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European Heart Journal Advance Access originally published online on August 16, 2005
European Heart Journal 2006 27(3):323-329; doi:10.1093/eurheartj/ehi446
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© The European Society of Cardiology 2005. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

How many patients with heart failure are eligible for cardiac resynchronization? Insights from two prospective cohorts

Finlay A. McAlister1,*, Jack V. Tu2,3, Alice Newman2, Douglas S. Lee2, Shane Kimber4, Bibiana Cujec4 and Paul W. Armstrong4

1The Division of General Internal Medicine, 2E3.24 Walter Mackenzie Health Sciences Centre, University of Alberta, 8440 112 Street, Edmonton, Alberta T6G 2R7, Canada
2The Institute for Clinical Evaluative Sciences, University of Toronto, Toronto, Canada
3The Division of General Internal Medicine, Sunnybrook and Women's College Health Sciences Centre, University of Toronto, Toronto, Canada
4The Division of Cardiology, University of Alberta, Edmonton, Canada

Received 14 April 2005; revised 10 June 2005; accepted 13 July 2005; online publish-ahead-of-print 16 August 2005.

* Corresponding author. Tel: +1 780 407 1399; fax: +1 780 407 2680. E-mail address: finlay.mcalister{at}ualberta.ca

See page 251 for the editorial comment on this article (doi:10.1093/eurheartj/ehi678)


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Acknowledgements
 References
 
Aims To determine what proportion of patients with heart failure are eligible for cardiac resynchronization therapy (CRT).

Methods and results Eligibility criteria from the trials establishing the efficacy of CRT were applied to two prospective cohorts: the first enrolled patients with newly diagnosed heart failure discharged from 103 hospitals between April 1999 and March 2001 (‘the hospital discharge cohort’); the second enrolled patients seen in a specialized clinic between August 2003 and January 2004 (‘the specialty clinic cohort’). In the hospital discharge cohort, 73 patients (3% of the 2640 patients with ischaemic or dilated cardiomyopathy and 1% of all 9096 patients with heart failure discharged alive) met trial eligibility criteria: LVEF≤0.35, QRS ≥120 ms, sinus rhythm, and NYHA class III or IV symptoms despite the treatment with ACE-inhibitor/angiotensin receptor blocker and beta-blocker. In the specialty clinic cohort, 54 patients (21% of the 263 patients with ischaemic or dilated cardiomyopathy and 17% of all 309 patients with heart failure) met these criteria. If persistent symptoms despite taking spironolactone were required for CRT eligibility, then the proportions qualifying dropped to 1% in the hospital discharge cohort and 18% in the specialty clinic cohort.

Conclusion Few heart failure patients meet trial eligibily criteria for CRT.

Key Words: Heart failure • Cardiac resynchronization therapy • Eligibility


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Acknowledgements
 References
 
Heart failure is the fastest growing cardiovascular disease and it carries a poor prognosis even with optimal pharmacotherapy. Hence, there is increasing enthusiasm for alternative options such as electromechanical therapy. Cardiac resynchronization therapy (CRT) improves haemodynamic variables, functional status, and quality of life and also reduces heart failure hospitalizations and all-cause mortality when added to optimal pharmacotherapy [ACE-inhibitors or angiotensin receptor blockers (ARBs) plus beta-blockers] in heart failure patients with ischaemic or dilated cardiomyopathy, left ventricular ejection fraction (LVEF)≤0.35, NYHA class III or IV symptoms, and evidence of electromechanical dys-synchrony (i.e. QRS duration on electrocardiogram ≥120 ms).1,2

Although it has been estimated that ~10% of heart failure patients meet criteria for CRT,3 this estimate was drawn from a limited number of studies which reported eligibility rates ranging from (i) 3% in a heart failure disease management database4 to (ii) ~5% in single-centre case series of patients either admitted with heart failure5–7 or being investigated for coronary artery disease,8 to (iii) 10% of patients with an implantable cardioverter-defibrillator,9 to (iv) between 14 and 23% of patients being evaluated at tertiary care clinics for potential heart transplantation.10,11

Given the highly select nature of trial participants, the key question of how many heart failure patients are eligible for CRT cannot be accurately answered by examining clinical trial databases or administrative databases that do not include electrocardiographic and echocardiographic data. Indeed, to answer this question properly, it requires clinically rich data from a heterogeneous population of patients with heart failure.

Given the substantial implications for those charged with estimating CRT needs at a regional level, we aim herein to address this issue by using data from two prospective cohort studies to examine the proportion of patients with heart failure who would be eligible for a CRT device in the relevant spectrum of clinical settings. The first cohort consists of patients discharged from 103 Canadian hospitals with a new diagnosis of heart failure. As the majority of patients with heart failure are hospitalized within the first year of diagnosis,12,13 this cohort provides insights into incident cases of heart failure in the population. The second cohort consists of patients with prevalent cases of heart failure seen in a specialized heart failure clinic serving a catchment area of 1.5 million Canadians.14


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Acknowledgements
 References
 
Hospital discharge cohort
As part of the Enhanced Feedback for Effective Cardiac Treatment (EFFECT) study, charts of all patients admitted to 103 hospitals (79 community hospitals, 11 small hospitals, and 13 teaching hospitals as defined by the Ontario Joint Policy and Planning Committee) in Ontario, Canada with a new primary diagnosis of heart failure were reviewed. Patients admitted for heart failure in the 3 years prior to the index hospitalization or who developed heart failure as an inpatient complication were excluded. Full details about the EFFECT study hospitals and patients, as well as variable definitions and data collection procedures, have been published.15 For the purposes of this study, only those patients who would be evaluated for CRT eligibility after hospital discharge were included in the analysis. Thus, we excluded patients who died or were transferred to another acute care hospital during the index hospitalization, those patients who were admitted with heart failure in the context of a recent myocardial infarction (MI) (within 1 month), those patients who did not have an objective measurement of their LVEF or formal NYHA assessment, those in whom treatment intent was palliative (as evidenced by orders for ‘comfort measures only’, ‘do not resuscitate’, or transfer to a palliative care institution), and those with heart failure aetiologies other than ischaemic or dilated cardiomyopathy (such as valvular heart disease, myocarditis, or peripartum cardiomyopathy).

Specialty clinic cohort
Details about the University of Alberta Heart Function Clinic cohort study have been published previously.14,16 In brief, all patients undergo a structured evaluation by a heart failure physician at baseline to confirm the diagnosis of heart failure, and data (both clinical and laboratory) are collected prospectively at all follow-up visits. Objective assessments of LVEF are obtained from all patients within 3 months of their baseline visits. For the purposes of this study, we used the same exclusion criteria as outlined earlier for the community-based cohort.

Eligibility criteria for CRT
We applied the same criteria in both cohorts to define what proportion of patients would be eligible for a CRT device. In both cohorts, a diagnosis of heart failure was only accepted if the patient met Framingham heart failure criteria.17 Extrapolating directly from the CRT trials,1,2 we defined ‘meeting trial eligibility criteria’ for CRT as having all of ischaemic or dilated cardiomyopathy, LVEF≤0.35 (assessed objectively by echocardiography, radionuclide imaging, or LV angiography), QRS duration ≥120 ms, sinus rhythm, and NYHA class III or IV symptoms despite the ‘optimal medical therapy’.

As the vast majority of the CRT trial participants were in sinus rhythm, we included this as one of the trial eligibility criteria. However, recognizing that data from small trials,18,19 a subgroup analysis within a large trial,20 and preliminary data from registry studies21 suggest that patients in atrial fibrillation also benefit from CRT, we defined those patients who were in atrial fibrillation but fulfilled all other CRT trial eligibility criteria as ‘meeting broader criteria for CRT’.

As per the CRT trials, optimal medical therapy was defined as taking an ACE-inhibitor and/or ARB plus a beta-blocker. Patients who had contraindications to any of these agents or had been unable to tolerate them were still counted as being on optimal medical therapy if they were taking the agents which were not contraindicated for them. For ACE-inhibitors/ARBs, contraindications were moderate or severe aortic stenosis, bilateral renal artery stenosis, documented allergy, serum creatinine >200 µmol/L, systolic blood pressure ≤90 mmHg, or serum potassium level >5.5 mmol/L. For beta-blockers, contraindications included second- or third-degree AV block, PR interval >240 ms, bradycardia (<60 b.p.m.) prior to initiation of rate-controlling agent, systolic blood pressure ≤90 mmHg, bronchospastic airways disease, or documented allergy. As none of the CRT trials have (at least so far) published information on the dosing of ACE-inhibitors, ARBs, or beta-blockers in trial participants or on the efficacy of CRT by ACE-inhibitor/ARB/beta-blocker dosing, we did not include ‘dosage’ in defining optimal medical therapy.

Although spironolactone was included only in the most recent CRT trials, it is beneficial in patients with NYHA class III or IV symptoms22 and thus we also examined how many patients who met ‘trial eligibility’ or ‘broader eligibility’ criteria were taking spironolactone. Any patients with prior intolerance or contraindications to spironolactone (documented allergy, serum creatinine level >200 µmol/L, or serum potassium level >5.5 mmol/L) were still counted as being on optimal pharmacotherapy if they were prescribed ACE-inhibitors/ARBs and beta-blockers.

Data analysis
We applied the trial eligibility criteria and the broader eligibility criteria outlined earlier to those patients in both cohorts who had a diagnosis of ischaemic or dilated cardiomyopathy. The baseline characteristics of those who were and were not deemed eligible for CRT were compared using the {chi}2 test for dichotomous variables and Student's t-test for continuous variables. As multiple comparisons were planned a priori, a modified Bonferroni correction was applied and statistical significance was assumed at P<0.005. All tests were two-sided.

In a sensitivity analysis, we applied the trial eligibility criteria and the broader eligibility criteria outlined earlier to those patients in both cohorts who had a diagnosis of heart failure, irrespective of aetiology. Furthermore, we also applied these criteria to patients in both cohorts who had a diagnosis of heart failure but had been excluded from our study sample.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Acknowledgements
 References
 
Hospital discharge cohort
Of the 9943 patients admitted to the 103 participating hospitals between 1 April 1999 and 31 March 2001 with heart failure, 847 (9%) died and 232 (2%) were transferred to another acute care hospital during the index hospitalization. Of those patients discharged alive, we excluded those patients who had heart failure in the context of a recent MI (n=1035, 10%), those patients who did not have an objective measurement of their LVEF (n=4297, 43%), those patients who did not have their NYHA formally assessed (n=363, 4%), those in whom treatment intent was palliative (n=225, 2%), and those with heart failure aetiologies which rendered them ineligible for CRT (n=304, including 283 with valvular heart disease, two with myocarditis, and 19 with hypertensive cardiomyopathy).

Thus, our study sample consisted of 2640 patients with a confirmed diagnosis of ischaemic or dilated cardiomyopathy and heart failure symptoms (Table 1): mean age was 73 (SD 12 years), 27% were older than 80 years, 55% were men, and 54% had left ventricular systolic dysfunction. Mean LVEF was 0.39 (SD 0.17) and 29% had a glomerular filtration rate <60 mL/min m–2. Of the 22% with prolonged QRS durations, two-third exhibited a left bundle branch block (LBBB) pattern. Patients excluded from our study sample were significantly older, more likely to be female and have diastolic dysfunction, and were significantly less likely to be treated with evidence-based heart failure medications (Table 1).


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  		Table 1 Baseline features of hospital discharge cohort
 
Only 179 patients (7% of those with ischaemic or dilated cardiomyopathy) had LVEF≤0.35, QRS ≥120 ms, sinus rhythm, and NYHA class III or IV symptoms and only 73 patients (3% of those with ischaemic or dilated cardiomyopathy) met trial eligibility criteria (Figure 1)—only 34 of these patients (1%) were also taking spironolactone. If patients with atrial fibrillation were included (broader eligibility criteria), then 106 patients (4%) would be deemed eligible for CRT—only 47 (2%) of these patients were taking spironolactone. If the CRT eligibility criteria were applied to all patients with incident heart failure discharged or transferred from these 103 hospitals (which requires assumptions that patients with a recent MI would remain in heart failure when re-evaluated two to three months later, that patients with palliative treatment intent would not be considered for CRT, that transferred patients would be discharged alive, and that patients who did not have their LVEF measured had less severe symptoms), then the proportion of patients with heart failure who would be eligible for CRT ranges from 0.4 (using spironolactone and met the trial eligibility criteria) to 1.1% (using the broader eligibility criteria).


Figure 4461
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  		Figure 1 Proportion eligible for CRT in hospital discharge cohort.

 
It deserves emphasis that, of the 2567 patients with ischaemic or dilated cardiomyopathy in our study sample deemed ineligible for CRT, 2461 (96%) were classified as such on the basis of their QRS duration, their symptom status, or their LVEF (Figure 1).

Specialty clinic cohort
Of the 309 patients seen in the clinic between 1 August 2003 and 31 January 2004 with a confirmed diagnosis of heart failure, we excluded those patients who had heart failure in the context of a recent MI (n=3, 1%), those patients who did not have an objective measurement of their LVEF (n=9, 3%), and those with valvular heart disease (n=31, 10%), myocarditis (n=2, 1%), or peripartum cardiomyopathy (n=1).

Thus, our study sample consisted of 263 patients with a cardiologist-confirmed diagnosis of heart failure and ischaemic or dilated cardiomyopathy (Table 2): mean age was 66 (SD 14), 18% were older than 80 years, 72% were men, and 70% had left ventricular systolic dysfunction. Mean LVEF was 0.34 (SD 0.16) and 56% had a glomerular filtration rate <60 mL/min m–2. Of the 54% with prolonged QRS durations, almost two-third exhibited an LBBB pattern. As with the hospital discharge cohort, patients excluded from this study sample were significantly older, more likely to be female and have diastolic dysfunction, and were significantly less likely to have ischaemic heart disease (Table 2).


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  		Table 2 Baseline features of specialty clinic cohort
 
In the specialty clinic cohort, 56 patients (21%) with ischaemic or dilated cardiomyopathy had LVEF≤0.35, QRS ≥120 ms, sinus rhythm, and NYHA class III or IV symptoms and 54 (21%) patients met trial eligibility criteria (Figure 2). As six of these patients were not taking (and did not have evidence of contraindications or prior intolerance to) spironolactone, only 48 (18%) met all CRT criteria. If one was to expand the cohort to include all patients seen in our clinic with heart failure (irrespective of aetiology and assuming that patients who did not have their LVEF measured had less severe symptoms and that patients with recent MI would remain in heart failure when re-evaluated in two to three months), then the proportion of patients with heart failure who would be eligible for CRT ranges from 16 to 20% (depending on whether the trial eligibility or the broader eligibility criteria are used and whether spironolactone use is a prerequisite).


Figure 4462
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  		Figure 2 Proportion eligible for CRT in specialty clinic cohort.

 
Akin to our findings in the hospital discharge cohort, of the 209 patients deemed ineligible for CRT, 207 (99%) were classified as such on the basis of their QRS duration, their symptom status, or their LVEF (Figure 2).


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Acknowledgements
 References
 
In summary, we found that the proportion of patients with heart failure who would be potentially eligible for CRT is much lower than the previous estimates. In our hospital discharge cohort, literature-based eligibility criteria (ischaemic or dilated cardiomyopathy, LVEF ≤0.35, QRS ≥120 ms, and NYHA class III or IV symptoms despite the treatment with ACE-inhibitors/ARBs and beta-blockers) were met by 1% of all patients with new onset heart failure who survived their index hospitalization and 3% of those patients with ischaemic or dilated cardiomyopathy. In our specialty clinic cohort, 17% of all patients with heart failure and 21% of those with ischaemic or dilated cardiomyopathy met these CRT eligibility criteria. Although only 10% of patients in the hospital discharge cohort with ischaemic or dilated cardiomyopathy had NYHA class III or IV symptoms, LVEF ≤0.35, and QRS ≥120 ms, specialty clinic patients were more likely to present with this ‘high-risk’ clinical spectrum (24% had NYHA class III or IV symptoms, LVEF≤0.35, and QRS ≥120 ms).

An important question about CRT, as with any new therapy, is whether efficacy proved in trials translates into effectiveness when applied in clinical practice. This is of particular concern for novel therapies which either have been tested in a selected spectrum of patients or depend on specialized technical expertise. Both caveats apply to CRT. Thus, although the trials proving the efficacy of CRT enrolled relatively young subjects (mean age 64), 74% of whom were male, our hospital discharge data conforms with other population-based cohort data13,23–26 in demonstrating that heart failure patients in clinical practice are almost a decade older than trial participants; indeed, the mean age of our hospital discharge patients who met CRT trial eligibility criteria was 73 years (SD 10 years). The impact of CRT in these patients (particularly given the higher peri-implantation risks in older patients) is unknown. Similarly, although experienced providers in high-volume institutions implanted CRT devices in the trials, any non-selective uptake of CRT beyond those highly specialized settings in which it was shown to be beneficial would be expected to attenuate its benefit–risk ratio and undermine its cost-effectiveness ratios.27

Some may question our use of the hospital discharge cohort to examine this issue because the CRT trials mandated 4–6 weeks of clinical stability before enrolment and some of the patients in our hospital discharge cohort are likely to improve over time after leaving hospital; indeed, two prospective studies have documented that as many as half of patients discharged after a heart failure admission have NYHA class I or II symptoms after 3–6 months.24,26 Thus, it is likely that our hospital discharge cohort overestimates the proportion of patients who would be eligible for CRT if they were re-assessed several months after hospitalization. However, it is important to highlight that this limitation biases our study to overestimating CRT eligibility rates and thus strengthens our key finding that CRT eligibility rates are lower than currently estimated.

There are some other limitations to our study; however, all of these would have also led us to overestimate CRT eligibility, thus further strengthening our conclusion that fewer patients are eligible for CRT than previously estimated in the literature. For example, although we acknowledge that not all trial participants benefited from CRT and a wide QRS does not always correlate with mechanical dys-synchrony,28 we chose QRS duration ≥120 ms to define CRT eligibility as this criterion was employed in three of the largest CRT trials2,29,30 and all patients in the CRT trials had QRS durations at least that long.1 If we were to apply a more stringent criterion (such as that employed in the CARE-HF Trial in which patients with QRS durations between 120 and 149 ms had to meet two other criteria for dys-synchrony),2 then our proportion eligible for CRT may be reduced by as much as one-third (as 52 of the 142 patients with prolonged QRS in our specialty clinic cohort had durations of 120–149 ms). Similarily, questions have been raised about whether CRT should be reserved for only those patients with prolonged QRS durations due to LBBB. Proponents of this viewpoint highlight the fact that ≤10% of CRT trial participants presented with right bundle branch block (RBBB) patterns.1 However, RBBB has been shown to be as highly associated with mortality as LBBB and a recent analysis confirmed that the degree of left ventricular activation delay and the pattern of activation were similar in patients with RBBB or LBBB.31 Although none of the current guidelines for CRT distinguish between RBBB or LBBB patterns in their eligibility criteria, even if future studies suggest that CRT should only be restricted to those with LBBB, it would again only strengthen our conclusion because even fewer patients would be eligible for CRT than we have documented.

We could also be criticized for choosing an LVEF ≤0.35 as one of our eligibility criteria (a level we chose because this was used in eight of the CRT trials).1,2 Although it is possible that newer techniques, such as tissue Doppler imaging, may improve patient selection in the future,28 such refinements are likely to reduce the proportion of heart failure patients who are deemed eligible for CRT when compared with the current QRS- and LVEF-based criteria. We defined optimal medical therapy as taking an ACE-inhibitor/ARB and beta-blocker, irrespective of dose. If optimal medical therapy was restricted to only those patients on medication doses used in the trials, then the proportion eligible for CRT would be reduced by almost one-half (in previous analyses, we have demonstrated that less than half of patients prescribed beta-blockers and/or ACE-inhibitors, even in a specialty clinic, achieve the doses used in the trials proving the efficacy of these agents).14,16 As clinicians tend to overestimate the severity of functional impairment in heart failure,28 it is possible that even fewer patients would require CRT if an objective functional assessment (such as 6-min walk test distance <450 m) were included in the evaluation. Although a number of patients in the hospital discharge cohort were excluded from our study sample as they did not have their LVEF measured or had not had their NYHA class assessed, it is unlikely that these excluded patients would be more likely to qualify for CRT than our study sample as they were older, more likely to be female, more likely to have a non-ischaemic aetiology, more likely to have a diagnosis of diastolic dysfunction, and had a higher burden of co-morbidities (Table 1)—all of which would suggest that the proportion of excluded patients who would qualify for CRT would be even lower than in those patients included in our study sample. Finally, we believe our cohorts are representative as the electrocardiographic and echocardiographic findings in both of our study samples are similar to data from comparable cohorts23,32,33 and our outcomes at 30 days and 1 year are similar to data from other cohorts.24–26

In conclusion, our study suggests that current estimates of 10% of all heart failure patients needing CRT are overstated.3 We found that <1% of patients discharged from hospital with new onset heart failure (and only 3% of those with new onset ischaemic or dilated cardiomyopathy) would be eligible for CRT; even in a specialized heart failure clinic, only one-fifth of patients are potentially eligible for CRT. In this context, we believe that the focus of guideline and physician education programmes should remain on optimizing the application of proven efficacious therapies for symptomatic heart failure (such as ACE-inhibitors/ARBs, beta-blockers, spironolactone, and specialized clinics) before consideration of CRT.


   Acknowledgements
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Acknowledgements
References
 
We thank Linda Donovan (coordinator of the EFFECT project) and the hospitals that participated in EFFECT, as well as Drs J. Ezekowitz, K. Woo, and I. Patterson, Ms L. Sanderson, Ms K. Dewart, and Ms L. Haykowsky for their expert assistance in the University of Alberta Heart Function Clinic, Drs S. Gulamhusein and S. Sivakumaran for assistance in developing CRT eligibility criteria, and Ms S. Knauer for assistance with data collection. F.A.M. is supported by the Alberta Heritage Foundation for Medical Research, the Canadian Institutes of Health Research, and the University of Alberta/Merck Frosst/Aventis Chair in Patient Health Management. J.V.T. is supported by a Canada Research Chair in Health Services Research and D.S.L. is supported by a CIHR clinician-scientist research award. The EFFECT study was supported by a grant from the Ontario Ministry of Health (Ontario Program for Optimal Therapeutics) and by a grant to the Canadian Cardiovascular Outcomes Research Team from the Canadian Institutes of Health Research and the Heart and Stroke Foundation.

Conflict of interest: none declared.


   References
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 Acknowledgements
 References
 

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