Download Electrocardiographic Monitoring During Cardiac

Electrocardiographic Monitoring During
Cardiac Rehabilitation*
Steven J. Keteyian, PhD; Peggy A. Mellett, RN; Frank J. Fedel, BS;
Cathy M. McGowan, MD; and Paul D. Stein, MD, FCCP
Study objective: This investigation compares the frequency of cardiac events during ECG-monitored cardiac rehabilitation in patients who meet the American
College of Cardiology (ACC) criteria for monitoring, to
the frequency of events in patients in the same program
who do not meet the ACC criteria.
Design and patients: Patient charts (n=289) from a 10month period were retrospectively reviewed for (1) major and minor cardiovascular events, (2) whether a physician was contacted, and (3) what change, if any, was
made in their care plan as a result.
Results: There were no sudden deaths, fatal or nonfatal
myocardial infarctions, or sustained arrhythmias requiring hospitalizations. The overall rate for minor events
(angina, nonsustained arrhythmia, ST segment depression) was 26.6%, with no difference noted between men
and women. The rate for a new-onset, asymptomatic
event was 3.8%. The rate of minor events was greater in
patients who met the ACC criteria vs those who did not
(p<O.Ol), with no detectable difference noted between
the two groups regarding the rate of new-onset, asymptomatic events. Four patients (1.4%) experienced a
change in their care plan as a result of ECG monitoring.
Conclusions: The occurrence of a minor cardiovascular
event is common during phase 2 cardiac rehabilitation,
and existing criteria satisfactorily distinguish those patients at high risk for experiencing such an event. However, the rate for new-onset, asymptomatic events is rare
for both patients classified at high risk and those classified not to be at high risk. Also, only four patients experienced a change in therapy secondary to an event
identified by ECG monitoring. (Chest 1995; 107:124246)
the past 15 years, there has been much discussion concerning the use of continuous ECG monitoring in early outpatient cardiac rehabilitation
programs (phase 2). Complicating the issue is the
absence of controlled prospective trials comparing
bilitation, not only is the high-risk patient identified
but the low- and intermediate-risk patient as well.2
Such classifications are based on (1) a patient's future
risk for experiencing a cardiac event and (2) certain
clinical characteristics such as left ventricular function and/or the presence of myocardial ischemia. A
clear statement, however, defining the type (continuous vs intermittent) and duration of ECG monitoring during exercise is not given for any of the three
risk groups. Instead, such a decision regarding ECG
monitoring is left up to the clinical judgment of the
program's staff. Included in the above guidelines is
the recommendation that, following an unspecified
period of monitoring, clinicians should progress patients to first less monitoring and then self -monitor-
I n
the safety and efficacy of two otherwise similar programs, one using ECG monitoring and the other
without.
In the 1986 Position Report published by the
American College of Cardiology (ACC) on cardiovascular rehabilitation, criteria (Table 1) are given to
identify patients at high risk who should be ECG
monitored during exercise.1 The same report estimated that 20 to 25% of the patients in cardiac
rehabilitation programs would be considered high
risk. Despite the ACC guidelines identifying which
patients should be ECG monitored during exercise, it
is not uncommon to find such a procedure still being
used in patients at low and moderate risk as well.
In guidelines recently established by the American
Association of Cardiovascular and Pulmonary Reha*From the Henry Ford Heart and Vascular Institute, Detroit.
Manuscript received July 13, 1994; revision accepted November
3.
Reprint requests: Dr. Keteyian, 2921 W. Grand Blvd., Room
1107, Detroit, MI 48202
ACC=American
College of Cardiology
Key words: electrocardiographic monitoring; exercise;
heart disease; rehabilitation
ing.
Greenland and Pomilla3 point out that the guidelines for ECG monitoring during cardiac rehabilitation represent empirically derived standards or are
based on expert panel consensus. To our knowledge,
no studies exist that validate the ACC criteria for
high-risk patients in need of ECG monitoring. This
investigation, therefore, compares the frequency of
cardiac events during ECG-monitored cardiac rehabilitation in patients who meet the ACC criteria for
monitoring, to the frequency of events in patients in
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Clinical Investigations
Table 1-American College of Cardiology Criteria
Identifying Patients in Whom ECG Monitoring Should
Be Included During Exercise*
Criteria
(a) Severely depressed left ventricular function (ejection fraction
under 30)
(b) Resting complex ventricular arrhythmia (Lown type 4 or 5)
(c) Ventricular arrhythmias appearing or increasing with exercise
(d) Decrease in systolic blood pressure with exercise
(e) Survivors of sudden cardiac index
(f) Patients following myocardial infarction complicated by congestive heart failure, cardiogenic shock, and/or serious ventricular arrhythmias
(g) Patients with severe coronary artery disease and marked exercise-induced ischemia
(h) Inability to self-monitor heart rate due to physical or intellectual impairment
*Reprinted with permission from American College of Cardiology.
Position paper on cardiac rehabilitation. J Am Coll Cardiol 1986;
7:451-53.'
the same program who do not meet the ACC criteria for monitoring.
METHODS
Study Group
Three hundred thirty-eight patients with known cardiac disease participated in the hospital's ECG monitored phase 2 cardiac
rehabilitation program during a 10-month period between October 1, 1992 and July 31, 1993. The charts from 289 of these patients were retrospectively reviewed and demographic information is given in Table 2. Patients excluded (n=49) from review
were those with a functional capacity less than 2 metabolic
equivalents (n=5), cardiac transplant (n=10), or insulin-dependent diabetes (n=34). The latter two groups may be insensitive to
angina.
Measurements and Patient Monitoring
Prior to starting in the cardiac rehabilitation program, each
subject underwent a brief history and physical examination and
a symptom-limited graded exercise test. The duration of their
participation in the program was tentatively based on their estimated risk level, allowable insurance reimbursement, return to
work status, and interest to participate. Actual length of involvement in the program was adjusted based on clinical findings and
an individual's progress. The total number of patient exercise
sessions was 3,979. The mean length of stay in the ECG-monitored
program was 14 ± 5 (mean ± SD) exercise sessions, which is both
consistent with previous reports suggesting that such programs be
limited to 6 to 12 sessions in duration4-6 and indicative of the fact
that 72% of our patients were stratified to the low- or intermediate-risk groups.
Each exercise session was 43 min, during which patients completed a 33-min aerobic phase (using three exercise modalities for
11 min each). The modalities available for use included motordriven treadmills, stationary cycles, arm ergometers, stationary
rowing machines, and stair-climbing machines. Exercise intensity
was guided using the heart rate reserve method and the Borg
Rating of Perceived Exertioni scale.7 All 289 patients, independent
of risk level, exercised while undergoing continuous ECG monitoring. Heart rates during exercise were measured from the ECG
recorder. The estimated metabolic equivalent level achieved
while treadmill walking during the first week of exercise training
was computed.7
Each patient's exercise training record was reviewed for the
presence and frequency of both major and minor cardiovascular
events. Major events were defined as sudden death, myocardial
infarction, and sustained arrhythmia requiring hospitalization or
electrical/chemical cardioversion. Minor cardiovascular events
were typical angina or angina-like equivalent, nonsustained
arrhythmia not requiring hospitalization, ST segment changes,
abnormal blood pressure responses, and syncope or near-syncope.
Chest pain determined to be noncardiac in nature was not
included. A minor event was further categorized as to whether it
was (1) new onset vs known to be part of a patient's medical history and (2) symptomatic vs asymptomatic. The term "new onset" included those patients in whom a low-grade arrhythmia had
been observed previous to starting the exercise classes and then
developed a higher-grade arrhythmia while being ECG monitored during therapy. Using the above definitions, we identified
the number of patients who experienced at least one new-onset,
asymptomatic event (eg, new-onset arrhythmia without symptoms; new or additional ST segment depression without angina).
The patients' charts were also reviewed to determine whether a
physician was contacted after an event and whether their care was
modified as a result.
Statistical Analysis
Based on the minimum number of occurrences in any one cell,
comparisons between groups were performed using either a x2 or
Fisher's Exact Test. The 95% confidence level was also computed.
An alpha level of p<0.05 was set to determine significance.
RESULTS
There were no major cardiovascular events during
exercise training. The overall rate for at least one
minor event was 26.6% (77/289), with no significant
difference detected between male (56/216=26%)
and female (21/73=29%) patients. The average
number of class sessions attended for patients who
experienced a minor event vs those patients who did
not experience a minor event was 15 and 14, respectively.
The rate for minor events was greater in those pa-
Table 2-Patient Demographics*
Age, yr
59+ 11
MET Level
During First
Week of Exercise
No. of
Exercise Classes -__
Attended
MI
Diagnosis or Procedure at Entry
CABG
PTCA
Angina
CHF
All patients (n=289)
4.2±1.3
82
121
41
32
13.8 ±5.4
Men (n=216)
59±11
4.5±1.3
13.8±5.6
64
31
95
19
Women (n=73)
10
3.5 ±0.8
13.8 ±4.9
18
26
13
60+±10
*Values are Mean + SD. CABG=coronary artery bypass grafting; CHF=congestive heart failure; MET=metabolic equivalent;
infarction; PTCA=percutaneous transluminal angioplasty; other=arrhythmia or coronary artery disease per angiography.
4
3
1
9
4
5
MI=myocardial
CHEST / 107/5/ MAY, 1995
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Other
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Table 3-Frequency of Minor Cardiovascular Events During ECG-Monitored Cardiac Rehabilitation
News-Onset, Asymptomatic Event
Any Event
At high risk per ACC
criteria (n=80)
Not at high risk per ACC
criteria (n=209)
All patients (n=289)
ECG event with
symptoms
ECG event without
symptoms
Symptoms without
ECG event
Other
No Event
No. of Patients
%
95% CI*
No. of Patients
%
95% CI*
No. of Patients
%
95% CI
34f
42.5
31.5-53.5
3
3.8
0.0-8.1
46
57.5
46.5-68.5
43
20.6
15.0-26.2
8
3.8
1.2-6.5
166
79.4
73.8-85.0
77
3
26.6
1.0
21.4-31.8
0.0-2.2
-
-
212
73.4
68.2-78.6
32
11.1
7.4-14.8
11
3.8
37
12.8
8.9-16.7
5
1.7
0.2-3.2
1.6-6.0
*Cl=confidence interval.
tp<0.01, event and high risk vs event and not at high risk; %=number of patients/corresponding sample.
tients who met the ACC criteria for ECG monitoring
vs those who did not (p<0.01) (Table 3). There was
no detectable difference, however, between the two
groups regarding the rate for new-onset, asymptomatic events. The average number of class sessions attended for patients who met the ACC criteria for
ECG monitoring vs patients who did not meet the
criteria was 15 and 14, respectively.
A categorization of the 77 minor events is also
given in Table 3. In 21 of the 32 patients who experienced a minor event without associated symptoms,
the observed event was known to be part of their
medical history. Therefore, the overall rate for at
least 1 new-onset, asymptomatic event was 3.8%
(11/289). The characteristics and clinical findings for
these 11 patients are given in Table 4.
The referring physician was contacted in 17 of the
66 patients who experienced a minor event during
exercise that was either symptomatic or known to be
part of their medical history. In 6 of these 17 patients,
there was a change in therapy or intervention; 2 had
a change in medical regimen (1 for elevated blood
pressure and 1 for an arrhythmia), 2 had their target
heart rate range lowered (1 for angina and 1 for an
arrhythmia), 1 had coronary angioplasty due to chest
pain and ECG changes first noticed during exercise
class, and 1 discontinued participation due to angina
that eventually required surgical intervention.
DiscussIoN
This study retrospectively examined 289 patients
who participated in an ECG-monitored phase 2 cardiac rehabilitation program between October 1992
and July 1993. Among these patients, there were no
major cardiovascular complications. This is consistent
with several previous reports that described the low
frequency of such events during cardiac rehabilitation programs.8'9
Seventy-seven of our patients (26.6%) experienced
at least one minor cardiovascular event which, at first
glance, might provide supporting evidence for the
use of ECG monitoring. A closer review, however,
reveals that 66 of the 77 events (86%) were either part
of a patient's medical history (n=21) or otherwise
identifiable without ECG monitoring (n=45). More
importantly, the rate of new-onset, asymptomatic
events was rare at 3.8% (11/289). This is consistent
with the 4.5% rate reported by Mitchell et al,4 and less
than the 14% (range, 7 to 22%) rate stated by
Greenland and Pomilla.3 In 4 of the 11 patients, the
event might have been avoided had the patient not
exercised above their prescribed target heart rate
range (Table 4). Unclear for these four patients is
whether they unintentionally or knowingly exceeded
their target heart rate range.
The ACC criteria for ECG monitoring did identify
patients more likely to experience a minor event
during exercise training (Table 3). There was, however, no detectable difference in the rate of new-onset, asymptomatic events between those patients who
met the ACC criteria (3.8%) and those who did not
(3.8%). The absence of any detectable difference
between these two groups questions the utility of the
ACC criteria for classifying patients at high risk. This
finding, however, may have been due, in part, to both
the low rate of events in the two study groups and the
low statistical power associated with these event rates.
Based on the ACC criteria, 28% of our patients
(n=80) were considered at high risk, which is consistent with the 20 to 25% rate that has been reported
previously.
A possible limitation of this study is that it did not
assess, in three patients, which was detected first, ST
segment depression or symptoms. As a result, the
overall rate of new-onset, asymptomatic events could
have been 4.8% (14/289) instead of 3.8%. In either
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Clinical Investigations
Table 4-Characteristics and Clinical Findings of Patients Who Experienced a New-Onset, Asymptomatic* Event
Subject No.
Age, yr/Sex
MET Level at
Entry Into Phase 2
Met ACC
Criteria
Session No. When
Event Occurred/
Total Sessions
156/71/M
248/58/M
260/67/M
4.4
4.4
3.0
Yes
Yes
Yes
3/12
11/12
1/12
ST segment depression
Ventricular bigeminy
RBBB
Lowered THRR
THRR violator
Physician-no change in
5/64/F
25/60/M
2.8
3.3
No
No
1/12
1/9
ST segment depression
Nonsustained VT
THRR violator
Physician-no change in
59/59/M
100/63/M
118/57/M
2.2
3.8
8.2
No
No
No
2/12
7/12
18/18
Inverted T waves
ST segment depression
Nonsustained VT
148/48/F
162/68/F
3.6
3.9
No
No
7/20
4/18
Wandering pacemaker
SVT
270/45/M
5.8
No
10/12
None taken
None taken
Physician-no change in
therapy; THRR violator
None taken
Physician-.-adrenergic
blocking agent added
Physician-THRR violator
Comment/Action
Event
therapy
therapy
Pacemaker related 3 to 1
AV block
*Likely not detectable without ECG monitoring. AV=atrioventricular; MET=metabolic equivalent; RBBB=right bundle branch block;
THRR=target heart rate range; VT=ventricular tachycardia; SVT=supraventricular tachycardia.
case, however, the event rate is still very low. Additionally, of the 32 patients who experienced any minor asymptomatic ECG event (new onset or previously known), 11 had their exercise session discontinued or the intensity of their effort reduced.
Unknown for these patients is whether a more severe
event was avoided as a result of ECG monitoring.
Of greatest potential importance is that only 4 of
289 patients (1.4%) experienced a change in their
care plan secondary to an ECG-identified event. Two
patients had a change in medical regimen and two
had their exercise heart rate range lowered. Our rate
for minor events leading to a change in care plan is
lower than the 3% rate reported by Mitchell et a14 and
the 5% rate suggested by Greenland and Pomilla.3
Electrocardiographic monitoring during cardiac
rehabilitation may help verify the safety of exercising patients with cardiac disease,10 provide validation of the prescribed exercise heart rate range,' 10
enhance a patient's perception of his or her ability to
safely exercise, and provide diagnostic information
not otherwise obtained by Holter monitoring or
graded exercise testing.10-13 Such information, therefore, should be considered when interpreting our
data. Due to the limited number of patients in this
study who experienced a new-onset, asymptomatic
event (n=11) and/or a change in care plan as a result of ECG monitoring (n=4), we could not conduct
multivariate regression analysis to predict patients in
need of such monitoring. A multisite prospective
randomized trial is needed to (1) assess the efficacy of
ECG monitoring and (2) establish guidelines meant
to identify patients at high risk for experiencing a
new-onset, asymptomatic cardiovascular event.
Recent guidelines published by the American As-
sociation of Cardiovascular and Pulmonary Rehabilitation do not specify the type or duration of ECG
monitoring needed for low-, intermediate-, or highrisk patients enrolled in cardiac rehabilitation.2 Instead, this decision is left up to the judgment of the
cardiac rehabilitation staff who are encouraged to
progress patients to less intensive monitoring when
judged clinically stable and responsive to therapy.
Electrocardiographic monitoring is indicated in
patients with atrial fibrillation (where measured
pulse rate is often inaccurate) and those unable to
self-monitor pulse rate. Patients with silent ischemia
and/or a known history of exceeding their prescribed
target heart rate range may also require such monitoring. Based on our data describing the overall low
frequency of both asymptomatic events and events
leading to a change in therapy, we encourage clinicians to limit the duration of continuous ECG monitoring in low-risk (and possibly moderate-risk) patients to 3 to 12 sessions. Clinicians may also wish to
consider using spot monitoring instead. The above
monitoring strategies have been suggested previously
for use in the cardiac rehabilitation setting,4-6,14,15
and in addition to helping maintain a low frequency
of adverse events, should minimize the cost associated
with the use of ECG monitoring. The value of continuous ECG monitoring during early outpatient
cardiac rehabilitation has been questioned previously, when Greenland and Pomilla3 estimated that
over $1 million would be spent in an 8-year period to
prevent one serious cardiovascular event.
In summary, we have shown that minor cardiovascular events are common during phase 2 cardiac
rehabilitation and that the ACC criteria appear to
satisfactorily distinguish those patients at risk for exCHEST / 107/5 / MAY, 1995
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1245
periencing such an event. We have also shown that
the overall rate for new-onset, asymptomatic events
is rare for both patients classified at high risk (3.8%)
and those not classified at high risk (3.8%). Of greatest importance, however, is the fact that changes in
therapy rarely occurred (1.4%) as a result of continuous ECG monitoring during cardiac rehabilitation.
Health-care providers should consider this information when determining to what extent, if any,
patients should be ECG monitored while participating in a phase 2 cardiac rehabilitation program.
6
7
8
9
10
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4 Mitchell M, Franklin B, Johnson S, et al. Cardiac exercise programs: role of continuous electrocardiographic monitoring.
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Clinical Investigations