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.
Credits:Kathleen T. Hickey 1, James Reiffel 2, Robert R. Sciacca 3, William Whang 4, Angelo Biviano 5, Maurita Baumeister 6, Carmen Castillo 7, Jyothi Talathothi 8, Hasan Garan 9
1Assistant Professor of Nursing, School of Nursing
2Professor of Clinical Medicine, College of Physicians & Surgeons, Columbia University, New York, NY
3Statistician, College of Physicians & Surgeons, Columbia University, New York, NY
4Assistant Professor of Clinical Medicine, College of Physicians & Surgeons, Columbia University, New York, NY
5Esther Aboodi Asst Professor of Clinical Medicine, College of Physicians & Surgeons, Columbia University, New York, NY
6Acute Care Nurse Practitioner, College of Physicians & Surgeons, Columbia University, New York, NY
7Research Coordinator, College of Physicians & Surgeons, Columbia University, New York, NY
8Research Assistant, College of Physicians & Surgeons, Columbia University, New York, NY
9Professor of Medicine, College of Physicians & Surgeons, Columbia University, New York, NY
Corresponding Address : Kathleen T. Hickey, EdD, ANP-BC, FNP-BC, Assistant Professor of Nursing, School of Nursing, Columbia University, 630 West 168th Street, New York, NY.
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 defined 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: Fifty-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 fibrillation was documented. In addition, 3 subjects had significant non-sustained ventricular tachycardia, and 4 individuals had severe bradycardia recorded on cardiac monitoring. These 7 individuals underwent placement of an implantable cardioverter defibrillator (ICD) or pacemaker based on the documented arrhythmias which may have otherwise gone undetected.
Conclusion: A substantial proportion of patients exhibited cardiac arrhythmias. Future morbidity was prevented because of the detection of arrhythmias on monitoring that led to specific therapies such as pacemaker or ICD implantation which otherwise may not have been implemented.
Atrial Fibrillation (AF) is the
most common arrhythmia encountered in clinical practice affecting several million
adults in the U.S. each year [1-3]. AF is
associated with an increased mortality rate as well as increased morbidity with
reduced quality of life (QoL). Although most patients with AF are symptomatic, a
significant minority of the elderly (up to ~30%) are asymptomatic when AF is
recorded on their electrocardiogram . Nonetheless, asymptomatic AF is still significant as it has
the same risk for thromboembolism as otherwise symptomatic AF and the same risk
for developing a tachycardic induced cardiomyopathy when rate control is
inadequate . Consequently and ideally, asymptomatic AF
needs to be recognized despite its absence of symptoms and needs appropriate prophylactic
therapy to be initiated if these important adverse outcomes are to be prevented.
As AF is most common in older patients and in those with underlying
cardiopulmonary disorders, including hypertension (HTN), heart failure (HF),
diabetes, and coronary artery disease, patients with these characteristics are
most likely to harbor asymptomatic “silent” AF. Similarly, such patients are more
likely than younger healthier patients to also suffer clinically important and/or
prognostically significant ventricular arrhythmias and bradyarrhythmias.
Additionally, AF in older patients and in those with HTN and other high-risk
markers is also a marker for an enhanced incidence of stroke and systemic
When AF is associated with
symptoms, they often include fatigue, palpitations, dyspnea, dizziness, and/or
exercise intolerance. However, these symptoms are non-specific in themselves
as they are also commonly associated with other underlying chronic conditions
such as HF, HTN, and/or diabetes, even in the absence of an arrhythmia. [6-9]. Thus such
symptoms, which are frequent in the populations at most risk for AF, may or may
not indicate the presence of AF but certainly do play a role in reducing QoL
regardless of a dysrhythmic or other cause. Furthermore, many individuals with
both HF and HTN are over 65 years of age which further increases their risk of
developing AF as well as other arrhythmias and their associated morbidity and
mortality risk and thus confounding symptom assessment. This number will likely
continue to grow as our population continues to live longer with these and
other chronic underlying diseases.
Finally, an estimated 20% of
strokes are secondary to embolism from AF with about 20% of these being fatal. Importantly,
stroke, both fatal and non fatal, may be the initial clinical presentation of
AF – the latter resulting from either new onset AF or previously asymptomatic
AF. Stroke and systemic embolism in patients with AF can be substantially
reduced with prophylactic anticoagulation (warfarin); however, in those with
asymptomatic AF, its recognition would be required to allow for treatment initiation.
As advances in the treatment and
management of HTN and HF continue to improve and mortality rates from these
disorders decline, practitioners will need to recognize which subgroups of
patients and which symptom patterns may be most likely to have or to be
associated with underlying cardiac arrhythmias and such practitioners may need
to consider routine screening of some manner in at-risk populations in order to
detect the presence of clinically important but still “silent” arrhythmias
deserving of more intensive follow up and evaluation and to best understand the
basis for symptoms as a guide to their reduction. More specifically, how
frequently asymptomatic AF or other significant but “silent” dysrhythmias might
occur in individuals with multiple underlying risk factors, such as older age,
HTN, HF but without arrhythmic symptoms or prior SSE, for example, is
currently unknown. Also poorly understood at present is what impact aging and chronic
diseases such as HTN and HF have on the frequency and nature of self reported
individual symptoms, or the frequency with which they are associated with an underlying
arrhythmia. Similarly, little research has been done to assess whether modest and
tolerable periods of continuous ambulatory ECG monitoring (e.g., 14-30 days) in
patients with risk factors for clinically important arrhythmias but no history
of any arrhythmia, might demonstrate its presence. If frequent, then a
positive impact on therapy initiation and outcome may be expected, similar to
screening blood tests or imaging studies for many cancers in men and women. It
is therefore, a logical extrapolation of the above to question whether
ambulatory recording of two weeks or so would be useful and cost-effective in
detecting previously unrecognized AF or other important dysrhythmias in at-risk
individuals prior to SSE thus becoming a useful screening tool for the
potential prophylactic anticoagulation for SSE prevention and/or whether it
would be clinically helpful in symptom evaluation so as to improve QoL with
targeted therapy. Towards this end we initiated the herein described pilot
The study was a
prospective feasibility pilot with an anticipated enrollment of at least 50
subjects which was conducted in a consecutive cohort of consenting patients
aged 65 years or older seen in the outpatient cardiac clinic of New York-Presbyterian
Hospital. Informed consent was obtained from all subjects under an IRB-approved
protocol, prior to participation. Inclusion criteria for study participation
was age 65 years or older plus a history of HF and/or HTN but no prior history of
arrhythmias. Subjects who agreed to participate were asked to wear an
auto-triggered external memory-loop EKG recorder for 14 days and to transmit
EKG strips via their home phone line in order to document the frequency and
duration of arrhythmias, both silent and symptomatic. In addition, subjects
were also requested to press an event recorder button on the monitor when
symptomatic and to record any associated symptoms in a diary. We sought to
determine whether AF or other significant underlying arrhythmias were present
frequently enough to warrant a larger study so as to demonstrate a more precise
incidence of their occurrence and the cost-effectiveness of this approach to
arrhythmia detection, and to determine how often potentially arrhythmia
associated symptoms in this population were actually arrhythmia related.
were given a LifeStar AF Express® monitor
[Figure 1] along with instructions in
Figure 1: LifeStar AF Express® Auto Triggered EKG device which is capable of recording
silent/symptomatic arrhythmias and was used exclusively in this investigation.
Spanish on how to transmit data from their device over the phone to a central receiving
service for analysis. This auto-triggered memory-loop recording system was
chosen because it has previously been demonstrated to be tolerable by most
patients and more effective than either 24-hr Holter monitoring or
transtelephonic event recording in capturing both symptomatic and significant
but asymptomatic arrhythmias . Detailed instructions were given to each patient on how
to apply, change, and properly place the monitor’s EKG leads on the chest, and how
to reconnect the EKG lead system to the recording unit. Subjects were
instructed to transmit at least once daily, as well as any time they experienced
any symptoms. Prior to the 14-day monitoring period, the subjects performed a
test transmission from the clinic or home. If subjects were unable to
successfully transmit data within 3 attempts, they were excluded from the
study. A total of 9 elderly subjects failed to transmit data successfully, and
found the task too complex. Active enrollment was ongoing and continued until a
final sample of 54 subjects with analyzable EKG data was achieved. All
transmitted EKG tracings were reviewed on a daily basis. If a rapid, sustained arrhythmia
such as VT or a supraventricular tachyarrhythmia (AT, AF, AFL) was detected,
the patient was called from a trained cardiac technician from the central
LifeStar AF monitoring service which provides patient monitoring 24 hours a
day/7 days a week. Based on the transmitted EKG the technician could assess the
patient’s cardiac rhythm and then status (via phone) and refer them the ER or
instruct them to call 911. The patient’s primary physician was also notified
via phone or pager, and the information forwarded on to them for further review
and management. During the beginning of the monitoring period, (baseline
enrollment in the cardiac clinic) all subjects were given and instructed to
keep a daily diary of symptoms (including date and time of occurrence).
However, most subjects chose not to complete the diary; rather, they reported
their individual symptoms for the 24-hr period to the technician at the time of
daily phone transmissions as well as when capturing a recording during a period
evaluations were conducted during semi-annual visits and by chart review. Subjects were considered to have had a cardiac event if they experienced a myocardial infarction (MI) or unstable angina, underwent coronary revascularization with CABG or percutaneous cardiac intervention, underwent insertion of a device to control arrhythmias, exhibited exercise induced symptoms of cardiac ischemia or HF, such as angina, or dyspnea on exercise stress testing, developed clinically recognized AF, AFL, VT, or had a syncopal episode.
analyses were performed using SAS 8.2 (SAS Institute, Cary, NC). Clinical data
are reported as means and standard deviations for continuous variables and as
frequencies for categorical variables. Kaplan-Meier event-free survival curves
were constructed and Cox proportional hazard models were used to determine the
effect of the presence of ectopic activity in both univariate and multivariable
models. Multivariable analyses were performed adjusting for potentially
confounding risk factors such as age, gender and body mass index (BMI). A p value <
0.05 was used for significance in all analyses.
and clinical characteristics of the study population are listed in [Table 1].
Table 1: Demographic and Clinical Characteristics of the Study Population
2006 until December 2007 a total of 54 subjects successfully performed
transmissions from home. The mean age was 73 ± 6 yrs (39% > 75 yrs); 59% were
female, 74% were Hispanic, 22% were African-American, and 4% were self reported
as white or other. All subjects with HF had systolic heart failure (class
II-III) and 94% also had a history of HTN. The mean ejection fraction was 49% ±
13. Hyperlipidemia was present in 65%, 46% had diabetes, and 4% were active
smokers. The baseline mean blood pressure was 139 ± 17 / 77 ± 11 mmHg. The mean
body mass index (34.0 ± 8.6) was above normal. A
total of 29% of subjects reported being hospitalized in the last year -- most
for shortness of breath or chest pain rather than an arrhythmia -- while
27% had visited an emergency room and 52% had seen a physician in the last 4
weeks. In the last 4 weeks 45% reported palpitations, 50% resting shortness of
breath, 70% shortness of breath with exercise. B-type Natriuretic Peptide (BNP) levels were not routinely collected in those hospitalized or in the out patient clinical setting.
Most subjects were on one or more medications: 73% were on a beta
blocker, 67% were taking an ACE inhibitor or angiotension receptor blocker, and
16% were taking a calcium channel blocker. These medications were prescribed by
their primary physician in the cardiac clinic to treat their underlying cardiac
conditions. We recognize that the use of these medications may have reduced the
incidence of atrial and ventricular arrhythmias detected on cardiac monitoring  and/or the awareness of them and hence made our results more
modest than they might otherwise have been in the absence of such medications.
presents the type and frequency of arrhythmias that were detected on cardiac monitoring
and the subsequent treatment. Ectopic activity was detected in 72% of subjects
but only 31% were symptomatic, including 9% with palpitations and 7% with
dizziness. One documented episode of atrial fibrillation was captured in a
female patient who was asymptomatic while wearing the monitor [Figure
2] but for whom therapy was then instituted. In addition, 3 subjects had 4
to 6 beat runs of self-terminating ventricular tachycardia that contributed to
a decision to implant an ICD for primary prevention of sudden cardiac death.
Figure 3 shows one strip of frequent ventricular ectopy captured by the
LifeStar AF Express® in one of these
subjects during the study. Four subjects underwent permanent pacemaker placement
for severe bradycardia: one for a prolonged pause, and the other 3 individuals
for advanced AV block. Figure 4 shows an example of an AV block captured during
the monitoring period. Therefore, in 8/54 subjects (15%), a significant,
otherwise unanticipated dysrhythmia of clinical importance was detected during
the two week period of continuous ECG monitoring.
Table 2: Type and Frequency of Arrhythmias Detected and Subsequent Treatment
Figure 2: Documented episode of atrial fibrillation captured in a female patient who was
asymptomatic while wearing the monitor. Circles represent isolated premature ventricular beats.
Figure 3: Strip of frequent ventricular ectopy captured by the LifeStar AF Express® in this study,
coupled with the subject’s low ejection fraction, led to placement of an ICD.
Figure 4: Asymptomatic second degree AV block captured by the LifeStar AF Express® on a
subject while sleeping, which led to placement of a permanent pacemaker.
The most common
symptoms reported by subjects were palpitations/heart racing in (9%) and
dizziness/lightheadedness in 7%. These symptoms correlated with isolated
ventricular or atrial ectopic beats in 28%. In addition, one subject with
palpitations had NSVT, while one subject who reported dizziness/lightheadedness
was noted to have second degree AV block. The AF event was without associated
followed for a median of 32 months (range 24 – 40 months). During that time, 15
subjects (28%) experienced cardiac events in addition to the 8 subjects (15%)
noted above in whom either AF was detected or a device was implanted for a
detected bradycardic or VT episode during monitoring. Two of these 15 subjects
suffered a MI or unstable angina, 1 underwent CABG, and 8 developed exercise
induced symptoms of cardiac ischemia confirmed on stress testing. Finally,
the same individual who suffered the MI also had a NSTEMI in the setting of new
onset unrecognized AF. One individual required hospitalization for a rapid symptomatic
2:1 atrial flutter. Of note, the individual with atrial flutter had sinus
bradycardia on cardiac monitoring. The two subjects who suffered cardiac events
were not wearing the loop recorder at the time of these events which occurred
outside the 14 day monitoring period. However, during their initial 14 day
recording period baseline ST/T waves were unremarkable. Finally, the individual
who suffered the NSTEMI was noted to have frequent premature atrial contractions
and atrial runs on cardiac monitoring.
Kaplan-Meier survival curve for cardiac events in these 15 subjects is shown in
Figure 5. The presence of atrial and ventricular ectopic activity during
cardiac monitoring was not significantly associated with increased risk of a
cardiac event in this population with already established hypertension and
heart failure in the univariate analysis (HR = 3.03, 95% C.L. 0.68 – 13.47) or
after adjusting for age, gender, and BMI (HR = 2.53, 95% C.L. 0.53 – 12.02)
(recognizing that 8 subjects with detected AF, VT, or a significant
bradyarrhythmia/AV block underwent therapy as noted above which might have
prevented some additional long-term outcome events). Only female gender was
significant in the multivariable model (HR = 0.25, 95% C.L. 0.07 – 0.86, p =
0.03). The power to detect a significant effect for the presence of ectopic
activity was 36%.
Figure 5: Kaplan-Meier Survival Curve for Cardiac Events. The frequency of individuals without cardiac events is presented over time.
was designed as a pilot study to attempt to determine if clinically important
previously unrecognized arrhythmias exist frequently in patients who would
appear to be at increased risk, such as the elderly with HTN and/or HF, as well as how frequently symptoms commonly encountered in a HF and HTN population,
have a dysrhythmic basis. It was conducted in an elderly population in a single
center outpatient cardiac population, which serves a primarily lower
socio-economic Hispanic population. All subjects who were enrolled had multiple
underlying cardiovascular risk factors for both arrhythmias and future cardiac
events as well as disease-related reasons for symptoms, but no previously
recognized arrhythmia. In this setting, our pilot study suggests that a two
week period of monitoring of elderly without previously recognized dysrhythmias
but with at-risk conditions such as HTN or HF can be of clinical value, and
cost-effective. Of the 54 patients enrolled, 72% had some form of an arrhythmia
detected with 8 subjects having a clinically significant dysrhythmia, including
silent AF, significant bradycardia/AV block, and VT. Notably, only 28% of the
detected dysrhythmias were symptomatic. Despite the absence of previously
recognized arrhythmias, once arrhythmias of clinical importance are detected by
such monitoring the existing guidelines for pacemaker and ICD implantation and/or
AF antiarrhythmic, rate-control, and anticoagulation therapy can be initiated, as
was the case in 8 of our 54 subjects—a not trivial minority. Monitoring is helpful is distinguishing symptoms that are
related to underlying CAD/HF vs. an underlying arrhythmia hence, it has a role
in patients with symptoms. Depending on the type of monitoring used it may also
have a role in assessing prognosis. A 14 day period seems feasible and
tolerable by most elderly individuals. As compared with 24 hour Holter
recordings, loop recorders are able to record a greater amount of data and
provide a more comprehensive evaluation of patients underlying heart rhythm
over time. Any fixed duration is arbitrary and increased yield has to be
balanced with value and feasibility.
of AF is particularly important in the population we studied as all had HF
and/or HTN, all were at least 65 years old, and 39% were above 75 yrs of age,
meaning that all had a CHADS2 score of at least 1, and most had a
score of at least 2, such that AF detected in this population would generally
indicate the need for anticoagulation with warfarin. Thus, even in this small
series, our results are clinically enticing as regards their importance to
prophylactic clinical therapy. For example, if our observation of an
approximately 2% incidence of silent AF in this high-risk population is
representative of what would be found in a larger series, and given an
approximately 3-6% yearly risk of stroke/systemic embolism in patients with their
CHADS2 scores, then there would be approximately 100 patients with
silent AF detected per 5000 patients studied, which would allow for
prophylactic anticoagulation and event prevention in 4/5000 patients. The cost
of the AF express device used in this investigation for a 2 week period of
cardiac monitoring was $125 and yielded a total of 7 events that would have
otherwise not been detected or treated. Despite the upfront cost of the
auto-triggered device, the yield offsets the initial cost, and is similar to
other investigations that found the use of an external loop recorder,
beneficial when confirming a diagnosis of syncope or pre-syncope, in an
ambulatory community setting . This also appears to be within the cost effectiveness of
other screening procedures such as mammography and PSA determination.
our results provide some insight as to how often in a population such as ours,
which is extremely typical demographically of patients in major clinical trials
of AF such as AFFIRM, ATHENA, and RACE, symptoms consistent with an
arrhythmia actually have a dysrhythmia associated with them [12-14]. Our observations confirm that self
reported symptoms of palpitations, and lightheadedness/dizziness may be
associated with an arrhythmia, such as isolated atrial and ventricular ectopy, NSVT and AV block in the elderly, but often they are not. Hence, such symptoms should not be
assumed to represent a dysrhythmic mechanism a priori. These symptoms would not
have been confirmed to have been associated with an underlying dysrhythmia, if
cardiac monitoring was not undertaken as part of this investigation. In fact,
such symptoms may not even have been reported by the subject at all if they had
not been wearing a cardiac monitor and queried as to if they were symptomatic
or asymptomatic at the time of their EKG transmission by the technician who was
assisting them in the data transmission over the phone. In fact even if these symptoms
are reported in a clinical setting it is possible no further work up, including
a cardiac event recorder, would have initiated because such symptoms are so commonly
associated with underlying HF, cardiovascular disease, medications, and age
related changes in the elderly and are commonly ignored when they do not seem
activity consisting of primarily isolated premature atrial and ventricular
beats, which were multifocal with occasional couplets were noted in 72% of our
older-aged subjects with HF and/or HTN during their EKG transmissions, with 31%
of subjects reporting they were symptomatic just prior to the recording to the
technician receiving the data via the telephone transmission. The symptoms noted
most frequently included palpitations (9%) and dizziness (7%). These findings
are consistent with those reported in the early years of using loop recorders in
clinical practice that demonstrated the highest yield of NSVT, atrial and
ventricular ectopy in those experiencing symptoms of palpitations and dizziness
or lightheadedness referred for monitoring . In those who experienced events in our series one
individual complained of palpitations and NSVT was documented, while one
subject with documented AV block noted mild dizziness, however the one
documented episode of atrial fibrillation was asymptomatic. Although the
presence of ectopic activity during 2 weeks of cardiac monitoring was not
significantly related to subsequent cardiac risk, the power of this preliminary
pilot feasibility study was clearly low due to limited sample of elderly
subjects who were capable of wearing the monitor for a two week period and able
to change EKG leads daily and transmitting daily strips utilizing their home
telephone, which many noted to be too complex. It is also most likely that the
presence of a heart failure history, itself a potent marker of subsequent
events, overwhelmed any additional prognostic value to detected arrhythmias in
our population, and the 2 week monitoring period was too short to allow us to
analyze if overall arrhythmia-burden (a product of frequency and time in an
arrhythmia) might have been of prognostic value, rather than just the presence
or absence of an arrhythmia. Finally, it should be noted here that in our initial
investigation the detection of arrhythmias led to implantation of either a pacemaker
or ICD in 7 subjects that may have otherwise remained silently at risk and would
not have undergone immediate appropriate clinical care. It thus remains plausible
that in the absence of this investigation, adverse outcomes would have occurred
that would have changed the observed rates of our arrhythmia-event
associations. Finally, our observations were useful to the patients enrolled in
our trial as noted by the frequency of clinical intervention and by implication
there may be value to similar detection in additional populations with other
underlying cardiovascular disorders, or even in those whose only risk marker is
age, which remains another study to consider.
Even though a
bilingual research assistant/translator was present in the cardiac clinic during
enrollment to enhance patient understanding of our study, many individuals
choose not to participate due to a wide variety of reasons (lack of interest,
viewed the study as burdensome and of no direct benefit to them). The reason
for refusal was not systematically collected on all subjects as many declined
to give a reason. This is a potential area that warrants further investigation.
Finally, many subjects reported they simply forgot to keep the requested daily
diary of symptoms, but instead verbally reported symptoms at the time of EKG
transmission, when prompted by a technician over the phone. Notably, however,
subsequent to the completion of our study, newer wireless technology has become
more widely available that could be used in future investigations which would
be less burdensome to the patient and yield even greater data for correlation
to underlying symptom and other clinical parameters. Finally, as noted
earlier, it is possible that the medications taken by our subjects for their
underlying HF and/or HTN could have reduced the number of arrhythmias we might
have detected and/or altered their perception. However, this is limitation in
any such a real-life scenario.
This study was novel in that it
explored the utility of cardiac arrhythmia screening in a primary underserved
urban elderly population living with two chronic diseases HF and HTN. Cardiac
monitoring demonstrated most of the subjects experienced isolated atrial and
premature beats during the two week cardiac monitoring period. In this at-risk population previously unrecognized AF was also recorded. Given the nature of this population, its implications for anticoagulation and SSE
prevention are substantial. Significant bradycardia and non sustained
ventricular tachycardia were also recorded; these led to implantation of a
pacemaker or ICD in patients who otherwise would not have received them, or
gotten them as early, possibly preventing additional adverse clinical outcomes
during follow up. Thus, our study raises the question as to whether we should
be monitoring more closely the at-risk elderly with or without symptoms to
determine if in fact their symptoms are related to an underlying arrhythmia vs.
a chronic condition such as HF or HTN and to detect silent but prognostically
and/or therapeutically important arrhythmias. Future research aimed at
replicating this pilot work is needed in larger more diverse patient population;
living with chronic diseases is needed. Finally, the role of access to cardiac
care, depression, anxiety, and knowledge regarding their underlying cardiac
conditions and medication compliance as well as other socio-demographic
variables which can all impact on cardiac outcomes, symptoms, and QOL warrants
This study was funded by
Grant R03 NR010001 “Utility of Trans Telephonic Monitoring in the Detection of
Silent Arrhythmias” and Grant P20 NR007799 “Center for Evidence-based Practice
in the Underserved.” The authors thank LifeWatch, Inc., for providing the
cardiac monitors for this investigation.
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