Effectiveness of Atrial Fibrillation Monitor Characteristics to Predict Severity of Symptoms of Atrial Fibrillation Nikhil Patel, BA, Eugene H. Chung, MD, John Paul Mounsey, MD, PhD, Jennifer D. Schwartz, MD, Irion Pursell, RN, and Anil K. Gehi, MD* The goal of treatment for atrial fibrillation (AF) is often to control symptoms. It remains unclear whether targets for treatment such as AF rate or AF burden are correlated with AF symptom severity. Two hundred eighty-six patients completed a questionnaire of their general health and well-being, including a detailed AF symptom assessment immediately followed by a 7-day continuous monitor. AF characteristics assessed from the monitor included AF burden, AF rate, sinus rhythm rate, frequency and severity of pauses, and premature atrial contraction or premature ventricular contraction burden. Characteristics were analyzed separately for patients with paroxysmal or persistent AF. Symptom severity was assessed using the University of Toronto Atrial Fibrillation Severity Scale. Monitor characteristics were compared with AF symptom severity. The mean age of the cohort was 61.8 years and the majority of subjects were male (65.4%). Co-morbidities included hypertension (64.5%), sleep apnea (38.4%), congestive heart failure (19.6%), and diabetes (16.4%). In those with persistent or paroxysmal AF, there were no significant predictors of AF symptom severity. Specifically, heart rate in AF or sinus rhythm, AF burden, or premature atrial contraction or premature ventricular contraction burden was not predictive of AF symptom severity. After adjusting for potential cofounders (including age, gender, and co-morbidities), these findings persisted. In conclusion, there is no value in using AF monitor characteristics to predict symptoms in patients with AF. Ó 2014 Elsevier Inc. All rights reserved. (Am J Cardiol 2014;113:1674e1678)
A number of potential rhythm characteristics may be predictive of atrial fibrillation (AF) symptom severity. Rapid ventricular response may lead to worsened symptom severity. However, previous studies of the correlation of ventricular rate and AF symptom severity have been inconsistent. Burden of AF (percentage of time in AF) in those with paroxysmal AF may be predictive of symptom severity, although there are limited data considering this possibility.1 Burden of premature contractions (percentage of beats that are premature atrial or ventricular contractions) may correlate with symptom severity. No previous studies have comprehensively investigated these rhythm characteristics of AF and their effects on AF symptom severity using an AF-specific symptom severity scale.2 To further characterize the effect of rhythm characteristics on AF symptom severity, we evaluated AF symptom severity in 286 participants enrolled in the Symptom Mitigation in Atrial Fibrillation (SMART) study with paroxysmal or persistent AF who underwent a 7-day continuous Holter monitor. Methods The SMART study is a prospective single-center cohort study of AF symptoms and health outcomes in stable Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina. Manuscript received November 21, 2013; revised manuscript received and accepted February 21, 2014. See page 1677 for disclosure information. *Corresponding author: Tel: (919) 966-4743; fax: (919) 966-4366. E-mail address: [email protected] (A.K. Gehi). 0002-9149/14/$ - see front matter Ó 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.amjcard.2014.02.022
outpatients with AF. Participants were recruited through electrophysiology clinics at the University of North Carolina at Chapel Hill. Participants were eligible to participate if they had at least 1 episode of AF not attributed to a reversible cause documented by electrocardiography or continuous looping monitor. From September 2008 to August 2012, a total of 450 participants were enrolled and completed a baseline questionnaire of their general health and well-being. Of these 450 participants, 286 underwent long-term (>1 week) continuous monitoring and were included in this substudy. The protocol was approved by the appropriate institutional review boards, and all participants provided written informed consent. Our primary predictor variables were measured from 7-day continuous monitors (ACT III; LifeWatch Corp, Rosemont, Illinois or ZIO Patch; iRhythm Technologies, Inc., San Francisco, California). Rhythm characteristics captured from the monitor included the percentage of time spent in AF (AF burden), the mean ventricular rate of AF, the maximum ventricular rate of AF, the minimum ventricular rate of AF, the mean ventricular rate in sinus rhythm, the maximum ventricular rate in sinus rhythm, the minimum ventricular rate in sinus rhythm, and the overall ventricular rate (either AF or sinus rhythm). Mean rate was calculated over the entire monitoring period. Other irregularities in heart rhythm measured included the number of pauses >2.5 seconds, the longest pause, total number of premature atrial contractions, premature atrial contraction burden, total number of premature ventricular contractions, and premature ventricular contraction burden. These www.ajconline.org
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Table 1 Baseline characteristics of 286 patients with atrial fibrillation (AF) stratified by severity of AF symptoms Mean SD or Percentage
Characteristic Overall (n ¼ 286)
Age (yrs) Men Hypertension Diabetes mellitus Coronary artery disease Heart failure Smoker Obstructive sleep apnea Medication b Blocker Calcium antagonist ACE/ARB Digoxin Antiarrhythmic Statin Persistent (vs paroxysmal)
Severe AF Symptoms
p Value
Yes (AFSS 20; n ¼ 74)
No (AFSS 7 days) stratified by severity of atrial fibrillation (AF) symptoms in the entire cohort Mean SD or Median (25%e75% IQR)
Variable Overall (n ¼ 286)
AF burden (%) Rate in AF mean Rate in AF maximal Rate in AF minimal Rate in sinus mean Rate in sinus maximal Rate in sinus minimal Overall rate No. of pauses >2.5 seconds Longest pause (seconds) Premature atrial contractions (n) Premature atrial contraction burden (%) Premature ventricular contractions (n) Premature ventricular contraction burden (%) Total recording time (days)
25.0 (0e100) 95.4 21.6 163.0 35.0 55.8 23.7 71.1 11.7 149.7 43.2 45.9 17.0 77.5 16.0 0 (0e0) 0 (0e0) 126 (0e1,859) 0 (0e0.33) 87.5 (9e1,432) 0 (0e0.1) 7.7 2.9
Severe AF Symptoms Yes (AFSS 20; n ¼ 74)
No (AFSS 0.05) for all comparisons between severe and nonsevere AF symptoms. IQR ¼ interquartile range.
predictor variables were all stratified between patients with paroxysmal or persistent AF. The University of Toronto Atrial Fibrillation Severity Scale (AFSS) was used as our primary outcome variable.3,4 The AFSS is an 18-item self-administered questionnaire to quantitatively describe subjective and objective ratings of AF. The 7-item AF symptom severity subscale was used in this analysis.5 Seven individual AF-related symptoms (palpitations, dyspnea at rest, dyspnea on exertion, exercise intolerance, tiredness at rest, light-headedness, and chest pain) generate a numerical description of symptom severity. Participants are asked to remark on how bothered they have
been by these AF symptoms in the past 4 weeks. The AFSS questionnaire was administered immediately before placement of the continuous monitor. Individual symptoms attributable to AF are scored on a 5-point Likert scale such that the total AFSS severity score ranges from 0 to 35, with higher scores indicating increased AF symptom severity. The AF symptom severity score was further dichotomized into those with severe (highest quartile: AFSS 20) versus nonsevere (lower 3 quartiles: AFSS
A number of potential rhythm characteristics may be predictive of atrial fibrillation (AF) symptom severity. Rapid ventricular response may lead to worsened symptom severity. However, previous studies of the correlation of ventricular rate and AF symptom severity have been inconsistent. Burden of AF (percentage of time in AF) in those with paroxysmal AF may be predictive of symptom severity, although there are limited data considering this possibility.1 Burden of premature contractions (percentage of beats that are premature atrial or ventricular contractions) may correlate with symptom severity. No previous studies have comprehensively investigated these rhythm characteristics of AF and their effects on AF symptom severity using an AF-specific symptom severity scale.2 To further characterize the effect of rhythm characteristics on AF symptom severity, we evaluated AF symptom severity in 286 participants enrolled in the Symptom Mitigation in Atrial Fibrillation (SMART) study with paroxysmal or persistent AF who underwent a 7-day continuous Holter monitor. Methods The SMART study is a prospective single-center cohort study of AF symptoms and health outcomes in stable Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina. Manuscript received November 21, 2013; revised manuscript received and accepted February 21, 2014. See page 1677 for disclosure information. *Corresponding author: Tel: (919) 966-4743; fax: (919) 966-4366. E-mail address: [email protected] (A.K. Gehi). 0002-9149/14/$ - see front matter Ó 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.amjcard.2014.02.022
outpatients with AF. Participants were recruited through electrophysiology clinics at the University of North Carolina at Chapel Hill. Participants were eligible to participate if they had at least 1 episode of AF not attributed to a reversible cause documented by electrocardiography or continuous looping monitor. From September 2008 to August 2012, a total of 450 participants were enrolled and completed a baseline questionnaire of their general health and well-being. Of these 450 participants, 286 underwent long-term (>1 week) continuous monitoring and were included in this substudy. The protocol was approved by the appropriate institutional review boards, and all participants provided written informed consent. Our primary predictor variables were measured from 7-day continuous monitors (ACT III; LifeWatch Corp, Rosemont, Illinois or ZIO Patch; iRhythm Technologies, Inc., San Francisco, California). Rhythm characteristics captured from the monitor included the percentage of time spent in AF (AF burden), the mean ventricular rate of AF, the maximum ventricular rate of AF, the minimum ventricular rate of AF, the mean ventricular rate in sinus rhythm, the maximum ventricular rate in sinus rhythm, the minimum ventricular rate in sinus rhythm, and the overall ventricular rate (either AF or sinus rhythm). Mean rate was calculated over the entire monitoring period. Other irregularities in heart rhythm measured included the number of pauses >2.5 seconds, the longest pause, total number of premature atrial contractions, premature atrial contraction burden, total number of premature ventricular contractions, and premature ventricular contraction burden. These www.ajconline.org
Arrhythmias and Conduction Disturbances/Effectiveness of AF Monitor
1675
Table 1 Baseline characteristics of 286 patients with atrial fibrillation (AF) stratified by severity of AF symptoms Mean SD or Percentage
Characteristic Overall (n ¼ 286)
Age (yrs) Men Hypertension Diabetes mellitus Coronary artery disease Heart failure Smoker Obstructive sleep apnea Medication b Blocker Calcium antagonist ACE/ARB Digoxin Antiarrhythmic Statin Persistent (vs paroxysmal)
Severe AF Symptoms
p Value
Yes (AFSS 20; n ¼ 74)
No (AFSS 7 days) stratified by severity of atrial fibrillation (AF) symptoms in the entire cohort Mean SD or Median (25%e75% IQR)
Variable Overall (n ¼ 286)
AF burden (%) Rate in AF mean Rate in AF maximal Rate in AF minimal Rate in sinus mean Rate in sinus maximal Rate in sinus minimal Overall rate No. of pauses >2.5 seconds Longest pause (seconds) Premature atrial contractions (n) Premature atrial contraction burden (%) Premature ventricular contractions (n) Premature ventricular contraction burden (%) Total recording time (days)
25.0 (0e100) 95.4 21.6 163.0 35.0 55.8 23.7 71.1 11.7 149.7 43.2 45.9 17.0 77.5 16.0 0 (0e0) 0 (0e0) 126 (0e1,859) 0 (0e0.33) 87.5 (9e1,432) 0 (0e0.1) 7.7 2.9
Severe AF Symptoms Yes (AFSS 20; n ¼ 74)
No (AFSS 0.05) for all comparisons between severe and nonsevere AF symptoms. IQR ¼ interquartile range.
predictor variables were all stratified between patients with paroxysmal or persistent AF. The University of Toronto Atrial Fibrillation Severity Scale (AFSS) was used as our primary outcome variable.3,4 The AFSS is an 18-item self-administered questionnaire to quantitatively describe subjective and objective ratings of AF. The 7-item AF symptom severity subscale was used in this analysis.5 Seven individual AF-related symptoms (palpitations, dyspnea at rest, dyspnea on exertion, exercise intolerance, tiredness at rest, light-headedness, and chest pain) generate a numerical description of symptom severity. Participants are asked to remark on how bothered they have
been by these AF symptoms in the past 4 weeks. The AFSS questionnaire was administered immediately before placement of the continuous monitor. Individual symptoms attributable to AF are scored on a 5-point Likert scale such that the total AFSS severity score ranges from 0 to 35, with higher scores indicating increased AF symptom severity. The AF symptom severity score was further dichotomized into those with severe (highest quartile: AFSS 20) versus nonsevere (lower 3 quartiles: AFSS
