The World Health Organization defines quality of life as “an individual’s perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards and concerns”; in other words, it is a person’s perception of his or her being. The concept of health related quality of life (HRQoL) was derived from that general definition and has been increasingly attracting consideration in the provision of health care. It gains its importance in coronary artery bypass grafting (CABG) surgery from the fact that the goal of such surgery is to improve quality of life and restore general well being, mainly through alleviation of symptoms, particularly angina, which is achievable in up to 80% of the patients.¹ The simple outcome measurements of morbidity and mortality are insufficient in assessing the real and full picture of the effect of CABG or any other procedure or intervention on patients, particularly in the presence of huge pressures on health care providers to run their services under certain economic constrains but still observe high level quality assurance.² On the other hand, HRQoL assessment is rather complicated by its subjective nature.³

The goal of the present study was to assess the determinants of poor mid-term HRQoL at one year after primary isolated CABG.

PATIENTS AND METHODS

Data collection

Four hundred and sixty three patients, who underwent primary isolated CABG for multivessel disease and came for their annual follow up at the outpatient clinic during one year at Harefield Hospital, Middlesex, were approached to participate in the present study. All the clinical data were collected prospectively in line with the appended minimum dataset defined by the Society of Cardiothoracic Surgeons of Great Britain and Ireland. The collected data are regularly validated locally and validated on a 3–5 yearly cycle by the Society. Those prospectively collected clinical data were retrieved from registry database, medical notes, outpatient notes, and intensive therapy unit (ITU) charts. The data were retrospectively analysed when the patients consented to participate in the study at their outpatient visit. Institutional approval was obtained for the study.

HRQoL assessment

Assessment of HRQoL was planned in a cross sectional survey format. All eligible patients were approached and given a brief explanation of the study and, if they consented to participate, they were given three self administered questionnaires to fill in: the 36 item short form health survey (SF-36), the hospital anxiety and depression scale (HADS), and Denollet’s personality type D scale-14 (DS14).

The SF-36 is a validated questionnaire widely used in medical practice and research, which has been used with cardiac surgery patients.^4,5 It consists of 36 items measuring eight domains of HRQoL: physical functioning, social functioning, role limitations due to physical problems, role limitations due to emotional problems, mental health, energy and vitality, body pain, and general health. Two summary scores are calculated from the eight domains’ scores. The physical component summary (PCS) score summarises four domains’ scores: physical functioning, role limitations due to physical problems, body pain, and general health. The mental component summary (MCS) score summarises the other four domains’ scores: social functioning, role limitations due to emotional problems, mental health, and energy and vitality. The two summary scores were calculated according to the method described previously by Ware et al.⁶ In the absence of recognised standards of high and low HRQoL scores, we dichotomised the PCS and MCS scores into high and low after assuming an elective cut off point based on the scores of the whole study group. The lower 33% of the PCS and MCS scores were regarded as low, which is a method that has been previously used by others to categorise the HRQoL performance.⁴ The wording of six items on the SF-36 were modified slightly to make it acceptable for British patients.⁷

The HADS questionnaire is a 14 item scale originally developed to assess both anxiety and depression in an outpatient setting irrespective of any physical symptoms.⁸ It consists of seven items to measure anxiety and seven items to measure depression. Each item is scored from 0 to 3, with total scores ranging from 0 to 21 for the anxiety and depression subscales. Higher scores indicate greater anxiety and depression. The four score ranges are classified as normal (0–7), mild (8–10), moderate (11–14), and severe (15–21). To simplify the statistical analysis, we grouped patients into those with scores from 0–10 as normal and those with scores from 11–21 as being significantly anxious or depressed.

The DS14 comprises 14 questions divided into two subscales: negative affectivity (NA) and social inhibition (SI). Each has seven questions. The answer to each question is scored from 0 to 4 with total scores ranging from 0 to 28 for the NA and SI subscales. Patients are classified as having “type D personality” if both NA and SI scores are 10 or greater. The NA questions measure the tendency to experience negative emotions across times and situations and the SI questions measure the tendency to inhibit the expression of emotions and behaviours in social interactions.⁹

Statistical analysis

Patient preoperative characteristics, operative variables, and postoperative complications were compared by univariate analysis, with Fisher’s exact test or χ² test where appropriate, with regard to high and low PCS and MCS scores of the SF-36 questionnaire. Values of p ⩽ 0.05 indicated a significant difference. Variables that proved to be significant (p ⩽ 0.05) were considered potential predictors of low PCS and MCS scores and were included in the multivariate logistic regression analysis to determine the independent predictors of poor HRQoL in this group of patients.

Participants greatly outnumbered non-participants. To facilitate comparison between the two groups a non-parametric bootstrap technique was used by generating a large number of datasets by sampling with replacement from the original sample of non-participants. This method works by constructing lots of datasets (1000 in the present study) similar to the actual dataset and then using these datasets to summarise the parameters of interest. Data were initially preprocessed on Microsoft Excel 2000 (Microsoft Corp, Redmond, Washington, USA) and subsequently exported into SPSS version 11 for Windows (SPSS Inc, Chicago, Illinois, USA) and Intercooled Stata 6.0 for Windows (StataCorp LP, College Statins, Texas, USA). Bootstrap simulations were done with Resampling Stats in Excel version 2 (Resampling Stats Inc, Arlington, Virginia, USA).

RESULTS

Four hundred and thirty seven (94.4%) patients consented to participate in the study and filled in the HRQoL questionnaires. Using the bootstrap method for comparison between non-participants and participants we did not identify any significant differences in sociodemographic parameters (age, sex, marital status, education > 10 years, employment status—for example, not working and retired from work) and clinical parameters (severity of angina status, extent of coronary disease, number of grafts, and postoperative length of stay).

The mean (SD) age at surgery was 65.24 (8.51) years (range 38–84 years). They had a mean body surface area of 1.92 (0.2) m² (range 1.21–2.5 m²) and a mean body mass index of 27 (4) kg/m² (range 16.9–51.12 kg/m²). The 201 (46%) patients who had cardiopulmonary bypass during surgery had a cumulative bypass time of 83.83 (36.38) minutes and a cumulative aortic cross clamp time of 28.1 (21.38) minutes. Table 1 shows other patient characteristics including preoperative and operative variables and postoperative complications. Appendix 1 lists definitions of the variables.

The univariate analysis showed that patients with low PCS scores differed significantly from patients with high PCS scores on 10 variables, which were considered potential predictors of low PCS scores. These were diabetes, gastrointestinal tract (GIT) problems, peripheral vascular disease (PVD), dyspnoea with New York Heart Association (NYHA) functional classes III and IV, congestive heart failure (CHF), preoperative cerebrovascular accidents or transient ischaemic attacks, body mass index > 30 kg/m², infective complications, readmission to the ITU, and type D personality trait. Only three variables—GIT problems, CHF, and type D personality trait—predicted low PCS scores independently (table 2). Eighty eight patients had preoperative GIT problems: 15 patients had hiatus hernia, three of whom had previous corrective surgery; 62 patients had diagnosed peptic ulcer disease; and 11 patients had GIT bleeding with normal endoscopic results and therefore no definite diagnosis was made.

The univariate analysis showed that patients with low MCS scores differed significantly from patients with high MCS scores in 11 variables, which were considered potential predictors of low MCS scores. These were age > 70, dyspnoea (NYHA III/IV), smoking, respiratory problems, PVD, CHF, preoperative cerebrovascular accidents or transient ischaemic attacks, infective complications, pulmonary complications, type D personality trait, and anxiety. Only three variables—PVD, infective complications, and type D personality trait—predicted low MCS scores independently (table 3). Infective complications occurred in 25 patients: 12 patients developed deep sternal wound infections that required resuturing; three patients developed septicaemia; and 10 patients developed leg vein harvest wound infection.

DISCUSSION

This cross sectional survey study, planned in a descriptive correlational design, aimed at assessing the determinants of poor mid-term HRQoL at one year after primary isolated CABG. The study showed that preoperative GIT problems, CHF, and type D personality trait were independent predictors of the poor physical component of HRQoL. PVD, infective complications, and type D personality trait were independent predictors of the poor mental component of HRQoL. One interesting finding of the present study was that patients with type D personality were more than twice as likely to have poor physical HRQoL and more than five times as likely to have poor mental HRQoL than patients without type D personality, independent of all other preoperative, operative, and postoperative variables.

Most patients with cardiac disease undergo CABG for prognostic reasons irrespective of the level of their cardiac symptoms. Randomised controlled studies in the 1970s and early ’80s provided the most reliable data that support the survival benefit of CABG surgery versus medical treatment.¹⁰ This survival benefit seemed to be more apparent in moderate risk and high risk patients than in low risk patients.¹¹ However, the survival benefit was not the only favourable outcome of CABG surgery over medical treatment: relief of symptoms and improved quality of life were also obtained.¹²

In the present study, GIT problems predicted a poor physical component of HRQoL. In patients with ischaemic heart disease (IHD) diagnosed either by exercise test or angiography, most chest and epigastric pains are primarily attributed to their “more serious” IHD rather than to other known or unknown GIT problems. This may delay or mask the diagnosis, and consequently treatment, of the relatively simple GIT problem and thus the quality of life of these patients may decrease further. On the other hand, the unstable course of IHD and its accompanying psychological and physical stresses may be responsible for the relapsing behaviour of the peptic ulcer disease.¹³ Thus, such an association between the two may be synergistic, but it remains difficult to ascertain which of the two is responsible for the bigger portion of the symptom burden, particularly pain.¹⁴ We believe that among the patients in our study who reported a poor physical component of their HRQoL after CABG, GIT problems were responsible for a major portion of their symptom burden to start with.

CHF, in the present study patients, was diagnosed clinically in the preoperative period, either by the referring cardiologist or by the operating surgeon, and the patient was labelled to have CHF irrespective of left ventricular systolic function as assessed by preoperative angiographic examination. In a recent cross sectional study of patients with CHF being considered for heart transplantation, the degree of CHF was correlated with the PCS and MCS scores of SF-36. Those MCS scores were relatively more affected,¹⁵ in contrast to our study, where CHF predicted only low PCS scores. Furthermore, the degree of CHF in that study was defined by several clinical indicators, among which was NYHA class III or IV. In our study, NYHA class III or IV on its own was significant in the univariate analysis but was not an independent predictor of poor HRQoL. More in-depth research into the HRQoL of this particular group of patients showed that some sort of cross link and integration exists between the mental and physical components of this type of patients’ quality of life.¹⁶ These patients can get more depressed as a result of their physical symptoms and this in turn causes a sharp decline in both their physical and mental HRQoL.¹⁷ Evidence still justifies operating on patients with advanced ischaemic CHF on the basis that even if their left ventricular function does not improve they still experience less risk of infarction and death.¹⁸

Postoperatively, it is frustrating for patients with IHD and PVD that they are restricted not by their cardiac function anymore but by ischaemic leg pains due to intermittent claudication. It is not surprising that a recent comparative study found that the impact of PVD on almost all the SF-36 domains of HRQoL was more significant than that of the IHD itself.¹⁹ Therefore, it is not surprising that, in the present study, patients with documented PVD preoperatively reported about two and a half times worse mental HRQoL than did patients without PVD. Those patients were found to have, in addition to the physical limitation, frustration, pain, limitation in social functioning, uncertainty, and fear, all of which contributed to the psychosocial and emotional impairment.²⁰

Infective complications had a significant impact on the mental component of HRQoL. A recent study showed that surgical site infections had a major effect on the HRQoL, assessed by the 12 item short form health survey (SF-12), in a group of orthopaedic surgery patients and that was correlated with length of stay, readmission, and cost.²¹ Furthermore, surgical site wound infections, diagnosed after discharge, still had the same negative effect on self reported HRQoL, as shown by a recent big community based study of several subgroups of surgical patients after hospital discharge, including a subgroup of CABG patients.²²

A significant finding of the present study is that patients with type D personality were more than twice as likely to have poor physical HRQoL and more than five times as likely to have poor mental HRQoL than patients without type D personality trait. In fact, type D personality trait was the only common predictor for both poor physical and poor mental HRQoL outcome.

Type D personality, where the letter D refers to “distressed”, is a stable personality profile characterised by both the tendency to experience negative emotions (NA subscale) and the tendency to inhibit self expression in social interaction (SI subscale).⁹ Such people experience high levels of chronic tension and anger, depressive symptoms, poor self esteem, dissatisfaction with life in general, low positive affect, and lack of social support.²² This personality trait has been correlated with fatal and non-fatal cardiac events, poor HRQoL, and inadequate response to treatment in several types of patients with IHD, including patients after an MI and those with poor left ventricular function.^23,24 However, to our knowledge, this is the first study to show that type D personality is also correlated with poor physical and mental HRQoL after CABG surgery. Recent evidence suggested a psychosomatic relation between type D personality and several active neuroendocrine and immune mechanisms found in these patients that may explain such findings.^25,26

The prevalence of relatively high anxiety and depression scores, as measured by HADS, among our study patient group conforms to similar previous reports in the literature. These two factors did not show up in this study as significant predictors of poor HRQoL.²⁷ However, poor HRQoL is different from the psychiatric clinical diagnosis of depression, which was found to be strongly correlated with HRQoL and clinical outcomes after CABG surgery.²⁸

In conclusion, this cross sectional survey study showed that patients with type D personality are more likely to have poor physical and mental components of HRQoL. However, further prospective studies are required to shed more light on the effect of the type D personality trait on HRQoL after CABG surgery. This will help to identify the group of patients at risk of developing suboptimal HRQoL postoperatively, who can then be targeted by various programmes of psychotherapy and behavioural therapy preoperatively, and perhaps to realistically predict HRQoL outcome after CABG surgery.

One important limitation of this study is its cross sectional design. Thus, by definition the study did not measure HRQoL preoperatively (baseline), which usually is the major determinant of postoperative HRQoL.²⁹ Therefore, we believe that a longitudinal sectional study comparing preoperative with postoperative HRQoL and its relation to other variables would be more valuable in this respect. However, the study still has some value in helping realise the factors that can affect the quality of life of this particular group of patients in the mid-term.

APPENDIX