demonstrated by this study and others, objective documentation of cardiac rhythm is essential, and increased monitoring intensity consistently yields higher rates of detection of arrhythmias. We recommend continuous home electrocardiographic monitoring to assess all patients both preoperatively and as postoperative follow-up. We believe that this rigorous methodology is essential to accurately assess the effectiveness of our therapy and for making any decisions regarding cessation of antiarrhythmic or anticoagulation regimens.

	References

Top Abstract Introduction Material and Methods Results Comment References

 

1. Gaynor SL, Schuessler RB, Bailey MS, et al. Surgical treatment for atrial fibrillation: predictors of late recurrence J Thorac Cardiovasc Surg 2005;129:104-111.[Abstract/Free Full Text]
2. Page RL, Wilkinson WE, Clair WK, et al. Asymptomatic arrhythmias in patients with symptomatic paroxysmal atrial fibrillation and paroxysmal supraventricular tachycardia Circulation 1994;89:224-227.[Abstract/Free Full Text]
3. Hindricks G, Piorkowski C, Tanner H, et al. Perception of atrial fibrillation before and after radiofrequency catheter ablation: relevance of asymptomatic arrhythmia recurrence Circulation 2005;112:307-313.[Abstract/Free Full Text]
4. Levy S, Maarek M, Coumel P, et al. The College of French Cardiologists Characterization of different subsets of atrial fibrillation in general practice in France: the ALFA study Circulation 1999;99:3028-3035.[Abstract/Free Full Text]
5. Bhandari AK, Anderson JL, Gilbert EM, et al. The Flecainide Supraventricular Tachycardia Study Group Correlation of symptoms with occurrence of paroxysmal supraventricular tachycardia or atrial fibrillation: a transtelephonic monitorinc study Am Heart J 1992;124:381-386.[Medline]
6. Savelieva I, Camm AJ. Clinical relevance of silent atrial fibrillation: prevalence, prognosis, quality of life, and management J Intervent Cardiac Electrophysiol 2000;4:369-382.[Medline]
7. AHA/ACC/ESC 2006 Atrial Fibrillation Guidelines: looking towards the future. Nat Clin Pract Cardiovasc Med 2997;4:59.
8. Nergardh A, Frick M. Perceived heart rhtyhm in relation to ECG findings after direct current cardioversion of atrial fibrillation Heart 2006;92:1244-1247.[Abstract/Free Full Text]
9. Senatore G, Stabile G, Bertaglia E, et al. Role of transtelephonic electrocardiographic monitoring in detecting short-term arrhythmia recurrences after radiofrequency ablation in patients with atrial fibrillation J Am Coll Cardiol 2005;45:873-876.[Abstract/Free Full Text]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): John R. Mehall Walter H. Merrill Randall K. Wolf Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mehall, J. R. Articles by Wolf, R. K. Search for Related Content PubMed PubMed Citation Articles by Mehall, J. R. Articles by Wolf, R. K. Related Collections Electrophysiology - arrhythmias