Predictors of improved quality of life 1 year after pacemaker implantation

Predictors of improved quality of life 1 year after pacemaker implantation J.W. Martijn van Eck, MD, a Norbert M. van Hemel, MD, PhD, b Arjan van den Bos, MD, PhD, c William Taks, c Diederick E. Grobbee, MD, PhD, a and Karel G.M. Moons, PhD a Utrecht and Breda, The Netherlands

Background Patient's health-related quality of life (HRQoL) of pacemaker (PM) patients has increasingly become an important issue of health care evaluation. Currently, knowledge of pacing performance and technology is more or less outlined. However, determinants of poor or good HRQoL of paced patients require further elucidation. Objectives

The purpose of this study is to determine the HRQoL 1 year after PM implantation and predictors of differences in HRQoL between pre- and post-PM implantation.

Methods We quantified the mean differences between HRQoL before implantation (baseline) and 1 year later, assessed with the generic Medical Outcomes Survey 36-Item Short-Form Survey and EuroQol (EQ5D), and the PM patient-specific AQUAREL (Assessment of QUality of life And RELated events) questionnaires, in 501 consecutively included patients in the Dutch multicenter longitudinal FOLLOWPACE cohort study. Multivariable linear regression modeling was then performed to determine predictive factors of the HRQoL 1 year after implantation. Results The HRQoL of the patients increased markedly in the first year after implantation. Seventy percent of the patients considered their health improved, whereas 11% experienced a complete recovery in HRQoL. The most important predictors for improved HRQoL after 1 year were HRQoL at baseline, age, presence of cardiac comorbidities, and atrial fibrillation with slow ventricular response as indication for chronic pacing. Conclusion

In most patients receiving a PM, HRQoL increased in the first year after PM implantation. Knowledge of the predictors of this increase may aid physicians to timely differentiate between patients who most likely will benefit most from PM implantation in terms of HRQoL. (Am Heart J 2008;156:491-7.)

Since the first pacemaker (PM) implantation in 1958 in Sweden,1 much attention has been paid to pacing technology and programming to achieve individually tailored cardiac stimulation and to prolong the longevity of the PM device. Besides mortality and morbidity of paced patients, also health-related quality of life (HRQoL) has benefited from these ongoing multidisciplinary efforts. Several reports have shown statistically significant HRQoL improvement in patients after first PM implanta-

From the aJulius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands, bDepartment of Cardiology, University Medical Centre Utrecht, Utrecht, The Netherlands, and cDepartment of Cardiology, Amphia Hospital Breda, The Netherlands. The FOLLOWPACE study is granted by the Dutch College of Health Care and Health Insurances (Diemen, The Netherlands) (CVZ/VAZ grant number 01236); the Netherlands Pacemaker Registry Foundation (Groningen, The Netherlands); the Jacques H. de Jong foundation (Nieuwegein, The Netherlands), the Rodger Crowson foundation for Cardiac Arrhythmias Studies (Odijk, The Netherlands), and all Dutch pacemaker distributors and manufacturers. Submitted February 14, 2008; accepted April 28, 2008. Reprint requests: J.W. Martijn van Eck, MD, Julius Center for Health Sciences and Primary Care, Bolognalaan 12, 3584 CJ Utrecht, The Netherlands. E-mail: [email protected] 0002-8703/$ - see front matter © 2008, Mosby, Inc. All rights reserved. doi:10.1016/j.ahj.2008.04.029

tion for conventional indications. However, these studies were based on small sample sizes, focused on a specific patient population (eg, elderly patients or patients with specific pacing indications), or used a nonvalidated HRQoL questionnaire.2-8 Patient's HRQoL has increasingly become an important issue of health care evaluation. Currently, knowledge of pacing performance and technology is more or less outlined. However, determinants of poor or good HRQoL of paced patients require further elucidation. Recently, in large prospective multicenter randomized clinical trials, the pacing mode was found to be an important determinant for HRQoL.2,4-7 However, the identification of other PM and patient characteristics that possibly undermine or promote HRQoL after PM implantation can improve patient management. The Dutch multicenter prospective longitudinal FOLLOWPACE study includes a large cohort of patients with conventional reasons for chronic pacing to assess determinants that are associated with HRQoL and events occurring during hospitalization for PM implantation and follow-up.9,10 In the present study, we compare the baseline HRQoL with that after 1 year of PM treatment and analyze determinants of this change in perceived health. Our results may improve patient counseling and

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management and provide additional evidence for developing guidelines on cardiac pacing therapy.11

Methods Patients The FOLLOWPACE study was conducted in 24 PM implanting centers in the Netherlands. The design and aims of this study have been published previously.9 FOLLOWPACE is a prospective, observational, prognostic cohort study with the following objectives: First, quantification of inhospital events during and after first PM implantation and events in the follow-up period. Second, the determination of HRQoL before the first PM implantation and during follow-up. Third, to assess which patient information measured at baseline and during implantation is predictive for the occurrence of inhospital and follow-up events and HRQoL. In brief, any consecutive patient aged 18 years or older receiving a first PM for a conventional reason11 in any of the participating centers was a candidate for inclusion. Reasons for PM therapy were atrioventricular conduction disturbances, sick sinus syndrome, bradytachycardias, atrial fibrillation with slow ventricular response, heart failure, and other infrequent indications as hypersensitive sinus carotis. Patients were not eligible for inclusion if they refused to sign an informed consent or were taking any investigational drug or received a nonapproved or investigational PM. In addition, patients having diseases that were likely to cause death or significant morbidity during the study period such as cancer and immune, infectious, or degenerative diseases were excluded. This article describes the data of a cohort of 501 patients included in the FOLLOWPACE study between September 2003 and September 2006 with at least 1 year of follow-up and paired data on HRQoL before (at baseline) and at 1 year after the initial PM implantation.

Health-related quality of life HRQoL was measured at baseline and at 1 year after first PM implantation using the generic Medical Outcomes Survey 36-Item Short-Form Survey12,13 (SF-36) questionnaire, the EuroQol (EQ5D),14,15 and the validated disease-specific AQUAREL (Assessment of QUality of life And RELated events) questionnaire,16,17 which were specifically developed for PM patients. Medical Outcomes Survey 36-Item Short-Form Survey. Results of the SF-36 can be summarized according to the 9 subscales that measure physical functioning, role limitations due to physical problems, social role functioning, role limitation due to emotional problems, bodily pain as well as sense of vitality, general health, and change in health.12,18,19 Scores of each subscale can be normalized to a scale ranging from 0 to 100, with lower scores representing a lower HRQoL. These 9 subscales were further comprised to 2 scales: a physical and a mental component summary scale each of 0 to 100. EQ5D. The EQ5D or EuroQol instrument has been designed for self-completion by the respondent to report their health state on 5 dimensions: mobility, self-care, usual activities, pain/ discomfort, and anxiety/depression.14,15 It can be comprised to one value ranging from 0 to 1, with 1 representing the highest possible HRQoL. Furthermore, it includes a visual analog scale (VAS) by which the patient marks his/her own health state on a

thermometer calibrated from 0 (worst imaginable health state) to 100 (best imaginable health state).15 One specific question was added to this questionnaire: “How would you consider your change in health after your pacemaker implantation?”Thepatients weregiventhefollowingchoices: “completely recovered,”“much better,” “no change,” “somewhat worse,” or “worse.” AQUAREL. The AQUAREL questionnaire was developed as a disease-specific extension to the SF-36, for patients with cardiac rhythm disorders requiring chronic pacing. This disease-specific questionnaire has been validated and tested for reliability.17 It consists of 23 additional questions related to cardiac complaints or rhythm disorders. The results of these questions can be summarized into 3 subscales: chest discomfort, dyspnoe at exertion, and arrhythmias, each ranging from 0 to 100, with lower scores representing a lower HRQoL.

Potential predictors of HRQoL at 1 year We a priori selected a total of 9 possible predictors of HRQoL 1 year after PM implantation based on the existing literature.3,5-7,20-22 These included the patients' sex, age, and presence of several comorbidities (total cardiac comorbidity, coronary pathology, heart failure, and diabetes) assessed at implantation and based on the data in the patients' file, the indication for PM implantation, the used PM chamber system (dual- vs single-chamber pacing), and the occurrence of an adverse event at PM implantation. Data analyses. For each HRQoL instrument, we first analyzed whether the HRQoL at 1 year after first PM implantation was changed from the baseline HRQoL by using the paired Student t test. Several studies reported on the interpretation of differences in mean scores in HRQoL parameters over time and when to consider a difference as clinically relevant. Cohen23 introduced the so-called effect sizes, computed by dividing the mean difference between a post- and preintervention HRQoL scores by the preintervention SD. An effect size of b0.20 can be considered as clinically irrelevant, 0.20 to 0.49 as small, 0.50 to 0.79 as moderate, and N0.80 as large. Furthermore, we analyzed the proportion of patients experiencing at least the minimally detectable differences (MDDs) in HRQoL at 1 year.24 This MDD is an arbitrary cutoff point at half a SD higher than the patients' preintervention, in this case, the value of HRQoL before PM implantation. Previous studies showed that both parameters— Cohen's effect sizes and the proportion of patients experiencing a MDD—are valid for this purpose.25,26 We used multivariable linear regression modeling to assess which predictors contributed to the prediction of HRQoL 1 year after implantation. Continuous predictors were analyzed as linear terms because there were no indications of nonlinearity based on cubic spline analysis. The initial overall model included all potential predictors including the baseline HRQoL score. This model was then reduced to a final model by deleting (one by one) predictors with P values N.20, where the baseline HRQoL score was retained in the model, regardless of its P value.27 In contrast to etiologic research it, is common and even recommended in prediction research to use more liberal P values N.05.27,28 We explicitly chose to predict the 1-year HRQoL (outcome) with baseline (preimplantation) HRQoL as a predictor rather than to predict the change or difference in HRQoL between before and after implantation. This is because the use of change

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Table I. Baseline characteristics of the patients with paired HRQoL data (n = 501) Male Age (y) Age categories 18-60 (n = 65) 61-70 (n = 118) 71-80 (n = 214) 81-100 (n = 104) Comorbidity Overall cardiovascular history ⁎ History of coronary pathology (in isolation) Present heart failure Present diabetes Main indication for implantation Atrioventricular conduction disturbances (n = 210) Sick sinus syndrome, bradytachycardias (n = 168) Atrial fibrillation with slow ventricular response (n = 86) Heart failure (n = 13) Other (n = 24) Dual-chamber PM Adverse event at implantation †

57.6 72.8 (10.5) 13.0 23.6 42.7 20.8 65.8 26.2 9.8 14.0 41.9 33.5 17.2 2.6 4.8 75.3 12.4

All numbers are percentages except for the mean age and SD (range 22-94 years). ⁎Including history or presence of coronary pathology, cardiac valve diseases, CVA/ TIA, or peripheral vascular disease. †Wound hematoma, infection, skin dehiscence, lead dislocation, lead disconnection, lead insulation problem, pneumothorax, hemothorax, ventricular fibrillation, asystoles at implantation, or acute myocardial infarction after PM implantation.

scores does not allow for optimal control of baseline imbalance due to potential regression to the mean.29,30 Baseline values are generally negatively correlated with change because patients with low scores at baseline generally improve more than those with high scores.31 For each predictor in the final model, the slope or regression coefficient was estimated, which indicates the strength of the relationship between the predictor and the outcome.32 Also, the final models' goodness of fit was estimated using the R 2, that is, the proportion of the total variation in the outcome (ie, 1 year HRQoL) explained by the model. A low R2 indicates that despite possible statistically significant regression coefficients, most of the observed variability in the outcome is not explained by the predictors in the model.32 Because some values of subscales of the used HRQoL questionnaires were missing and missing values seldom occur at random and simply deleting these records leads to biased results,33,34 we imputed the missing values using single imputation by linear regression with the addition of a random error term. All analysis were performed using S-Plus Version 6.2.1 (Insightful Corp, Seattle, WA).

Results The mean age of the study population was 73 years, and 58% were males (Table I). Cardiac comorbidity was present in most of the patients. The mean difference in HRQoL according to the different questionnaires are depicted in Table II. All questionnaire subscales showed a significant improvement except for the SF-36 subscale “General Health.” The SF-36 subscales “Role limitation due to Physical func-

tioning” and “Change in Health” and the Aquarel subscale “Arrhythmias” showed a moderate (≥0.50) to large (≥0.80) improvement according to the effect size categories. These findings correspond with the relatively higher percentages of patients who experienced a “Minimal Detectable Difference” on these subscales (last column of Table II). The question added to the EuroQol HRQoL questionnaire (“How would you consider your change in health after your pacemaker implantation?”) was answered by 465 (92.8%) patients and showed that 10.8% of all patients considered their health status as completely recovered after PM implantation, 58.7% as much better, 18.2% as unchanged, 3.8% as somewhat worse, and 1.4% as worsened. Hence, almost 70% of all patients considered their health status at least “much better” after PM implantation. This is also reflected in the SF-36 “Change in Health.” Results of the multivariable linear regression analysis are given in Table III for the 2 summarized SF-36 scales. Predictors of the SF-36 Physical Component Summary scale 1 year after PM implantation were the “Physical Component Summary scale” at baseline (Figure 1), age at implantation, presence of heart failure at implantation, and implantation of a dual-chamber PM system. Neither the grouped overall cardiovascular comorbidities nor the separate components of this group, that is, cardiac valve disease, cerebrovascular accident/transient ischemic attack, or peripheral vascular disease, did have any predictive value on the change in the assessed HRQoL, except for coronary pathology. The occurrence of an inhospital adverse event did not have any impact on how HRQoL was perceived 1 year after the PM implantation. Figure 1 graphically shows the association between the “Physical Component Summary scale” at baseline and 1 year after PM implantation. A regression coefficient or slope of 0.53 means that for each unit increase in the Physical Component Summary scale, the HRQoL 1 year after implantation increases with 0.53. The 3 AQUAREL summary scales, the EuroQol, and the VAS largely showed similar results, that is, the same predictors and similar associations. Only, for the AQUAREL questionnaire subscales “Chest Discomfort” and “Dyspnoe at Exercise,” the main indication for implantation—notably atrial fibrillation with slow ventricular response—was an extra predictor for postimplantation HRQoL: the regression coefficient was 4.85 (95% CI 1.45-7.16) with atrioventricular conduction disturbances as reference category (Table III).

Discussion Health-related quality of life increased significantly in most of the patients in the first year after first PM implantation. Almost 70% consider their quality of life completely recovered or much better than before

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Table II. Changes in HRQoL between baseline and 1 year after PM across the different HRQoL questionnaires and subscales (n = 501) Paired t test

SF-36 subscales Physical functioning Social functioning Role limitation due to physical problems Role limitation due to emotional problems Mental health Energy vitality Pain General health perception Change in health Physical component summary score Mental component summary score AQUAREL subscales Chest discomfort Dyspnoe at exertion Arrhythmias EQ5D Total end score EuroQol VAS score

% of patients reaching the MDD †

Baseline

1y

Change

95% CI

P

Cohen's effect size ⁎

53.26 70.79 29.99 50.26 69.11 50.09 70.24 56.93 38.24 39.94 44.41

57.91 77.81 52.21 69.93 74.39 59.33 76.33 57.41 66.14 42.43 48.70

4.65 7.02 22.2 18.38 5.28 9.24 6.09 0.48 27.90 2.49 4.29

2.27-7.03 4.18-9.85 17.84-26.60 13.69-23.06 3.56-7.00 7.16-11.31 3.21-8.97 −1.50-2.47 24.55-31.25 1.49-3.48 3.07-5.50

b.001 b.001 b.001 b.001 b.001 b.001 b.001 .633 b.001 b.001 b.001

0.16 0.23 0.56a 0.41 0.26 0.42 0.23 0.02 1.12b 0.24 0.33

25 24 39 34 30 36 24 28 59 35 35

75.11 53.99 65.93

79.31 57.06 79.28

4.20 3.07 13.35

3.17-5.24 2.12-4.02 11.77-14.93

b.001 b.001 b.001

0.34 0.27 0.68a

39 37 59

0.69 63.39

0.75 69.16

0.07 5.77

0.04-0.09 3.95-7.59

b.001 b.001

0.22 0.34

30 35

⁎An effect size of b0.20 can be considered as clinically irrelevant, 0.20 to 0.49 as small, 0.50 to 0.79 as moderate,a and N0.80 as large.b †Percentage of patients that experienced an MDD (see text).

implantation. The most marked differences were seen in the SF-36 subscales “Role limitation due to Physical functioning” and “Change in Health” and the AQUAREL subscale “Arrhythmias.” Remarkably, the patients' “General Health” does not appear to be different between preand postinitial PM implantation. It is possible that this subscale of the SF-36 questionnaire is not sensitive enough to detect the benefits of chronic pacing. As expected, the most important predictor seems to be the HRQoL before implantation, followed by age, cardiac comorbidity, the use of a dual-chamber PM system, and the indication for PM implantation. The uniqueness of the FOLLOWPACE study relies on the assessment of pre- and postimplantation HRQoL and its predictors in patients without specific selection criteria reflecting daily practice. Hence, our results have a general and wide applicability. The FOLLOWPACE study ended, including patients in September 2007. Therefore, the results could not describe the entire cohort because some patients did not have 1 year of follow-up. Furthermore, the cohort size of patients included in the FOLLOWPACE with 1 year of follow-up at time of the start of the analysis was 623, meaning that 122 patients were not able to fill out one or more questionnaires. A total of 80 patients did not fill out any questionnaire, neither at baseline nor at 1 year. Fifteen of 42 patients that filled out a baseline questionnaire died during follow-up. The reason why the remaining 27 cases did not fill out a second questionnaire remained unclear. In this cohort, there were no patients lost to follow-up. Analysis on

factors related to this inability only revealed higher age as an important factor. There were no other differences in baseline characteristics between patients that were or were not able to fill out the questionnaires. To appreciate our findings, several aspects should be considered. First, we applied the SF-36 and EuroQol questionnaire to assess HRQoL. Although these instruments are widely used, they are not disease-specific questionnaires and are not sensitive enough to determine all aspects of HRQoL in PM patients. For this reason, we also used the AQUAREL questionnaire, specifically designed for HRQoL measurements in PM patients.16,17 Second, statistically significant mean differences in HRQoL do not always reflect clinically relevant changes in HRQoL. Therefore, we estimated the so-called effect sizes in our analysis.23 Although frequently used, these effect sizes are still based on arbitrary cutoff values. However, to our knowledge, this is currently the best method to describe clinical relevance of differences in HRQoL. To further address the clinical relevance of our results, we quantified proportions of patients experiencing at least the MDD in improved HRQoL at 1 year.24,26 Third, to allow for more valid linear regression analysis on predictors of HRQoL 1 year after the initial implantation, missing values in several HRQoL subscales had to be imputed. This imputation had to be performed for a maximum of 18.8% missing values in the SF-36 subscale “Bodily Pain” at baseline. The imputation itself did not have any influence on the distribution of the means in all studied subscales. Baseline patient information regarding

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Table III. Multivariate linear regression analysis on SF-36 Physical and Mental component summary scales, AQUAREL subscales, the EuroQol, and the VAS at 1 year after the initial implantation (n = 501) Regression coefficient (slope)

95% CI ⁎

P

0.53 −0.19 −3.80 2.36

0.44-0.62 −0.27 to −0.10 −6.79 to −0.80 0.28 to 4.44

bb.001 bb.001 .013 .026

0.37 0.03

0.29-0.45 0.01-0.05

bb.001 .027

0.39 0.02

0.32-0.47 −0.002 to 0.04

bb.001 .082

REF 1.05 5.31 −0.83

−2.18 to 3.02 1.68-10.12 −14.25 to 10.47

.624 b.001 .386

0.43 −0.14 −3.03

0.36-0.50 −0.22 to −0.07 7.47 to −1.33

bb.001 bb.001 .001

REF 0.01 4.85 0.03

−1.20 to 2.83 1.45-7.16 −13.71 to 14.12

.552 bb.001 .086

0.46

0.40-0.53

bb.001

EuroQol at 1 y (R2 = 0.22) EuroQol at baseline Age at implantation

0.35 −0.01

0.27-0.43 −0.01 to 0.004

bb.001 b.001

VAS at 1 y (R2 = 0.18) VAS at baseline Female sex Age at implantation Present heart failure at implant

0.32 3.84 −0.27 −6.72

0.24-0.40 1.06-6.62 −0.40 to −0.14 −11.24 to −2.20

bb.001 .007 b.001 .004

SF-36 physical component subscale at 1 y (R2 = 0.32) SF-36 physical component scale at baseline Age at implantation Present heart failure at implantation Dual-chamber vs single-chamber system SF-36 mental component subscale at 1 y (R2 = 0.18) SF-36 mental component scale baseline Coronary pathology in history AQUAREL chest discomfort at 1 y (R2 = 0.24) AQUAREL chest discomfort at baseline Coronary pathology in history Main indication Atrioventricular conduction disturbances Sick sinus syndrome or bradytachycardias Atrial fibrillation Heart failure AQUAREL dyspnoe at exercise at 1 y (R2 = 0.33) AQUAREL dyspnoe at exercise at baseline Age at implantation Cardiac history Main indication Atrioventricular conduction disturbances Sick sinus syndrome or bradytachycardias Atrial fibrillation Heart failure AQUAREL arrhythmia at 1 y (R2 = 0.30) AQUAREL arrhythmia at baseline

REF, reference group. ⁎95% CI of the regression coefficient (B).

comorbidities was entered in our data set based on patients hospital files; however, no data on mental wellbeing (ie, depression) was gathered and could, therefore, not be analyzed. Finally, this study was an observational prognostic cohort study and, thus, lacks a (randomized) control group of patients who did not receive a PM and were followed up for 1 year. This was obviously not an issue for the analysis of the predictors of HRQoL 1 year after PM implantation. However, for the comparison between HRQoL pre- and postimplantation, placebo effect or spontaneous recovery or regression to the mean could play a role and partially explain the observed increase in HRQoL after 1 year. However, we believe it is unlikely that the observed major changes in HRQoL are

solely attributable to regression to the mean or a spontaneous recovery of the underlying rhythm disorder. Nevertheless, only a randomized pragmatic trial comparing 2 similar patient groups requiring PM therapy, one receiving a PM and the other group not, could address this issue properly. To our knowledge, such a trial is not yet undertaken, most likely because of ethical constraints. However, in the next studies on HRQoL, we intend to validate the entire model and the observed predictors in other data sets. Although most previous studies investigated HRQoL changes as a result of different PM modes in specific patient populations (ie, elderly patients or patients with specific pacing indications or modes), our results are in

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Figure 1

be sufficient to improve their HRQoL and may require closer follow-up postimplantation. The authors would like to thank all the patients included in this study and all cardiologists and pacemaker technicians of the following hospitals in the Netherlands: Bernhoven Hospital, Veghel; Amphia Hospital, Breda; Reinier de Graaf Ziekenhuis, Delft; Diaconessen Hospital, Meppel; Medical Center Alkmaar, Alkmaar; Hospital group Twente, Hengelo; VieCuri Medical Center, Venlo; Zaans Medical Center, Zaandam; St Antonius Hospital, Nieuwegein; Alysis Rijnstate Hospital, Arnhem; Vlietland Hospital, Schiedam; Deventer Hospital, Deventer; VU Medical Center, Amsterdam; Twenteborg Hospital, Almelo; Spaarne Hospital, Heemstede; Westfries Hospital, Hoorn; Atrium Medical Center, Heerlen; Rijnland Hospital, Leiderdorp; University Medical Center, Groningen; Maxima Medical Center, Veldhoven; Antonius Hospital, Sneek; Hospital De Tjongerschans, Heerenveen; Canissius Wilhelmina Hospital, Nijmegen; Diaconessen Hospital, Leiden.

Scatterplot and slope of the linear association between the SF-36 Physical Summary Score (SF-36 PCS) measured at baseline and 1 year after PM implantation (n = 501). The formula of the regression line is SF-36 PCS 1 year after the PM implantation = 20.05 + 0.53 * SF-36 PCS at baseline.

agreement with these previous studies.2-5,7 In our study, PM mode (dual- vs single-chamber PM implantation) was a predictor for improved HRQoL 1 year after the implantation as well as atrial fibrillation with slow ventricular response as main indication for chronic pacing. Interestingly, these results were solely found for the 2 AQUAREL subscales, “Chest Discomfort” and “Dyspnoe at Exercise,” and not for the generic HRQoL instruments (SF-36 and EuroQol), indicating that the AQUAREL questionnaire is indeed a better or rather more subject sensitive instrument for assessing HRQoL in PM patients, as compared with the generic SF-36 and EuroQol questionnaires.

Conclusion In most patients receiving a PM, HRQoL increased in the first year after PM implantation. Almost 70% of patients consider their HRQoL much better or even completely recovered. The most important predictors of HRQoL after 1 year are the HRQoL at baseline, patients' age, cardiac comorbidities at baseline, and atrial fibrillation as the indication for PM implantation. These predictors may aid physicians to discern between patients who will most likely benefit from PM implantation and those in whom PM implantation alone may not

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