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To evaluate the effect of the drug Montelukast on the brachial artery's function. By giving a drug like Montelukast, which blocks the effects of inflammation in the lungs arteries and controls asthma, we hope to see positive effects in other arteries such as in the heart.

To measure the benefit of cysteinyl leukotriene blockade in favourably altering the pathophysiology of coronary artery disease. We hypothesize that patients admitted to hospital with acute coronary syndromes will have markedly abnormal endothelial function as measured by peripheral vasomotor responses to forearm ischemia. Patients with myocardial infarction and unstable angina have markedly increased renal excretion of the cysteinyl leukotriene metabolite LTE4 as observed in patients with asthma. Observations that coronary vessel tone is negatively affected by leukotrienes C4,D4 and E4 which influences the atherosclerotic process in these arteries. Studies that isolated the epicardial coronary arteries and challenged the vessels with an LTC4 and LTD4 concentration showed that coronary arterial myocytes were found to produce cysteinyl leukotrienes which lead to responsive vasoconstriction. The continued stimulus of vasoconstriction over time leads to endothelial dysfunction and disruption of the endothelium integrity which then leads to stressors that encourage a disease state and atherosclerosis.In this study we will specifically assess peripheral endothelial function by measuring brachial artery diameter changes and PAT responses to temporary forearm ischemia in patients that have had an acute coronary event before and after receiving Montelukast. As well we will measure leukotriene assays both in blood and urine .

Inclusion Criteria:

• male or female age 18-80 years, diagnosis of acute coronary syndrome with one increased Troponin assay,chest pain or chest pain syndrome, stable on initial medical therapy, painfree x 6 hours prior to enrollment

Exclusion Criteria:

• STEMI, Q-wave MI, < 18years, women of childbearing potential, new LBBB, recurrent chest pain since hospitalization, IV nitroglycerine drip, hemodynamically unstable, history of asthma, history of liver disease or abnormal liver enzymes