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const str = `OR I GI N AL AR TI CL E
Home-based interval training increases endurance capacity
in adults with complex congenital heart disease
Camilla Sandberg RPT, PhD 1,2
| Magnus Hedstr€ om MD 1 |
Karin Wadell RPT, PhD 2
| Mikael Dellborg MD, PhD 3 | Anders Ahnfelt MD 3 |
Anna-Klara Zetterstr€ om RPT 4
| Amanda
€
Ohrn RPT 4
| Bengt Johansson MD, PhD 1
1 Heart Center and Department of Public
Health and Clinical Medicine, Umeå
University, Umeå, Sweden
2 Department of Community Medicine and
Rehabilitation, Physiotherapy, Umeå
University, Umeå, Sweden
3 Department of Molecular and Clinical
Medicine, Sahlgrenska Academy, University
of Gothenburg, Gothenburg, Sweden
4 Department of Physiotherapy and
Occupational Therapy, Sahlgrenska
University Hospital, Gothenburg, Sweden
Correspondence
Camilla Sandberg, RPT, PhD, Heart Center
and Department of Public Health and
Clinical Medicine, Umeå University,
SE-90185, Umeå, Sweden.
Email: camilla.sandberg@umu.se
Funding information
Swedish Heart-Lung Foundation, Grant/
Award Numbers: 20100355, 20130472;
Heart Foundation of Northern Sweden;
Research Foundation of The Swedish Heart
and Lung Association, Grant/Award Num-
ber: E116/12, E115/13, E129/14; Research
Foundation of Healthcare Professions
within Cardiology, Umeå University; Väster-
bottens läns landsting, Umeå, Sweden,
Grant/Award Number: 316351; and ALF-
LUA grants at Sahlgrenska University Hos-
pital, G€ oteborg, Sweden
Abstract
Objective: The beneficial effects of exercise training in acquired heart failure and coronary artery
disease are well known and have been implemented in current treatment guidelines. Knowledge
on appropriate exercise training regimes for adults with congenital heart disease is limited, thus
further studies are needed. The aim of this study was to examine the effect of home-based interval
exercise training on maximal endurance capacity and peak exercise capacity.
Design: Randomized controlled trial.
Methods: Twenty-six adults with complex congenital heart disease were recruited from special-
ized units for adult congenital heart disease. Patients were randomized to either an intervention
group—12 weeks of home-based interval exercise training on a cycle ergometer (n516), or a con-
trol group (n510). The latter was instructed to maintain their habitual physical activities. An
incremental cardiopulmonary exercise test and a constant work rate cardiopulmonary exercise test
at 75% of peak workload were performed preintervention and postintervention.
Results: Twenty-three patients completed the protocol and were followed (intervention n513,
control n510). Postintervention exercise time at constant work rate cardiopulmonary exercise
test increased in the intervention group compared to controls (median[range] 12[–4 to 52]min vs 0
[–4 to 5]min, P5.001). At incremental cardiopulmonary exercise test, peak VO 2 increased 15%
within the intervention group (P5.019) compared to 2% within the control group (P5.8). How-
ever, in comparison between the groups no difference was found (285[–200 to 535] ml/min vs 17
[–380 to 306] ml/min, P5.10). In addition, peak workload at incremental cardiopulmonary exer-
cise test increased in the intervention group compared to controls (20[–10 to 70]W vs 0[–20 to
15]W, P5.003).
Conclusion: Home-based interval exercise training increased endurance capacity and peak exer-
cise capacity in adults with complex congenital heart disease. Aerobic endurance might be more
relevant than peak oxygen uptake with regard to daily activities, and therefore a more clinically rel-
evant measure to evaluate.
K EY WO RD S
adult, cardiopulmonary exercise testing, congenital heart disease, constant work rate, exercise
training, interval training
254
|
V C 2017 Wiley Periodicals, Inc. wileyonlinelibrary.com/journal/chd Congenital Heart Disease. 2018;13:254–262.
Received: 3 January 2017
|
Revised: 21 August 2017
|
Accepted: 19 October 2017
DOI: 10.1111/chd.12562
1
|
INTRODUCTION
During the past decades there have been substantial improvements
in survival and reduction in the need of reoperations for adults
with congenital heart disease (CHD), especially among those with
more complex lesions. 1–3 There is a well-known impairment in
exercise capacity in these patients compared to healthy controls. 4,5
To what extent this impairment is due to abnormal cardiovascular
physiology, per se, or to other factors such as physical inactivity or
lack of exercise training, that is, deconditioning, is unknown. Fur-
thermore, reduced exercise capacity is an important prognostic
predictor of cardiovascular morbidity and mortality. 6 In addition,
impaired muscle function has been observed, especially in adults
with CHD that have complex lesions. 7–10 According to current rec-
ommendations of the European Society of Cardiology, adults with
CHD are encouraged to be physically active and exercise training
should be prescribed individually. 11 However, due largely to the
low numbers of studies on effects of exercise training in adults
with CHD, there are no specific recommendations regarding train-
ing mode, intensity, duration, and frequency. 12,13 Previous studies
show that exercise training seems to be safe and to have positive
effects on aerobic exercise capacity without adverse effect on ven-
tricular function. 14–21 Home-based continuous moderate exercise
training on an cycle ergometer increased the exercise capacity in
adults with a systemic right ventricle. 17 In patients with acquired
heart failure, interval training was shown to improve exercise
capacity more than continuous moderate exercise training. 22 Inter-
val training at moderate to high intensity (75%–95% of maximum
HR) was also reported to be safe and increase exercise capacity in
these patients. 15,18 To improve adherence to study protocol,
home-based exercise training has been used in a number of previ-
ous studies. 17,23,24
Incremental cardiopulmonary exercise testing (incremental
CPET) on a cycle ergometer or treadmill is frequently used and often
considered the “gold standard” when evaluating aerobic exercise
capacity and change in aerobic capacity after intervention. 25,26
Changes in peak aerobic capacity, total exercise time and peak work
load are variables commonly used to report study results. 12 Constant
work rate CPET is a method commonly used to evaluate endurance
exercise capacity in patients with chronic obstructive pulmonary dis-
ease (COPD) 27 and it has emerged as the most responsive test
method to evaluate change in exercise capacity in these patients
after rehabilitation intervention. 28 At present, this test has not been
used to evaluate outcome of exercise training in the setting of adult
CHD.
The present study was a randomized controlled trial that used
CPET aimed to evaluate the effect of home-based interval exercise
training on submaximal exercise capacity (endurance) and peak exercise
capacity (peak work load, peak oxygen uptake) in adults with complex
CHD. The hypothesis was that interval training increases endurance
capacity as well as peak exercise capacity in an intervention group
compared to a control group.
2
|
METHODS
2.1
| Study population
Twenty-six patients (13 women) with complex CHD and reduced exer-
cise capacity were recruited from specialized units for adults with CHD
in the northern health care region (Umeå) and the region of Västra
G€ otaland (G€ oteborg) in Sweden. The inclusion criteria were complex
CHD, as defined by Erikssen et al., 1 (eg, palliated with variants of Fontan
procedure [Fontan/TCPC], pulmonary atresia [PA], tetralogy of Fallot
[ToF], congenitally corrected transposition of the great arteries [ccTGA],
dextro-transposition of the great arteries repaired with Mustard or Sen-
ning procedure [d-TGA]), clinically stable condition over the past 3
months, adult age (?18 years of age), and informed consent. The
patients with PA, as well as those with ToF, had undergone surgical
repair and were not cyanotic. The exclusion criteria were present strat-
egy for executing exercise training?2 times/week aimed at increasing
or sustaining exercise capacity, arrhythmia or other adverse events (eg,
important symptoms, drop in blood pressure) at CPET, clinically relevant
arrhythmia, intellectual disability or mental illness affecting independent
decision making, extracardiac disease affecting physical activity, peak
VO 2 >30ml/kg/min at run-in CPET, or no internet access. At the time
of screening (October 25, 2012) the outpatient register of CHD in the
northern health care region, 391 patients were registered. Seventy-
seven patients met the inclusion criteria of complex CHD. Of these, 39
patients met at least one exclusion criteria. Thus, 38 patients were eligi-
ble and were asked to participate; 17 declined participation, 1 was
excluded due to arrhythmia (short periods of atrial fibrillation) and 1
was excluded due to peak VO 2 ?30 ml/kg/min at run-in CPET and 19
(53%) were finally included. There were no differences regarding age
and sex between those who declined participation and those who par-
ticipated. In the region of Västra G€ otaland, a convenience sample was
collected, that is, when patients fulfilling the inclusion criteria were
scheduled for a regular follow-up visit they were asked to participate.
Thus, these patients were not strictly consecutively recruited. Eight
patients were tested with run-in CPET, of these 1 was excluded due to
arrhythmia. This gave an additional 7 patients. Finally, a total of 26
patients were included and were randomized to an exercise-training
group, that is, intervention group (n516), or a control group (n510).
Two patients that had been randomized to the intervention group dis-
continued study participation due to personal reasons. For another
patient, the exercise training was discontinued after 14 training sessions
due to the patient experiencing discomfort and possible arrhythmia.
Therefore, 23 patients consisting of 13 in the intervention group and 10
in the control group were followed after intervention. All patients gave
their written informed consent for participation. The study was
approved by the regional Ethics Review Board in Umeå (Dnr 2011-51-
31 M, 2011-03-29, and 2012-143-32 M, 2012-04-04).
2.2
| Exercise capacity
At the incremental CPET peak VO 2 , peak work load, respiratory
exchange ratio (RER) and peak heart rate were registered. 25 To ensure
standardization, the participants were instructed that when rating ?17
SANDBERG ET AL .
|
255
(very hard) on the Borg Rated Perceived Exertion scale, 29 this corre-
sponded to perceived exertion of “not coping with an additional
increase of work load.” The subsequent endurance test, constant work
rate CPET, was performed at 75% of peak work load that had been
achieved at the initial incremental CPET. The exercise test duration
was the main outcome. 27,30 In one patient in the intervention group,
the postintervention constant work rate CPET was not performed due
to technical issues. Therefore, for this patient we only used the incre-
mental CPET data. For pre- and postexercise tests the Jaeger Oxycon
Pro CareFusion (GmbH, Hoechberg, Germany) or Schiller CS-200 Ergo-
spirometry (Schiller AG, Baar, Switzerland) was used for analysis of
breathing-gases.
2.3
| Randomization process
The present study was a two-armed randomized controlled trial.
Patients were randomly assigned to intervention or control group in
the ratio of 2:1 that was applied by computer generated block random-
ization. The group allocation sequence was kept in an opaque, sealed,
and stapled envelope to prevent prior knowledge, and was revealed to
patients and researchers after completion of run-in tests. At the first
center, the technicians performing the tests and the physician (MH)
analyzing the tests were blinded for group allocation. Furthermore, the
patients were instructed not to reveal their group allocation. At the
second center, the investigators were not blinded. However, the tests
strictly followed the prespecified protocol.
2.4
| Exercise training protocol
The exercise training was home-based and was performed three times
a week for 12 weeks on a cycle ergometer with a manually adjusted
brake system (Tunturi T 20/Tunturi, Tunturi- Hellberg Oy Ltd, Åbo, Fin-
land or Bremshey BF3, Escalade Int. Ltd, Nottingham, UK). The time
between completion of the run-in tests, and start of intervention was
approximately 1 week due to delivery of the cycle ergometers. To indi-
vidually adjust the intensity of the exercise training protocol, the train-
ing heart rate (THR) was calculated according to the Karvonen method
based on the individual peak heart rate. 31 In addition to the heart rate
intervals, patients were instructed to achieve perceived exertion corre-
sponding to BORG 15–16. 29 All patients randomized to exercise train-
ing received one occasion with familiarization training. The exercise
training had an initial 8 min warm-up without load or with very low
load. During the first 2 weeks the protocol consisted of three intervals
at THR 75%-80%, and thereafter four intervals. The duration of the inter-
vals was also individually adjusted according to total exercise time dur-
ing the initial constant work rate CPET. When the total time at
constant work rate CPET was less than 5 minutes, the interval time
was calculated as total exercise time minus 1 minute. The maximum
interval time was 5 minutes. The intervals were separated by an active
recovery periods of 3 minutes without load or with very low load (Sup-
porting Information Figure S1). During the exercise training sessions,
participants wore a heart rate monitor (Polar RS 300X, Polar Electro
Oy, Kempele, Finland). The registered heart rate was regularly
transferred to a personal webpage that was accessed by the physio-
therapist and participant. A weekly contact by phone was used to pro-
mote compliance, to provide feedback, and, when appropriate, to
increase training time if a shorter interval time than 5 minutes. The par-
ticipants were instructed to pay attention to symptoms such as dizzi-
ness, palpitations, chest pain, and other experiences of discomfort, and
if these occurred, abort exercise and contact investigators. The maxi-
mum number of training sessions was 36 and the goal was that every
participant should complete a minimum of 28 (78%) sessions. The
patients randomized to control group were instructed to continue with
their habitual physical activities.
2.5
| Questionnaires
In addition to exercise test data, self-reported quality of life was eval-
uated using the EuroQol Vertical Visual Analogue Scale (EQ-VAS). 32
The Hospital Anxiety and Depression scale (HADS) 33,34 was used for
assessing prevalence of anxiety and depression. Finally, self-efficacy for
exercise was evaluated using the Exercise Self-Efficacy Scale (ESE). 35
All three scales are validated and were used preintervention and
postintervention.
2.6
| Statistics
The data were tested for normality. Data are presented as mean 61
standard deviation (SD) or median with range (min-max). Differences
in means, ranks, and ratios were tested by Student’s t test, Mann-
Whitney U test, or chi-square test as appropriate. Paired samples t
test and Wilcoxon’s signed ranks test were applied for within group
comparisons. The null-hypothesis was rejected for P values<.05. All
calculations were performed using SPSS 22 (IBM, Armonk, NY,
USA).
3
|
RESULTS
Twenty-three patients were analyzed after follow-up that included 13
in the intervention group and 10 in the control group. There were no
differences in baseline data between the intervention group and con-
trol group (Tables 1–3). In the population, the mean predicted peak
heart rate was 88%67.5% and the mean predicted peak VO 2 was
72%613.7%. Moreover, there were no differences between interven-
tion group and control group regarding these data.
3.1
| Exercise capacity
The median test duration at constant work rate CPET increased 89%
post intervention in the intervention group compared to no change in
the control group (median[range] 12[–4 to 52] min vs 0[–4 to 5] min,
P5.001). Furthermore, the peak workload (20[–10 to 70] W vs 0[–20
to 15] W, P5.003) at incremental CPET increased post intervention in
the intervention group compared to the controls. The peak VO 2 (ml/
min) at incremental CPET increased 15% within the intervention group
(P5.019) compared to no change (2%) within the control group
(P5.8). The results were similar regarding VO 2 indexed for body
256 | SANDBERG ET AL .
weight and peak O 2 pulse. However, in comparison between the inter-
vention group and control group no differences were found regarding
absolute peak VO 2 (ml/min) or peak VO 2 indexed to body weight (ml/
kg/min) (285[–200 to 535] ml/min vs 17[–380 to 306] ml/min, P5.10)
(3.6[–2.6 to 6.4] ml/kg/min vs 0.6[–3.5 to 4.9] ml/kg/min, P5.12).
Furthermore, the increase in peak O 2 pulse did not differ between
the groups (1.3[–1.7 to 4.2] ml/heartbeat vs 0.4[–1.2 to 2.4], P5.21
(Table 2, Figure 1A–D).
3.2
| EQ-VAS, HADS, and ESE
No differences were found within or between groups preintervention
and postintervention regarding self-reported QoL, prevalence of anxi-
ety and depression or exercise self-efficacy (Table 3).
3.3
| Compliance
Compliance to exercise training protocol, defined as the number of
completed training sessions in relation to the possible number of ses-
sions, was in mean 79%617 (median 83%, 47%–100%). The number
of registered exercise occasions ranged from 17 to 36 of 36 possible
occasions.
3.4
| Adverse event
In one case, the exercise training was discontinued due to the patient
experiencing discomfort and possible arrhythmia during a session of
exercise training. No arrhythmia was detected on a subsequent exer-
cise test or at Holter registration. No other adverse events occurred.
TABLE 1 Descriptive data on included patients
All patients (n523) Intervention group (n513) Controls (n510) P value
Sex
M n (%) 12(52) 8(62) 4(40) .31
F n (%) 11(48) 5(39) 6(60)
Age, years Median(IQR) 30.1(22.9–36.6) 31.3(26.9–36.6) 26.3(22.9–35.6) .38
Height, m Mean6SD 1.72(0.10) 1.72(0.09) 1.72(0.10) .85
Weight, kg Mean6SD 77(15) 77(10) 76(21) .90
BMI, kg/m 2 Mean6SD 25.8(3.9) 26.0(3.6) 25.5(4) .77
Diagnosis n (%)
ToF 5(22) 4(31) 1(10) .19
ccTGA 3(13) 3(23) 0(0)
d-TGA 5(22) 2(15) 3(30)
TCPC 5(22) 3(23) 2(20)
PA 2(9) 0(0) 2(20)
Complete AV-septal defect 1(4) 0(0) 1(10)
Ebstein 1(4) 0(0) 1(10)
Miscellaneous 1(4) 1(8) 0(0)
Surgical intervention, yes n (%) 21(91) 11(85) 10(100) .19
Age at intervention, years* median(IQR) 3.1(1.1–6.8) 3.6(1.2–7.6) 3.0(0.7-6.1) .74
PM, yes n (%) 2(9) 2(15) 0(0) .19
Cardiovascular medication, yes n (%) 10(44) 5(39) 5 (50) .58
ACE/ARB n (%) 6(26) 4(31) 2(20) .56
Beta-blockers n (%) 2(9) 1(8) 1(10) .85
Diuretics n (%) 2(9) 1(8) 1(10) .85
Warfarin n (%) 5(22) 3(23) 2(20) .86
Aspirin n (%) 3(13) 2(15) 1(10) .70
Abbreviations: ACE, angiotensin converting enzyme; ARB, angiotensin receptor-2 blockers; AV, atrioventricular; ccTGA, congenitally corrected transposi-
tion of the great arteries; d-TGA, dextro-transposition of the great arteries; F, female; IQR, interquartile range; M, male; n, number; PA, pulmonary atre-
sia; PM, pacemaker; TCPC, total cavo-pulmonary connection; ToF, tetralogy of Fallot.
*Age at TCPC surgery or correction or ToF. Presented P values represent comparison between intervention group and controls. Mann-Whitney U test
was applied in comparison of age and age at intervention; in all other comparisons chi-square or Student’s t test was used.
SANDBERG ET AL .
|
257
4
|
DISCUSSION
This is the first study to evaluate endurance capacity in addition to
peak aerobic capacity after exercise training in adults with complex
CHD. The present study shows that home-based high intensity interval
training on a cycle ergometer has a great impact on endurance capacity
as well as on maximum exercise capacity in adults with complex CHD.
4.1
| Exercise capacity
Peak VO 2 (ml/min) increased within the intervention group but not in
comparison to the control group. However, the peak work rate for the
intervention group increased in comparison to the control group which
altogether indicates an improvement in peak aerobic capacity. The
increase in peak VO 2 in previous studies was approximately 8%, 14,15,18
and in the present study the corresponding increase within the inter-
vention group was 15%. An increase in aerobic capacity could be of
significance in daily activities. In patients with complex congenital heart
lesions, especially with impaired NYHA class, activities of daily living
might be in line with or even exceed their individual exercise capacity. 5
In these cases, an exercise training induced improvement of exercise
capacity could play an important role in coping with activities of daily
living. In adults with complex CHD, the central adaption to exercise
training is usually blunted, 36,37 which might lead peripheral mecha-
nisms, that is, increased muscle capillarization and oxidative capacity, to
play an even greater role in the response to exercise training. 38 The
important increase in endurance capacity may actually reflect this
mechanism. It is noteworthy that modest increases in peak VO 2 (ml/
min) and peak work rate after exercise training corresponded to a sub-
stantial increase in time duration at constant work rate CPET; this
result was previously reported in patients with COPD. 28,39 Our results
imply that endurance capacity might be a more clinically relevant mea-
sure of change in exercise capacity after exercise training in adults with
complex CHD.
4.2
| Exercise testing
Peak VO 2 derived from incremental CPET is frequently used and often
considered the “gold standard” measure of peak aerobic exercise
capacity. 25,26 When assessing the peak aerobic exercise capacity, it is
important that the test is performed with maximum effort. The
RER?1.10 is considered as a measure of maximum effort being
reached. 25 In the present study, this limit was reached by the majority
of the participants (Table 2). However, in adults with complex CHD dif-
ficulties in reaching this limit was previously reported. 6,40 This phenom-
enon was to some extent also observed in our population. Pulmonary
limitation of the exercise capacity has been proposed to cause this lim-
ited ability to reach RER ?1.10. 25 Recently, submaximal outcome
measures calculated from the incremental CPET, that is, ventilatory
anaerobic threshold (VAT), oxygen uptake efficiency slope (OUES), and
VE/VCO 2 slope, have emerged as useful in evaluation of exercise
capacity and as prognostic tools. Furthermore, these parameters do not
require a test performed with maximum effort. 26,40,41 In our study, we
TABLE 2 Preintervention, postintervention, and change in cardiopulmonary exercise test data in intervention group vs control group
Preintervention Postintervention Change after intervention
Intervention group Control group P Intervention group Control group P Intervention group Control group P
CPET incremental
VO 2 peak, ml/min 1865 (1191–2355) 1601 (1215–2650) .74 1870 (1040–2642) 1688 (1326–2367) .26 285 (–200 to 535) 17 (–380 to 306) .10
VO 2 peak, ml/kg/min 23.4 (14.8–29.4) 23.6 (18.1–28.1) .98 26.9 (13.0–33.6) 24.8 (18.1–28.4) .23 3.6 (–2.6 to 6.4) 0.6 (–3.5 to 4.9) .12
Peak O 2 pulse, ml/heartbeat 10.3 (7.3–13.7) 9.5 (6.8–15.1) .99 12.0 (8.3–15.0) 10.8 (8.2–14.0) .48 1.3 (–1.7 to 8.5) 0.4 (–1.2 to 2.4) .21
Peak workload, W 155 (100–220) 150 (110–200) .69 170 (90–240) 140 (110–200) .07 20 (–10 to 70) 0 (–20 to 15) .003
RER 1.19 (0.99-1.51) 1.22 (1.02-1.36) .61 1.20 (1.13-1.40) 1.20 (0.98-1.29) .52
Constant work rate at 75% of peak workload:
Test duration min 14 (4–33) 9 (3–20) .11 28 (8–68) 9 (5–16) .001 12 (–4 to 52) 0 (–4 to 5) .001
Abbreviations: CPET, cardiopulmonary exercise test; RER, respiratory exchange ratio.
Data are presented as median (range). Bold text indicates a P value<.05.
258 | SANDBERG ET AL .
took this a step further and used a submaximal exercise test in addition
to the incremental CPET and found a substantially larger (median
change 12 min, 89%) increase in submaximal exercise capacity in com-
parison to peak VO 2 (15%). With reference to the patients’ perform-
ance capacity in daily activities, increased endurance might better
illustrate the benefits of improved aerobic capacity and thereby be a
more clinically relevant measure. The increase in endurance capacity
we found is in line with previous studies in patients with COPD. Pors-
zasz et al. 39 reported a mean increase of 11.668.1 minutes in duration
at constant work rate CPET after exercise training, while Cambach
et al. 42 reported a mean increase of approximately 7 minutes in dura-
tion. An increase of 1.6–3.3 minutes has been suggested as a minimal
clinically important difference in response to exercise training in
patients with COPD. 43,44 In our intervention group, all patients except
one increased the time duration at constant work rate CPET above this
suggested level of minimal clinical importance. This particular patient
did not comply fully with the exercise training protocol fulfilling only
17 of 36 (47%) of the possible exercise training sessions.
4.3
| Exercise training protocol
As stated in the current recommendations on physical activity and rec-
reational sports in adults with CHD, exercise prescriptions should be
individualized. 11 We aimed to provide the patients in the intervention
group with an individually adjusted exercise training protocol based on
the results of the cardiopulmonary exercise tests. Different modes of
exercise training, for example, walking, interval training with step aero-
bics, and moderate continuous training on a cycle ergometer have been
used in previous studies. 17,18,23,24 The present study is the first to use
home-based moderate to high intensity interval exercise training on a
cycle ergometer in a population of adults with different complex con-
genital heart lesions. Studies in adults with systemic right ventricle
have shown that home-based exercise training is safe, feasible and
effective with regard to exercise capacity without negative effects on
the systemic right ventricle. 17,18,24 In patients with heart failure, inter-
val training was reported to improve exercise capacity more than a
moderate continuous exercise training mode. 22 The present study
FIGURE 1 A-D, Individual cardiopulmonary exercise test data at baseline, at 12-week follow-up and change from baseline to follow-up in
intervention group
TABLE 3 Preintervention, postintervention and change in data regarding self-reported prevalence of anxiety and depression (HADS), quality
of life (EQ5D VAS), and exercise self-efficacy (ESE)
Preintervention Postintervention Change after intervention
Intervention
group Control group P
Intervention
group
Control
group P
Intervention
group Control group P
HADS Anxiety 4(1–9) 4(0–7) .69 5(2–9) 6(0–8) .72 1(–3 to 3) 1(0–3) .28
HADS Depression 2(0–9) 2(0–5) .26 2(0–5) 2(0–6) .97 0(–4 to 2) 0(–1 to 4) .18
EQ-VAS 77.5(35.0–99.0) 89.5(70.0–99.0) .10 78.8(48.0–99.0) 85.5(35.0–99.0) .31 0(–21.0 to 25.0) 0(–55.0 to 9.0) .42
ESE 32(16–39) 30(15–40) .88 28(11–40) 29(18–40) .67 25(–12 to 8) 21(–6 to 6) .23
Abbreviations: EQ-VAS, EuroQol Vertical Visual Analogue Scale; ESE, Exercise Self-Efficacy Scale; HADS, Hospital and Anxiety and Depression scale.
Data are presented as median (range).
SANDBERG ET AL .
|
259
showed that home-based interval exercise training increased endur-
ance capacity as well as peak aerobic exercise capacity in adults with
complex congenital heart lesions. The finding of markedly increased
endurance capacity, in addition to peak capacity, contributes important
information to previous exercise training studies in this population.
4.4
| Quality of life
In CHD, self-reported quality of life is known to be associated with
physical activity level. 45 Here, we report that self-reported quality of
life remained unchanged after intervention which is in line with results
previously shown by others. 15 In contrast, positive effects of exercise
on quality of life has been reported. 23 The population in the present
study rated their quality of life as rather high preintervention which
might explain the unchanged results.
4.5
| Compliance
As many patients with complex heart lesions are in the “middle of life”
and occupied with studies, work, children, and family activities, a
home-based exercise training protocol was chosen to improve adher-
ence to study protocol. In addition, participants were contacted by
phone every week, which probably also contributed to compliance. The
mean compliance in the present study (79%) was in line with previously
presented results (68%-77%). 14,17,18
4.6
| Limitations
As in previously presented studies on exercise training in adults with
CHD, our study population was rather small which somewhat limits the
generalizability of the results. However, the results are in line with pre-
vious studies which further strengthen exercise training as a part of the
rehabilitation of adults with complex CHD. Furthermore, our study
population consisted of patients with different complex diagnoses that
to a greater extent reflect the diversity seen in the clinic, thus enhanc-
ing the generalizability.
This study was performed at two centers. The center recruiting 5
patients (22%) was not able to keep the investigators performing the
exercise tests strictly blinded for group allocation. However, there was
a prespecified protocol that was strictly followed in both centers. Fur-
thermore, the same center had a different recruitment strategy that
possibly could involve patients with more frequent clinical visits and
thus potentially patients with more complex lesions. However, the
numbers are small and the two patients performing the exercise proto-
col did not obviously differ from the rest of the study population.
One concern of the constant work rate CPET that has been dis-
cussed previously in patients with COPD is the power/duration rela-
tionship. 28 This means that the endurance time varies depending on
the workload (power) used during the test. However, there is no con-
sensus on optimal power to use which complicates comparison of
results between studies. To standardize, we used 75% of peak work
rate that was used previously in COPD patients. 39,42
4.7
| Conclusions
Home-based interval exercise training increased the endurance
capacity at 75% of peak work load by 12 minutes as well as peak exer-
cise capacity in adults with different complex congenital heart lesions.
Substantially increased endurance capacity in the spectrum of daily
activities is what most patients need. Therefore, endurance capacity
might be a more clinically relevant target than solely peak oxygen
uptake in patients with complex congenital heart lesions.
ACKNOWLEDGMENT
We are grateful to the personnel at the department of Clinical Phys-
iology at the Heart Center, Umeå University Hospital who con-
ducted the exercise tests and to the staff at the GUCH-center in
G€ oteborg.
CLINICAL TRIAL REGISTRATION
ClinicalTrials.gov, identification:NCT01671566
CONFLICT OF INTEREST
None
AUTHOR CONTRIBUTIONS
All authors read and approved the final version of the manuscript.
Concept/design: Camilla Sandberg, Magnus Hedstr€ om, Karin Wadell,
Mikael Dellborg, Bengt Johansson
Data collection: Camilla Sandberg, Magnus Hedstr€ om, Mikael Dell-
borg, Anders Ahnfelt, Anna-Klara Zetterstr€ om Amanda
€
Ohrn, Bengt
Johansson
Data analysis: Camilla Sandberg, Magnus Hedstr€ om, Mikael Dellborg,
Bengt Johansson
Interpretation: Camilla Sandberg, Magnus Hedstr€ om, Mikael Dellborg,
Anders Ahnfelt, Bengt Johansson
Drafting: Camilla Sandberg, Karin Wadell, Bengt Johansson
Critical revision: Camilla Sandberg, Magnus Hedstr€ om, Karin Wadell,
Mikael Dellborg, Anders Ahnfelt, Anna-Klara Zetterstr€ om, Amanda
€
Ohrn, Bengt Johansson
Approval of article: Camilla Sandberg, Magnus Hedstr€ om, Karin
Wadell, Mikael Dellborg, Anders Ahnfelt, Anna-Klara Zetterstr€ om,
Amanda
€
Ohrn, Bengt Johansson
ORCID
Camilla Sandberg RPT, PhD http://orcid.org/0000-0002-4043-7130
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SUPPORTING INFORMATION
Additional Supporting Information may be found online in the sup-
porting information tab for this article.
FIGURE S1 Example of the interval exercise training protocol. The
exercise training session had an initial 8 min warm-up without load
or with very low load. During the first two weeks, the protocol con-
sisted of three intervals and thereafter four intervals. The work load
during each interval was adjusted by the patient to reach the indi-
vidual training heart rate. The patients were also instructed to reach
a perceived exertion corresponding to 14-16 on the Borg scale. The
intervals were separated by an active recovery periods of 3 minutes
without load or with very low load. Each session ended with a cool
down period of approximately 5 min
How to cite this article: Sandberg C, Hedstr€ om M, Wadell K,
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