Key words
aortic valve disease - coronary artery disease - mitral valve insufficiency - physical
activity
Introduction
Globally, almost one-third of deaths are due to cardiovascular diseases (CVDs) [1]. The most frequent CVD diagnosis is coronary artery
disease (CAD) [2]
[3]. In
addition, aortic valve stenosis (AVS) and mitral valve insufficiency (MVI)
constitute an increasing disease burden [3]
[4]. Percutaneous coronary intervention (PCI), coronary
artery bypass grafting (CABG), aortic valve replacement (AVR), mitral valve
replacement (MVR) and mitral valve repair (MVP) are invasive procedures of high
importance to these patients [5].
High cardiorespiratory fitness is associated with a lower CVD risk independently of
other risk factors [6]
[7]. Low cardiorespiratory fitness is also associated with a higher risk
for all-cause and CVD mortality [8]
[9]. In addition, poor preoperative cardiorespiratory
fitness has been associated with higher mortality after CABG [10]. The 6-minute walk test (6MWT) is a simple,
affordable and safe method to evaluate the functional capacity of cardiac patients
[11]
[12]
[13]. Furthermore, 6MWT has also been reported to be a
highly reliable means of predicting cardiorespiratory fitness in population-based
samples [14]. It has been suggested that preoperative
6MWT could be a useful tool for assessment of recovery after cardiac surgery [13]
[15].
In addition to cardiorespiratory fitness, physical activity (PA) is an important
factor in preventing CVDs [16], whereas sedentary
behavior (SB) is a risk factor for CVDs [17].
Decreased PA is associated with complications after elective cardiac surgery [18]. Furthermore, SB may contribute to mortality after
elective cardiac surgery [19]. On the other hand,
accelerometer-based information about PA and SB in secondary prevention of CVDs is
scarce.
Low peak exercise oxygen consumption is concluded to be a very powerful predictor
of
future fatal cardiac events, additionally to many conventional risk factors [20]. Further, a recent meta-analysis suggests that
exercise-based coronary rehabilitation reduces mortality, cardiac events and
hospitalizations, and improves quality of life [21].
Therefore, both preoperative cardiorespiratory fitness and exercise-based
rehabilitation are clinically important predictors of postoperative complications
and physical functioning. In this study, we hypothesized that patients scheduled for
elective open-heart surgery (CABG, AVR or mitral valve surgery (MVS)) have lower
cardiorespiratory fitness than patients scheduled for elective non-surgical cardiac
procedures (PCI or coronary angiography (PCI-CA)). We evaluated cardiorespiratory
fitness using 6MWT in patients scheduled for elective PCI-CA, CABG, AVR or MVS, and
further compared the results with those measured in general age-matched Finnish
reference population. In addition, correlations between 6MWT distance and different
parameters of previously reported accelerometer-measured PA and SB of the patients
were calculated for the first time in these cardiac patients using measured values
of both fitness and activity with a great number of participants [22].
Materials and Methods
Participants
The current study is based on the baseline measurements of the ongoing trial
“Personalized intervention to increase physical activity and reduce
sedentary behaviour in rehabilitation after cardiac operations” (PACO)
[23]. The data we used in this study were
collected from May 2018 until fall 2022. Patients were scheduled for elective
open-heart surgery [i. e. coronary artery bypass surgery (CABG), aortic
valve replacement (AVR), and mitral valve surgery (MVS)] or coronary angiography
(CA) at Kuopio university hospital. Patients also met the inclusion criteria: 1)
participating in the scheduled cardiac operation above; 2) willing to wear an
accelerometer, and 3) willing and capable of using a smartphone app, if
randomized to the intervention group for the PACO trial. Additionally, patients
showed no exclusion criteria for the PACO trial. Exclusion criteria included: 1)
no severe disease or functional reasons limiting PA (other than CVD); 2) patient
ends up in prolonged intensive care; 3) surgery type changes during the
operation; 4) patient has a memory disorder; or 5) patient does not use
accelerometer as instructed. Patients who met the inclusion criteria were
contacted and asked whether they would be willing to participate in the trial.
If patients showed interest, they were sent the patient information sheet and
informed consent form (ICF) with return envelope. Patients were also advised to
contact the study personnel for additional information, if necessary. Once the
patient had signed and returned the ICF, the baseline measurements were
activated (see below).
For the baseline measurements, patients carried a triaxial accelerometer
24/7 for measurements of PA and SB (described in detail below). Patients
returned the accelerometer upon arrival at the hospital for the scheduled
cardiac operation. 6MWT was performed after admission to the hospital on the
first preoperative day and supervised by a study nurse (in details below). The
final allocation to the study groups was performed after the cardiac scheduled
operation. For example, in some cases, patients scheduled for CABG who showed
more severe mitral valve regurgitation than expected were switched to combined
CABG and MVS, and reallocated into MVS group. Correspondingly, in some patients,
CA indicated percutaneous coronary intervention (PCI). In most patients, PCI was
performed ad-hoc (immediately following the angiography). Patients undergoing
coronary angiography and PCI were combined into PCI-CA group [19]
[22].
Reference group for population-based sample
The population-based sample of Finnish adults of the FinFit2017 study was used
for comparison with the cardiac procedure patients [24]. From that study, two 10-year age group and sex matched reference
subjects were drawn for each patient. For patients over 69 years old, matched
reference subjects were drawn from the FinFit2017 60–69 age group. The
FinFit2017 study was selected, as it includes the same 6MWT and 24/7
accelerometer measurements, the collection of the data was done almost at the
same time as in this study, and the FinFit2017 sample serves well as a sample of
the general population of Finnish adults [24].
The 6-minute walk test
The cardiorespiratory fitness of the patients was evaluated preoperatively with
6MWT during the index hospitalization. 6MWT was done using the protocol
instructed by the American Thoracic Society (ATS) [25]. Blood pressure (Omron M6, Omron Healthcare Co, Kyoto, Kapan) was
measured at baseline, immediately after 6MWT and after 3-minute recovery. Heart
rate (Polar M430, Polar Electro Ltd. Kempele, Finland) was recorded at baseline,
during maximal heart rate, after 1-minute and 3-minute recovery, as well as the
heart rate during possible angina pectoris. The 6MWT was conducted using a
30-meter indoor track in the corridor of the study hospital. The walking
distance was measured, and if the 6MWT was interrupted, the time elapsed,
distance walked and the reason why the test was interrupted were recorded. If
the patient complained of angina pectoris, the time and heart rate when it
occurred, together with angina severity, were recorded. Basically, a similar
protocol was used in the FinFit 2017 study.
Based on 6MWT, the maximal oxygen consumption (VO2max,
ml/kg/min) was estimated in men from walking distance, age, BMI,
heart rate at the end of test and height, and in women, from walking distance,
age, and weight [14]. Ten patients discontinued
the 6MWT: five because of chest pain, two feeling out of breath, one facing
tiredness of legs, and two feeling dizziness.
Accelerometer measurements
The patients wore a triaxial accelerometer (UKK RM42, UKK Terveyspalvelut Oy,
Tampere, Finland) on their right hip while awake and on their wrist while
sleeping [23]. The accelerometer was used for one
week during the month before the scheduled cardiac procedure but was advised not
to be used during any exposure to water. Instructions for the correct use of the
device were provided both orally and in writing. The criterion for sufficient
accelerometer carrying was 24 hours for at least four days [22]. The raw data collected by the accelerometer
were stored on a hard drive for further analyses.
In 6-second epochs, the resultant acceleration (vector sum of three orthogonal
components) was calculated to determine the mean amplitude deviation (MAD). As
MAD values accurately predict VO2 consumption, they were converted
into metabolic equivalents (MET, 3.5 mL/kg/min of oxygen
consumption) [26]
[27]. Using 6-second epochs, the one-minute exponential moving average
of MET values was calculated.
PA (corresponding to movement-related energy expenditure>1.5 METs) was
classified according to the MET levels as follows: light (LPA, 1.5–2.9
METs) and moderate-to-vigorous (MVPA,≥3.0 METs) [22]
[28]. Moreover, SB (energy
expenditure≤1.5 METs in sitting or reclined position) and standing
(energy expenditure≤1.5 METs in upright position) were identified using
the angle for posture estimation (APE) algorithm [29]
[30]. The parameters of PA, SB and
standing, reported in a previous study [22], were
investigated for their possible correlations with 6MWT result.
Based on our earlier studies [31] and the interview
executed by the study nurse, the majority of patients do not report regular
physical activity. Therefore, we measured physical activity using an
accelerometer. We also know that the majority of the physical activity is
accumulated from walking different bout lengths. In addition, some patients
bicycle during summer and some do cross-country skiing during winter, but the
amount and intensity of the physical activity is generally quite low in these
patient groups.
Ethics
The ethical approval of this study was received from The Research Ethics
Committee of the Northern Savo Hospital District (304/2017). Prior to
the participation, a written informed consent was signed by all patients.
Regarding the FinFit2017 study, the ethical approval was received from The
Regional Ethics Committee of the Expert Responsibility Area of Tampere
University Hospital (R17030). A written informed consent was also signed by the
participants before their participation.
Statistical analysis
Characteristics of the patients are shown as means with standard deviations for
numerical variables and counts with percentages for categorical variables. For
demographics, clinical characteristics and medications, the Kruskall-Wallis test
for numerical variables and Fisher’s Exact test for categorical
variables were used to test the differences between patient groups. A general
linear model (GLM) multivariate analysis of variance was used to test the
differences in fitness tests and accelerometer variables between patient groups.
The Sidak adjustment for p-values and confidence intervals was used to account
for multiple comparisons between patient groups. Spearman’s rank
correlation coefficient was used for correlation between 6MWT and accelerometer
variables. An independent samples t-test, assuming that variances are not equal,
was used to test the differences between patients and FinFit2017 reference
subjects. Fisher’s Exact tests were conducted in R (R Core Team, 2020)
and other analyses in SPSS 28 (IBM Corp. 2020, Armonk, NY).
Results
A total of 620 patients were invited, and 359 patients participated in the trial
([Fig. 1]). The group sizes per cardiac procedure
were: 1) PCI-CA (n=180); 2) CABG (n=38); 3) AVR (n=67); and
4) MVS (n=74). Of those, 234 performed 6MWT (PCI-CA: 122; CABG: 19; AVR: 39;
MVS: 54). Accelerometer data were sufficient in 265 patients (PCI-CA: 141; CABG: 25;
AVR: 51; MVS: 48). The demographics, clinical characteristics, and medications are
presented in [Table 1]. The mean age of all patients
was 63.9 years (SD±9.4), and 257 (71.6%) were men.
Fig. 1 Study participation flow diagram. Abbreviations: CABG: coronary
artery bypass grafting; AVR: aortic valve replacement; MVS: mitral valve
surgery; PCI-CA: percutaneous coronary intervention or coronary angiography;
6MWT: six-minute walk test.
Table 1 Characteristics of the patients.
|
CABG (n=38)
|
AVR (n=67)
|
MVS (n=74)
|
PCI-CA (n=180)
|
p-value
|
|
Age (y)
|
65.1 (7.2)
|
61.5 (12.4)
|
60.0 (11.7)
|
66.1 (6.3)
|
<0.001
|
|
Male†
|
25 (65.8)
|
51 (76.1)
|
64 (86.5)
|
117 (65.0)
|
0.003
|
|
BMI (kg/m2)
|
29.2 (4.5)
|
28.1 (4.9)
|
26.6 (4.4)
|
27.3 (4.0)
|
0.034
|
|
Total cholesterol (mmol/l)
|
3.6 (0.8)
|
4.0 (1.0)
|
4.3 (0.9)
|
3.8 (1.0)
|
0.038
|
|
HDL cholesterol (mmol/l)
|
1.44 (0.42)
|
1.50 (0.30)
|
1.50 (0.27)
|
1.48 (0.51)
|
0.41
|
|
LDL cholesterol (mmol/l)
|
1.99 (0.77)
|
2.40 (0.88)
|
2.65 (0.94)
|
2.07 (0.85)
|
0.002
|
|
Triglycerides (mmol/l)
|
1.09 (0.36)
|
1.10 (0.77)
|
1.15 (0.47)
|
1.27 (0.72)
|
0.21
|
|
Smoking†
|
1 (3.0)
|
1 (1.7)
|
1 (1.5)
|
6 (4.3)
|
0.82
|
|
Diabetes†
|
17 (51.5)
|
10 (16.9)
|
2 (3.1)
|
28 (19.9)
|
<0.001
|
|
Hypertension†
|
30 (90.9)
|
34 (57.6)
|
26 (41.3)
|
93 (67.4)
|
<0.001
|
|
Hypercholesterolemia†
|
30 (90.9)
|
40 (70.2)
|
41 (66.1)
|
133 (95.0)
|
<0.001
|
|
Atrial fibrillation†
|
4 (13.3)
|
13 (23.2)
|
16 (25.0)
|
15 (11.3)
|
0.142
|
|
Heart failure†
|
0
|
2 (3.4)
|
2 (3.1)
|
1 (0.7)
|
0.31
|
|
Coronary artery disease†
|
33 (100)
|
17 (29.3)
|
17 (26.2)
|
95 (70.9)
|
<0.001
|
|
Arteriosclerosis obliterans†
|
2 (6.1)
|
0
|
0
|
1 (0.7)
|
0.080
|
|
Stroke or transient ischemic attack†
|
3 (9.1)
|
4 (6.8)
|
3 (4.6)
|
8 (5.8)
|
0.78
|
|
Myocardial infarction†
|
6 (18.2)
|
2 (3.4)
|
0
|
14 (10.1)
|
0.001
|
|
Previous percutaneous coronary intervention†
|
9 (27.3)
|
6 (10.2)
|
3 (4.6)
|
28 (20.0)
|
0.003
|
|
Previous CABG†
|
0
|
0
|
0
|
6 (4.3)
|
0.12
|
|
Previous valve surgery†
|
0
|
4 (6.8)
|
2 (3.1)
|
3 (2.1)
|
0.31
|
|
Pacemaker†
|
1 (3.0)
|
2 (3.4)
|
1 (1.5)
|
1 (0.7)
|
0.34
|
|
Lung disease†
|
7 (21.2)
|
9 (15.3)
|
8 (12.3)
|
21 (15.1)
|
0.71
|
|
Cancer†
|
0
|
1 (1.7)
|
3 (4.6)
|
11 (7.9)
|
0.19
|
|
Thyroid gland disease†
|
3 (9.1)
|
2 (3.4)
|
2 (3.1)
|
22 (15.8)
|
0.007
|
|
LVEF (%)
|
59.6 (9.0)
|
57.8 (9.4)
|
64.2 (10.2)
|
61.0 (7.9)
|
0.003
|
|
Medication†
|
|
Beta blocker
|
21 (63.6)
|
22 (37.3)
|
23 (35.4)
|
73 (51.8)
|
0.014
|
|
Calcium blocker
|
14 (42.4)
|
17 (28.8)
|
12 (18.8)
|
33 (23.4)
|
0.075
|
|
ACE inhibitor/Angiotensin receptor blocker
|
23 (69.7)
|
33 (55.9)
|
28 (43.1)
|
77 (54.6)
|
0.090
|
|
Acetylsalicylic acid
|
25 (75.8)
|
23 (39.0)
|
16 (25.0)
|
95 (67.4)
|
<0.001
|
|
Adenosine-diphosphate receptor antagonists
|
5 (15.2)
|
3 (5.1)
|
2 (3.2)
|
6 (4.3)
|
0.11
|
|
Warfarin
|
1 (3.0)
|
6 (10.3)
|
5 (7.8)
|
8 (5.7)
|
0.55
|
|
Novel oral anticoagulant
|
4 (12.1)
|
5 (8.5)
|
11 (17.2)
|
8 (5.7)
|
0.068
|
|
Statin
|
30 (90.9)
|
38 (64.4)
|
34 (53.1)
|
115 (81.6)
|
<0.001
|
|
Ezetimibe
|
12 (36.4)
|
4 (6.8)
|
4 (6.3)
|
22 (15.6)
|
<0.001
|
|
Nitrate
|
30 (90.9)
|
38 (64.4)
|
34 (53.1)
|
115 (81.6)
|
<0.001
|
Mean (standard deviation) or number (percentage)†. Kruskall-Wallis
test was used to analyse group differences for numerical variables and
Fisher’s Exact test for categorical variables. Abbreviations: CABG:
coronary artery bypass grafting; AVR: aortic valve replacement; MVS: mitral
valve surgery; PCI-CA: percutaneous coronary intervention or coronary
angiography; BMI: body mass index; HDL: high density lipoprotein; LDL: low
density lipoprotein; LVEF: Left ventricular ejection fraction; ACE:
angiotensin-converting enzyme.
The mean (±SD) 6MWT distances (meters) in the patient groups were CABG:
452±73, AVR: 499±84, MVS: 496±85 and PCI-CA: 519±90
([Fig. 2]). With respect to the differences
between the patient groups, the 6MWT distance in the CABG group was significantly
shorter compared to the PCI-CA group (p=0.001). This difference remained
significant after the Sidak adjustment (p=0.008). The four patient groups,
separately and combined, had significantly shorter mean 6MWT distances than the
FinFit2017 population (623±81) (all p-values<0.001).
Fig. 2 6MWT distance and VO2max of cardiac procedure patients and
FinFit2017 reference population (mean and SD). *Indicates
statistically significant difference (p<0.001) in both 6MWT distance
and VO2max, FinFit2017 as reference group. (Independent samples
t-test assuming that variances are not equal.) Abbreviations: 6MWT:
six-minute walk test; VO2max; maximal oxygen consumption; SD: standard
deviation; CABG: coronary artery bypass grafting; AVR: aortic valve
replacement; MVS: mitral valve surgery; PCI-CA: percutaneous coronary
intervention or coronary angiography; FinFit2017: population-based sample of
60–69-year-old Finnish adults.
The mean (±SD) VO2max (ml/kg/min) of the four patient groups were
CABG: 24.3±6.9, AVR: 27.6±7.2, MVS: 27.4±7.3 and PCI-CA:
27.3±6.9 ([Fig. 2]). The FinFit2017
population had significantly higher mean VO2max (31.7±6.1) than
any of the patient groups, and all cardiac patients combined (all
p-values<0.001). None of the VO2max differences between patient
groups were statistically significant.
The diastolic blood pressures at baseline and maximal heart rates during 6MWT were
significantly lower in all patient groups compared to the FinFit2017 reference
population (all p-values<0.001) ([Table 2]).
Additional information on [Table 2] is available in
the supplementary material.
Table 2 Blood pressures and heart rates (mean and SD) of
cardiac procedure patients and FinFit2017 reference population during
6MWT.
|
CABG (n=19)
|
AVR (n=36–38)
|
MVS (n=49–53)
|
PCI-CA (n=115–122)
|
FinFit2017 (n=468)
|
|
Mean
|
SD
|
Mean
|
SD
|
Mean
|
SD
|
Mean
|
SD
|
Mean
|
SD
|
|
Baseline SBP
|
134.3
|
14.5
|
140.4
|
16.2
|
140.0
|
13.6
|
142.5*
|
15.6
|
138.2
|
16.3
|
|
Baseline DBP
|
77.1*
|
12.4
|
74.8*
|
12.3
|
82.2*
|
9.9
|
81.5*
|
9.3
|
86.5
|
10.3
|
|
Max SBP
|
153.9
|
20.4
|
150.3
|
18.6
|
153.5
|
18.2
|
157.5
|
21.4
|
|
|
|
Max DBP
|
78.1
|
13.3
|
76.8
|
13.1
|
83.2
|
10.7
|
83.7
|
11.6
|
|
|
|
Baseline HR
|
68.5
|
11.3
|
73.0
|
13.3
|
71.9
|
13.3
|
71.6
|
15.1
|
|
|
|
Max HR
|
96.9*
|
12.7
|
102.1*
|
15.9
|
101.3*
|
16.2
|
105.1*
|
15.6
|
141.1
|
23.5
|
*Indicates statistically significant difference
(p<0.05), FinFit2017 as reference group. (Independent samples t-test
assuming that variances are not equal.). Abbreviations: SD: standard
deviation; 6MWT: six-minute walk test; CABG: coronary artery bypass
grafting; AVR: aortic valve replacement; MVS: mitral valve surgery; PCI-CA:
percutaneous coronary intervention or coronary angiography; FinFit2017:
population-based sample of 60–69-year-old Finnish adults; SBP:
systolic blood pressure; DBP: diastolic blood pressure; HR: heart rate.
The correlations between 6MWT distance and different parameters of PA, standing and
SB, among all cardiac patients, are presented in [Table
3]. The mean daily accumulated MVPA time (r=0.418,
p<0.001), the mean number of daily steps (r=0.417, p<0.001)
and the mean daily accumulated time of MVPA bouts lasting<5 min
(r=0.376, p<0.001) yielded the strongest positive correlations with
6MWT distance. The mean daily accumulated SB time (r=–0.283,
p<0.001) and the mean daily accumulated time of SB bouts lasting
20–60 min (r=–0.248, p<0.001) yielded the
strongest negative correlations with 6MWT distance. The mean daily accumulated time
of physical activity, sedentary behavior, standing and time in bed among cardiac
patients and the FinFit2017 population can be seen in Supplementary Figure1.
Daily steps and accumulation of SB and MVPA from different bout lengths among
cardiac patients are presented in Supplementary Table1.
Table 3 Correlations between 6MWT distance and parameters of
PA, standing and SB per day among cardiac procedure patients
(n=189).
|
Correlation coefficient (r)
|
p-value
|
|
Steps (number)
|
0.417
|
<0.001
|
|
MVPA (min)
|
0.418
|
<0.001
|
|
LPA (min)
|
0.203
|
0.005
|
|
Standing (min)
|
0.074
|
0.31
|
|
SB (min)
|
−0.283
|
<0.001
|
|
<5 min MVPA bouts (min)
|
0.376
|
<0.001
|
|
5–10 min MVPA bouts (min)
|
0.236
|
0.001
|
|
>10 min MVPA bouts (min)
|
0.282
|
<0.001
|
|
<20 min SB bouts (min)
|
-0.039
|
0.60
|
|
20–60 min SB bouts (min)
|
-0.248
|
<0.001
|
|
>60 min SB bouts (min)
|
-0.099
|
0.17
|
The correlations were measured using Spearman’s Rank correlation
coefficient. Abbreviations: 6MWT: six-minute walk test; PA: physical
activity; SB: sedentary behaviour; MVPA: moderate-to-vigorous physical
activity; LPA: light physical activity.
Discussion
To our knowledge, this study is the first one to investigate the cardiorespiratory
fitness of patients scheduled for elective CABG, AVR, MVS or PCI-CA, and to compare
it with a population-based sample of Finnish adults. The study showed that patients
who were scheduled for elective CABG had the shortest 6MWT distance of the four
patient groups. In addition, all four patient groups separately and combined, had
markedly shorter 6MWT distances and lower VO2max values than the
population-based sample of 60–69-year-old Finnish adults. For example, the
FinFit2017 population sample had a 30% higher VO2max than the
CABG group.
In a previous study of the PACO trial [22], we found
that CABG patients had the worst activity profile of the same four patient groups,
which is in line with the present results. These results suggest that CABG patients
are in a vulnerable position regarding their cardiorespiratory fitness and daily
activity profiles, as both potentially influence the recovery after the surgery
[10]
[18]. CABG
patients had lower cardiorespiratory fitness than PCI-CA patients, which is
potentially attributable to a more diffuse CAD. Of note, the CABG and PCI-CA groups
did not differ with respect to age or sex, i. e. factors known to influence
exercise capacity. The cardiorespiratory fitness in both the AVR and MVS groups was
quite similar to that of PCI-CA, which is in line with PA and SB levels from the
previous PACO trial results [22].
A recent study by Steinmetz et al. (2020) reported that an exercise-based
preoperative intervention among CABG patients can increase 6MWT distance both pre-
and postoperatively [32]. In that study, the
preoperative 6MWT distances were 443 meters in the intervention group and 446 meters
in the control group, which are close to the mean result of 452 m among the
CABG group in the present study. Therefore, these patients should be encouraged to
exercise and increase their PA. A previous exploratory study suggested that
preoperative rehabilitation, also known as prehabilitation, for frail patients
undergoing CABG or valve surgery might reduce the length of hospital stays [33].
The differences in 6MWT distances and VO2max values between the FinFit2017
population and cardiac patients, both in groups and combined, were large.
Additionally, maximal heart rate during 6MWT was about 40 bpm higher in FinFit2017
group than in any patient group. Medication (e. g. beta blockers) may
explain some differences between cardiac patients and FinFit2017 reference
population, especially regarding blood pressures and heart rates. A prior study
reported that a previous CABG or valve surgery were strongly associated with reduced
exercise capacity in elderly CAD patients [34]. This
indicates that cardiac patients’ already worse cardiorespiratory fitness
compared to other population is likely to deteriorate even further after these
procedures. Therefore, it is important to identify the patients with low
cardiorespiratory fitness before the procedure, so that they can be a target for
rehabilitation either pre- or postoperatively. The postoperative rehabilitation
program could be tailored according to the patients’ preoperative functional
capacity [15].
The mean daily accumulated MVPA time and the mean number of daily steps were the
parameters of PA and SB that yielded the highest positive correlations with 6MWT
distance among the cardiac patients, whereas the mean daily accumulated SB time
yielded the highest negative correlation. These results are in line with a study by
Vaara et al. (2020) reporting that MVPA and SB time are associated with
cardiorespiratory fitness among healthy, young men [35]. Additionally, in a previous study, participants with a higher
cardiorespiratory fitness accumulated the most MVPA among a subsample of FinFit2017
[36]. Moreover, cardiorespiratory fitness, total
daily MVPA and different MVPA bouts have been shown to associate with lower
Framingham CVD risk score, whereas total daily SB and different bouts of SB have a
positive association with CVD risk [31].
It is notable that the mean daily accumulated time of MVPA bouts
lasting<5 min had a high correlation with 6MWT distance. This
correlation was the highest regarding different MVPA bout lengths. Further, the
cardiac patients accumulated more minutes of MVPA from bouts
lasting<5 min than from longer 5–10 min
or>10 min bouts [22]. These findings
may indicate that the shortest bouts of MVPA are of crucial importance in cardiac
patients [22]. Accordingly, only the most recent
guidelines of PA have stated that also PA lasting<10 min is
associated with health benefits [37], while the
previous recommendations used the threshold of 10 min for PA sessions
beneficial for health [38].
Another interesting finding was the surprisingly strong correlation of the mean daily
accumulated time of SB bouts lasting 20–60 min with 6MWT compared to
other SB bout lengths. In a previous study of PACO trial, we found that regarding
different SB bout lengths, 20–60 min was also the one with most
variation between patient groups, even though<20 min bouts
accumulated longer mean time of SB [22]. Therefore,
especially these 20–60 min bouts of SB could be potentially targeted
with interventions, which could have a positive effect on both cardiorespiratory
fitness and even postoperative recovery.
We chose 6MWT to measure the cardiorespiratory fitness, as it is a safe, simple, and
commonly used test for cardiac procedure patients and patients with heart failure
[25]. The measurement of PA and SB were done
objectively with accelerometer for higher reliability and greater precision [39]. We combined the patients who had both CABG and
valve surgery with the corresponding valve surgery groups. This method has been used
previously [19].
This study has several strengths. We had a rather large sample of cardiac procedure
patients, and used universal and accurate measurements of cardiorespiratory fitness,
PA, and SB. In addition, we included a large reference group of
60–69-year-old Finnish adults from the FinFit2017 study. On the other hand,
we also acknowledge some limitations. The cross-sectional design of the study
prevents recognizing any causative influence. In addition, the results should be
interpreted cautiously, as the patient sample size per procedure group was
limited.
Conclusions and clinical implications
Conclusions and clinical implications
Our study revealed that patients scheduled for elective open-heart surgery or
non-surgical cardiac procedure (CABG, AVR, MVS and PCI-CA) have poorer
cardiorespiratory fitness than the population-based sample of age- and
gender-matched Finnish adults. Since patients scheduled for CABG had the poorest
cardiorespiratory fitness, they should be considered a target group for preoperative
rehabilitation. As suggested by previous studies, preoperative cardiorespiratory
fitness might influence the postoperative recovery and complications. Therefore,
recognizing patients with low preoperative fitness would allow interventions to be
targeted at them. For example, rehabilitation programs could be applied to increase
PA and thereby cardiorespiratory fitness of cardiac patients, preoperatively as well
as postoperatively. Precise information about the cardiorespiratory fitness, PA and
SB allows creating individualized rehabilitation programs based on the preoperative
fitness and activity of the patients.
