Myocardial Infarction as the First Manifestation of Coronary Heart Disease: Rates of Heralded and Unheralded Myocardial Infarction

This study is part of the CALIBER (Cardiovascular disease research using linked bespoke studies and electronic records) programme funded over 5 years from the NIHR and Wellcome Trust. The central theme of the CALIBER research is linkage of the Myocardial Ischaemia National Audit Project (MINAP) with primary care (GPRD) and other resources. The overarching aim of CALIBER is to better understand the aetiology and prognosis of specific coronary phenotypes across a range of causal domains, particularly where electronic records provide a contribution beyond traditional studies. CALIBER has received both Ethics approval (ref 09/H0810/16) and ECC approval (ref ECC 2-06(b)/2009 CALIBER dataset).

Using data from MINAP and GPRD, patients experiencing their first myocardial infarction (MI) will be separated into three categories:

• 'Heralded MI': patients who have been diagnosed or treated for cardiovascular disease for more than 90 days before MI.
• 'MI with premonitory symptoms': patients who have been diagnosed or treated for cardiovascular disease within the 90 days prior to MI.
• 'Unheralded MI': patients without a cardiovascular disease diagnosis or treatment at any time before MI.

Patients with MI will be identified in the linked GPRD-MINAP record. Using GPRD population denominators, this study will establish the absolute incidence rates of first 'unheralded' MI by calendar year, age, sex, season, MI subtype (ST-elevation MI and non ST-elevation MI) and region and compare these to the rates of first 'heralded' MIs and first 'MI with premonitory symptoms'.