text: Depending on the marker, it can take between 2 and 24 hours for the level to increase in the blood. Additionally, determining the levels of cardiac markers in the laboratory - like many other lab measurements - takes substantial time. Cardiac markers are therefore not useful in diagnosing a myocardial infarction in the acute phase. The clinical presentation and results from an ECG are more appropriate in the acute situation.
  However, in 2010, research at the Baylor College of Medicine revealed that, using diagnostic nanochips and a swab of the cheek, cardiac biomarker readings from saliva can, with the ECG readings, determine within minutes whether someone is likely to have had a heart attack.