In this study the most important determinant for a change in HRQL 1 year after CABG was preoperative HRQL. Higher preoperative physical HRQL led to improved outcomes regarding physical and mental HRQL at 1 year after surgery considering other clinical risk factors. Lower mental HRQL before surgery increased the chance to improve in mental HRQL at 1 year after surgery. The influence of preoperative HRQL on a change after surgery illustrates the vital importance of acquiring information on HRQL in the preoperative setting in order to fully inform patients on expected patient-centred outcomes.
Change in HRQL
In the majority of patients physical HRQL hardly changed, as was reflected by a mean increase of 0.7 points. Mental HRQL increased in half of patients, with a mean increase of 5.5 points.
Contrasting to our findings, other studies using the SF-36, showed a mean increase in physical HRQL ranging from 4.8 to 5.3 points and a mean increase in mental HRQL of 1.2 to 1.9 points [17, 18]. In a cohort of 1744 patients, Rumsfeld et al. assessed SF-36 before and 6 months after CABG surgery. Health related quality of life increased 5.3 and 1.9 points for physical and mental HRQL respectively. Comparable to our results, preoperative physical HRQL was identified as the most important risk factor for a change in HRQL after taking other preoperative cardiac and non-cardiac risk factors into account .
Deutsch et al. performed a study in 106 octogenarians undergoing CABG, valve surgery or CABG combined with valve surgery. They assessed HRQL by SF-36 three and 12 months after surgery and compared it to preoperative scores. At 3 months physical HRQL significantly increased with 5.1 points and mental HRQL was comparable to preoperative levels. Cardiac and non-cardiac comorbidities and procedural data were not identified as relevant risk factors for change in HRQL. Unfortunately, baseline HRQL was not considered as possible risk factor for a change in HRQL in their study .
In contrast to other literature reports, physical HRQL at 1 year after surgery increased to a lesser extent in our study, while the increase in mental HRQL was more eminent [15, 17, 18].
These differences could be due to the moment of measuring HRQL. At 1 year after surgery, which was the moment of measurement in our study, HRQL could have been affected by other factors as well, resulting in lower scores.
Furthermore, CABG is mainly performed to relieve complaints of angina, which is likely to result in improved physical functioning. In our cohort less than 10% of patients suffered from unstable angina while this was present in up to 28–61% in patients in other articles [17, 19]. It is conceivable that patients in this study suffered from fewer complaints before surgery and therefore did not notice a relevant increase in physical HRQL. Also, questions regarding mental HRQL in the SF-12 include items as feeling full of energy, calm and peaceful or feeling downhearted. Although patients did not report an improvement in questions on physical functioning, CABG surgery may have improved mental status by relieving anxiety and enhancing feelings of security and self-esteem. The increase in mental HRQL in our study could reflect the overall benefit of the surgery.
Risk factors for change in HRQL after cardiac surgery
Preoperative risk stratification based on patient-centered outcomes, such as HRQL, could have great additional value in cardiac surgery but remains challenging as well designed risk models are lacking. Possible risk factors for change in HRQL that are readily available such as comorbidities, laboratory values or LVEF have been considered by others but resulted in conflicting results. Female gender [20, 21], older age , diabetes mellitus [15, 21, 23], body mass index > 35 , low LVEF , pulmonary disease , vascular disease , EuroSCORE > 3 , deprived socio-economic status  and smoking  have been associated with worse HRQL following cardiac surgery. Older age , high social support , and EuroSCORE > 6  have been associated with better HRQL after cardiac surgery. However, several other studies, including ours, found no association between preoperative clinical factors and change in postoperative HRQL [17, 19]. Studies that included preoperative HRQL in their analysis concluded that HRQL prior to surgery was the most promising predictor for postoperative change in HRQL [15, 17, 19] and that routine preoperative assessment of HRQL should be incorporated in standard care to supplement current risk assessment [25, 26].
Some limitations should be addressed. First, the retrospective design limited the amount of available data. Comparison of responders versus non-responders showed that non-responders were older, more often male and showed a higher prevalence of diabetes mellitus, myocardial infarction, lower LVEF and higher euroSCORE. These factors can have a negative effect on postoperative HRQL [15, 20,21,22,23]. With inclusion of these patients likely greater differences in HRQL might have been present and possibly more preoperative predictors would have been identified. A possible reason for non-responding could be the method of approach during the follow up period, where questionnaires were sent by email without a reminder for unanswered questionnaires. Not all patients have email, which is more often the case for elderly. Second, obviously no SF-12 scores were available for deceased patients and these patients were excluded from the analysis. Mortality risk is highest for patients with more comorbidities. It is conceivable that this excluded group of patients had more comorbidities, leading to lower scores for preoperative HRQL and, subsequently different change scores. However, 1 year mortality was merely 2.6% and it seems unlikely this had a major influence on results. Third, only elective surgery patients were analysed limiting the generalisability and excluding patients with emergency CABG. However, the indication for emergency surgery is focussed on survival, while the main indication for elective CABG is to relieve angina. In elderly patients scheduled for elective surgery risk factors for postoperative HRQL are more essential for the decision making process than in patient presenting for emergency surgery.