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.