Introduction
Heart failure (HF) is a complex and debilitating clinical syndrome, characterized by symptoms of fatigue, dyspnea, diminished exercise capacity, fluid retention, reduced quality of life, and reduced survival [
1]. Cardiac resynchronization therapy (CRT), with or without an implantable cardioverter-defibrillator, is a well-established treatment in selected patients with drug-refractory HF and an electrical conduction delay [
2]. Several large-scale randomized controlled trials have demonstrated that CRT improves not only prognosis, but also patient-reported health status [
3,
4].
Patient-reported health status, including symptoms, functioning, and health-related quality of life, has become an increasingly important outcome measure in cardiac patients [
5]. Thus far, the majority of studies on health status in CRT and HF patients reported on prevalence rates or change in mean scores over time [
3]. However, change in health status of the total sample is fairly meaningless if there are in fact multiple subgroups that have different means and different patterns of change over time (i.e., trajectories) [
6]. Although it is well known that a significant proportion of patients (10–44 %) do not show improvement in symptoms or functioning from CRT [
7], no study to date has examined patient-reported health status trajectories after implantation.
Latent class analysis would permit the identification of patients reporting persistently low health status, who need additional care above and beyond standard HF management. This is of utmost importance, since poor patient-reported health status has been shown to predict mortality and rehospitalization in HF patients independent of traditional risk factors [
8]. Additionally, CRT studies have shown that the majority of established outcome measures, including New York Heart Association (NYHA) functional class and echocardiographic and hemodynamic parameters, are only marginally associated with patient-reported outcomes [
9]. By contrast, the role of psychological factors has largely been neglected in this context, although such factors may contribute more to differences in patient-reported outcomes [
9]. Knowing which factors are characteristics of patients with (persistently) reduced patient-reported health status after implantation may provide targets for intervention, thereby improving the clinical response to CRT.
Hence, the goal of the current study was to identify the trajectories and demographic, clinical, and psychological associates of disease-specific health status in the first 14 months after CRT-defibrillator (CRT-D) implantation.
Methods
Study design and participants
The sample comprised HF patients receiving a first-time CRT-D between January 2009 and August 2011 at the University Medical Center Utrecht (UMCU), the Netherlands. All patients participated in the ‘The influence of PSYchological factors on health outcomes in HEART failure patients treated with Cardiac Resynchronization Therapy (PSYHEART-CRT): A prospective, single-center, observational study’. Patients were not eligible for participation: when aged <18 or >85 years; if they had insufficient knowledge of the Dutch language; a history of psychiatric illness other than affective/anxiety disorders; cognitive impairments; or if they were on the waiting list for heart transplantation. Patients were asked to complete a set of standardized and validated questionnaires 1 day prior to implantation (baseline) and 2, 6, and 12–14 months after implantation. The study protocol was approved by the Medical Ethics Committee of the UMCU. The study was conducted in accordance with the Helsinki Declaration.
Measures
Demographic and clinical variables
Information on demographic and clinical characteristics was captured via purpose-designed questions in the baseline questionnaire and/or via patients’ medical records.
Patient-reported health status
The Kansas City Cardiomyopathy Questionnaire (KCCQ) was used to assess HF-specific health status [
10]. The KCCQ is a 23-item self-report questionnaire that taps into the following dimensions: physical limitation, symptoms, social function, and quality of life. In the current study, the following summary scores within the KCCQ were calculated: clinical summary score (KCCQ-CS), quality of life (KCCQ-QoL), and social limitation (KCCQ-SL). The KCCQ-CS is the mean of the physical limitation and symptoms score, thus representing physical health status. Scores are transformed into a score from 0 to 100, with higher scores representing less physical or social limitation, less symptoms, or better quality of life. Poor health status is defined as a KCCQ (sub)scale score of <50 points. The minimal clinically meaningful difference in KCCQ scores is 5 points [
11]. The validity and reliability of the KCCQ have previously been established and the measure was shown to be highly sensitive to clinical change in HF patients [
10,
11].
Psychological variables and personality
The Patient Health Questionnaire (PHQ-9) was used to measure depressive symptoms at baseline. This is a nine-item questionnaire with the items mirroring the diagnostic criteria for major depressive disorder. Patients are asked to rate how often each symptom has bothered them during the past 2 weeks on a scale from 0 (‘
not at all’) to 3 (‘
nearly every day’) (score range 0–27). Patients who score ≥10 points are considered to have moderate or severe depressive symptoms [
12]. The PHQ-9 is brief, responsive to change over time, and has good reliability and validity in medical outpatients and patients with HF.
The state anxiety subscale of the State-Trait Anxiety Inventory (STAI-S) was used to measure baseline symptoms of anxiety [
13]. All items are rated on a four-point Likert scale ranging from 1 (‘
not at all’) to 4 (‘
very much so’) (score range 20–80). Higher scores indicate higher levels of anxiety. A cutoff score ≥ 40 indicates probable clinical levels of anxiety. The STAI-S has shown to be a valid and reliable measure [
13].
The 14-item type D scale (DS14) was administered at baseline to assess Type D personality, which is defined as the tendency to experience negative emotions across time and situations paired with the tendency to inhibit these emotions [
14]. The DS14 comprises two subscales, ‘negative affectivity’ (e.g., ‘
I often feel unhappy’) and ‘social inhibition’ (e.g., ‘
I am a closed kind of person’), each consisting of seven items. Items are answered on a five-point Likert scale ranging from 0 (‘
false’) to 4 (‘
true’), with total scores ranging from 0 to 28 for both subscales. A standardized cutoff score of ≥ 10 on both subscales was used to identify patients with a Type D personality [
15]. The DS14 is a valid and reliable scale [
14].
Statistical analyses
All patients (n = 139) had at least 1 measurement of health status and were included in the analyses. With respect to physical health status, 112 (81 %), 13 (9 %), 12 (9 %), and 2 (1 %) patients had 4, 3, 2, and 1 measurement(s), respectively. With respect to quality of life, 111 (80 %), 13 (9 %), 13 (9 %), and 2 (1 %) had 4, 3, 2, and 1 measurement(s), respectively. With respect to social limitation, 96 (69 %). 25 (18 %), 15 (11 %), and 3 (2 %) had 4, 3, 2, and 1 measurement(s), respectively. All available data were used in the analyses.
Latent GOLD 5.0 [
16] was used to fit a number of latent class regression models in order to determine how many latent classes (i.e., health status trajectories) could be identified. Time was entered as a nominal predictor, whereas health status (KCCQ-CS, KCCQ-QoL, or KCCQ-SL) was treated as continuous outcome. For each dependent variable (i.e., KCCQ-CS, KCCQ-QoL, and KCCQ-SL), eight models were compared with an increasing number of trajectories (1–8 trajectories). To determine the optimal number of trajectories, the Bayesian information criterion (BIC) was used. The BIC is a criterion for model selection among a finite set of models, with a lower BIC indicating a better fit. In case of a difference in BIC of <3 between two consecutive models, the least complex model was preferred (i.e., with the lowest number of trajectories). Subsequently, SPSS 20.0 for Windows (SPSS Inc., Chicago, IL, USA) was used to determine which variables were univariately associated with health status class membership, while the corresponding
p values were obtained using the Step-3-Dependent analysis procedure in Latent GOLD which corrects for classification error to prevent bias [
16]. This correction is performed by obtaining estimates of the number of classification errors when assigning individuals to latent classes, which enables for proportional assignment in which individuals are treated as belonging to each of the classes with weights equal to the posterior membership probabilities. Step-3-Dependent analysis yields a separate bivariate analysis for each dependent variable (i.e., demographic, clinical, or psychological variable), which is similar to cross-tabulations (for categorical variables) and ANOVAs (for continuous variables). The Wald (=) statistic, which tests the equality of each set of regression effects across classes, was used to evaluate statistical significance. In order to correct for multiple comparisons, the Bonferroni correction was applied.
Discussion
This is the first study to examine the trajectories and associates of disease-specific health status in HF patients receiving a CRT-D device. Latent class analyses identified five trajectories for physical health status and quality of life, and four trajectories for social limitation. All health status trajectories showed an initial improvement in the first 2 months post-implantation, after which most trajectories displayed a stable pattern between short- and long-term follow-up. Low educational level, NYHA class III/IV, smoking, no use of beta-blockers, use of psychotropic medication, anxiety, depression, and Type D personality were found to be associated with poorer health status in univariate/unadjusted analyses. The relationship between ICD shocks/use of amiodarone and health status was less clear. Interestingly, subgroups of patients (12–20 %) who reported poor health status at baseline improved to a good health status level at 2-month follow-up, with these patients being able to retain their improved health status up to 14 months post-implantation.
The results of the present study indicate that levels of disease-specific health status vary considerably across subgroups of CRT-D patients, which is not surprising given the inherent heterogeneity of HF and differences in patients’ response to CRT. However, these subgroups would not have been identified if we had only calculated changes in health status for the total sample.
The finding of early improvement in disease-specific health status after CRT-D implantation followed by stabilization between short- and long-term follow-up is in line with a recent study examining mean and individual health status scores of HF patients receiving a left ventricular assist device [
17]. The early health status improvement could be the result of incipient reverse remodeling and enhanced exercise capacity induced by the implanted device. However, it could also represent a study bias, as patients participating in research might exhibit better compliance with respect to intake of medication, recommended health behaviors, etc. Finally, a placebo effect could contribute to the early health status improvement observed after device implantation. Irrespective of the cause(s) of this early improvement, our results indicate that levels of disease-specific health status at short-term follow-up are a good indicator of experienced health status at long-term follow-up. However, this needs to be confirmed in future studies, before any implications for clinical practice can be drawn with respect to advocating a one-time assessment of patient-reported health status rather than multiple assessments.
With respect to demographic characteristics, a lower educational level was found to be a significant associate of poorer health status trajectories. This result is in agreement with the finding of an earlier HF study, suggesting that poorly educated patients [
18] may require different or additional interventions to improve their health status. In addition, female gender was identified as a variable distinguishing between patients improving versus not improving from impaired to good health status between baseline and short-term follow-up. Female patients might be more prone to experience placebo effects and therefore have a greater chance of being in the improved health status trajectory compared with men. Moreover, women have shown greater echocardiographic evidence of reverse cardiac remodeling after CRT than men [
19].
With respect to clinical characteristics, only NYHA III/IV classification was found to be clearly related with classification into poorer health status trajectories, which is in line with the findings of previous HF studies in which a higher NYHA classification independently predicted impaired HF-specific health status [
20,
21]. Furthermore, results from the HF-ACTION trial found that NYHA class III was associated with a 12.73-point lower KCCQ score than NYHA II [
22]. However, NYHA classification has been criticized for its interrater reliability and validity problems, and most of the variation in health status cannot be explained by NYHA class alone [
23]. Hence, assessment of HF-specific health status might have additional value in clinical practice to assess patients’ functional status. Although we found a significant association between ICD shocks and classification into health status trajectories, we could not identify a clear direction of the relationship with the highest percentage of shocks found in patients reporting adequate to good health status. This corroborates earlier findings on the influence of ICD shocks on patient-reported outcomes, which are mixed [
24]. Finally, with respect to echocardiographic CRT response, our research group has demonstrated a large discrepancy between echocardiographic response and health status improvement after CRT [
25]. However, although echocardiographic response was not identified as an associate of poorer health status in the current study, patients reporting the lowest health status levels over time also showed the lowest percentage of response. Furthermore, echocardiographic response was identified as a variable distinguishing between patients improving versus those not improving from poor to good health status between baseline and short-term follow-up. So, patients reporting persistently poor health status after implantation might constitute end-stage HF patients, with enlarged hearts that are ‘beyond repair.’
Classification into poorer disease-specific health status trajectories was found to be particularly associated with patients’ psychological profile (i.e., use of psychotropic medication, anxiety, depression, and Type D personality) and less with their clinical status (except for NYHA classification), which seems to be consistent with earlier research [
17,
20,
26,
27]. Identification of patients with a vulnerable psychological profile would provide the opportunity to offer them appropriate treatment. It seems feasible to simultaneously screen for patients’ health status and their personality. For patients reporting poor health status without experiencing anxiety/depression or having a Type D personality, cardiac rehabilitation may suffice. While for patients reporting poor health status and having a distressed personality profile, additional psychological and behavioral intervention may be desirable. Anxiety and depression may be improved by cognitive behavioral therapy, mindfulness, relaxation therapy, and supplementary pharmacotherapy depending on patients’ preferences and needs, while intervention strategies for Type D could focus on improvement in mood, health status, health-related behaviors, and interpersonal functioning [
28].
This study is limited by the relatively small patient sample, making it underpowered to perform multivariable analyses to examine which demographic, clinical, and psychological characteristics independently predict health status class membership. However, the present study also has several strengths, including the repeated assessment of disease-specific health status at four time points and the use of a novel and innovative latent class regression technique, which permits the identification of patients reporting persistently low health status, who may need additional care above and beyond standard HF management.