Herlev University Hospital is serving a local population of 200,000. The Danish National Registry of Patients (NRP) identified patients referred to the outpatient clinic (OPC), heart failure clinic (HFC), or those admitted to the cardiology ward in Herlev University Hospital and discharged with a HF diagnosis, during the period July 1, 2005 to June 30, 2007. This register contains 99.4% of all discharge records from Danish hospitals including outpatient visits, and information about the diagnoses has been coded according to the International Classification of Diseases, 10th edition (ICD-10).10
The codes used for identification of heart failure patients were: I11.0 (hypertensive heart disease with heart failure), I13.0 (hypertensive heart and renal disease with heart failure), I13.2 (hypertensive heart and renal disease with both heart failure and renal disease), I42.0 (dilated cardiomyopathy), I42.6–9 (other cardiomyopathies), I50.0–I50.1 and I50.9 (heart failure).
The authors systematically reviewed the records of all patients with a discharge diagnosis of heart failure during the period of October 14, 2009 to March 23, 2010. Author SM, who is following a clinical and research training programme in cardiology, initially reviewed the records. The recorded data were checked and transferred to a database by author FN, who is a specialist in cardiology. If the two authors disagreed about a HF diagnosis, the case was adjudicated by consensus agreement after discussion.
The following information was obtained from the records: age; gender; weight; height; tobacco use and alcohol consumption; results of laboratory tests; the probability of heart failure, and if the registered heart failure diagnosis was a primary or secondary diagnosis, and if heart failure was new, onset or chronic heart failure; New York Heart Association class (NYHA); history of ischemic heart disease (IHD), ie, angina pectoris, previous myocardial infarction, previous performed percutanous coronary intervention (PCI) or coronary artery by-pass grafting (CABG); history of valve disease; other comorbidities, ie, chronic pulmonary disease, hypertension, diabetes mellitus, stroke, atrial fibrillation, thyroid disease; and pacemaker or implantable cardioverter defibrillator unit implant. Diabetes mellitus was considered present if the patients were on antidiabetic therapy with diet or medication. Hypertension, chronic pulmonary lung disease, and thyroid disease were defined as a history of the specific diseases diagnosed by the patient’s doctor. Previous stroke was considered present if the diagnosis was confirmed from the records.
The 12-lead electrocardiogram (ECG) were reviewed and analyzed for rhythm (sinus rhythm, atrial fibrillation, other rhythms), bundle branch block, left ventricular hypertrophy (LVH), and ischemia. LVH was determined as the voltage sum SV1 + RV5 or RV6 ≥ 35 mm using Sokolow–Lyon voltage criteria, and myocardial ischemia was considered present if a ≥1 mm horizontal or downward sloping ST shift in >1 of the 12 electrocardiographic leads was found.
All echocardiographic descriptions were reviewed by the authors and information on dimensions of the left chambers, left ventricular ejection fraction (LVEF), and severity of valve diseases was registered. Information on pulmonary congestion was obtained from the descriptions of the chest X-ray.
Information was obtained from the records regarding medical treatment, referral to the HFC or the OPC after discharge, referrals for invasive examinations (coronary angiography) and invasive treatments (PCI, CABG, valve operation), and readmissions during the first years.
Inadequate information about some of the variables (eg, NYHA classification, chamber dimensions on echocardiograms, laboratory tests) excluded them from further analyses.
Data on survival were obtained from the Danish Civil Registration System. The study was registered and approved by the Danish Data Protection Agency.