Sudden cardiac death due to a heart rhythm disturbance after a heart attack (myocardial infarction) is a common cause of death. It is well documented that sudden cardiac death after a myocardial infarct (MI) is associated with low or poor heart rate variability (HRV). HRV is a measure of beat-to-beat changes in heart rate, with a greater variation associated with a "healthier" heart. The effect of caffeine on HRV in patients at high risk for sudden cardiac death is unknown. We, the investigators at the Royal Bournemouth Hospital, aim to study the effect of coffee or tea on HRV after MI.

120 post MI patients on CCU will be studied during the first week of admission. Patients will be categorised using the following criteria: Infarct size and site; PMH; Co-morbidities; Drugs; Regular caffeine ingestion.

Patients will be randomised to receive either caffeinated or de-caffeinated coffee or tea during admission. HRV will be assessed by non-invasive Holter-monitoring on the fifth day. Salivary caffeine concentration will be assessed concurrently to assess compliance.

Inclusion Criteria:

• ST-segment elevation (trans-mural) MI; sinus rhythm.
• Age < 80 years.

Exclusion Criteria:

• Cardiogenic shock
• Nothing by Mouth (NBM)
• Caffeine intolerance
• Atrial fibrillation, temporary or permanent pacing
• Complete heart block, bundle branch block, severe left ventricular impairment, non-ST segment MI/acute coronary syndrome

Patients of either gender, over 18 and under 80 years of age, admitted to the Coronary Care Unit following myocardial infarction.