Impact of stable coronary artery disease on quality of life: the patient’s perspective

Third Division of Cardiology
Medical University of Silesia
Katowice, POLAND

Impact of stable coronary artery disease on quality of life: the patient’s perspective

by M. Tendera, Poland

Patients with stable coronary artery disease (CAD) most often present with effort angina. Angina is an important predictor of cardiac death and hospitalization and to a large extent determines health-related quality of life (QOL) in this patient group. However, the relationship between prognosis and QOL is complex, since asymptomatic patients may be at high risk and QOL may be determined by multiple factors other than angina. Thus, in order to achieve optimal quality of care, treatment goals should include both prevention of clinical events and improvement of QOL. Patients with stable CAD generally have a good prognosis for survival, making QOL even more important. Therefore, QOL assessment should be regarded as an essential measure of the impact of the disease, not only in domains related to physical functioning, but also to psychological well-being and social functioning. Negative disease perception by the patient and poor social support, which may be accompanied by depression or a high level of stress, should always be considered when QOL is assessed. In summary, QOL in CAD patients should be considered as an essential component in patient assessment and follow-up, and should influence the choice of treatment strategy, as well as being a goal per se of management in stable CAD.

Medicographia. 2014;36:25-30 (see French abstract on page 30)

Management standards come from randomized controlled trials (RCTs) that objectively measure the outcomes related to the efficacy and safety of an intervention. Stable coronary artery disease (CAD) is no exception to this rule. However, studies provide statistical data, giving a probabilistic view and describing the impact of treatment on the outcome in the whole study group or in subgroups rather than in an individual subject. It is now generally accepted that the benefits of different treatment strategies and risks related both to the disease itself and to the different therapeutic options should be viewed from an individual patient’s perspective. One should take into consideration not only the physical aspects of the disease, but also the impact it has on mental status and social functioning. These principles are the cornerstone of the “person-centered care” concept that is being dynamically developed in management of different cardiovascular diseases.1

From the patient’s viewpoint, treatment success is determined by 2 factors: survival and quality of life (QOL). Thus, any therapeutic intervention should be aimed at improvement of survival, provision of symptomatic relief, increase in functional activity, and enhancement of overall well-being.

There is no direct relationship between the real threat and the perceived threat of death. This is especially true in patients with stable CAD. It is due to the fact that patients with stable CAD may have various clinical presentations. Many of them present with angina pectoris, but a significant proportion may be asymptomatic. Angina is an important predictor of cardiac death and hospitalization, and also to a large extent determines health-related QOL. The asymptomatic group includes patients with known CAD, defined as having had a history of myocardial infarction (MI) with or without left ventricular systolic dysfunction; patients after percutaneous coronary interventions (PCI) or coronary artery bypass grafting (CABG); and also patients with diabetes mellitus, whose clinical course is often asymptomatic. The prognosis of asymptomatic patients may vary, and their QOL may depend on symptoms other than angina, eg, heart failure, or be determined by psychosocial factors.

It needs to be emphasized that a substantial proportion of CAD patients also suffer from hypertension, heart failure, diabetes mellitus, chronic obstructive pulmonary disease (COPD), peripheral artery disease (PAD), and other comorbid conditions. Both CAD and comorbidities have an impact on a patient’s clinical outcome and health-related QOL.

While, from the patient’s perspective, prognosis is related to esoteric future events that may or may not happen, QOL refers to the present time and answers the general question: “To what extent does the disease prevent me from living a normal life?” Therefore, QOL is often perceived as more important than prognosis. On the other hand, a threat of coronary hospital admission or death related to CAD, even in low-risk patients, may dominate a patient’s thoughts and dramatically impair QOL. Thus, a comprehensive approach is necessary to take into account the real and the perceived disease burden in stable CAD patients, as health-related QOL is an important health measure and an indicator of outcome.

Instruments used to measure QOL in patients with stable CAD

Both disease-specific and generic assessment tools have been used to study QOL in patients with CAD. The Seattle Angina Questionnaire (SAQ)2,3 is the most widely used instrument to measure the disease-specific QOL domains in patients with stable CAD. However, not all aspects of QOL are directly related to CAD symptoms. Therefore, the use of general QOL evaluation tools is also warranted in order to have a wider view of the patient’s QOL. Of those tools, the 36-item short-form health survey (SF-36) has the most established role.4

The instruments most commonly used to assess health-related QOL in patients with stable CAD are listed in Table I. Kim and Bernstein5 provide an extensive overview of different tools used to measure QOL in patients with this condition. Here, only the SAQ and SF-36 will be described in more detail.

Table I
Table I. Disease-specific and generic tools commonly used to
evaluate quality of life in patients with coronary artery disease.

Modified after reference 5: Kim and Bernstein. Expert Rev Pharmacoeconomics
Outcomes Res. 2003;3:637-650. © 2013, Expert Reviews.

The SAQ is a self-administered, disease-specific tool comprising 19 questions, evaluating 5 dimensions of health status in patients with CAD, and generating 5 different scales: physical limitation, stability and frequency of angina, treatment satisfaction, and disease perception. In each scale, the worst status or response to treatment on follow-up is assigned 1 point, and the best, 5 points, except for angina frequency, for which the best is assigned 6 points. All scales are treated separately and there is no overall assessment.2,3

The SF-36 is also self-administered, but is a general QOL assessment tool developed within the Medical Outcomes Study (MOS) and includes 8 health domains reflecting a patient’s general functional status and well-being. The 36 questions included in the questionnaire cover such domains as physical, social, and emotional functioning; pain; general health; and vitality. The scores are transformed to a 0-100 scale, with higher values meaning better functioning. The components can be clustered to address the physical and mental aspects of QOL.4

The comparison of generic and disease-specific tools has been extensively studied. It appears that the 2 kinds of tools are supplementary rather than competitive. For example, Dougherty at al6 compared the usefulness of 3 different tools for QOL assessment in patients with stable CAD receiving medical therapy, in a longitudinal randomized study. The disease-specific SAQ was able to reflect the differences in angina as measured by the Canadian Cardiovascular Society (CCS) grading scale, in all subscales except treatment satisfaction. The SF-36, which is a general tool, not specific to CAD, was able to detect the difference in the CCS class only in the general health subscale. On the other hand, in a group of 253 consecutive patients with CAD followed for 2 years, QOL evaluation using generic instruments was unable to detect an apparent improvement in the CCS class. Although the authors conclude that the major part of health related QOL is unresponsive to change in chest pain symptoms, their negative results might also have been due to the use of tools that are not sensitive enough to detect a relevant change.7

Determinants of QOL in patients with stable CAD

Norris et al8 found that age, coronary anatomy, ejection fraction, physical limitation, angina frequency, and gender explain more than 50% of the variance in health-related QOL. Among these factors, physical limitation due to angina and the influence of gender are worth a comment.

It is important to acknowledge that physical disability caused by angina pectoris has an impact on prognosis as well as on QOL. In a cohort of 5558 outpatients with CAD, QOL scores in the domains of physical limitation and angina frequency were found to independently predict all-cause mortality on 1-year follow-up. Odds ratios for mild, moderate, and severe physical limitation were 1.5, 2.0, and 4.0 versus minimal limitation (P<0.001; Figure 1).9 For angina frequency, respective values were 0.8, 1.2, and 1.6 (P=0.078). Hospital admissions for an acute coronary syndrome (ACS) were significantly more frequent in patients with severe angina frequency (P=0.016).9 Gender appears to be an important predictor of QOL in patients with CAD. Norris et al10 compared the changes in QOL in 3392 male and female patients included in the APPROACH registry (Alberta Provincial PRoject for Outcome Assessment in Coronary Heart disease) at 1 year after the first cardiac catheterization. Using the disease-specific SAQ questionnaire, they found that men reported significantly better health related QOL than women in all 5 dimensions. They pointed out that sex-related differences cannot be explained by traditional clinical variables, and more research in this area is needed, especially to study psychosocial adjustment of women following treatment of CAD.10 Worse QOL outcomes in female as compared with male patients have also been reported elsewhere.11,12

Figure 1
Figure 1. Kaplan-Meier survival curves by range of Seattle Angina Questionnaire
(SAQ) physical limitation score.

After reference 9: Spertus et al. Circulation. 2002;106:43-49. © 2002, American Heart Association.

Other factors, such as ethnic origin, obesity, mental status, social support, and disease perception, may also have an impact on QOL. However, most important is the fact that resting heart rate (HR), which is a well-established prognostic factor in the general population as well as in patients with CAD13 may also be a determinant of QOL in this patient population.

In a large study of CAD patients of different ethnic backgrounds, 1 year after coronary angiography proving the presence of CAD, South Asian patients residing in Canada showed a worse QOL response than subjects of European background. This may be due to the fact that in South Asian individuals, CAD tends to be more diffuse, or may be due to a suboptimal treatment applied in this population.14

Obesity negatively affects QOL in patients with CAD. In a large cohort (N=5262) from the APPROACH registry, patients with severe obesity showed significantly lower QOL scores, with regard to physical function and overall health-related QOL. Depression symptoms accounted for an important part of this phenomenon.15 Stafford et al16 found that depressive symptoms significantly undermine QOL in patients with CAD despite successful revascularization or medical therapy. They suggest that treatment of depression may be a valuable addition to the overall management plan in this patient population. The same phenomenon was reported by Dudek et al,17 who investigated a group of 156 patients after successful PCI. In the entire study group, QOL up to 1 year post intervention was significantly improved. However, there was a significant correlation between QOL, severity of depressive symptoms, and parameters describing depressive changes in thinking.

Disease perception plays an important role in patients with CAD. In a study of 193 patients recently hospitalized for CAD, Stafford et al18 found that negative illness beliefs, particularly those associated with potential consequences of the disease, were predictive of higher levels of depressive symptomatology. On the contrary, positive beliefs led to better QOL outcomes. Older and socially disadvantaged patients had a more negative disease perception, and therefore a close monitoring of this aspect of the illness should be carried out in this group. They can also potentially benefit the most from counseling.

Perceived social support and stressful life events have independent significant effects on QOL in patients with CAD. This is especially important in female patients, in whom both physical and psychological domains were associated only with social characteristics, especially with perceived social support.19

Resting HR is a well-established risk factor for clinical events in patients with CAD.13 Andrikopoulos et al20 studied a group of 280 patients with CAD and coexisting COPD. They found that subjects with a resting HR >70 beats per minute (bpm) had more frequent angina attacks (P<0.001), were less satisfied with treatment (P<0.001), and had lower QOL (P<0.001). In this specific population, an inadequate HR control was due to the underuse of β-blockers. However, a significant proportion of patients with CAD who receive β-blockers still have suboptimal HR control. In the large contemporary CLARIFY registry (ProspeCtive observational LongitudinAl RegIstry oF patients with stable coronary arterY disease),21 comprising over 33 400 patients with chronic stable CAD, 44% had a HR ≥70 bpm. Among almost 25 000 patients treated with β-blockers, over 41% had a HR ≥70 bpm. In this study, a HR ≥70 bpm was independently associated with higher prevalence and severity of angina. One can expect that appropriate HR control may positively alter QOL in these patients.

Whether lowering of HR improves QOL is currently being specifically investigated in a substudy of SIGNIFY (Study assessInG the morbidity-mortality beNefits of the If inhibitor ivabradine in patients with coronary arterY disease).22 In SIGNIFY, for which results are expected in 2014, QOL is assessed in patients presenting with angina CCS class II or higher, by means of SAQ and the visual analog scale, based on long-term follow-up.

Impact of different therapeutic strategies on QOL

A large number of studies have addressed the impact of different therapeutic strategies on health-related QOL in patients with stable CAD.

In 301 patients with symptomatic CAD aged 75 years and over included in the TIME study (Trial of Invasive versus Medical Therapy in Elderly),23 QOL was measured at baseline and 6 months after revascularization or administration of optimalmedical therapy, using CCS classification, the Rose Angina Score,24 and the 36-item short-form health survey (SF-36).4 At baseline, severity of angina significantly correlated with physical domains and daily activities. At the 6-month follow-up, antianginal treatment not only relieved angina and improved physical components, but also lead to an improvement in mental and social domains.23

In a large cohort of patients from the APPROACH registry (N=3392), QOL evaluation by SAQ revealed that patients who underwent coronary revascularization (either by CABG or PCI) fared better than those treated medically.25 It must be emphasized, however, that these findings pertain to the data acquired about 15 years ago and, in light of progress in both drug and interventional therapy, must be interpreted with caution.

More recent research, however, appears to lead to the same conclusions. A post hoc analysis of the MASS II trial (Medicine, Angioplasty or Surgery Study), which randomly assigned CAD patients to CABG, PCI, or medical treatment, revealed that on 1-year follow-up, QOL was better in patients who received revascularization than in those treated medically. CABG patients had a greater and progressive improvement in QOL. The differences were detected even though the assessment tool used was a generic test (SF-36).26

Krecki et al reported a better improvement in QOL on 1-year follow-up in patients treated surgically versus those receiving medical treatment. This was true with respect to physical functioning, bodily pain, vitality, mental health, and mental component summary scores, as assessed by the SF-36 questionnaire.27

The results of some other studies did not support the view that revascularization is superior to medical treatment in terms of QOL change.

In the COURAGE trial (Clinical Outcomes Utilizing Revascularization and Aggressive druG Evaluation),28 QOL was assessed in 1domain only. The SAQ treatment satisfaction score tended to increase over time both in PCI-treated patients and in those receiving medical treatment. There were no differences between treatment groups over time.

The SYNTAX study (SYNergy between percutaneous coronary intervention with TAXus and cardiac surgery) compared different outcomes in patients with CAD treated with PCI or CABG. QOL was measured at baseline, and thereafter at 1, 6, and 12 months, using SAQ and SF-36 questionnaires.29 In both groups, scores in all subscales were significantly higher after 6 and 12 months. At the end of follow-up, there were no between-groups differences in physical limitation, treatment satisfaction, and angina stability as measured by SAQ. There was some advantage of CABG with regard to angina frequency and SAQ-assessed QOL, but the absolute differences were small.

Several studies compared the impact of 2 different revascularization methods (CABG and PCI) on QOL. In ARTS-II (the Arterial Revascularization Therapies Study part II), QOL was assessed using the SF-36.30 This study, conducted for up to 36 months post intervention, showed that both stenting and CABG result in an improvement in QOL and angina severity. With reduction of restenosis rates seen with drug-eluting stents (DES), QOL in this group showed a positive response similar to that observed in CABG patients.29

Hlatky et al31 carried out a very long (10- to 12-year) observation of patients who underwent either CABG or PCI. CABG patients showed a significantly greater improvement in QOL over the first 3 years of follow-up. Afterwards, the advantage of CABG over PCI was no longer present. Recurrent angina was the main factor causing a reduction in all QOL measures throughout the study.

The impact of cardiac rehabilitation programs on the QOL and well-being of patients with CAD is not well established. For example, Tavella and Beltrame32 studied 221 consecutive patients post coronary intervention. They found an improvement both in disease-specific and generic scores, but no impact of participation in a rehabilitation program on QOL. Michalsen et al33 studied the effect of a structured stress reduction and modification program on QOL and psychological outcomes. They detected no difference between program participants and patients receiving standard care. Finally, it needs to be emphasized that mood disturbances may have a strong influence on QOL, to the extent that they prevail over the effect of the treatment method itself.34

Summary and conclusions

Looking at the disease and its treatment from the patient’s perspective is a matter of increasing significance. Therefore, self-reported health-related QOL has become an important outcome measure. In patients with stable CAD, QOL has to be taken into account to the same degree as the prognostic considerations.

Although angina is a major determinant of QOL, other factors, such as mental status, and the presence of depression in particular, as well as social support, disease perception, or the presence of comorbidities, may play a major role. Medical history taking alone is unlikely to allow an adequate QOL assessment. Thus, special tools should be used for QOL evaluation. Both disease-specific and generic tools are useful in patients with stable CAD. In summary, QOL in CAD patients should be considered as an essential component in patient assessment and follow-up, and should influence the choice of treatment strategy, as well as being a goal per se of management in stable CAD.

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Keywords: CAD treatment; coronary artery disease; person-centered care; quality of life; stable angina