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European Journal of Heart Failure 2005 7(2):235-242; doi:10.1016/j.ejheart.2004.05.012
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© 2005 European Society of Cardiology

Reliability and validity of the Kansas City Cardiomyopathy Questionnaire in patients with previous myocardial infarction

Kjell I. Pettersena,b,*, Aasmund Reikvamc, Arnfinn Rollagb and Knut Stavema,b

a Quality Evaluation Department, Norwegian Health Services Research Centre P.O.B. 55, NO-1474 Nordbyhagen, Norway
b Department of Medicine, Akershus University Hospital NO-1474 Nordbyhagen, Norway
c The Department of Pharmacotherapeutics, University of Oslo PB 1065 Blindern, NO-0316 Oslo, Norway

* Corresponding author. Quality Evaluation Department, Norwegian Health Services Research Centre, P.O.B. 55, NO-1474 Nordbyhagen, Norway. Tel.: +47 67929460; fax: +47 67929469. E-mail address: kjell.pettersen{at}kunnskapssenteret.no


   Abstract
Top
 Abstract
1. Introduction
 2. Material and methods
 3. Results
 4. Discussion
 References
 
Background: The Kansas City Cardiomyopathy Questionnaire (KCCQ) is a recently developed disease-specific instrument for measuring health-related quality of life (HRQoL) in patients with chronic heart failure (CHF) regardless of aetiology.

Aim: To assess the reliability and validity of the KCCQ in patients with previous myocardial infarction (MI).

Methods and results: In 754 myocardial infarction patients who were discharged alive, we collected clinical data from the patients' medical records. Two and a half years after the acute myocardial infarction, we mailed a self-administered questionnaire to the 548 patients still alive. The response rate was 74%. Internal consistency reliability, assessed with Cronbach's {alpha}, ranged 0.66–0.95. Test-retest reliability, tested with an intraclass correlation coefficient (ICC), ranged 0.41–0.83. The pattern of association between similar and dissimilar scales of the KCCQ and Short Form 36 (SF-36) supported the convergent/divergent validity of the KCCQ. Four of the KCCQ scales and the two summary scores discriminated between patients with and without medication for heart failure, and between different levels of left ventricular ejection fraction (LVEF) supporting different groups validity.

Conclusions: The Norwegian version of the KCCQ showed acceptable reliability and cross-sectional validity, which support the use of this questionnaire to measure health-related quality of life after myocardial infarction.

Key Words: Quality of life • Heart failure • Myocardial infarction

Received November 7, 2003; Revised March 31, 2004; Accepted May 12, 2004


   1. Introduction
Top
 Abstract
 1. Introduction
2. Material and methods
 3. Results
 4. Discussion
 References
 
Patients with previous myocardial infarction (MI) constitute a heterogeneous group. Many patients have few symptoms after an MI, while others have symptoms of angina pectoris, chronic heart failure (CHF), anxiety, or depression that might influence their health-related quality of life (HRQoL). Following MI, both disease-specific and non-disease-specific (generic) questionnaires have been used in assessment of HRQoL [1–3]. After acute MI, HRQoL appears to improve with time, but few studies report on long-term HRQoL [3].

The Kansas City Cardiomyopathy Questionnaire (KCCQ) is a recently developed disease-specific instrument for measuring HRQoL in patients with CHF. It reports on more dimensions and is more sensitive to change than some other questionnaires [4]. The documentation on the KCCQ is, however, limited. The reliability, validity, and responsiveness have only been reported among American patients with CHF and left ventricular ejection fraction (LVEF) <40%, and recently in Italian patients with CHF [4,5]. It is not known whether the KCCQ has similar properties in populations with less pronounced heart failure, such as survivors after MI or in other cultural settings, and if the questionnaire is sensitive to capture differences in HRQoL after MI.

In this study, we wanted to assess the reliability and validity of a Norwegian version of the KCCQ in patients with previous MI, a population at risk of developing CHF [6–8]. The study assesses patients about 2.5 years after MI, at a time when many patients have recovered from their acute MI.


   2. Material and methods
Top
 Abstract
 1. Introduction
 2. Material and methods
3. Results
 4. Discussion
 References
 
This study was a postal survey of patients who, about 2.5 years earlier had been hospitalised for acute MI.

2.1. Sample selection
We wanted to obtain a representative sample of survivors after MI. We included patients from 15 Norwegian hospitals. The participating hospitals were: 9 of 10 hospitals in Health Region I (population 850,000), and 6 hospitals from the remaining four health regions.

We included all patients discharged alive from hospital with a main diagnosis of acute MI, defined as ICD 10 (The International Statistical Classification of Diseases and Related Health Problems, tenth revision) codes I21 and I22. Each hospital included all patients treated for MI who were discharged alive during three consecutive months between August 1999 and January 2000, in total 754 patients. The treating physician's diagnosis was accepted without revision, as previously reported [9].

From the patients' medical records, we abstracted patient characteristics, previous medical history, presenting features, and treatment. For each cardiovascular drug prescribed at discharge the indication for use was classified as secondary prevention, hypertension, angina pectoris, or heart failure. Each drug was assigned one indication. In 406 patients LVEF was measured by echocardiography or multiple gated acquisition radionuclide ventriculography and categorised as <40%, 40–50% or >50%.

2.2. Postal survey
Two and a half years after the index MI, we mailed questionnaires to patients who were alive according to the hospital information systems and linkage to the national population register of Statistics Norway. We mailed the questionnaires from the hospital where the patients were discharged, with a cover letter signed by the head of the cardiology unit of the hospital. After 4 weeks, we sent a reminder to non-respondents.

At the time of the survey, 191 patients had died, eight had unknown address and seven were excluded for miscellaneous reasons. Hence, we mailed the questionnaire to the remaining 548 patients, and 408 patients (74%) completed the questionnaire. To assess test–retest reliability, we mailed a second questionnaire to 100 of the respondents 4 weeks after receiving their first response. The response rate in the retest was 81%.

2.3. Assessment of health-related quality of life
We assessed HRQoL using the KCCQ and the Short Form 36 (SF-36) questionnaires. The KCCQ is a self-administered 23-item questionnaire measuring HRQoL in patients with CHF regardless of aetiology. Each item has a five-, six- or seven-point Likert scale. The questionnaire assesses six domains of HRQoL: Physical limitation, Symptoms, Symptom stability, Social limitation, Self-efficacy and Quality of life (Table 1). We calculated each domain's score as the mean of its item scores. Domain scores were transformed to 0–100 (highest level of functioning) scales. In addition, the KCCQ domains were aggregated into two summary scores, the Functional status summary score (the mean of the Physical limitation- and the Symptoms domain scores) and the Clinical summary score (the mean of the Physical limitation-, Symptoms-, Social limitation- and Quality of life domain scores) (Table 1) [4].


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  		Table 1 Kansas City Cardiomyopathy Questionnaire (KCCQ) scales content and expected association with the Short Form 36 (SF-36) scales from a priori content analysis

 
The cultural and language adaptation of the KCCQ was done according to a recommended procedure [10]. Two people independently translated the questionnaire into Norwegian. After discussion with a third person, they agreed on a consensus version. This version was then back-translated into English by a professional translator. Comparison of the back-translation with the original English version revealed only minor discrepancies.

SF-36 is a generic HRQoL questionnaire for use across diseases and populations. It reports on eight scales: Physical functioning, Role functioning-physical, Bodily pain, General health, Vitality, Social functioning, Role functioning-emotional, and Mental health. The scales are scored from 0 to 100 (highest level of functioning). The SF-36 has been extensively validated and used in patients with many diseases including coronary artery disease and CHF [1,3,11–13]. We used the Norwegian standard SF-36 version 1.2 [14].

2.4. Statistical analyses
We present descriptive statistics with means and standard deviations, or proportions. Categorical variables were compared with chi-square tests and continuous variables with t-tests. We assessed test–retest reliability of the KCCQ using an intraclass correlation coefficient (ICC) [15]. Patients who had been hospitalised between the two assessments, and who reported change in health status, were excluded. We assessed internal consistency reliability of the scales with Cronbach's {alpha} [16].

When assessing validity, we examined two aspects of construct validity; convergent/divergent validity, and different groups validity. We evaluated convergent/divergent validity by investigating the pattern of correlation between similar and dissimilar scales of the KCCQ and the SF-36, using Spearman's rank correlations ({rho}) [17,18]. Based on item content analysis, we hypothesised which scales would correspond between the KCCQ and the SF-36 (Table 1). Corresponding scales would be expected to show substantial association ({rho}=0.61–0.80), diverging scales would be expected to show moderate ({rho}=0.41–0.60) or fair ({rho}=0.21–0.40) association [19].

We assessed different groups validity using proxies for heart failure or measures that are closely associated with heart failure, comparing scores in groups of patients categorised according to (i) medication at discharge for heart failure, angina pectoris, and other indications for medication, and (ii) LVEF.

We predicted that patients with medication for heart failure would (i) score lower on all KCCQ scales except Symptom stability and Self-efficacy than patients with other medications; (ii) score lower on Physical limitations, Symptoms, and the KCCQ functional status than patients with medication for angina pectoris; (iii) score higher on the Self-efficacy scale than the two other medication groups; and (iv) score lower on the SF-36 scales Physical functioning, Role functioning-physical, and General health than the two other groups.

LVEF >50% is considered to indicate normal left ventricular function, while LVEF <40% indicates a reduced function. On all KCCQ scales except Symptom stability and Self efficacy, and the SF-36 scales Physical functioning, Role functioning-physical, and General health, we expected patients with normal LVEF at hospital discharge to report better HRQoL in the survey, than patients with intermediate (40–50%), or reduced LVEF.

We compared mean HRQoL scores using ANCOVA, adjusting for age, gender, and education. To assess the impact of events between the index MI and the survey, we also did an ANCOVA adjusting for later MI, percutaneous coronary intervention (PCI), and coronary artery bypass graft surgery (CABG).

The SPSS statistical software version 11.5 was used for all analyses (SPSS, Chicago, IL). The Regional Committee for Medical Research Ethics and the Norwegian Data Inspectorate approved the survey.


   3. Results
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
4. Discussion
 References
 
Respondents were younger with a larger proportion of men, than non-respondents. Additionally, they had a history of less angina pectoris and CHF and used fewer cardiovascular drugs at admission for their index MI (Table 2). The number of cardiovascular drugs prescribed at discharge was equal among respondents and non-respondents. Among respondents, a higher proportion used aspirin, beta-blockers, and statins, and a lower proportion used angiotensin converting enzyme-inhibitors, diuretics, and digitalis, than among non-respondents (Table 2). There was a tendency towards a higher LVEF in respondents than in non-respondents (Table 2).


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  		Table 2 Baseline characteristics, left ventricular ejection fraction (LVEF), and drug use at discharge

 
The proportion of scorable multi-item dimensions was >90% for both the KCCQ and the SF-36. Except for the Symptom stability scale, we observed some degree of ceiling effect on all KCCQ scales, with 13% to 36% of the respondents scoring the highest possible value (Table 3). Less than 3% of the respondents scored the lowest possible value (at the floor) on any of the KCCQ scales. Mean scores on the KCCQ scales, except Symptom stability, ranged from 75 to 82 (Table 3), while mean scores on the SF-36 scales ranged from 47 to 79. With the SF-36, there was some degree of floor effect on the Physical and Emotional role functioning scales, and some degree of ceiling effect on all scales except Vitality and General health, ranging from 11% to 53% (Table 3).


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  		Table 3 Health-related quality of life scores and internal consistency reliability

 
Internal consistency reliability assessed with Cronbach's {alpha}, ranged from 0.66 to 0.95 on the KCCQ scales, compared with 0.82 to 0.93 on the SF-36 scales (Table 3). In the test–retest, the ICC on the different KCCQ scales were: Physical limitation 0.79, Symptoms 0.78, Symptom stability 0.60, Social limitation 0.73, Self-efficacy 0.41, Quality of life 0.57, KCCQ functional status 0.83, and KCCQ clinical summary 0.83.

In assessing convergent/divergent validity, the hypothesised associations generally had the highest correlations (Table 4). All the 20 predicted substantial correlations between KCCQ and SF-36 were ≥0.56, and 16 were above 0.60 (Table 4). The SF-36 scale General health had unpredicted substantial correlations with the KCCQ scales ({rho}=0.65–0.73), except for the Symptom stability and Self-efficacy scales. As expected, Symptom stability ({rho}=–0.06–0.02) and Self-efficacy ({rho}=0.20–0.27) showed at most fair correlations with the SF-36 scales.


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  		Table 4 Spearman's rank correlation between the KCCQ scales and the SF-36 scales

 
Patients with medication for heart failure scored lower on all KCCQ scales, except Symptom stability and Self-efficacy, than patients with other medications (Table 5). Patients with medication for heart failure scored lower on the KCCQ scales Physical limitations and KCCQ Functional status than patients with medication for angina pectoris (Table 5). With the SF-36, patients with medication for heart failure scored lower on the scales Physical functioning, Role functioning-physical, Bodily pain, General health, and Vitality, than patients with other medications (Table 5).


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  		Table 5 Health-related quality of life scores in patients according to medical regimen at discharge

 
Among the respondents, 256 had their LVEF measured before hospital discharge. Adjusted HRQoL scores differed between patients with normal LVEF and reduced LVEF on all KCCQ scales, except the Symptom stability and Self-efficacy scales (Table 6). Patients with intermediate LVEF scored lower on the Physical limitation, Social limitation, and the two KCCQ summary scales, than patients with normal LVEF. With the SF-36, patients with normal LVEF scored higher than patients with reduced LVEF on the Physical functioning, Role functioning-physical, and General health scales. Patients with normal LVEF scored higher on all SF-36 scales except the Bodily pain and Mental health scales, than those with intermediate LVEF (Table 6). Adjusting for later MI, PCI or CABG, did not materially change the results (data not shown).


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  		Table 6 Health-related quality of life scores grouped after left ventricular ejection fraction (LVEF)

 

   4. Discussion
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
 4. Discussion
References
 
We have shown that the KCCQ, a questionnaire designed for assessing health-related quality of life in patients with CHF, had an acceptable reliability and validity in an unselected population of patients 2.5 years after MI. Two of the KCCQ scales, Symptom stability and Self-efficacy showed less consistent results in our population, than the other scales and should be used with caution. The reliability of most KCCQ scales was above 0.7, which is frequently cited as acceptable at group level [20]. Finally, we have shown that the properties of the Norwegian adaptation of the KCCQ were similar to the original version. Few studies report on the long-term effect of MI on HRQoL [3]. Our results add to this literature.

The high response-rate and the high proportion of scorable multi-item dimensions indicate that the KCCQ was accepted in patients with previous MI. The KCCQ has previously only been tested in populations with reduced LVEF and a clinical diagnosis of CHF [4,5]. In our sample, 20% of the patients had medication for heart failure at discharge. Only 15% of patients with LVEF measured during hospitalisation had values less than 40%. Accordingly, the unadjusted mean scores in our sample were higher on most KCCQ scales, than in a group of patients with more pronounced CHF, and many of the KCCQ domains showed some ceiling effect [4]. On the Symptoms scale, the difference in score between Green and colleagues' sample and our sample was smaller [4]. This finding is in accordance with reports suggesting that patients with previous MI frequently experience symptoms consistent with CHF [21,22].

On the Self-efficacy scale, our patients scored lower than reported for patients with confirmed CHF [4]. This scale had lower internal consistency reliability and test–retest reliability than the other KCCQ scales. The Self-efficacy scale consists of only two items; knowledge of what to do if the heart failure worsens, and how to prevent worsening. These items may not be relevant for patients without a known clinical diagnosis of CHF. In our sample, patients with medication for heart failure and patients with LVEF <40% did not score higher on the self-efficacy scale than other patients. The low number of items and less relevance might explain the low reliability in this domain.

The Symptom stability scale consists of only one item about change in symptoms over the last 2 weeks. Evaluation of the Symptom stability domain requires a longitudinal study and could not be assessed with our study design. A previous study has reported the usefulness of this scale in unstable patients with known CHF [4].

The observed associations between the KCCQ and the SF-36 scales were in line with our a priori expectations. This supports the convergent/divergent validity of the KCCQ.

When assessing different groups validity, we divided patients into groups according to indication for medication at discharge and LVEF, while others have used the NYHA-classification as grouping variable [4]. Patients with medication for heart failure scored in line with our predictions compared with the other two groups, supporting the validity of the KCCQ in this population.

Our finding of an association between LVEF measured during the hospitalisation for acute MI and HRQoL during follow-up supports previous reports in studies using the generic Nottingham Health Profile, parts of the SF-36, the Duke Activity Status Index, and components from the disease-specific Minnesota Living With Heart Failure Questionnaire (LiHFe) [23,24]. In the present study, the score gradient between patients with normal, intermediate, and reduced LVEF indicated that the scales of the disease-specific KCCQ discriminated better between patients with different levels of LVEF, than scales of the generic SF-36.

Compared with the KCCQ, the SF-36 has a more comprehensive coverage of mental aspects. In contrast, the KCCQ includes topics not assessed with the SF-36. Two studies of patients with CHF have compared the KCCQ and the LiHFe suggesting that both instruments are reliable and valid [4,5]. The KCCQ, however, was more responsive and reports on more scales than the LiHFe. Additionally, the KCCQ was more responsive than the SF-36 [4].

Some limitations of the study should be noted. Patients were selected based on ICD 10 codes, hence some MI patients that were not coded as MI or with coding errors might not be included. We included patients with acute MI, as defined by the treating physician in the hospital, without further verification of the diagnosis. However, all hospitals used international criteria for the diagnosis of MI at the time of the study, i.e. at least two of three "classical" criteria, typical symptoms, typical ECG changes, and increase in serum cardiac markers. With this definition, some very early MIs with fatal outcome might not be included in our population, however, our interest was in the survivors of MI. We did not include patients with unstable angina pectoris. With the more recent definitions of acute MI, some of the patients with unstable angina would have been classified as having MI.

In assessment of different group validity, some of our groups were relatively small, reducing the power of the analyses. We measured LVEF with two different methods. Radionuclide imaging is established as a reliable reference method, and the more widely used echocardiographic assessments correlate fairly well with this method [25,26]. Our use of wide and few categories for LVEF may reduce possible measurement errors. Events during the 2.5 years lag-time between the index MI and the survey might have influenced the associations between variables from the acute phase and the current HRQoL. We did not include comorbidity in the analysis, and there might still be other important variables that were not included. Adjusting for later MI, PCI, or CABG, however, did not change the results.

We think this study supports the use of KCCQ in assessing HRQoL in patients after MI. This questionnaire, however, has some limitations and does not cover all aspects relevant to patients following MI. Hence, it might be useful to supplement with one or more instruments assessing other aspects of HRQoL, such as mental health. A generic measure, such as the SF-36, enables comparisons with patients with other disorders and general reference populations, in contrast to disease-specific questionnaires such as the KCCQ. Accordingly, the choice of assessment tools would depend on the objective of a study.

In conclusion, the Norwegian version of the KCCQ showed acceptable reliability and cross-sectional validity to encourage its further use as a disease-specific questionnaire for assessing HRQoL in patients with CHF and after MI, when many patients develop symptoms associated with CHF. Our results add to the data on the KCCQ by reporting on psychometric properties in a new cultural setting and by applying the KCCQ in a different patient population.


   Acknowledgements
 
We thank the following physicians for participating in the study: E. Anker, Innlandet Hospital, Kongsvinger; T. Dahl, Aker University Hospital, Oslo; H.P. Dørum, Innlandet Hospital, Lillehammer; T. Grønvold, Innlandet Hospital, Elverum; J. Hærem, Innlandet Hospital, Hamar; T. Indrebø, Innlandet Hospital, Gjøvik; K. Knutsen, Vestfold Hospital, Tønsberg; K.T. Lappegård, Nordland Central Hospital, Bodø; A. Mangschau, Ullevål University Hospital, Oslo; C. Platou, Levanger Hospital; J. Vegsundvåg, Ålesund Hospital; A. von der Lippe, Diakonhjemmet Hospital, Oslo; K. Waage, Haugesund Hospital; A. Zalmai, Lovisenberg Diakonale Hospital, Oslo.


   References
Top
 Abstract
 1. Introduction
 2. Material and methods
 3. Results
 4. Discussion
 References
 

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