Epidemiology of heart failure and ventricular dysfunction

Transcription

1 Epidemiology of heart failure and ventricular dysfunction Norman Sharpe, Robert Doughty During the past years, coronary heart disease mortality rates have declined steadily in western countries) '2 Despite this trend, which has been attributed to a combination of primary preventive measures and improved disease management, 2'3 heart failure remains an important and increasing public-health problem. 4-7 Admissions to hospital because of heart failure seem to be increasing, due partly to ageing of populations and greater survival of patients with coronary heart disease. Substantial health-care expenditure is required for heartfailure management, of which hospital-related costs account for the largest proportion. 7' Clinical research on heart failure has been mainly aimed at identifying better therapies for advanced disease. Although the n~anagement of heart failure has improved, there is no clear evidence that therapeutic advances have made any impact on the overall burden of disease in the community. Broader management strategy is required with vigorous preventive measures and earlier intervention, together with a more comprehensive disease-management approach, especially in the elderly population. This strategy should be accompanied by regular and standardised monitoring of disease trends and management practices for the most effective application of limited health-care resources. Incidence and prevalence of heart failure Epidemiological data on heart failure have been summarised elsewhere2 11 With varying methods of ascertainment, these data vary widely and some cannot be compared, but they do provide a perspective on the size of the problem and are consistent in some respects. Incidence data are limited but provide a generalpopulation range from one to five cases per 1000 population each year, increasing steeply with age to more than 30 cases per 1000 population each year among people aged 7 years or older. 9: Prevalence data are available from many more studies, with wide variation because of a great difference in methods used. Generalpopulation prevalence ranges between three and 20 individuals per 1000, increasing to between 0 and 160 individuals per 1000 among those aged 7 years or older. 9: These data show consistently the pronounced influence of age, such as the doubling-by-decade effect on incidence recorded in the Framingham study (figure 1). 12 Prognosis In the Framingham study, only 2% of men and 3% of women were alive years after diagnosis of heart failure. 1~ Hospital series, which include more severe cases, show a 1-year mortality of 30-0%3 ~'6 By contrast, annual mortality for patients with chronic stable heart failure is Lancet 199; 32 (suppl I): 3-7 Department of Medicine, University of Auckland, 4th Floor, Auckland Hospital, Grafton, Private Bag , Auckland, New Zealand (Prof N Sharpe MO, R Doughty MRCP) ( n.sharpe@auc kland.ac.nz) Correspondence to: Prof Norman Sharpe Figure 1: Average annual incidence of new cases of heart failure per 1000 population in Framinghara Heart Study Adapted with permission from ref 12. about 10% Heart-failure mortality data are comparable to those for the worst forms of malignant disease, although they are not generally taken to be so. Hospital admissions Hospital admissions because of heart failure seem to have increased during the past decade2 ~ In the USA, this increase may be attributed partly to the introduction of Medicare Diagnostic Related Groups with coding practices that reflect reimbursement rates. Although admissions have risen, total days in hospital have levelled because of decreases in the average length of stay. I1 Readmission rates of heart-failure patients remain very high, reflecting to some extent inevitable progression of underlying severe disease and possibly influenced by shorter lengths of stay and early readmission. Data on hospital discharge from New Zealand, where a centralised health information service has been created, show more than 200 hospital admissions per individuals each year with a primary or secondary diagnosis of heart failure: By diagnostic category, heart failure, cause unspecified, accounted for most people with primary diagnoses of heart failure. Secondary diagnosis of heart failure, which accounted for 30% of all admissions related to heart failure, was associated with ischaemic heart disease in most of these cases. About 40% of admissions were readmissions in the same year. Average duration of hospital stay increased with age, with about two-thirds of all bed-days taken by patients aged 7 years or older. The average duration of stay was similar for men and women until the age of years, after which women consistently had longer stays. Mortality Although the number of deaths due to heart failure has risen generally with the ageing of populations, ageadjusted rates in the elderly have also risen, 11 which Heart failure Vo s~3

2 THE LANCET I Ma,es N s Figure 2: Yearly age-specific mortality rates for heart failure in men and women per people in New Zealand Adapted with permission from ref 20. probably reflects longer survival with hypertension and coronary heart disease. Mortality statistics do, however, differ in countries with different coding practices. In the U K in particular, where heart failure cannot be recorded on death certificates as a primary cause of death, mortality data are of limited value. New Zealand data, as elsewhere, show increased mortality rates with age (figure 2). Only % of deaths occurred in patients younger than 4 years and about a third in patients younger than 7 years.2 Aetiology There is an apparent disparity in the relative importance of hypertension and coronary heart disease as causes of heart failure suggested from cohort studies and from current clinical experience. In the Framingham cohort Risk factor and sex Hazard ratio adjusted for age and risk factor (9% CI) Prevalence (%) Population attributable risk (%)* Hypertension 2.07 ( ) 3.3 ( ) Myocardial infarction 6.34 ( ) 6.01 (4-37-,2) Angina pectorie 1.43 ( ) 1-6 ( ) 11 9 Diabetes 1.2 (1.2-2.) 3.73 ( ) 6 12 Left-ventrlcular hypertrophy 2.19 ( ) 2. ( ) Valvular heart disease 2.47 ( ) 2-13 ( ) 7 *Defined as: (looxprevalencex[hazard ratio 1])/(prevalenceX[hazard ratio-i]+1), Adapted with permission from ref 21. Table 1: Population attributable risk for development of heart failure si4 study, for example, most of the population attributable risk for heart failure was due to hypertension (table 1 ). 21 Although risk factors were well characterised in that study, objective evidence of left-ventricular dilatation and systolic dysfunction was not a requirement for the diagnosis of heart failure, which lacked specificity and may have included patients with dyspnoea due to myocardial ischaemia or diastolic dysfunction. Such patients would currently be excluded from trials of heart failure treatment, which generally select mainly patients with left-ventricular systolic dysfunction of ischaemic aetiology. Many patients in trials with heart failure attributed to coronary disease may, however, have had previous important long-term hypertension, perhaps undetected or historically obscure, that eventually contributed to coronary heart disease and consequent heart failure. Alternatively, in elderly patients, hypertension and progressive left-ventricular hypertrophy may precede primary diastolic dysfunction; such patients would generally be excluded from consideration for clinical trials. Diabetes mellitus is an important risk factor for heart failure2~ that potentially contributes to coronary heart disease or directly to myocardial disease. Obesity may confound diagnosis and be a contributory cause. ='23 Almost all epidemiological data reviewed are from western countries and reliable data from Asian and undeveloped countries are sparse. Valvular heart disease remains an important cause of heart failure in many regions. In developing countries, however, coronary heart disease is increasingly evident clinically and is likely to become more important as a cause of heart failure in the next few decades. Current issues Diagnosis of heart failure and left-ventricular dysfunction Previous epidemiological data have generally used different combinations of symptoms, signs, and scoring systems, with varying sensitivity and specificity2'~ No standard definition for heart failure has been agreed, and Heart failure Vol

3 THE comparison between epidemiological and clinical data has often been inappropriate. The general availability of echocardiography for reliable assessment of leftventricular characteristics has allowed a more objective definition of heart failure that incorporates a requirement for images to show left-ventricular systolic dysfunction.24 Improvement of symptoms in response to treatment adds support to the diagnosis. It is now well recognised that symptomless leftventricular dysfunction can exist and progress for a long time before the development of overt clinical congestive heart failure. Conversely, many patients treated for congestive heart failure will have well-preserved leftventricular systolic function that may reflect inaccuracy in diagnosis, or important myocardial ischaemia or diastolic dysfunction (figure 3). Definition of significant leftventricular dysfunction by echocardiography is arbitrary. Community prevalence studies vary in the degree of leftventricular ejection fraction used to define ventricular dysfunction. Overall, the studies suggest that between 1% and 2% o f."~ adults in the community may have symptomless 'left-ventrlcular dysfunction, with leftventricular ejection fraction of less than 3%. 1 Natriuretic peptide concentrations reflect the severity of underlying ventricular dysfunction and are of prognostic value. 2~ These measurements may also help to guide optimum treatment since they reflect ventricular filling pressures Atrial (ANP) and brain natriuretic peptide (BNP) are increased early in the presence of symptomless left-ventricular dysfunction. N-terminalANP may be more accurate and stable than ANP. 26'~' BNP, secreted primarily from the cardiac ventricles, is the strongest predictor of subsequent left-ventricular function and events after myocardial infarction.2~4~'32bnp is also a sensitive indicator of heart failure as the cause of dyspnoea in patients admitted to hospitap 3 and in primary care. 34 Natriuretic peptide concentrations are increased with renal impairment and must be assessed together with serum creatinine. Natriuretic peptides will also be decreased by treatments that lower cardiac filling pressures. Age Sex Diagnosis Treatment Compliance LANCET Clinical-trial patients Communitypatients 0-70 years M>F CHF primary CHF Optimum />70 years M=F Comorbidity Concomitant treatments Variable CHF=congestive heart failure. Table 2: Clinical trials in community Measurement of natriuretic-peptide concentrations and echocardiography now offer the possibility of improved accuracy of diagnosis of heart failure and left-ventricular dysfunction and guidance for treatment. Screening of high-risk groups, especially after myocardial infarction, is justifiable to aid the selection of patients for treatment that is of proven benefit2 Importantly, for future epidemiological studies, these methods will greatly improve the reliability of diagnosis and allow a more standardised approach. Clinical impression and community reality Many clinical-trial results on heart-failure treatments are published and many other trials continue. Such trials, based mainly on secondary and tertiary hospital centres, have generally included groups of patients who may not be representative of heart-failure patients in the community (table 2). Patients in clinical trials are generally younger, higher proportions are male, and heart failure is generally the primary diagnosis. The typical patient with heart failure in the community is older than 70 years, sex distribution is more equal, and comorbidity is usual. Heart failure in the elderly may be a different syndrome from that encountered in younger patients (panel). Diagnostic difficulty is increased because the specificity of symptoms and signs is decreased with increased inactivity and comorbidity. Multiple aetiological and precipitating factors may interact and diastolic dysfunction may be more important. Pharmacokinetics and renal clearance are altered and concomitant medications enhance compliance difficulties. In clinical trials, the preferred primary endpoint, commonly influenced by regulatory requirements, is Ventricular dysfunction Heart-failure therapy $ s t rule of halves 2nd rule of halves Figure 3: Rule of halves for ventricular dysfunction and for heart-failure therapy Ventricular dysfunction: about half of patients with systolic dysfunction receive treatment for chronic heart failure and half of these seem to receive appropriate therapy. Heart-failure therapy: only about half of patients who receive heart-failure therapy have ]eft-ventricular dysfunction on investigation and only half of these are on appropriate therapy. Adapted with permission from ref 10. Heart failure Vol si

4 Diagnostic difficulty (specificity symptoms and signs are decreased) ComoriOld ~sorders common (eg, respiratory disease, physical decondition ng) Systolic vs diastolic dysfunction (distinguish ageing changes~ Interact on of multiple aetiologies and precipitating factors Altered pharmacokinetics, renal Clearance Concomitant medicat;,ons Compliance Treatment priorities--symptoms vs survival generally mortality. Quality of life measures may be neglected. Treatment aims and priorities will, however, vary, especially with increased age and frailty; relief of symptoms rather than lengthened survival will be of primary importance. Management Health-care provision varies greatly between and within different countries. In many countries there is a tension between the move to enhanced primary care and the development of specialty centres. Heart failure is common mainly in the elderly in the community, and episodes of hospital care are expensive and potentially preventable. However, the budget-holding or so-called gate-keeping roles of primary-care physicians in some cases may potentially discourage appropriate specialist referral, limit early more effective intervention, and possibly lead to greater treatment costs later. Management guidelines for heart failure have commonly been developed by specialist groups with token input from health-care professionals in primary care2 6,37 Effective implementation of well-intended evidence-based guidelines is generally lacking. With changing pattems in health-care provision worldwide, especially the decreased availability of hospital beds, health-care funders and providers are increasingly looking towards more efficient integration of primary and secondary care and the development of community-based programmes for the management of chronic diseases. An integrated management approach for heart failure, which is based in the community with ready access to secondary care, is likely to be most effective. Consistent with the aims of improvement of symptoms, maintenance of comfort and mobility, and improvement of survival is the potential to decrease health-care expenditure through lowering the number of hospital admissions. Several comprehensive management programmes with varied approaches in different settings have been shown to be effective, and local conditions will determine the most appropriate approach2 s 40 The challenge is to provide optimum management for patients with heart failure in the community, taking into account the epidemiological reality of the problem and the need for efficient application of limited health-care resources. As well as an expanded management approach for established heart failure, improved preventive measures and early intervention should be promoted. Specifically, the management of hypertension and diabetes should be more vigorous and patients with symptomless leftventricular dysfunction after myocardial infarction should be identified and treated. 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