Myocardial Infarction Health Atlas for Norway

Assessment of variation in rehabilitation

To determine whether the variation in the use of services is undesirable/unjustified, we compared the use of health services with the prevalence of myocardial infarction. Larger discrepancies between prevalence and use of health services indicate unjustified variation.

About the Measures of Variation The Extremal Quotient is simple measure of variation. The EQ shows the ratio between the highest and lowest rate, while EQ2 shows the ratio between the second highest and second lowest rate. Higher EQ values therefore indicate greater variation in the rates. The coefficient of variation (CV) takes all the rates into account and is thus a more comprehensive measure of variation. The coefficient of variation is the standard deviation of the rates, divided by the mean of the rates, multiplied by 100. The systematic component of variation (SCV) highlights systematic variation and is therefore considered the most decisive measure of variation. Technically, SCV represents total variation minus random variation between areas. For SCV2, the highest and lowest values are excluded, which makes the measure less sensitive to extreme values. It has been suggested that SCV values greater than 3 are likely to be largely due to differences in practice within the healthcare service. We define the magnitude of variation as follows:

• SCV less than 3 indicates low variation,
• SCV between 3.1–5.4 indicates moderate variation,
• SCV between 5.5–10.0 indicates high variation, and
• SCV greater than 10.0 indicates extremely high variation.

Assessment of variation in rates

To determine whether the variation in the use of services is undesirable/unjustified, we compared the use of health services with the prevalence of myocardial infarction. Larger discrepancies between prevalence and use of health services indicate unjustified variation.

About the Measures of Variation The Extremal Quotient is simple measure of variation. The EQ shows the ratio between the highest and lowest rate, while EQ2 shows the ratio between the second highest and second lowest rate. Higher EQ values therefore indicate greater variation in the rates. The coefficient of variation (CV) takes all the rates into account and is thus a more comprehensive measure of variation. The coefficient of variation is the standard deviation of the rates, divided by the mean of the rates, multiplied by 100. The systematic component of variation (SCV) highlights systematic variation and is therefore considered the most decisive measure of variation. Technically, SCV represents total variation minus random variation between areas. For SCV2, the highest and lowest values are excluded, which makes the measure less sensitive to extreme values. It has been suggested that SCV values greater than 3 are likely to be largely due to differences in practice within the healthcare service. We define the magnitude of variation as follows:

• SCV less than 3 indicates low variation,
• SCV between 3.1–5.4 indicates moderate variation,
• SCV between 5.5–10.0 indicates high variation, and
• SCV greater than 10.0 indicates extremely high variation.

A myocardial infarction occurs when the blood supply to parts of the heart is blocked, causing damage to the heart muscle. A myocardial infarction is a serious condition that develops quickly. It is therefore important to start treatment early.

Each year, just under 11,000 Norwegians suffer from an acute myocardial infarction, with an annual decrease of about 3% since 2015 (Annual Report 2022, Norwegian Myocardial infarction Register). In about 25% of patients, one of the coronary arteries is completely blocked, often due to a rupture in the surface of a narrow part of the blood vessel and the formation of a thrombus (blood clot). In the remaining 75% of myocardial infarction, there are minor ECG changes, and the coronary artery is usually not completely blocked.

In Norway, there are no specific guidelines for rehabilitation after a myocardial infarction, and the European guidelines are followed (Ambrosetti et al. 2020 and Visseren et al. 2021), as well as the National Professional Guideline for the Prevention of Cardiovascular Disease (Norwegian Directorate of Health).

For all hospital referral areas, there was a decrease in the rate of admission for acute myocardial infarction for the elderly, with the largest changes seen in the hospital referral areas of Finnmark, Telemark, and Inner Oslo. The change in rate is illustrated by calculating the ratio between the average annual rate for the periods 2018-2022 and 2013-2015.

In other words, there was a reduction in the number of myocardial infarction patients during a period when the number of elderly increased (from 359,928 elderly on average per year in 2013-2015 to 409,950 in 2018-2022).

The main goal of acute treatment for myocardial infarction is to limit damage to the heart muscle by opening up blood vessels; revascularization. Depending on the distance to the hospital and the type of infarction, it is recommended that patients receive thrombolytic treatment (clot-dissolving treatment), percutaneous coronary intervention (PCI, angioplasty), or bypass surgery.

X-ray examination of the coronary arteries in the heart with the injection of contrast fluid, and possible mechanical angioplasty, is performed at ten hospitals in Norway. Patients can be directly admitted to such an “invasive hospital” or transferred from other hospitals. Heart surgery is also performed at five of the hospitals (Annual Report 2021 Norwegian Myocardial infarction Register).

As in the Elderly Health Atlas, acute treatment with thrombolysis is not included in the analyses, and revascularization is not limited to patients with myocardial infarction.

There was no clear change in the use of heart revascularization for the elderly in Norway from 2013-2015 to 2018-2022. The change is illustrated by calculating the ratio between the average annual revascularization rate for the periods 2018-2022 and 2013-2015 (see Elderly Health Atlas). However, in the hospital referral areas of Nordland and UNN, the rate increased, while in the Telemark area, it decreased.

Rehabilitation has a clear secondary preventive effect on heart attacks, significantly impacting both individuals and society. Rehabilitation as part of secondary preventive treatment is recommended for all patients after a heart attack. Rehabilitation is cost-effective, improves quality of life, reduces the risk of recurrence, death, and rehospitalization. Research in the field is of the highest quality (class 1A) and provides clear recommendations (Visseren et al. 2021, Ambrosetti et al. 2020).

About This Healthcare Atlas

The Healthcare Atlas examines the cardiac rehabilitation that the patient received in the period from discharge from the hospital after an acute myocardial infarction and six months forward.

Activity in specialist health services coded as rehabilitation with the codes

• Z50.0 Rehabilitation after heart disease,
• Z50.80 Complex rehabilitation,
• Z50.89 Simple rehabilitation, and
• Z50.9 Treatment involving the use of unspecified rehabilitation measures is called “standard rehabilitation” in this health atlas.The use of these codes should indicate that the activity is targeted, planned, and interdisciplinary. See more about code quality under the discussion of the method.

To get a broader picture of the services offered to patients in the first six months after the infarction, we supplemented analyses of standard rehabilitation after a myocardial infarction with participation in Learning and Mastery Courses (LMS courses) and training in specialist health services, and training with a physiotherapist with municipal operating grants / who has billed Helfo. That the health services for patients vary geographically in terms of content, duration, and organization is also evident from feedback from the field.

Based on the Myocardial infarction Register’s definition of cardiac rehabilitation; “education on how to reduce the risk of a new myocardial infarction and the offer of physical training” (Annual Report 2022), we understand that participation in LMS courses and training is part of cardiac rehabilitation, and including LMS courses and training for more pragmatic reasons seems natural. To what extent such services meet the conditions for achieving rehabilitation results, which are the basis for the guidelines (Visseren et al. 2021), is not available through the data we have.

The analysis results of cardiac rehabilitation will be influenced by how we understand the concept of rehabilitation, what data and methods we have used in the analyses, and the quality of the registered data.

Definitions and Operationalization of the Concept of Rehabilitation

The definition of rehabilitation can vary in different contexts. Here we briefly mention the understanding of cardiac rehabilitation that this health atlas is based on:

“The sum of activities and interventions necessary to ensure physical, mental, and social conditions so that patients with chronic or post-acute heart disease can return to their previous place in society and live an active life” (Helsebiblioteket).

Further on the content of rehabilitation: “Cardiac rehabilitation consists of complex, long-term programs involving medical evaluation, prescription of physical activity, reduction of risk factors, education, and psychosocial support. The programs are carried out by a multidisciplinary team with a minimum of 4 different professional groups for simple rehabilitation and a minimum of 6 different professional groups for complex rehabilitation” (Helsebiblioteket).

The European guidelines, which are supported in Norway, recommend that multidisciplinary cardiac rehabilitation should include exercise, education, follow-up, and management of lifestyle and risk factors, as well as psychosocial support (Visseren et al. 2021).

The analyses of standard rehabilitation in the health atlas are based on data from the Norwegian Patient Register (NPR). The regulations for activity-based funding (ISF regulations 2022, chapter 6.12) set requirements for the use of rehabilitation codes, including the number of professional groups that must be involved. The concept of rehabilitation is thus operationalized through activity-based funding (ISF), while funding is linked to rehabilitation activities that meet the requirements and are correctly coded.

Quality of Rehabilitation Coding

The main data source for the analyses of rehabilitation in the health atlas is the Norwegian Patient Register (NPR), a national health register containing information about all patients who have received rehabilitation in specialist health services in Norway, both public health services and private ones with agreements with the public sector. NPR is primarily developed for administrative purposes. In the health atlas, the information is used to assess whether there is geographical variation in rehabilitation in the six months after patients were acutely admitted with a heart attack.

A challenge related to the analysis of this type of data is whether the coding quality is good enough. Errors or omissions in coding will result in inaccuracies in describing rehabilitation in specialist health services. Much has been done to improve and harmonize coding practices, but we cannot rule out that there are some errors or omissions in our dataset, meaning the data may not fully reflect the actual activities performed.

The Norwegian Directorate of Health comments on the quality of rehabilitation coding in general in the report “Rehabilitation in Specialist Health Services 2017-2021”. They mention that there may be underreporting of outpatient and day rehabilitation but have not investigated the extent of this or how it manifests. Stays have previously been incorrectly registered as inpatient stays instead of a series of outpatient contacts in some health trusts (Annual Reports from 2019 and 2021, Settlement Committee).

The Norwegian Directorate of Health also mentions in the report that in recent years more private providers have reported to NPR, but there is still uncertainty in the coding. Analyses of day and outpatient activities related to private rehabilitation institutions should therefore be interpreted with caution.

To minimize the challenge of coding errors, including the procedure codes and tariff codes we have used, we have spent time preparing and quality-checking the datasets from NPR and KPR, familiarizing ourselves with the coding rules, and talking to professionals about the coding of activities. We have assessed that the results contain as few errors as possible based on the available data.

Cohort Analysis

In the Health Atlas for Heart Attack, we used cohort analysis where we followed patients with acute myocardial infarction from discharge after the myocardial infarction for the first six months forward, examining participation in rehabilitation during this period.

We used a narrower definition of patients with myocardial infarction in the analyses related to rehabilitation (I21 acute myocardial infarction as the main condition) than in the analysis of admissions with myocardial infarction(I21 acute heart attack, or I22 subsequent heart attack, as the main or secondary condition). The analyses of admissions with myocardial infarction are an update of analyses in the Elderly Health Atlas, and we have therefore used the same codes as in the Elderly Health Atlas. By using a strict definition in the analyses of rehabilitation after an acute heart attack, we are more confident that we include the correct patient group. We saw in the data from NPR that most of the rehabilitation occurred after inpatient stays with I21 (acute heart attack) as the main condition, and not after stays with I22 (subsequent heart attack), or where the codes were used as secondary conditions. The ICD-10 codes for acute myocardial infarction have been found to be of good quality (Varmdal et al. 2021).

We found that 75% of rehabilitation episodes were completed within the first six months. Extending the period would have resulted in slightly more episodes. On the other hand, a cohort analysis over a longer period would entail greater uncertainty regarding whether the rehabilitation was related to the myocardial infarction.

Need for Guidelines and Quality Indicators

The geographical variation in cardiac rehabilitation, based on our analyses and information from professionals from different parts of the country, appears to be supply-driven rather than need-driven. We find areas in Norway with a high prevalence of heart attacks, such as Finnmark, where the provision and use of cardiac rehabilitation are limited. We would characterize the geographical variation as undesirable, despite the caveat about coding quality. The analyses show an underuse of rehabilitation after heart attacks, and there is a need for measures to improve the service offering for patients after heart attacks.

To achieve a more equitable rehabilitation service regardless of where one lives, it seems there is a need for national guidelines for rehabilitation after heart attacks - and that effective rehabilitation services are established for patients across the country. The work on guidelines started in 2023. Specific quality indicators could also be measures to improve the extent and quality of services.

The Health Atlas for Myocardial infarction is based on information provided by the Norwegian Directorate of Health from the Norwegian Patient Register (NPR) and the Municipal Patient and User Register (KPR) for the period 2018 to 2022. 

From KPR, information about training with physiotherapists for patients after an acute myocardial infarction has been collected. Other analyses are based on information from NPR. 

Population numbers are obtained from Statistics Norway (SSB). 

Disclaimer 

Helse Førde is solely responsible for the interpretation and presentation of the data provided. NPR and KPR are not responsible for analyses or interpretations based on the data they have provided.

The four regional health authorities have a statutory responsibility to provide specialist health services to the population, and the services should be equitable regardless of where one lives (Specialist Health Services Act). In assessing geographical variation in the population’s use of health services, the country is therefore divided according to the health authorities’ referral areas. 

The analyses in the healthcare atlas are conducted based on the hospital referral area where the patient lives, not where they received treatment. The inhabitants of the different hospital referral areas have different age and gender compositions. The rates in the atlas are therefore age and sex adjusted to compare more homogeneous groups’ use of health services than without such adjustment. If information about the municipality where the patient lived was missing in the datasets, the patient was excluded from the analyses. Through the analyses, the regional health authorities can form a picture of how the healthcare responsibility for their referral area is being fulfilled. 

Information about the division into catchment areas, population numbers, and median age of the inhabitants (2020) used in this atlas can be found below.

The list below shows which health trusts or hospitals have defined hospital referral areas and the short names used in the atlas. Which municipalities and districts belong to each referral area can be found here.

The referral areas of Diakonhjemmet Hospital and Lovisenberg Diaconal Hospital (i.e., districts in Oslo) are combined into one referral area; Inner Oslo, where results from 2018-2022 are compared with the Elderly Health Atlas (2013-2015), and in analyses concerning training with physiotherapists due to the small number of patients.

The Health Atlas for Myocardial infarction is developed in collaboration with a resource group consisting of: 

• Torstein Hole, Specialist in Internal Medicine and Cardiology, MD, Helse Møre og Romsdal, NTNU 
• Charlotte B. Ingul, Specialist in Internal Medicine and Cardiology, MD, St. Olavs Hospital, NTNU, Nord University 
• Tove Johansen, Analyst, SKDE 
• John Munkhaugen, Specialist in Internal Medicine and Cardiology, MD, Drammen Hospital, UiO 
• Tone Merete Norekvål, PhD, Research Group Leader, Cardiology Department, Haukeland University Hospital, Professor, University of Bergen and Western Norway University of Applied Sciences 
• Barthold Vonen, Director, SKDE 

During the project period, we have been in contact with professional environments and individuals in various parts of the country. This is to ensure that the analysis results can provide the best possible picture of practice. 

Thank you for contributing to making the atlas practical and relevant. 

The Healthcare Atlas is developed by Helse Førde HF by Marte Bale, Haji Kedir Bedane, Maria Holsen, Knut Ivar Osvoll, and Oddne Skrede.