Trial of Caffeine to Alleviate Dyspnea Related to Ticagrelor

Inclusion Criteria: * Age ≥ 18 years * Recent acute coronary syndrome with ongoing ticagrelor treatment * Stabilized clinical condition with no plans of additional revascularization * Dyspnea with onset after start of ticagrelor treatment * Willingness to abstain from caffeine intake (e.g. coffee, tea, cola-type beverages; other foods, nutritional supplements or medications containing caffeine) for the duration of the study * Provision of signed informed consent form Exclusion Criteria: * Chronic obstructive pulmonary disease, asthma or other known pulmonary disease requiring daily medical therapy * Obstructive sleep apnea syndrome requiring therapy * Ongoing signs and symptoms of heart failure\*, or evidence of moderately to severely reduced left ventricular (LV) function * Renal failure, glomerular filtration rate (GFR) \<30 or on dialysis * Pregnancy or lactation * Known allergy to ticagrelor, or caffeine, or known intolerance of caffeine * Ongoing treatment with any of the following: quinolone antibiotics, fluvoxamine, phenylpropanolamine, carbamazepine, clozapine, lithium, non-steroidal anti-inflammatory drugs (NSAIDs); or any drug containing theophylline or caffeine. * Any condition that seriously increases the risk of non-compliance or loss of follow-up