'Real-world' observational studies in arrhythmia research: data sources, methodology, and interpretation. A position document from European Heart Rhythm Association (EHRA), endorsed by Heart Rhythm Society (HRS), Asia-Pacific HRS (APHRS), and Latin America HRS (LAHRS)

The field of observational studies or "real world studies" is in rapid development with many new techniques introduced and increased understanding of traditional methods. For this reason, the current paper provides an overview of current methods with focus on new techniques. Some highlights can be emphasized: We provide an overview of sources of data for observational studies. There is an overview of sources of bias and confounding. Next There is an overview of causal inference techniques that are increasingly used. The most commonly used techniques for statistical modelling are reviewed with focus on the important distinction of risk versus prediction. The final section provides examples of common problems with reporting observational data.

Determinants and patterns of utilization of primary percutaneous coronary intervention across 12 European countries: 2003-2008.

BACKGROUND: Important differences exist between European countries in the degree of implementation of primary percutaneous coronary intervention (PPCI) for patients with ST-elevation myocardial infarction (STEMI). To investigate whether health care-associated economic and demographic country-level characteristics were associated with differences in utilization of PPCI, we aimed to examine 5-year trends in the implementation of PPCI for STEMI across 12 EU countries. METHODS: An ecological study of aggregated data from national and international registries. Main outcome was the number of PPCI per 1,000,000 population, collected annually for the years 2003 to 2008. Impact of year on PPCI implementation was modeled using linear regression and mixed effects models used to quantify associations between PPCI use and country-level parameters. RESULTS: The annual growth in utilization of PPCI was 1.11 (1.03,1.20) per million. Country-level utilization rates varied from 0.82 (95% CI 0.52, 1.30) to 1.38 (95% CI 1.15, 1.64) per million per year. Number of physicians per 100,000 population, number of nurses and midwifes per 100,000 population, number of acute care beds per 100,000 population, population density per km(2), and proportion of population under 50 years old were associated with PPCI utilization. CONCLUSIONS: All 12 EU countries demonstrated evidence of PPCI implementation from 2003 to 2008. However, there was substantial variation in the use and rate of uptake of PPCI between countries. Differences in utilization rates of PPCI are associated with supply factors, such as numbers of beds and physicians, rather than healthcare economic characteristics. Further studies are needed to explore the influence of patient-level factors.