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The changing course of aortic valve disease in Scotland: temporal trends in hospitalizations and mortality and prognostic importance of aortic stenosis

Colin Berry, Suzanne M. Lloyd, Yanzhong Wang, Alyson MacDonald, Ian Ford
DOI: http://dx.doi.org/10.1093/eurheartj/ehs339 1538-1547 First published online: 30 October 2012

Abstract

Aims To investigate the contemporary clinical course of aortic valve disease types.

Methods and results We performed a retrospective population-level epidemiological study of hospitalized care in Scotland from 1 January 1997 to 31 December 2005 using electronic case identification of hospital admissions and deaths. Time-to-event analyses were performed using Cox Proportional-Hazards models. A total of 19 733 adults with an index hospitalization and a final diagnosis of non-congenital aortic valve disease were identified. Aortic stenosis, aortic insufficiency, mixed aortic valve disease, or unspecified aortic valve disease occurred in 13 220 (67.0%), 2807 (14.2%), 699 (3.5%), and 3007 (15.2%), individuals, respectively. The majority of hospitalizations occurred in elderly persons aged 80 and older. In total, 9981 (50.6%) patients had died by 31 December 2006. When compared with aortic stenosis, the risk of death was less with aortic insufficiency [hazard ratio (95% confidence interval) 0.79 (0.74, 0.84)] and mixed aortic valve disease [0.83 (0.74, 0.93)]. Female gender, admission year, and hypertension were associated with lower mortality in patients with aortic stenosis. Patients with aortic stenosis had increased risk of death or heart failure (adjusted P < 0.001). Of all, 3673 (19.4%) patients had a first aortic valve replacement of whom 73.2% had aortic stenosis, 11.9% aortic valve disease (unspecified),10.0% aortic insufficiency, and 4.9% aortic stenosis with insufficiency. Patients with aortic stenosis with insufficiency had increased likelihood of aortic valve replacement [1.19 (1.02, 1.38)]. Age, female gender, and co-morbidity reduced the likelihood of aortic valve replacement.

Conclusion The incidence of aortic valve stenosis has substantially increased in Scotland in recent years. Aortic stenosis predicts morbidity and mortality when compared with other types of aortic valve disease.

  • Aortic valve
  • Aortic stenosis
  • Epidemiology
  • Prognosis

Introduction

Aortic valve disease includes, aortic stenosis, aortic insufficiency, and mixed aortic valve disease, which are distinct pathologies leading to reduced survival.13 A stenosis of the aortic valve obstructs left-ventricular outflow leading to pressure-overload hypertrophy, exercise intolerance, and heart failure. Aortic insufficiency is a different condition. The haemodynamic problem is volume overload and unlike aortic stenosis, aortic insufficiency may develop either acutely or progressively over several years.

Despite its importance, little is known about the contemporary clinical course and comparative prognostic significance of different types of aortic valve disease.4 The public health burden of heart valve disease increases with age,5,6 and until recently, valve replacement was the only treatment which could improve prognosis.7,8 However, new treatment options are emerging. Transcatheter aortic valve implantation (TAVI) improves prognosis in inoperable patients when compared with standard medical care,9 and in high-risk patients, outcomes after TAVI are similar to outcomes after surgical valve replacement.10 For these reasons, information on the burden of aortic valve disease and its prognosis are urgently required.

Accordingly, we studied the changing course of each type of aortic valve disease in Scotland and addressed the following questions: first, what are the temporal trends in hospitalizations for aortic stenosis, aortic insufficiency, and mixed aortic valve disease at a population level? Secondly, what is the clinical course of each type of aortic valve disease and what is the comparative prognostic significance of one type of aortic valve disease vs. another. Thirdly, what are the demographic factors and co-morbidities which might influence prognosis for each type of aortic valve disease? Finally, what are the temporal trends and predictors of aortic valve replacement?

In order to answer these questions, we studied contemporary information extracted from national databases for hospital admissions and deaths in Scotland with follow-up over a 10-year period.

Methods

Record linkage

We obtained data from the Information Services Division (ISD) of National Health Service (NHS) Scotland, an extract of linked data containing all hospitalization and mortality records of all patients in Scotland who have a hospitalization code for heart valve disease since 1981. The national record linkage scheme for discharges from Scottish hospitals and deaths11,12 has been used in other studies of cardiovascular epidemiology.13,14

In brief, the ISD of the NHS in Scotland collates data on all hospital discharges using the Scottish Morbidity Record Scheme (SMR01). These are then linked to the death records held by the General Register Office for Scotland. Diagnoses in the records are coded using the International Classification of Diseases codes (ICD9 or ICD10) and operations are coded using Office of Population, Censuses, and Surveys Classification of Surgical Operations and Procedures Fourth Revision (OPCS-4) codes.

Definitions of disease

Acquired aortic valve disease was taken to represent all forms of non-congenital heart disease. We identified the first report of aortic valve disease in a principal (primary) or secondary discharge diagnostic position with the following codes: I35 [‘I350’ (aortic stenosis), ‘I351’ (aortic insufficiency), ‘I352’ (aortic stenosis with insufficiency), ‘I358’ and ‘I359’ (other and unspecified aortic valve disease)] from ICD10. The diagnostic categories of aortic valve disease are available from ICD10 (but not ICD9). Aortic valve replacement was identified using OPCS-4 codes ‘K261-K264’ and ‘K268’. Aortic valve replacement included elective or non-elective operations. Aortic balloon valvuloplasty was identified using OPCS- codes ‘K265’ and ‘K352’.

Patients with congenital aortic valve disease (n = 203, codes ICD-9 746, ICD10 Q22, Q23) and endocarditis (n = 485, codes I011, I33, I38–I39) were excluded. Pulmonary and tricuspid valve disease was not studied since disease of these valves is strongly associated with congenital heart disease and pulmonary hypertension, respectively.

Data were available in the Scottish national databases from 1 January 1981 and complete records up to 31 December 2006 were obtained. Our analyses are based on new incident cases of aortic valve disease from 1 January 1997, from which point all records are fully coded using ICD10. OPCS-4 included a code for aortic valve replacement. To ensure that all patients in our database had a minimum of 1 year of follow-up, we included all index cases up to 31 December 2005 and incorporated follow-up until 31 December 2006.

Co-morbidity and hospital admission history

We identified the baseline medical history from events prior to the index event, co-morbidities for the index event, and various individual and composite clinical outcomes and also outcomes for valve intervention by surgery or balloon valvuloplasty. Co-morbidity was defined as concomitant or prior diagnoses (within 5 years) of the index hospitalization with aortic valve disease for the following diseases: diabetes (ICD-10 codes E10–E14); respiratory disease (J10–J18, J40–J47); cancer (C00–C99); hypertension (I10); renal disease (N17–N19); and rheumatoid arthritis (M05–M06).

Cardiovascular hospitalization history was identified from cardiac diagnosis or procedures separately on whether they are concurrent or in a prior admission within 5 years of the index admission. Cardiovascular events during follow-up were also identified. The ICD-10 codes used to identify these events are listed in the Supplementary material online.

The following cardiac procedures were included: aortic valve replacement (OPCS-4 codes K261–K264, K268), coronary artery bypass grafting (CABG) (OPCS-4 codes K401–K404, K408–K414, K418–K419, K421–K424, K428–K429, K431–K434, K438–K439, K441–K442, K448–K449, K451–K456, K458–K459, K461–K465, and K468–K469; OPCS-3 codes 323 and 324), and percutaneous coronary intervention (PCI) (OPCS-4 codes K491–K493, K498–K499, K501–K503, K508–K509, K511, and K518–K519).

Socio-economic status

Socio-economic status was determined using the Deprivation Category score.11 This is an ordinal index of socio-economic status in Scotland based on the place of residence, as defined by postcode. The score includes contemporary census-based information on the percentage of the population within attributes related to poverty (e.g. % without a car, % subject to overcrowding, % male unemployment, and % low social class). The 5-point scale was recategorized for analysis as 1 (high socio-economic status/affluent, scores 1–2) to 3 (low socio-economic status/most deprived, scores 4–5).

Quality assurance

Quality assurance analyses of heart valve disease codes in our data set were performed using SMR01 data for 2004–2006. Aortic valve diagnoses [106 rheumatic aortic valve diseases, 135 non-rheumatic aortic valve diseases, but excluding 108 multiple valve diseases (whether rheumatic or not)] were recorded at 3-digit level with an accuracy of 87.9% (95% confidence interval 76.7%, 99.0%), and at the 4-digit level with an accuracy of 81.8% (95% confidence interval 68.7%, 95.0%), and had a sensitivity of 70.7% and completeness of 80.5%.

Statistics

Continuous variables are summarized as mean (standard deviation) and categorical data as count (percentage). Time to event analyses were undertaken using Cox Proportional-Hazards models. Time was derived from the date of index admission to the date of the event; for those subjects not experiencing an event a censoring date of 31 December 2006 was used. Backwards selection was used to identify the independent predictors of events using the baseline characteristics available (age, gender, calendar year of index diagnosis, deprivation, co-morbidity, and hospitalization history). The events studied were all-cause mortality, aortic valve replacement, myocardial infarction plus all-cause mortality, heart failure plus all-cause mortality, and stroke/transient ischaemic attack plus all-cause mortality. Only subjects with the full set of baseline characteristics recorded were included in this analysis.

Differences in time to event between aortic valve disease types were investigated using unadjusted and adjusted Cox-Proportional-Hazards models. The unadjusted models included a covariate for disease type only and the adjusted models included all independent predictors identified from the backwards selection for each endpoint.

Incidence of aortic valve disease was age–sex standardized based on the age and sex distribution of the population in 2005. Incidence was presented as the standardized number of events per 1 million of the population. We also investigated the incidence of the specific types aortic valve disease within four age groups (<60, 60–69, 70–79, and over 80 years). We plotted the standardized incidence over time to investigate any trends over time.

Results

Patient characteristics and temporal trends in hospitalizations for each type of aortic valve disease in Scotland

A total of 19 733 patients aged ≥18 years had an index hospitalization with a final diagnosis of aortic valve disease in a primary [n = 5176 (26.2%)] or secondary diagnostic position [2nd–6th positions, n = 14 557 (73.8% cases), Table 1] of the SMR01 record.

View this table:
Table 1

Clinical characteristics at baseline and cardiovascular events

Aortic stenosis n = 13 220Aortic insufficiency n = 2807Aortic stenosis with insufficiency n = 699Other and unspecified aortic valve disorders n = 3007P-value
Baseline characteristics
 Age, years75.70 (10.96)68.30 (14.33)73.60 (11.50)71.80 (12.06)<0.0001
 Sex, males (%)6160 (46.6)1311 (46.7)356 (50.9)1419 (47.2)0.1592
Deprivation, %
  Least deprived5477 (42.0)1057 (38.3)301 (43.4)1135 (38.1)<0.0001
  Medium2714 (20.8)513 (18.6)146 (21.1)687 (23.1)
  Most deprived4843 (37.2)1193 (43.2)246 (35.5)1157 (38.8)
Co-morbidities, %
  Diabetes1497 (11.3)169 (6.0)52 (7.4)293 (9.7)<0.0001
  Respiratory disease2225 (16.8)434 (15.5)107 (15.3)490 (16.3)0.2551
  Cancer1239 (9.4)185 (6.6)54 (7.7)254 (8.4)<0.0001
  Hypertension3688 (27.9)808 (28.8)183 (26.2)868 (28.9)0.3812
  Renal disease1080 (8.2)183 (6.5)44 (6.3)203 (6.8)0.0015
  Rheumatoid arthritis228 (1.7)71 (2.5)16 (2.3)73 (2.4)0.0064
Cardiovascular event
 Concurrent procedures, %
  AVR528 (4.0)94 (3.3)49 (7.0)109 (3.6)0.0001
  Aortic balloon  valvuloplasty3 (0.0)0 (0.0)0 (0.0)0 (0.0)0.6873
  CABG328 (2.5)47 (1.7)18 (2.6)70 (2.3)0.0805
  PCI165 (1.2)35 (1.2)12 (1.7)48 (1.6)0.3545
 Concurrent complications of admission, %
  MI932 (7.0)146 (5.2)40 (5.7)168 (5.6)0.0003
  UAP2040 (15.4)403 (14.4)99 (14.2)486 (16.2)0.2138
  Heart failure3318 (25.1)684 (24.4)164 (23.5)553 (18.4)<0.0001
  NH stroke380 (2.9)90 (3.2)17 (2.4)79 (2.6)0.5207
  Atrial fibrillation or  flutter2116 (16.0)571 (20.3)142 (20.3)501 (16.7)<0.0001
 Prior procedures, %
  CABG96 (0.7)22 (0.8)5 (0.7)26 (0.9)0.8791
  PCI104 (0.8)27 (1.0)11 (1.6)32 (1.1)0.0878
 Prior events, %
  MI582 (4.4)130 (4.6)26 (3.7)153 (5.1)0.2847
  UAP1864 (14.1)455 (16.2)81 (11.6)488 (16.2)0.0002
  Heart failure1392 (10.5)322 (11.5)59 (8.4)359 (11.9)0.0155
  NH stroke374 (2.8)70 (2.5)22 (3.1)85 (2.8)0.7232
  Atrial fibrillation or  flutter1175 (8.9)338 (12.0)76 (10.9)326 (10.8)<0.0001
  • The P-value signifies a difference between aortic valve disease types.

  • AVR, aortic valve replacement; CABG, coronary artery bypass graft; PCI, percutaneous coronary intervention; MI, myocardial infarction; UAP, unstable angina pectoris; NH, non-haemorrhagic.

The average age at the time of a first presentation with aortic valve disease was 71 and 76 years in men and women, respectively. Age at first presentation differed between types of aortic valve disease (Table 1) and patients with isolated aortic stenosis at first presentation were older than patients with other types of aortic valve disease. Although gender was not related to the type of aortic valve disease, deprivation and several co-morbidities were, including a history of diabetes, cancer, and renal disease which were more common in patients with aortic stenosis. History of rheumatoid arthritis was more common in patients with isolated aortic insufficiency (Table 1). The most common cardiovascular problem overall was heart failure which was a complicating factor in one quarter of all index admissions (Table 1). Atrial fibrillation or flutter occurred in nearly one-fifth of all index admissions and was most common in patients with aortic insufficiency.

The temporal trends in the incidences of different types of aortic valve disease are shown in Figure 1. The (age–sex standardized) incidence of isolated aortic stenosis increased from 246 cases per 1 million of the population in 1997 to 365 per 1 million population in 2005. The incidence of hospitalizations with mixed aortic valve disease increased from 13 cases per 1 million population in 1997 to 24 per 1 million population in 2005, whereas the incidences of other forms of aortic valve disease were relatively unchanged. The majority of hospitalizations occurred in elderly persons aged 80 and older (Figure 2).

Figure 1

Temporal trends for hospitalization with a first report of aortic stenosis (ICD code I350), aortic insufficiency (ICD code I351), mixed aortic valve disease (ICD code I352), and other and unspecified forms of aortic valve disease (ICD codes I358 and I359) from 1 January 1997 to 31 December 2005.

Figure 2

Temporal trends for hospitalization with a first report of aortic stenosis (upper figure) or aortic stenosis with insufficiency (lower figure) according to age category.

Changing course of health outcomes following a first hospitalization with each type of aortic valve disease

All-cause mortality

Among 19 733 patients with a first admission of aortic valve disease between 1 January 1997 and 31 December 2005, 9981 (50.6%) patients had died (all causes) by 31 December 2006 (Figure 3) and the majority of these patients (71.6%) had aortic stenosis (Table 2). When compared with aortic stenosis, the likelihood of death was less with aortic insufficiency [hazard ratio (95% confidence interval) 0.79 (0.74, 0.84)] and mixed aortic valve disease [0.83 (0.74, 0.93)]. The independent predictors of subsequent all-cause mortality are described in Table 2. Female gender, year of admission, and hypertension reduced the likelihood of mortality in patients with aortic stenosis. Deprivation increased the likelihood of mortality following a diagnosis of aortic stenosis.

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Table 2

Predictors of all-cause mortality by type of aortic valve disease

Aortic stenosis n = 13 220Aortic insufficiency n = 2807Aortic stenosis with insufficiency n = 699Other and unspecified aortic valve disorders n = 3007
Number of events, %7147 (54.1)1134 (40.4)304 (43.5)1396 (4)
Age (5-year change)1.33 (1.31, 1.35)1.29 (1.26, 1.33)1.35 (1.27, 1.45)1.34 (1.30, 1.37)
Year of admission (5-year change)0.88 (0.83, 0.92)0.85 (0.75, 0.98)0.86 (0.77, 0.98)
Sex (female vs. male)0.88 (0.84, 0.93)0.67 (0.53, 0.86)
Deprivation
 Medium vs. least deprived1.06 (1.00, 1.13)
 Most deprived vs. least deprived1.09 (1.03, 1.15)
Co-morbidities
 Diabetes1.33 (1.24, 1.43)1.44 (1.16, 1.79)1.40 (1.18, 1.66)
 Respiratory disease1.38 (1.30, 1.47)1.66 (1.43, 1.91)1.42 (1.24, 1.62)
 Cancer1.53 (1.43, 1.65)1.52 (1.25, 1.86)2.05 (1.46, 2.89)1.61 (1.36, 1.89)
 Hypertension0.92 (0.87, 0.97)0.87 (0.77, 0.98)
 Renal disease1.65 (1.53, 1.78)1.93 (1.58, 2.36)2.09 (1.44, 3.04)2.15 (1.80, 2.56)
Concurrent procedures
 AVR0.45 (0.37, 0.54)0.55 (0.31, 0.98)0.56 (0.37, 0.85)
 PCI0.61 (0.44, 0.84)
Concurrent complications of admission
 MI1.36 (1.25, 1.48)
 UAP0.88 (0.82, 0.94)0.76 (0.63, 0.92)0.77 (0.66, 0.90)
 Heart failure1.68 (1.60, 1.77)1.52 (1.33, 1.73)1.71 (1.33, 2.21)1.50 (1.32, 1.70)
 NH stroke1.47 (1.11, 1.95)
 Atrial fibrillation or flutter1.07 (1.01, 1.14)
Prior procedures
 CABG0.30 (0.09, 0.93)
Prior events
 MI1.33 (1.04, 1.70)
 Heart failure1.43 (1.34, 1.54)1.38 (1.17, 1.62)1.43 (1.00, 2.03)1.23 (1.05, 1.45)
 NH stroke1.20 (1.06, 1.36)
 Atrial fibrillation or flutter1.20 (1.02, 1.41)
  • AVR, aortic valve replacement; CABG, coronary artery bypass graft; PCI, percutaneous coronary intervention; MI, myocardial infarction; UAP, unstable angina pectoris; NH, non-haemorrhagic.

Figure 3

Kaplan-Meier plot for all-cause mortality by type of aortic valve disease. The hazard ratios (95% confidence interval) for all-cause mortality for aortic insufficiency, aortic stenosis with insufficiency, and other/unspecified aortic valve disease compared with aortic stenosis are shown beneath the figure. Hazard ratios (95% confidence interval) are shown unadjusted and adjusted for other predictors of mortality (Table 2), including deprivation.

Death or index rehospitalization for heart failure, myocardial infarction, or stroke according to aortic valve disease type

Death or rehospitalization for heart failure

A total of 10 604 (53.7%) deaths or index heart failure hospitalizations occurred (see Supplementary material online, Table S1 and Figure S1). Of these, 619 (5.8%) and 1961 (18.5%) subjects experienced a fatal or non-fatal hospital index admission with heart failure, respectively. When compared with other types of aortic valve disease, aortic stenosis increased the risk of death following a heart failure hospitalization (adjusted P < 0.001).

Death or rehospitalization for myocardial infarction or stroke

In total, 10 301 (52.2%) deaths or rehospitalization for myocardial infarction and 10 688 (54.2%) deaths or rehospitalization for stroke or transient ischaemic attack occurred (Supplementary material online, Figures S1 and S2, respectively). Overall, a hospital admission for myocardial infarction was fatal in 38% of patients with aortic stenosis with or without insufficiency, whereas the fatality rate was much lower for hospitalization with stroke (18.8 and 20.3%, respectively) and for heart failure (24.8 and 28.9%, respectively) (Supplementary material online, Table S1).

When compared with other forms of aortic valve disease, aortic stenosis had a higher hazard ratio for time to death following myocardial infarction or stroke, although this was not significant after adjustment for age, year of admission, and co-morbidity (Supplementary material online, Table S2).

Aortic valve replacement according to the type of aortic valve disease

The first aortic valve replacement took place in 3 367 (19.4%) patients of whom 73.2% had aortic stenosis, 11.9% had an unspecified type of aortic valve disease, and 10.0% had aortic insufficiency and 4.9% had aortic stenosis with insufficiency (Figure 4 and Table 3). Seven hundred and eighty patients had an aortic valve replacement during their index hospital admission. The likelihood of aortic valve replacement in patients with aortic stenosis (isolated or mixed) was reduced with female gender, co-morbidities (e.g. renal disease, respiratory disease), and concurrent myocardial infarction (Table 3). In patients with aortic stenosis, the likelihood of aortic valve replacement increased with the year of admission and decreased with concurrent coronary artery bypass surgery and PCI.

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Table 3

Predictors of aortic valve replacement by type of aortic valve disease

Aortic stenosis n = 12 692Aortic insufficiency n = 2713Aortic stenosis with insufficiency n = 650Other and unspecified aortic valve disorders n = 2898
Number of events, %2689 (21.2)367 (13.5)180 (27.7)437 (15.1)
Age (5-year change)0.85 (0.84, 0.87)0.88 (0.85, 0.91)0.81 (0.77, 0.85)0.90 (0.87, 0.93)
Year of admission (5-year change)1.15 (1.06, 1.24)
Sex (female vs. male)0.70 (0.65, 0.76)0.53 (0.43, 0.66)0.63 (0.46, 0.86)0.67 (0.56, 0.82)
Co-morbidities
 Respiratory disease0.52 (0.45, 0.60)0.53 (0.36, 0.79)0.59 (0.36, 0.96)0.65 (0.47, 0.90)
 Cancer0.61 (0.51, 0.73)
 Hypertension0.78 (0.71, 0.85)0.75 (0.58, 0.97)0.64 (0.50, 0.82)
 Renal disease0.45 (0.35, 0.59)0.47 (0.24, 0.91)0.21 (0.05, 0.84)0.27 (0.11, 0.66)
 Rheumatoid arthritis0.65 (0.44, 0.95)
Concurrent procedures
 CABG0.17 (0.08, 0.38)
 PCI0.34 (0.21, 0.55)
Concurrent complications of admission
 MI0.46 (0.37, 0.59)0.42 (0.21, 0.84)0.19 (0.05, 0.78)0.32 (0.15, 0.68)
 UAP0.83 (0.74, 0.92)0.73 (0.54, 0.99)0.62 (0.47, 0.83)
 Heart failure0.72 (0.63, 0.81)0.61 (0.43, 0.87)
 NH stroke0.27 (0.18, 0.41)
 Atrial fibrillation or flutter0.67 (0.58, 0.77)0.42 (0.29, 0.61)0.60 (0.43, 0.84)
Prior procedures
 CABG0.39 (0.21, 0.74)
Prior events
 MI0.49 (0.36, 0.67)0.20 (0.08, 0.54)
 UAP0.69 (0.61, 0.80)
 Heart failure0.68 (0.55, 0.85)
 NH stroke0.52 (0.36, 0.76)0.30 (0.10, 0.93)
  • CABG, coronary artery bypass graft; PCI, percutaneous coronary intervention; MI, myocardial infarction; UAP, unstable angina pectoris; NH, non-haemorrhagic.

Figure 4

Cumulative incidence plot for aortic valve replacement by type of aortic valve disease. The hazard ratios (95% confidence interval) for all-cause mortality for aortic insufficiency, aortic stenosis with insufficiency, and other/unspecified aortic valve disease compared with aortic stenosis are shown beneath the figure.

Discussion

Our results provide insights into the distinct and changing course of different types of aortic valve disease in Scotland over a 10-year period.

Aortic stenosis was the commonest type of aortic valve disease and its incidence in Scotland has nearly doubled from 1997 to 2005. The rising incidence is mainly in elderly persons aged 80 and older. Our results identify the prognostic importance of aortic stenosis when compared with other types of aortic valve disease. Aortic stenosis conferred a higher risk of death, or death and heart failure when compared with other types of aortic valve disease. The fatality rate associated with a hospitalization for myocardial infarction was 38% which was approximately double the rate of death associated with a hospitalization for heart failure or for stroke. The cumulative incidence of aortic valve replacement has nearly doubled during the past 10 years and aortic stenosis with insufficiency was the commonest indication for surgery.

Our findings indicate a striking rising trend in hospitalizations for aortic valve disease in Scotland in recent years. This trend is most pronounced for aortic stenosis which appears to have a distinct clinical course. The possible reasons to explain this finding include a lower threshold for patients to seek medical care and improved diagnostic methods. One other important factor is increased longevity in the general population since degenerative aortic valve disease is much more common in the elderly.6

There were notable differences in the characteristics of patients according to the type of aortic valve disease. Patients with aortic stenosis were older than patients with mixed aortic valve disease or isolated aortic insufficiency. Deprivation status also differed according to type of aortic valve disease and a higher proportion of patients with aortic stenosis (with or without insufficiency) were deprived. Heart failure was a common complicating problem, affecting a quarter of patients with either aortic stenosis, aortic insufficiency, or mixed aortic valve disease. Cancer was more common in aortic stenosis, perhaps because patients with this type of aortic valve disease were older.

Natural history following a diagnosis of aortic valve disease

Our findings point to differences in the health outcomes following a diagnosis of aortic stenosis, aortic insufficiency, or mixed aortic valve disease. When compared with other types of aortic valve disease, aortic stenosis conferred an increased risk of mortality or of adverse cardiovascular events including myocardial infarction, heart failure, and stroke. Year of admission reduced the likelihood of mortality in patients with aortic stenosis. One explanation for this finding could be earlier detection of aortic stenosis and the presence of less advanced cardiovascular health problems at the time of first hospitalization. We also found that deprivation increased the likelihood of mortality and cardiovascular morbidity following a diagnosis of aortic stenosis.

Our observations draw attention to the prognostic implications of aortic stenosis. When compared with other types of aortic valve disease, aortic stenosis was an independent predictor of all-cause mortality and of all-cause mortality plus heart failure hospitalization. We also observed that the mortality rate associated with a subsequent hospitalization for myocardial infarction was very high. The fatality rate with myocardial infarction was highest (41%) in patients with aortic stenosis with or without aortic insufficiency. This finding suggests that patients with aortic valve disease, and aortic stenosis in particular, have a limited capacity to tolerate the negative inotropic effects of acute myocardial infarction.

Strengths and limitations of current epidemiology of heart valve disease

Nkomo et al.6 have provided information about the prevalence and age distribution of valvular heart disease from a randomly selected population of patients from Rochester, USA. They found that the prevalence of heart valve disease was strongly influenced by age, with the cumulative prevalence of aortic and mitral valve disease ranging from 0.7% in adults aged 18–44 to 13.2% in the elderly (age ≥ 75 years). Although mitral insufficiency was the commonest valve pathology, aortic stenosis was also common, particularly in the elderly.6 The only other contemporary epidemiological study is the EuroHeart Survey5 which was a prospective multicentre European study of planned and unplanned hospital visits by patients with a diagnosis of aortic and mitral valve disease (April–July 2001). Our study is different since we have provided a population-level analysis in a much larger cohort during a 10-year period.

Treatment of aortic valve disease

Increasingly, heart valve disease is being recognized as a public health concern with requirements for healthcare planning.15 The treatment of heart valve disease can be difficult. Drug therapies alleviate symptoms but do not modify prognosis.7,8,16 Aortic valve replacement improves prognosis17 and the proportion of patients >75 years undergoing valve replacement has steadily increased in the UK since 1999.18 Therefore, because of increasing longevity, the number of aortic valve replacements is projected to rise markedly in the coming years.4,14

Many elderly persons with heart valve disease are unsuitable for surgical valve replacement9,10,18,19 and this area of unmet need has stimulated new therapeutic approaches. Transcatheter aortic valve implantation is a promising emerging treatment for patients who are unsuitable for surgery.9,10,20,21 The PARTNER trial demonstrated that in patients with inoperable aortic stenosis, TAVI reduced all-cause mortality and hospitalizations compared with usual care9 confirming that TAVI represents an alternative to surgical aortic valve replacement in high-risk patients.

Limitations of the current study

We accept that the data on incidence of aortic valve disease may be affected by detection bias. However, we believe the distinct trends over time for each aortic valve entity are correct and cannot simply be explained by increased detection such as through improved access to echocardiography, since uniform increases in the incidences of different types of aortic valve disease did not occur. For example, the number of first hospitalizations with a diagnosis of aortic stenosis increased markedly over time, whereas the number of hospitalizations with a diagnosis of aortic insufficiency remained reasonably constant. We accept that a small minority of patients with undisclosed bicuspid aortic valve disease may have been included, although imaging typically detects this pathology. We also accept that coding of some clinical characteristics, such as hypertension, may be incomplete.

The management of heart valve disease in Scotland may differ in some ways (e.g. concomitant revascularization rates with valve surgery) compared with other countries. However, the prognostic models in our study will be relevant to populations elsewhere, since our data are derived from the full spectrum of socio-economic backgrounds.

In conclusion, we report the epidemiology and temporal trends of different types of acquired aortic valve disease at a population level. The incidence of aortic stenosis has increased in Scotland in recent years. Probably because of increased longevity in general, aortic stenosis will become an increasingly important public health problem.

Authors' contributions

C.B. conceived the idea for the study, interpreted the data, and wrote the first and final drafts of the manuscript. S.M.L. conducted the final statistical analyses and contributed to the writing of the manuscript. Y.W. conducted the initial statistical analyses and contributed to the writing of the manuscript. A.M. performed the data extraction and reviewed the manuscript. I.F. developed the design of the study, contributed to data analyses and interpretation, and helped write the manuscript.

Funding

C.B. was supported by a British Heart Foundation International Fellowship and a Senior Clinical Fellowship from the Scottish Funding Council. I.F. was supported by a grant from The Wellcome Trust for the Scottish Health Informatics Programme (SHIP). I.B., C.B., and S.M.L. were supported by a grant from the Chief Scientist Office, Scotland to study the epidemiology of heart valve disease in Scotland.

Conflict of interest: none declared.

Acknowledgements

We thank staff from the Information and Statistics Division, NHS Scotland National Services. C.B. had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analyses.

References

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