High validity of cardiomyopathy diagnoses in western Sweden (1989–2009)

Abstract

AimHospital discharges with a diagnosis of cardiomyopathy have more than doubled in Sweden since 1987. We validated the cardiomyopathy diagnoses over this time period to investigate that the increase was real and not a result of improved recognition of the diagnosis and better diagnostic methods.Methods and resultsEvery fifth year from 1989 to 2009, records for all patients with a cardiomyopathy diagnosis were identified by searching the local registers in three hospitals in Västra Götaland, Sweden. The diagnoses were validated according to criteria defined by the European Society of Cardiology from 2008. The population comprised 611 cases with cardiomyopathy diagnoses [mean age 58.9 (SD 15.5) years, 68.2% male], divided into three major groups: dilated, hypertrophic, and other cardiomyopathies. Hypertrophic cardiomyopathy and hypertrophic obstructive cardiomyopathy were analysed as a group. Cardiomyopathies for which there were few cases, such as restrictive, arrhythmogenic right ventricular, left ventricular non‐compaction, takotsubo, and peripartum cardiomyopathies, were analysed together and defined as ‘other cardiomyopathies’. Relevant co‐morbidities were registered. The use of echocardiography was 99.7%, of which 94.6% was complete echocardiography reports. The accuracy rates of the diagnoses dilated cardiomyopathy, hypertrophic cardiomyopathy, and other cardiomyopathies were 85.5%, 87.5%, and 100%, respectively, with no differences between the three hospitals or years studied; nor did the prevalence of co‐morbidities differ.ConclusionsThe accuracy rate of the cardiomyopathy diagnoses from in‐hospital records from >600 patients in western Sweden during a 20 year period was 86.6%, with no significant trend over time, strengthening epidemiological findings that this is likely due to an actual increase in cardiomyopathy diagnoses rather than changes in coding practices. The use of echocardiography was high, and there was no significant difference in co‐morbidities during the study period. The accuracy rate of the cardiomyopathy diagnoses during the 20 year period was high. The use of diagnostic tools did not increase under the study period, and once cardiomyopathy diagnoses were suspected, echocardiography was performed in almost all cases. In this study, the occurrence of cardiomyopathy was increasing over time without significant increase of co‐morbidity, supporting that an actual increase of cardiomyopathy has occurred.

Young patients with heart failure: clinical characteristics and outcomes. Data from the Swedish Heart Failure, National Patient, Population and Cause of Death Registers

“…It would add value to this study but, according to the latest definition of cardiomyopathies, presence of comorbidities does not preclude a diagnosis of cardiomyopathy 27 . A recently published study from our group showed a high validity of diagnoses of cardiomyopathy in western Sweden 28 …”

Higher Body Mass Index in Adolescence Predicts Cardiomyopathy Risk in Midlife

“…In a recent study from our group in which we validated hospital diagnoses of cardiomyopathy against predefined criteria and the use of echocardiography was nearly 100% throughout the study period, diagnoses of dilated cardiomyopathy, hypertrophic cardiomyopathy, and other cardiomyopathies were found to be accurate in 86%, 88%, and 100% of cases, respectively. 4 Although that study included 3 hospitals in different settings, in 3 cities, and in an unselected population covering a large part of western Sweden, there were no significant changes in accuracy between the hospitals or over the extended study period of 20 years. Furthermore, of the individuals with dilated and alcohol-associated cardiomyopathies in the present study, 69% were diagnosed with heart failure at some point, but the absence of a heart failure diagnosis does not exclude the presence of symptoms, and clinical heart failure is not a prerequisite for a diagnosis of cardiomyopathy.…”

“…In a validation study of cardiomyopathy diagnoses in the Swedish National Hospital Register, dilated cardiomyopathy was the most common diagnosis (67%), followed by hypertrophic cardiomyopathy (16%), whereas other types were rare. 4 Modifiable causes listed for dilated cardiomyopathy include myocarditis, drugs, alcohol, endocrine disorders, and nutritional deficiencies, 3 with ≈25% estimated to have genetic causes resulting from specific genetic defects linked to cardiac muscle development. 5 Hypertrophic cardiomyopathy is mostly a familial dominant inheritable disease, 6 with obesity and athletic training listed as potential acquired causes.…”

“…Diagnoses of different types of cardiomyopathy in the Swedish National Hospital Register have been shown to be accurate in at least 85% of cases. 4 In the present study, we set out to investigate the risk of specific types of cardiomyopathy across categories of BMI in late adolescence.…”

Elevated resting heart rate in adolescent men and risk of heart failure and cardiomyopathy

“…However, validation studies have been performed and showed generally high validity, with a positive predictive value of 82–88% for heart failure diagnoses 29 . Furthermore, in a recent study from our group validating hospital‐registered diagnoses of cardiomyopathy, the diagnoses were found to be highly accurate 30 . The single measurement of resting heart rate used does not allow for studying the effects of temporal changes of the exposure and introduces risk of regression to the mean, underestimating our results.…”