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Clopidogrel and ticagrelor are two different antiplatelet agents with significant difference in their pharmacokinetics and onset of action. It is known that ticagrelor gives better outcomes in patients with acute coronary syndromes (ACS) when compared with clopidogrel. It has been also reported that it reduces cardiac and total mortality in ACS. The mechanism of better mortality outcomes is not clear. We report the effect of those two agents on silent ambulatory myocardial ischemia studied by holter.
We randomized 50 patients admitted with ACS to a loading dose of 600mg of clopidogrel followed by 75mg daily as a maintenance dose (Clopid group) or to a loading dose of 180 mg of ticagrelor followed by 90mg twice daily as a maintenance dose (Tica group). After having complete coronary revascularization by catheter interventions during the admission for ACS, a holter study was done the following day to check the number of episodes of silent ischemia. All of the patients were discharged on optimal therapy coronary artery disease (CAD) including high dos statin, ACEi beta blockers. Ambulatory holter monitoring was repeated after 4 to 6 months of therapy. The two groups were comparable with respect to baseline characteristics, number of episodes of STsegment depression, and baseline serum cholesterol levels. Holters were read by a blinded cardiologist.
The ticagrelor group experienced a significant reduction in the number of episodes of ST-segment depression compared with the clopidogrel group. ST segment depression was completely resolved in 13 of 25 patients (52%) in the Tica group versus 3 of 25 (12%) in the Clopid group. The Tica group exhibited a highly significant reduction in ambulatory ischemia (P<.001). By logistic regression, treatment with ticagrelor was an independent predictor of silent ischemia resolution.
Treatment with ticagrelor can result in reduction or resolution of myocardial silent ischemia detected by ambulatory holter monitoring of the ECG. A larger study is required to confirm these results. This may explain why ticagrelor reduces total mortality in patients with CAD. It is well known that silent ischemia has a prognostic effect on patients with CAD and treatments of silent ischemia had reduced mortality in some studies.