Mcotrothma
Mcotrothma
Mcotrothma
Utility of Mobile Outpatient Telemetry. 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. (J Cardiovasc Electrophysiol, Vol. 18, pp. 1-7,
March 2007)
loop recorder, event monitor, syncope, palpitations, arrhythmia
Introduction
A variety of methods can be used in the outpatient evaluation of symptoms suggestive of a cardiac arrhythmia. The
diagnostic yield of these technologies for identifying clinically significant but infrequent, brief, and/or intermittently
symptomatic arrhythmias, however, is low. Holter monitoring for 2448 hours is typically employed, but has a diagnostic yield of only 1528%, depending on symptoms and
frequency.1-3 External, patient-activated loop recorders can
improve the diagnostic yield to up to 63%,4 but require appropriate patient activation during the recurrence of symptoms, which can limit their usefulness.5 Mobile cardiac outpatient telemetry (MCOT) allows patients to be monitored
continuously for an extended period and has been effective in the diagnosis of clinically significant, symptomatic,
and asymptomatic cardiac arrhythmias.6 This technology
has the potential to reduce patient error, enhance diagnostic accuracy, decrease time to diagnosis, and improve patient
care. The purpose of this study was to compare the relative
value of a MCOT system with a patient-activated external
loop event monitor for symptoms thought to be due to an
arrhythmia.
Methods
Study Design
The study was a regional, 17-center, 300-subject, prospective parallel clinical trial with patients randomized to either standard patient-activated external loop event monitoring
(LOOP) or to mobile automated cardiac outpatient telemetry
for up to 30 days.
Equipment
Both LOOP and MCOT utilized cutaneous ECG harnesses
and sensors that the patients wore continuously. Two lead
arrhythmias as either clinically significant or clinically insignificant and then evaluated the temporal relationship of
any symptoms and the likelihood that a clinically significant
arrhythmia caused the patients presenting symptoms. Exclusion of an arrhythmic cause was determined if any reported
symptoms were not associated with an arrhythmia, including
a temporally related, clinically significant arrhythmia. Monitoring was considered nondiagnostic if patients remained
asymptomatic with either no arrhythmia or only a clinically
insignificant arrhythmia documented.
Secondary endpoints included time-to-diagnosis utilizing time-to-event methods, and proportion of subjects with
clinically significant arrhythmias. Clinically significant arrhythmias were defined as pauses 3 seconds (excluding
compensatory pauses following VPDs); complete atrioventricular (AV) block; Mobitz type-2 second-degree AV block;
atrial fibrillation or flutter (AF/AFL) (symptomatic with ventricular response >120 or <35 beats per minute (BPM),
asymptomatic >150 or <30 BPM); symptomatic bradycardia
<40 BPM in adults or age-appropriated lower normal limits; sustained (>10 seconds) or symptomatic supraventricular
tachycardia (SVT) >120 BPM; ventricular tachycardia (VT)
>100 BPM and >3 beats; and any arrhythmia requiring therapeutic intervention.
All tracings were reviewed by an independent academic
electrophysiologist blinded to patient randomization and history. The diagnosis of the blinded independent electrophysiologist was used as the study endpoint for purposes of data
analysis.
Statistics
The projected goal was enrollment of 300 patients to
power the study to detect a 33% difference in the primary
endpoint to evaluate MCOT versus LOOP in confirming or
excluding the diagnosis of an arrhythmia as the cause of presenting symptoms. This provided a power of 80% for comparison, using a standard Chi-square test with alpha of 0.05
to assess statistical significance. All alpha values presented
were prepared in this fashion. KaplanMeier analyses were
performed to assess time to diagnosis and time to diagnosis of significant arrhythmia. Log rank tests were performed
to evaluate differences between the cohorts. All study end
points, including subgroup populations, were compared using Chi-square analysis. Patient demographics were analyzed
by using ANOVA for age and Fishers Exact test for categorical variables. Presenting symptoms were compared using
Fishers Exact test and the two-sample median test. Since
this was a trial comparing diagnostic yields of two different technological approaches, the analysis was performed on
those subjects with >80% compliance, i.e., used the monitor
for 25 days or more, unless a diagnosis was made.
The primary endpoint was counted once per patient, with
subsequent primary endpoints during the monitoring period
recorded as secondary endpoints. Subgroup analyses were
performed for patients presenting with syncope/presyncope
and for detection of clinically significant arrhythmias. Time
to diagnosis was analyzed for all patients, those with clinically significant arrhythmias, and those presenting with syncope/presyncope. A subgroup analysis was performed of
those sites that utilized looping event recorders with autotrigger algorithms.
Rothman et al.
TABLE 1
Patient Demographics
Characteristic
Gender, %male
Age (SD), years
Ethnicity or Race, n (%)
Hispanic or Latino
Black/African American
White
Other
Missing
Cardiac History, n (%)
Hypertension
Coronary Artery Disease
Previous Myocardial Infarction
Congestive Heart Failure
Pacemaker
TABLE 2
Presenting Symptoms
Monitoring Method
MCOT
(N = 134)
LOOP
(N = 132)
Monitoring Method
P Value
Subject Symptoms
MCOT
(N = 134)
Presyncope, n (%)
Median, (min, max)
Syncope, n (%)
Median, (min, max)
Palpitations, n (%)
Median, (min, max)
50 (37)
4.0 (1, >99)
23 (17)
1.0 (1, 10)
105 (78)
10.0 (1, >99)
37.3
57 (16)
31.1
55 (16)
NS
NS
17 (12.7)
15 (11.2)
94 (70.1)
7 (5.2)
1 (0.7)
25 (18.9)
11 (8.3)
93 (70.5)
3 (2.3)
0 (0.0)
NS
NS
NS
NS
NS
70 (52.2)
22 (16.4)
6 (4.5)
8 (6.0)
7 (5.2)
60 (45.5)
30 (22.7)
8 (6.1)
6 (4.5)
5 (3.8)
NS
NS
NS
NS
NS
NS = nonsignificant.
Results
Patient Demographics
A total of 305 patients were randomized. We analyzed 266
patients who completed a minimum of 25 days of monitoring: 132 patients in the LOOP group and 134 patients in the
MCOT group (the perprotocol population). Of the 39 nonperprotocol patients, 23 were in the MCOT group and 16 in the
LOOP group. The most common reason for not completing
the protocol was patient noncompliance (13 MCOT subjects
and seven LOOP subjects), with seven patients finding the
devices too difficult or cumbersome to use, seven patients
describing an allergic reaction or skin irritation to the electrodes, and six patients stating that the monitors interfered
with their work or travel. Other reasons for not completing
the protocol included withdrawal of consent prior to receiving
the device, inability to contact the patient for delivery of the
device, and one patient who did not have adequate telephone
service for using the MCOT device.
Demographics are shown in Table 1. There was no significant difference between groups in age, gender, or race.
Patients were predominantly female with a mean age of 56
years, and of a diverse ethnic background. There was no significant difference between groups in patient history. Presenting symptoms are shown in Table 2, along with the mean
number of episodes and their range prior to randomization.
While the majority of patients had palpitations prior to randomization, 114 patients (43%) presented with either syncope
or presyncope. Sixty-two of these patients used MCOT and
52 patients used LOOP. There was no significant difference in
either demographics or cardiac history between patients presenting with syncope/presyncope or palpitations only.
Primary Endpoint
Classifications of the subjects by endpoint scenarios are
shown in Table 3. A diagnostic endpoint was not determined
for three subjects due to an independent cardiac outcome assessment not being performed. Scenarios 1 through 4 were
considered as confirming an arrhythmic cause for the pa-
LOOP
(N = 132)
P Value
41 (31)
4.0 (1, >99)
20 (15)
2.0 (0, 5)
111 (84)
10.0 (1, >99)
NS
NS
NS
NS
NS
NS
tients symptoms while scenarios 5 and 6 excluded an arrhythmogenic etiology. Scenarios 7 and 8 were considered a
nondiagnostic result; these included subjects with no symptoms during the monitoring and no documented clinically
significant arrhythmias. Mobile automated cardiac telemetry demonstrated a significant advantage over looping event
monitors, with a diagnosis made in 88% of MCOT subjects,
compared with 75% of LOOP subjects (Table 4, P = 0.008).
There was a similar result in the subgroup of patients presenting with syncope or presyncope, with a higher diagnostic
yield in the MCOT group (89% in MCOT subjects vs. 69%
in LOOP subjects, P = 0.008).
The ability to detect or exclude a cardiac arrhythmia at the
time of symptoms was similar in both groups. Simultaneous
recording of an arrhythmia at the time of the patients symptoms (Table 3, scenarios 1 and 4) occurred in 40% of MCOT
patients and 47% of LOOP patients (42% and 40%, respectively, in the syncope/presyncope subgroup). There was also
a similarly large proportion of subjects who had symptoms,
but without a temporally related arrhythmia (Table 3, scenarios 2, 5, and 6). In the MCOT group, there were 52 such
subjects (39%), but 40 of the 52 subjects did have an arrhythmia documented at other times during their monitoring
period. In 15 of these subjects, the arrhythmia was considered
clinically significant. In the LOOP cohort, 36 subjects (27%)
had symptoms without temporally related arrhythmias, but
only nine subjects had an asymptomatic arrhythmia documented during the monitoring period, which could account
for their symptoms. None of these arrhythmias were considered clinically significant. These results were similar in the
syncope/presyncope subgroup, where 37% of the MCOT cohort and 27% of the LOOP cohort had no temporally related
arrhythmias detected during symptoms. In the MCOT group,
however, 20 of these 23 subjects had arrhythmias documented
at other times, compared with only four of 14 LOOP subjects.
In the per-protocol population, there were 60 subjects
(23%) who had no symptoms during monitoring, including
28 subjects (21%) in the MCOT group and 32 (24%) in the
LOOP group. Twelve of the MCOT subjects were found
to have an asymptomatic clinically significant arrhythmia
that would account for their presenting symptoms, compared
with no subjects in the LOOP group. For patients presenting
with syncope/presyncope, a similar proportion of patients
(25%) remained asymptomatic. In this subgroup, six of 13
asymptomatic subjects in the MCOT cohort had a clinically
significant arrhythmia accounting for their presenting symptoms, compared with none of 16 LOOP subjects.
TABLE 3
Categorization of Subjects by Endpoint Scenarios
All Subjects
Scenario
Confirmation/Exclusion
1
2
3
4
5
6
Nondiagnosis
7
8
Present
Symptoms
Simultaneous
Yes
Yes
No
Yes
Yes
Yes
No
No
Monitoring Method
MCOT, n
LOOP, n
(%) (N = 133)
(%) (N = 130)
Present
Arrhythmia
Significant
Diagnostic
Yes
No
Yes
No
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
No
28 (20.9)
15 (11.2)
12 (9.0)
25 (18.7)
25 (18.7)
12 (9.0)
19 (14.4)
0 (0.0)
0 (0.0)
43 (32.6)
9 (6.8)
27 (20.5)
Yes
No
No
No
14 (10.4)
2 (1.5)
6 (4.5)
26 (19.7)
Scenario
Confirmation/Exclusion
1
2
3
4
5
6
Nondiagnosis
7
8
Present
Symptoms
Simultaneous
Yes
Yes
No
Yes
Yes
Yes
No
No
Monitoring Method
MCOT, n
LOOP, n
(%) (N = 62)
(%) (N = 51)
Present
Arrhythmia
Significant
Diagnostic
Yes
No
Yes
No
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
No
17 (27.4)
9 (14.5)
6 (9.7)
9 (14.5)
11 (17.7)
3 (4.8)
8 (15.4)
0 (0.0)
0 (0.0)
13 (25.0)
4 (7.7)
10 (19.2)
Yes
No
No
No
7 (11.3)
0 (0.0)
5 (9.6)
11 (21.2)
Present = presence or absence of symptoms/arrhythmia during the monitoring period; Simultaneous = symptoms that are temporally related to a recorded
arrhythmia; Significant = an arrhythmia defined as Clinically Significant (see text); Diagnostic = recorded arrhythmia determined to be the most likely
cause of the subjects presenting symptoms (palpitations, syncope or presyncope).
Although looping event recorders with an autotrigger algorithm were not required during this study, a post hoc analysis was performed of subjects who were enrolled at sites utilizing this type of monitor. These monitors were programmed
to automatically record bradyarrhythmias, tachyarrhythmias,
pauses, and irregular heart beats. Each monitoring companys
standard parameters were used. Fifty of the 266 patients in
the perprotocol population were evaluated: 24 subjects in the
MCOT group and 26 subjects in the LOOP group. In this subgroup of patients, an arrhythmia was confirmed or excluded
in 88% of MCOT subjects, compared with 46% in the LOOP
cohort (P = 0.002). In subjects who remained asymptomatic
throughout the monitoring period, a cardiac arrhythmia was
TABLE 4
Primary Endpoint: Confirmation or Exclusion of an Arrhythmia
Monitoring Method
Endpoint Outcome
MCOT
LOOP
All Subjects
P Value
133
117 (88.0)
16 (12.0)
130
98 (75.4)
32 (24.6)
263
215 (81.7)
48 (18.3)
0.008
62
55 (88.7)
7 (11.3)
51
35 (68.6)
16 (31.4)
113
90 (79.6)
23 (20.4)
0.008
24
21 (87.5)
3 (12.5)
26
12 (46.2)
14 (53.8)
50
33 (66.0)
17 (34.0)
0.002
Rothman et al.
TABLE 5
Classification of Documented Arrhythmias in All Subjects
Monitoring Method
Subjects with Arrhythmias
MCOT
(N = 134)
LOOP
(N = 132)
All Subjects
(N = 266)
P Value
112 (84.2)
55 (41.4)
6 (4.5)
0 (0.0)
1 (0.8)
31 (23.3)
10 (7.5)
23 (17.3)
0 (0.0)
14 (10.5)
24 (18.0)
0 (0.0)
1 (0.8)
67 (51.5)
19 (14.6)
0 (0.0)
1 (0.8)
0 (0.0)
10 (7.7)
10 (7.7)
0 (0.0)
0 (0.0)
5 (3.8)
4 (3.1)
0 (0.0)
0 (0.0)
179 (68.1)
74 (28.1)
6 (2.3)
1 (0.4)
1 (0.4)
41 (15.6)
20 (7.6)
23 (8.7)
0 (0.0)
19 (7.2)
28 (10.6)
0 (0.0)
1 (0.4)
<0.001
<0.001
0.014
NS
NS
<0.001
NS
<0.001
NC
0.036
<0.001
NC
NS
advantage using MCOT in the detection of atrial fibrillation or flutter; both monitoring arms documented a similar
percentage of patients with symptomatic atrial fibrillation or
flutter (8% in both cohorts), but 17% of the MCOT group also
had asymptomatic atrial fibrillation/flutter with rapid ventricular rates of >150 bpm. Clinically significant arrhythmias
were even more prevalent in patients with syncope or presyncope. In this cohort, a clinically significant arrhythmia was
detected in 52% of the MCOT subjects, compared with 16%
of the LOOP subjects (P < 0.001) (Table 6). Figure 1 shows
a KaplanMeier event curve for the cumulative proportion of
patients diagnosed with a clinically significant arrhythmia for
the total study group (Fig. 1A) and the syncope/presyncope
subgroup (Fig. 1B). The median time to diagnosis in the total
study population was seven days (95% CI 411 days) in the
MCOT group and nine days (95% CI 715 days) in the LOOP
group. In the syncope/presyncope subgroup, the median time
to diagnosis was six days (95% CI 316 days) and 10 days
(95% CI 721 days), respectively. In the total population,
70% of the patients who had a clinically significant arrhythmia were diagnosed by the 15th day, regardless of monitoring
method, but there was a much higher yield (29% vs 11% of
TABLE 6
Classification of Documented Arrhythmias in Subjects with Syncope/Presyncope
Monitoring Method
Subjects with Arrhythmias
MCOT
(N = 62)
LOOP
(N = 52)
All Subjects
(N = 114)
P Value
55 (88.7)
32 (51.6)
3 (4.8)
0 (0.0)
1 (1.6)
15 (24.2)
4 (6.5)
12 (19.4)
0 (0.0)
10 (16.1)
14 (22.6)
0 (0.0)
1 (1.6)
25 (49.0)
8 (15.7)
0 (0.0)
1 (2.0)
0 (0.0)
1 (2.0)
1 (2.0)
0 (0.0)
0 (0.0)
4 (7.8)
2 (3.9)
0 (0.0)
0 (0.0)
80 (70.8)
40 (35.4)
3 (2.7)
1 (0.9)
1 (0.9)
16 (14.2)
5 (4.4)
12 (10.6)
0 (0.0)
14 (12.4)
16 (14.2)
0 (0.0)
1 (0.9)
<0.001
<0.001
NS
NS
NS
<0.001
NS
<0.001
NC
NS
0.005
NC
NS
Rothman et al.
6.
7.
8.
9.
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