Electrocardiographic Monitoring During Cardiac Rehabilitation

Electrocardiographic Monitoring During Cardiac Rehabilitation* Steven]. Keteyian, PhD; Peggy A. Mellett, RN; Frank]. Fedel, BS; Cathy M. McGowan, MD; and Paul D. Stein, MD, FCCP

Study objective: This investigation compares the frequency of cardiac events during EGG-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<0.01), with no detectable difference noted between

Jn the past 15 years, there has been much discus-

sion 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 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.l 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

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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; 107:1242-46)

ACC=American College of Cardiology

Key words: electrocardiographic monitoring; exercise; heart disease; rehabilitation

bilitation, not only is the high-risk patient identified but the low- and intermediate-risk patient as weli.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-monitoring. 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 EGG-monitored cardiac rehabilitation in patients who meet the ACC criteria for monitoring, to the frequency of events in patients in Clinical Investigations

Table !-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 com plex 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 ischem ia (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 Coli Cardiol 1986; 7:451-53 1

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 EGG-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 duration 4· 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 tfi·e Borg Rating of Perceived Exertion scale 7 All289 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*

All patients (n=289) Men (n=216) Women (n=73)

Age, yr

MET Level During First Week of Exercise

No. of Exercise Classes Attended

Diagnosis or Procedure at Entry MI

CABG

PTCA

Angina

CHF

Other

59±11 59±11 60±10

4.2± 1.3 4.5± 1.3 3.5±0.8

13.8±5.4 13.8±5.6 13.8 ±4.9

82 64 18

121 95 26

41 31 10

32 19 13

4 3

9 4 5

*Values are Mean±SD. CABG=coronary artery bypass grafting; CHF=congestive heart failure; MET=metabolic equivalent; MI=myocardial infarction; PTCA=percutaneous transluminal angioplasty; other=arrhythmia or coronary artery disease per angiography. CHEST / 107 / 5/ MAY, 1995

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Table 3-Frequency of Minor Cardiovascular Events During ECGMonitored Cardiac Rehabilitation Any Event

At high risk p er ACC criteria (n=80) 1\ot 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

New-Onset, Asymptomatic Event

No Event

No. of Patients

%

95% CI*

No. of Patients

%

95% CI*

No. of Patients

%

95 % C I

34 1

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

37

12.8

8.9-16.7

5

1.7

0.2-3.2

11

3.8

1.6-6.0

*CI=confidence interval.

1p<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 . DISCUSS! OJ'\

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 1244

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 .1 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 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

5/ 64/ F 25 / 60/ M

2.8 3.3

No No

1/ 12 1/ 9

ST segment depression Nonsustained VT

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

Event

Pacemaker related 3 to 1 AV block

Comment/ Action Lowered THRR THRR violator Physician-no change in therapy THRR violator Physician-no change in therapy None taken None taken Physician-no change in therapy; THRR violator None taken Physician-{J-adrenergic blocking agent added Physician-THRR violator

*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 al 4 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, 5·10 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 Pomilla 3 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 /107/51 MAY, 1995

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.

REFERENCES

2

3 4

5

American College of Cardiology. Position report on cardiac rehabilitation. JAm Coli Cardiol1986; 7:451-53 American Association of Cardiovascular and Pulmonary Rehabilitation. Guidelines for cardiac rehabilitation programs. 2nd ed. Champaign, Ill: Human Kinetics Books, 1995; 27 Greenland P, Pomilla PV. ECG monitoring in cardiac rehabilitation: is it needed? Phys Sports Med 1989; 17:75-82 Mitchell M, Franklin B, Johnson S, et al. Cardiac exercise programs: role of continuous electrocardiographic monitoring. Arch Phys Med Rehabil 1984; 65:463-66 Fletcher BJ, Thiel J, Fletcher GF. Phase II intensive monitored

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6 7

8 9

10 11

12 13

14 15

cardiac rehabilitation for coronary artery disease and coronary disease risk factors-a six session protocol. Am J Cardioll986; 57:751-56 Fletcher GF. Current status of cardiac rehabilitation. Curr Probl Cardia! 1992; 17:143-203 American College of Sports Medicine. Guidelines for exercise testing and prescription. 4th ed. Philadelphia: Lea & Febiger, 1991; 98-102, 289-90 Haskell WL. Cardiovascular complications during exercise training of cardiac patients. Circulation 1978; 57:920-24 Van Camp SP, Peterson RA. Cardiovascular complications of outpatient cardiac rehabilitation programs. JAMA 1986; 256:1160-63 Franklin BA. The role of electrocardiographic monitoring in cardiac exercise programs. J Cardiac Rehabil1983; 3:806-10 Dolatowski RP, Squires RW, Pollock ML, et al. Dysrhythmia detection in myocardial revascularization surgery patients. Med Sci Sports Exerc 1983; 15:281-86 Fardy P, Doll N, Taylor J, et al. Monitoring cardiac patients: how much is enough? Phys Sports Med 1982; 10:146-52 Simoons M, Lap C, Pool J. Heart rate levels and ventricular ectopic activity during cardiac rehabilitation. Am Heart J 1980; 100:9-14 Cantwell JD, Fletcher GF. Instant electrocardiography: use in cardiac exercise programs. Circulation 1974; 50:962-66 Franklin BA, Reed PS, Gordon S, et al. Instantaneous electrocardiography: a simple screening technique for cardiac exercise programs. Chest 1989; 96:17 4-77

Clinical Investigations