Discussion
Percutaneous coronary intervention on SVGs has been in continuous
evolution over recent decades. It currently represents approximately 6%
of all percutaneous coronary procedures in the US22.
Patients undergoing PCI in SVGs have more early and late adverse cardiac
events23, which might predispose them to a
deterioration of their HRQoL and increase the burden for healthcare.
This is the first study to show a better HRQoL after PCI in no-touch
versus conventional vein grafts.
Few studies have evaluated HRQoL outcomes after PCI in a vein
graft. Our
group11 used the EQ-5D-3L questionnaire to examine
HRQoL in individuals after CABG, and concluded that the graft patency
was associated with better HRQoL. However, the HRQoL outcome of the
no-touch or conventional vein graft technique was not evaluated
separately.
The present study evaluated HRQoL using the RAND-36 health survey in
patients treated with no-touch or conventional vein grafts. Our primary
analysis showed significant differences between the two treatment groups
in four of the eight RAND-36 domains (PF, GH, EF, EW), indicating better
HRQoL in the no-touch group at a mean of 5.4 ± 3.6 years after PCI. The
effect size estimates (Cohen’s d ) indicated better HRQoL in the
no-touch group in five domains (PF, P, GH, EF, EW). Effect sizes were
small, but the difference in scale scores on the physical functioning
and energy/fatigue scales was approximately 10 points, which has been
referred to as a medium group difference24. The
energy/fatigue domain showed the largest difference (p=0.010; ES=0.43).
One possible explanation for these results could be the higher in-stent
restenosis rate after PCI in the conventional group, and its
consequences in terms of quality of life. Further clarifications in
terms of clinical outcomes are under investigation with a larger patient
cohort (ClinicalTrials.gov no. NCT03999398).
Few studies have estimated the minimal clinically important difference
(MCID) for the RAND-36/SF-36 scales in cardiopathic populations. Bjorner
et al. evaluated MCID for energy/fatigue in individuals with chronic
conditions including congestive heart failure, and recommended a MCID of
5–10 points25. In the present study, the difference
between the no-touch and the conventional group was 9.6 points for
energy/fatigue, indicating a clinically important difference.
The patients who received a
no-touch vein graft estimated their physical health (PF, RP, P, GH) more
positively than the conventional group, although the differences in RP
and P were not significant. The positive effect on physical health in
the no-touch group was further confirmed by the PSM analysis, showing
statistically significant differences in two domains (PF, GH).
Comparison of the average treatment effects according to the PSM
analysis (Table 6) and the differences between the treatment groups
according to the primary analysis (Table 5) showed that the results were
roughly equal. The general similarity between the primary analysis and
the PSM indicates that no predictor variable behaved as a confounder in
the analysis.
The confirmed positive effect on the physical health components supports
the clinical relevance of the HRQoL difference between the two
techniques; since, the scales that primarily measure physical health are
associated particularly with the health condition in cardiac and
cardio-operated patients26.
Hokkanen et al.6used RAND-36 to examine both short-term (1 year) and long-term (12
years) changes in HRQoL in patients treated with CABG. Their 1-year
results27 demonstrated that all RAND-36 domains
improved significantly; however, this improvement was significant only
among patients under 75 years. At the 12-year follow-up, significant
improvements were observed in all RAND-36 domains except general health.
Moreover, patients younger than 65 years at baseline maintained their
physical health status after 12 years, whereas the older patients
reported a pronounced decrease in both the physical and mental component
summary scores. The present study was similar in terms of follow-up
time, although it was not prospective and did not analyse changes over
time. However, an analysis of our results for patients under 65 years
showed RAND-36 scores comparable to those reported by Hokkanen et al.,
particularly in the no-touch group. It is noteworthy that the general
health domain did not improve in the earlier study, with a mean value of
54.2 at baseline and 54.5 at 12 years6. Our study
found a significant difference in general health between the no-touch
and conventional group, with a
mean value of 61.0 in the no-touch group; the effect size was in the
upper range of a small difference (ES=0.41). This result can be
explained by the already-known fact that no-touch vein graft patients
tend to have reduced atherosclerosis over time and lower rates of
adverse cardiac events28, with an expected positive
impact on general health.
Few studies have evaluated HRQoL after PCI using the SF-36 or the
RAND-3629, 30. In 2008, Günal et
al.30 reported SF-36 results for octogenarians treated
with PCI that partially differ from our results. Their study group
showed a markedly lower mean value on the physical functioning scale (41
± 28) than we found in our study, which may be explained by the
demographic characteristics of the study population (patients over 80
years). However, scores on the pain, role-emotional, and emotional
well-being scales were comparable with the results for the conventional
group in the present study. Cohen et al.29investigated HRQoL using the SF-36 after either a PCI or a CABG at 1
month, 6 months, and 1 year after the intervention, finding no change in
HRQoL at the 1-year follow-up. Their SF-36 results after 1 year were
equivalent to those observed in the no-touch group in our study, except
for physical functioning, which was better in the study by Cohen et al.,
and mental health/emotional well-being, which was better in our study.
This comparison between the PCI of a native vessel31and the PCI of a no-touch vein graft suggests the hypothesis that
no-touch SVGs are as suitable for PCI as a native coronary artery. A
better HRQoL score thus correlates with the reduced intimal damage and
subsequent atherosclerosis in the long term during the harvesting of the
no-touch veins18.
The main limitation of the present study is the small number of
individuals in the no-touch group (n=48), despite the high response rate
(87.3%). However, the power was sufficient to detect significant
differences between the two study groups on four of the eight RAND-36
scales. We also calculated effect sizes, which are independent of sample
size, to estimate the magnitude of group differences. A second
limitation is the retrospective study design, which means that HRQoL
data before the operation were not available.
Another possible limitation is the
difference between the study groups in terms of follow-up time.
Individuals treated with no-touch had shorter follow-up time than the
conventionally treated patients (4.4 vs. 5.9 years; see Table 1).
According to Hokkanen et al.6, a main predictor of
HRQoL after CABG is the initial age at CABG, with declining RAND-36
scores at the 12-year follow-up in patients who were older than 65 years
at the time of the CABG. Our study groups showed comparable age at time
of CABG, PCI, and HRQoL follow-up, indicating that age was not a
confounding factor in the comparison between the two groups.