• First myocardial infarction (MI) [ Time Frame: Average time frame: patients in the GPRD are followed from registration until they experience the outcome, leave the practice, die, or 31st December 2009, whichever occurs first. ] [ Designated as safety issue: No ]

  First MIs will be divided into three groups:

  (i) Those with previous manifestations of cardiovascular disease, diagnosed or treated more than 90 days before the MI. These are the 'Heralded MIs'.

  (ii) Those with a diagnosis or treatment of cardiovascular disease occurring only within 90 days before MI. These are the 'MIs with premonitory symptoms'.

  (iii) Those without any previous manifestation of cardiovascular disease at any time before MI. These are the 'Unheralded MIs'.

  
  

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'.