The diagnosis of myocardial infarction in critically ill patients: an agreement study

The aim of the study was to assess agreement among 4 intensivists in diagnosing myocardial infarction (MI) in critically ill patients based on screening electrocardiograms (ECGs) and cardiac troponin (cTn) levels.

Consecutive patients admitted to a medical-surgical intensive care unit (ICU) underwent systematic screening with 12-lead ECGs and cTn measurements throughout their ICU stay. Independently, 4 raters interpreted the ECGs assessing for changes indicative of ischemia and then classified each patient as to whether they met diagnostic criteria for MI based on the screening cTn measurements and ECG results. A priori, 2 raters were designated the primary adjudicators, and their consensus was used as the reference for the agreement statistics. Agreement on MI diagnosis was calculated for the 4 raters and expressed as raw agreement, kappa (chance-corrected agreement) and varphi (chance-independent agreement, calculated using pairs).

Among 103 enrolled patients, 37 (35.9%) had MI according to the primary adjudicators. The raw agreement for diagnosing MI was 79% (substantial), kappa was 0.24 (fair), and varphi ranged from 0.12 to 0.73 (slight to substantial).

Diagnosing MI in the ICU remains a challenge due to variable agreement in 12-lead ECG interpretation. Such variation in practice may contribute to underrecognition of MI during critical illness.